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Polka-dotted treasures: Revising a clade of ascidian- and bivalve-associated shrimps (Caridea: Palaemonidae)

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Most marine shrimp species of the family Palaemonidae are characterized by symbiotic associations with hosts that belong to a wide range of invertebrate phyla. One clade of related endosymbiotic species has evolved to live inside the branchial chambers of ascidians and the mantle cavities of bivalve molluscs. The phylogeny of this clade (comprising 15 bivalve-associated species in the genera Anchistus, Neoanchistus, and Paranchistus, and three species of ascidian-associated species in the genus Dasella) is the topic of the present study, which is based on both morphological and molecular data. A concatenated phylogeny reconstruction was built by using the markers coi and 16S. With the help of a total evidence approach (with a scored morphological datamatrix), species could be added for which no molecular data were available. An ancestral character state analysis was performed to detect host switches. In contrast to another endosymbiotic clade, the ancestral host state was found to be slightly in favour of bivalves. The phylogenetic relevance of morphological features is discussed with a focus on a tympanal organ located in the major chelipeds of some bivalve-associated shrimp species. This little-known anatomical structure is illustrated by sem and µCT scans. Its possible function is discussed. In the phylogeny reconstructions, both Anchistus and Paranchistus were found to be polyphyletic. They were reclassified to obtain a more natural classification: Anchistus custoides and Anchistus custos were transferred to the resurrected genus Ensiger. Paranchistus liui, P. nobilii, P. pycnodontae, and P. spondylis were transferred to Polkamenes gen. nov. Anchistus pectinis and P. ornatus were transferred to Tympanicheles gen. nov. Per genus, a key to the species is provided.
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©      ... , |: - (print) - (online)
Polka-dotted treasures: Revising a clade of ascidian- and
bivalve-associated shrimps (Caridea: Palaemonidae)
Werner de Gier | : ---
Naturalis Biodiversity Center, Darwinweg 2, 2333 CR Leiden, The Netherlands
Groningen Institute for Evolutionary Life Sciences, University of Groningen, P.O. Box 11103,
9700 CC Groningen, The Netherlands
werner.degier@naturalis.nl
Charles H.J.M. Fransen | : ---
Naturalis Biodiversity Center, Darwinweg 2, 2333 CR Leiden, The Netherlands
 18  2023;    20  2023
: . 
Abstract
Most marine shrimp species of the family Palaemonidae are characterized by symbiotic associations with
hosts that belong to a wide range of invertebrate phyla. One clade of related endosymbiotic species has
evolved to live inside the branchial chambers of ascidians and the mantle cavities of bivalve molluscs. The
phylogeny of this clade (comprising 15 bivalve-associated species in the genera Anchistus, Neoanchistus,
and Paranchistus, and three species of ascidian-associated species in the genus Dasella) is the topic of
the present study, which is based on both morphological and molecular data. A concatenated phylogeny
reconstruction was built by using the markers  and 16S. With the help of a total evidence approach
(with a scored morphological datamatrix), species could be added for which no molecular data were
available. An ancestral character state analysis was performed to detect host switches. In contrast to
another endosymbiotic clade, the ancestral host state was found to be slightly in favour of bivalves. The
phylogenetic relevance of morphological features is discussed with a focus on a tympanal organ located
in the major chelipeds of some bivalve-associated shrimp species. This little-known anatomical structure
is illustrated by  and CT scans. Its possible function is discussed. In the phylogeny reconstructions,
both Anchistus and Paranchistus were found to be polyphyletic. They were reclassied to obtain a more
natural classication: Anchistus custoides and Anchistus custos were transferred to the resurrected genus
Ensiger. Paranchistus liui, P. nobilii, P. pycnodontae, and P. spondylis were transferred to Polkamenes gen.
nov. Anchistus pectinis and P. ornatus were transferred to Tympanicheles gen. nov. Per genus, a key to the
species is provided.
 18  2023
20March2023
;    20  2023
   () –
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Keywords
commensal shrimp – host switching – symbiosis – taxonomic revision – total evidence
ZooBank: urn:lsid:zoobank.org:pub:17A6B0AD-48CC-4B62-8949-12376BBF5EAB
Introduction
The shrimp family Palaemonidae (Crustacea:
Decapoda: Caridea) includes a large num-
ber of ecto- and endosymbiotic lineages
(Kou et al., 2015; Horká et al., 2016; Chow et
al., 2021). Its species are known to be associ-
ated with hosts belonging to a wide variety
of invertebrate taxa, including echinoderms,
cnidarians, sponges, molluscs, and ascidians
(e.g., Bruce, 1976a; Horká et al., 2016; Chow
et al., 2021). Two lineages are known to con-
sist of symbionts that live either inside soli-
tary ascidians or bivalve molluscs, and in one
instance of a gastropod mollusc (Bruce, 1995;
Fransen, 2002). Most shrimp species within
these lineages seem to be characterised by a
set of morphological features that appear to
be linked to their cryptic lifestyle, including:
(1) reduced frontal, dorsal and lateral protru-
sions for easier movement within the host
(e.g., shortening of the rostrum, reduction of
the number of rostral teeth, absence or reduc-
tion of the antennal and hepatic spines); (2)
the development of scales and microsetae
on the dactyls of ambulatory pereiopods to
increase grip; (3) an adaptive (often cryptic)
colouration; (4) a roughly cylindrical body
shape with a body size that is adapted to the
dimensions of the host’s body cavity; and
(5) diferences in eye morphology (de Gier
et al., 2022 and references herein). In addition,
Bruce (1972a) mentions bivalve-associated
shrimps bear bigger claws on their second
chelipeds, possibly caused by intraspecic
competition. There are numerous other crus-
tacean clades bearing similar morphological
characters, which are thought to result from
their endosymbiotic lifestyle. This is the case
for the palaemonid genus Periclimenaeus
Borradaile, 1915, associated with colonial
ascidians and sponges (Fransen, 2006), and
ascidian and mollusc-associated alpheid
shrimps (e.g., Betaeus harfordi (Kingsley, 1878)
and Synalpheus herdmaniae Lebour, 1938; see
Lebour, 1938; Jensen, 1995). In addition, vari-
ous symbiotic leucothoid amphipods (Vader,
1983) and most pinnotherine pea crabs (de
Gier & Becker, 2020) show adaptive features
related to a life within a host.
The two lineages mentioned above were
dened by large-scale (molecular) phyloge-
netic studies (Kou et al., 2015; Horká et al.,
2016 (parts of clades 5 and 6); Chow et al.,
2021 (parts of clades  and )). The lin-
eage including the larger genera Ascidonia
Fransen, 2002, Conchodytes Peters, 1852,
Dactylonia Fransen, 2002, Odontonia Fransen,
2002, and Pontonia Latreille, 1829 (together
with smaller related genera) was studied in
detail by combining both morphological and
molecular data, which showed monophyly
in both the studied genera and the entire
ingroup (de Gier et al., 2022). The other,
smaller lineage consists of four genera, which
are characterized by a conspicuous polka-dot-
ted colouration: Anchistus Borradaile, 1898,
Dasella Lebour, 1945, Neoanchistus Bruce, 1975,
and Paranchistus Holthuis, 1952. Members
of Anchistus, Neoanchistus, and Paranchistus
are all reported as endosymbionts, associated
with bivalve molluscs, such as giant clams,
fan shells, scallops, oysters and spiny oysters
(Fransen, 1994a; De Grave, 1999). Species of
./-|   
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Dasella are endosymbionts of large solitary
ascidians (Bruce, 1981a, 2003a; Berggren,
1990). Species of these genera can be found
in the Indo-West Pacic region. A revision of
the taxa in this clade, including morphologi-
cal diagnoses, keys, colour descriptions, host
ranges, and geographical distribution is pro-
vided in the systematic account below.
Although various members of Anchistus
and Paranchistus (both s.l.) have been stud-
ied for their ecological role (Johnson & Liang,
1966), mating systems and lifecycles (Baeza et
al., 2013; Ghory & Kazmi, 2018), or the char-
acterisation of their symbioses (De Grave et
al., 2021), the systematic positions of its spe-
cies remain elusive. While the four genera
are known to be closely related (Horká et
al., 2016; Chow et al., 2021), true monophyly
of the clade (including all members), has
not been proven yet. In addition, Chow et al.
(2021) showed that the placement of species
attributed to Paranchistus was polyphyletic.
They recognized two distinct lineages, plac-
ing an unknown species of Paranchistus and
Paranchistus pycnodontae Bruce, 1978 away
from Paranchistus ornatus Holthuis, 1952. In
this study, we revise the four genera and aim
to construct a more robust phylogeny, parallel
to the study of de Gier et al. (2022).
Host switching, an evolutionary process
of a symbiotic lineage shifting from one host
to another, has been a major topic in marine
palaemonid shrimp phylogenetics (Horká
et al., 2016; Chow et al., 2021). While lineages
of ectosymbiotic palaemonids seem to switch
commonly between genera or families, ascid-
ian- and mollusc-associated species have been
proven to have switched between entire phyla:
the common ancestor of the before-mentioned
clade containing the (mostly) bivalve-associ-
ated genera Conchodytes and Pontonia, as well
as the predominantly ascidian-associated
genera Ascidonia, Dactylonia, and Odontonia,
was recovered as an ascidian-associated
species. Within the clade, at least six difer-
ent interphyla host switches were recognized,
with Odontonia and Notopontonia Bruce, 1991
switching back to an ascidian host aliation
after an ancestral switch from an ascidian- to
a bivalve host within the clade consisting of
Conchodytes, Odontonia, and related genera
(de Gier et al., 2022). We aim to detect possible
host switches in the currently studied clade
and recover the host of its common ancestor.
Material and methods
Taxon sampling
A total of 18 ingroup and nine outgroup species
were selected, all occurring in the Indo-West
Pacic region () (supplementary table S1).
Nine palaemonid outgroup taxa were selected
across the host spectrum, representing echi-
noderm and cnidarian associates: Actinimenes
inornatus (Kemp, 1922), Actinimenes orna-
tus (Bruce, 1969), Lipkemenes lanipes (Kemp,
1922), Periclimenes colemani Bruce, 1975,
Periclimenes kempi Bruce, 1969, Zenopontonia
rex (Kemp, 1922), and Zenopontonia soror
(Nobili, 1904). The predominantly free-
living Cuapetes tenuipes (Borradaile, 1898)
and Palaemonella rotumana (Borradaile,
1898) were added to the outgroup. All associ-
ated species are part of Clade 5 of Horká et al.
(2016), which is closely related to the ingroup.
Specimens were collected by  div-
ing or other standard collection methods
during various expeditions (supplementary
table S1). For more information, eld reports
were published for the expeditions to Ambon
(Strack, 1993), the Seychelles (Van der Land,
1994), Lombok (Hoeksema & Tuti, 2001),
Berau (Hoeksema, 2004), Santo (Vanuatu;
Bouchet et al., 2011), Raja Ampat (Hoeksema
& van der Meij, 2008), Ternate (Hoeksema &
van der Meij, 2010), and Semporna (Kassem
et al., 2012). Recently sampled specimens were
-  - |./-
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directly stored in 96% ethanol for  bar-
coding and identication. Subsampling was
done by removing the left second and third
pleopods or left third and fourth pereiopods.
After subsampling, specimens were moved
to 70% ethanol for morphological analy-
sis and long-term storage in the Naturalis
Biodiversity Center decapod collection
(..) at Leiden, The Netherlands.
The newly sequenced material consists of six
species (supplementary table S1). In addition,
sequence data from GenBank (Sayers et al.,
2020) was used (supplementary table S1).
 extraction, amplication and
sequencing
Of the four analysed markers (, H3, 16S,
and 18S), only two were selected ( and 16S)
for their phylogenetic relevance.  extrac-
tion, amplication and sequencing were done
using the same methods for  and 16S as
described in de Gier et al. (2022), partially
based on the protocols described by Horká
et al. (2016), Fransen & Reijnen (2012), and
Brinkman & Fransen (2016).
Morphological character state analysis and
taxonomic study
The morphology of all in- and outgroup spe-
cies was scored, based on specimens in the
Naturalis collection (...), as
well as descriptions and gures found in lit-
erature (supplementary table S1). Characters
were selected based on their visibility in adult
specimens, which may difer in juveniles. The
resulting morphological data matrix con-
tains 35 characters for 27 species, of which 11
multi-state characters were coded as ordered
(character 1, 2, 5, 6, 9, 17, 20, and 29 to 32)
(Fitch, 1971). The remaining binary and mul-
ti-state characters were coded as unordered
(Farris, 1970). Character state 0 was usually
attributed to the outgroup species. Unknown
character states were treated as missing data,
coded as question marks (?) (supplementary
appendix S1, supplementary table S2).
Specimens were studied and dissected
using a dissecting stereomicroscope (Zeiss
Discovery.V8) and a compound microscope
(Olympus BX53), both equipped with a
Camera Lucida drawing tube. Of the ingroup
species found in .., new illus-
trations were made for use in both the tax-
onomic revision and the morphological
character state analysis. Illustrations were
inked, scanned on 600 dpi, and subsequently
mounted into plates using Adobe Photoshop
software (Adobe Systems, USA).
Macro-photographs showing the life col-
ouration of several specimens were made
during eld expeditions. When available,
museum-collection accession numbers are
given for the specimens: ...
(Naturalis Biodiversity Center decapod col-
lection, Leiden, the Netherlands); 
(Muséum national d’Histoire naturelle, Paris,
France);   (Florida Museum of
Natural History, University of Florida, USA).
Phylogeny reconstructions and ancestral
character state analysis
Sequence alignments were obtained using the
ClustalW (Thompson et al., 1994) algorithm
(default settings) in  v10.2.5. (Kumar
et al., 2018). Ends of the  and 16S align-
ments were trimmed manually in  to
582bp and 426bp respectively. The alignment
of the protein-coding gene  was subjected
to Xia’s test of nucleotide substitution satura-
tion (Xia et al., 2003) in  v7.3.0. (Xia,
2009). None of the codon positions of 
was found to be saturated and thus no data
was excluded. After alignment, the non-cod-
ing ribosomal 16S gene was examined for
highly divergent blocks using Gblocks v0.91b
(Talavera & Castresana, 2007) using default
parameters but allowing gap positions and
smaller ner blocks. Additionally, the settings
./-|   
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were changed to allow less strict anking
positions. This resulted in the retention of all
bases in the alignment.
Both  and 16S were analysed individ-
ually, and a complement dataset was made
for all specimens where both gene sequences
were obtained or already available (+16S).
A concatenated dataset containing both
genes was also constructed in , to also
include specimens where only one of the two
sequences was obtained. This alignment con-
sisted of 43 sequences and 1008 positions. A
Total Evidence () analysis was performed
by combining all data from the concatenated
alignment and the morphological dataset, to
include all ingroup species in the resulting
phylogenetic trees.
Models for sequence evolution were calcu-
lated in  using default settings (table 1).
Best models were chosen based on values for
the Akaike Information Criterion () and
Bayesian Information Criterion ().
Phylogenetic analyses were performed
under the maximum likelihood () and
Bayesian Inference () criteria using RAxML
via the on-line  (Miller et al., 2010) with
the RAxML-NG BlackBox v1.0.0 tool (Kozlov
et al., 2019) and MrBayes v3.2.7 (Ronquist
& Huelsenbeck, 2003), respectively. For the
single-gene  analyses default settings were
used and automatic bootstrapping with a cut-
of of 0.03, under an unpartitioned model.
The dual-gene alignment used a partitioned
model for both genes, with scaled branch
length linkage and automatic bootstrapping
with a cut-of of 0.03. Consequently, the con-
catenated dataset used a similar partitioned
method. The  analyses were conducted
using a Markov Chain Monte Carlo ()
method with two independent runs and four
chains. Analyses were run with a minimum of
5,000,000 generations to ensure that the aver-
age standard deviation of split frequencies
() reached a value < 0.01, which would
indicate that the two runs have converged to
a stationary distribution. Trees were sampled
each 500 generations. The initial 25% of trees
was discarded as burn-in and the remaining
trees were used to generate consensus trees
and to estimate Bayesian posterior proba-
bilities (). In all instances, the topology of
the  analyses was displayed in the results,
with annotations to the Bayesian posterior
probabilities and  RAxML values at each
intraspecic node.
The analysed sequences resulted in four
phylogeny reconstructions: the single gene
(, 16S) and dual gene (+16S) phylogeny
 1 Analytical methods and models used for sequence evolution. For the alignments of the concatenated
dataset and the  analysis, partitioned models (based on the single gene and morphological analyses)
were used
Alignment Model(s) for sequence evolution Trimmed fragment length
Single gene:  ++ 582bp.
Single gene: 16S ++ 426bp.
Dual gene: , 16S ++, + 1008bp.
Morphology* 4_ 35 char.
* The mixed model for the MrBayes analysis of the morphological data in the TE analysis was coded to be gamma-
distributed. In addition, the Multi4_ model was selected in the RAxML-server to deal with the morphological
dataset, with 4 being the maximum number of character states per character (0–3).
-  - |./-
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reconstructions can be found in the appendi-
ces (supplementary gs. S1–S3); the concat-
enated alignment resulted in the phylogeny
reconstruction presented in the results sec-
tion below.
The Total Evidence analyses were per-
formed similar to the phylogenetic analyses of
the concatenated alignment, but with the addi-
tion of morphological data. The integrative
dataset consisted of 52 taxa and 1043 codon/
character positions. The following species
were only represented by morphological data:
Anchistus gravieri Kemp, 1922, Tympanicheles
pectinis (Kemp, 1925) comb. nov. (was
Anchistus pectinis), Dasella ansoni Bruce, 1983,
Dasella brucei Berggren, 1990, Neoanchistus
cardiodytes Bruce, 1975, Neoanchistus nasalis
Holthuis, 1986, Polkamenes liui (Li, Bruce & R.B.
Manning, 2004) comb. nov. (was Paranchistus
liui), Polkamenes nobilii (Holthuis, 1952)
comb. nov. (was Paranchistus nobilii), and
Polkamenes spondylis (Suzuki, 1971) comb. nov.
(was Paranchistus spondylis). All sequences
were accompanied by conspecic morpho-
logical data, assuming absence of intraspecic
morphological variations in the chosen char-
acters and specimens. To check the results of
our combined dataset, an analysis only using
morphological characters was performed,
based on the methods used by Fransen (2002),
de Gier and Fransen (2018), and de Gier et
al. (2022), using  v4.0a (Swoford, 2003)
under the maximum parsimony () criterion,
with ordered characters and step matrices as
mentioned above. A heuristic search was per-
formed with 10.000 repetitions, with a number
of trees that was automatically increased with
100. The strict consensus and the 50% major-
ity rule consensus trees were obtained.
To reconstruct the evolution of host associa-
tions, an ancestral-character-state reconstruc-
tion was performed in R using the  criterion
and the  tree from the  analysis as a back-
bone. The R-packages ape v. 5.5 (Paradis &
Schliep, 2019), Geiger 2.0.7 (Penell et al., 2014)
and phytools (Revell, 2012) were used. To get
probability values for polytomous branches,
the phytools function ‘rerootingMethod()
was used, following Yang et al. (1995). The
host-choice of Zenopontonia rex was changed
from ‘Echinoderm and Mollusc (nudibranch/
gastropod) associate’ to ‘Echinoderm associ-
ate’, due to technical limitations. Pie-charts
displaying -values similar to the ones seen
in comparable studies (e.g., Salis et al., 2018)
were added in Abode Illustrator  (Adobe
Systems, USA). The actual -probabilities
are presented in supplementary table S3 and
supplementary g. S4.
Phylogenetic trees were initially rooted and
sorted in FigTree v1.4.4 (Rambaut, 2009), and
consequently edited in Adobe Illustrator ().
Additional gures
Captures of one of the major claws of
Anchistus miersi (De Man, 1888) (taken from
specimen ...58030, found in a
Tridacna squamosa Lamarck, 1819), and of
Tympanicheles ornatus (Holthuis, 1952) comb.
nov. (taken from ...41491, from
an unknown bivalve host) were made using a
Scanning Electron Microscope () (
 6480LV; Naturalis Imaging Facilities)
according to the protocol by de Gier and
Fransen (2018). After chemical dehydration
(twice 15min in 80% ethanol, followed by
twice 15min in 96% ethanol, followed by
twice 30min in 100% acetone) the samples
were dehydrated using Critical Point Drying-
methods () with a Leica  300.
Additional captures were made of a claw
of Anchistus australis Bruce, 1977 (.
..53540 found in T. squamosa) with
a Zeiss Xradia 520 Versa 3D X-ray micro-
scope (CT-scanner) (Naturalis Imaging
Facilities). A specimen was mounted in a
1.5ml tube lled with 70% ethanol. Staining
was performed for 1 day in a 1%  solu-
tion. Settings were used as follows: Optical
magnication 0.396; Scanning current 87 A;
./-|   
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Scanning voltage 80kV; Exposure time 3ms.
Reconstruction (3D) data was edited in Avizo
9.5.0 (ThermoScientic).
Results
Molecular phylogeny reconstructions
The phylogenetic analysis using the concat-
enated alignment was resolved with mod-
erately high support values (g. 1). Most
outgroup species were recovered as basal to
the ingroup, with the tree being rooted with
the two free-living species (Cuapetes tenuipes
and Palaemonella rotumana). This is the case
for three Cnidaria associates (two species of
Actinimenes and Periclimenes kempi), and
one Echinodermata associate (Lipkemenes
lanipes). The other echinoderm-associated
(and gastropod-associated) outgroups (two
species of Zenopontonia Bruce, 1975, and
Periclimenes colemani) were recovered in a
large polytomy together with Paranchistus
armatus (H. Milne Edwards, 1837) and a
clade of all other ingroup species. Because
of the polyphyly found in Paranchistus and
Anchistus, a number of species from these
genera were designated to three new genera,
in both the molecular and combined ()
phylogeny reconstructions. The species are
formally transferred to their new genera in the
systematic account below.
The ingroups consists of three main clades.
The ascidian-associated genus Dasella, repre-
sented by Dasella herdmaniae (Lebour, 1938)
in the molecular phylogeny reconstruction, is
placed basal to the other (bivalve-associated)
ingroup species (except for P. armatus), fol-
lowed by a clade of Ensiger custoides (Bruce,
1977) comb. nov. and Ensiger custos (Forskål,
1775) comb. nov. Two species with now newly
described genera, Polkamenes pycnodontae
(Bruce, 1978) comb. nov. and Tympanicheles
ornatus, are branching of respectively, after
which an Anchistus clade consisting of three
species is recovered. This clade is represented
by one basal branch of A. australis, and one
branch including Anchistus demani Kemp,
1922 and A. miersi. Anchistus demani is man-
ifested as paraphyletic, with one species
branching of earlier (...48354).
The placement of this specimen is discussed
below.
Total Evidence approach
Four ingroup clades can be recognized in the
phylogeny reconstruction resulting from the
Total Evidence approach (g. 2). The com-
bined dataset using both morphology, as well
as molecular data, recovered the outgroup in a
similar way as the above mentioned topology
(g. 1). Zenopontonia rex and Periclimenes cole-
mani were recovered as the outgroups being
most related to the ingroup. This ingroup was
recovered with low support values (51/--).
The rst clade containing the three species
of Dasella was split of with high support
values (98/75). Dasella ansoni and D. brucei,
only represented by morphological data, were
recovered as a sister clade of D. herdmaniae.
The next clade branches of with somewhat
low support values (86/--), containing three
species: Paranchistus armatus, Ensiger custos,
and E. custoides, of which the last two were
recovered as most related to each other. The
remaining ingroup species were recovered in
two clades, one of which only includes spe-
cies previously attributed to Paranchistus,
but now to Polkamenes gen. nov.: P. liui (only
represented by morphological data) branches
of rst in this clade, after which a polytomy
of P. pycnodontae, P. nobilii, and P. spondylis
was recovered. The latter two species were
only represented by morphological data. The
remaining ingroup species were recovered
as a part of a large polytomy including three,
now monophyletic genera: Tympanicheles
gen. nov., Neoanchistus, and Anchistus.
-  - |./-
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 1 Phylogeny reconstruction based on the MrBayes tree topology of the concatenated molecular dataset (, 16S). RAxML bootstrap support and Bayesian
posterior probabilities expressed as percentages are indicated respectively. Dashes (--) indicate values <50; asterisk (*) indicates diferent topology of RAxML or
MrBayes tree. Barcodes are indicated by a collection accession number (...) or a GenBank accession number. Species are listed in the appendices
(supplementary table S1). Colours indicate various host associations. Zenopontonia rex (Kemp, 1922) is represented as a symbiont with two kinds of host
associations: holothurians and nudibranchs.
./-|   
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 2 Phylogeny reconstruction based on the MrBayes tree topology of the  approach. RAxML bootstrap support and Bayesian posterior probabilities expressed
as percentages are indicated respectively. Dashes (--) indicate values <50; asterisk (*) indicates diferent topology of RAxML or MrBayes tree. Barcodes are
indicated by a collection accession number (...) or a GenBank accession number. Species are listed in the appendices (supplementary table S1).
Species of which only morphological data was analysed are indicated with an asterisk (*) and no accession number. Colours indicate various host associations.
Zenopontonia rex (Kemp, 1922) is represented as a symbiont with two main host associations: holothurians and nudibranchs.
-  - |./-
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
 3 Phylogeny reconstruction based on the MrBayes tree topology of the  approach (g. 2), with ancestral character state reconstructions on the internal nodes
(probabilities are shown as pie charts). Colours indicate various host associations, both for the species as well as the ancestral character states. Zenopontonia rex
(Kemp, 1922) is represented as a symbiont with two kinds of host associations (holothurians and nudibranchs), but was only classied as an echinoderm associate
in the analysis. Species of which only morphological data was analysed are indicated with an asterisk next to the species names (*).
./-|   
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
Tympanicheles pectinis (only represented by
morphological data) is grouped together with
T. ornatus with somewhat low support values
(51/--), while the two species of Neoanchistus
are recovered as closely related sister species
(although both species are only represented
by morphological data). A branch containing
four species of Anchistus (A. miersi, A. demani,
A. australis, and A. gravieri) is recovered with
higher support values, with A. gravieri (being
represented by morphological data) as the
most basally placed species.
Ancestral character state analysis
An ancestral character state reconstruction
analysis resulted in Maximum Likelihood
probabilities for all 24 internal nodes, which
translate to the probabilities that an ancestral
shrimp clade would have been associated to
a certain host (g. 3). One internal node was
recovered as polytomous, but did not interfere
with the resulting probabilities (see g. 3). As
expected, all internal nodes of the bivalve-as-
sociated clade containing all ingroup genera
(except for Dasella) are fully resolved as asso-
ciates of bivalve molluscs (
p= 0.99
to 1.00).
Similarly, the internal nodes in the clade con-
taining the three species of Dasella are fully
resolved as symbionts of ascidians.
The common ancestor of the entire ingroup
is recovered as a bivalve associate, but the prob-
ability for this character state barely reaches
51% (
p= 0.508
) (g. 3A). The chances of this
common ancestor being an ascidian (
p= 0.180
)
or echinoderm associate (
p= 0.299
) are
much smaller. The common ancestor of a
clade including the ingroup and the two most
related outgroup species (Zenopontonia rex
and Periclimenes colemani) is recovered as an
echinoderm associate (
p= 0.991
). The ances-
tral character state of the clade described by
Horká et al. (2016) (thus, also including the
echinoderm associated Z. soror and Lipkemenes
lanipes, and the cnidarian-associated species of
Actinimenes and Periclimenes kempi) is recov-
ered to most likely be cnidarian-associated
(
p= 0.483
) (g. 3B).
Systematic account
Genera and species within the ‘Anchistus
clade‘ are revised with remarks on their syn-
onymy. Diagnoses, identication keys, geo-
graphical distributions, and host ranges are
provided. Drawings of diagnostic characters
and color photographs are added based on
available material. Special attention is given to
novel features of the ingroup species, mostly
concerning mouthparts.
Abbreviations
coll. collected by
don. donated by
fcn. eld collection number
pocl. postorbital carapace length, meas-
ured from the posterior orbital mar-
gin to the posterior margin of the
carapace in the dorsal midline
R rostral formula indicated by the num-
ber of dorsal rostral teeth/number of
ventral rostral teeth
Stn eld station; measurements are in mm
Family Palaemonidae Ranesque, 1815
Genus Anchistus Borradaile, 1898
Anchistus Borradaile, 1898: 387. Type species,
by original designation: Harpilius Miersi De
Man, 1888. Gender: masculine. Name placed
on the Ocial List of Generic Names in
Zoology in Opinion 470, in 1957.
Tridacnocaris Nobili, 1899: 234. Replacement
name for Anchisus Borradaile, 1898. Type
-  - |./-
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
species therefore: Harpilius Miersi De Man,
1888. Gender: feminine. Name placed on the
Ocial Index of Rejected and Invalid Generic
Names in Zoology in Opinion 470, in 1957.
Diagnosis (emended from Bruce, 1995: 29).
Small-sized shrimps of subcylindrical body
form. Rostrum well developed, compressed,
with teeth in distal part, lateral carinae fee-
bly developed. Carapace smooth, glabrous;
orbit feebly developed, inferior orbital angle
distinct, antennal spine present or absent,
supraorbital, hepatic and epigastric spines
absent, anterolateral margin not produced.
Abdomen smooth, glabrous, third segment
not posterodorsally produced, anterior pleura
rounded, posterior blunt. Telson with two
pairs of small dorsal spines, three pairs of
posterior spines. Eye small, cornea globular.
Antennula normal, upper agellum biramous,
short ramus reduced. Antenna with basicerite
unarmed, scaphocerite well developed with
large distolateral tooth. Epistome unarmed.
Mandible normal, without palp, molar pro-
cess robust, incisor process dentate; maxil-
lula with feebly bilobed palp, laciniae broad;
maxilla with simple palp, basal endite broad,
bilobed, coxal endite obsolete, scaphog-
nathite broad; rst maxilliped with slender
palp, basal endite broad, fused with coxal
endite, exopod well developed, caridean lobe
broad, agellum with numerous plumose
setae distally, epipod bilobed; second maxil-
liped with normal endopod, dactylar segment
small, exopod well developed, coxa feebly
medially produced, epipod rounded, without
podobranch; third maxilliped with endopod
slender, ischiomerus and basis fused, exo-
pod with numerous plumose setae distally,
coxa with oval lateral plate, with rudimentary
arthrobranch. Fourth thoracic sternite with-
out median process. First pereiopods slender,
chelae with ngers spatulate, non-cannulate,
cutting edges minutely pectinate. Second
pereiopods well developed, similar, unequal,
dactylus with large acute triangular tooth
in proximal half, xed nger with series of
teeth in proximal part; propodus with ventral
oval tympanal organ proximally. Ambulatory
pereiopods with simple or biunguiculate dac-
tyli, without basal protuberance; unguis with
dorsal pad of ne scale-like spinules. Uropod
with protopodite posterolaterally acutely pro-
duced or rounded, exopod with small mobile
distolateral spine, without distolateral tooth.
Four Anchistus species are recognized, all
from bivalve hosts: Anchistus australis Bruce,
1977, Anchistus demani Kemp, 1922, Anchistus
gravieri Kemp, 1922, and Anchistus miersi
(De Man, 1888). Anchistus pectinis Kemp,
1925 is herein transferred to the new genus
Tympanicheles.
Key to the species of Anchistus
1. Carapace without antennal spine; pro-
topodite of uropod rounded...……………2
Carapace with antennal spine; protopo-
dite of uropod acute ...……………..............3
2. Rostrum with two dorso-distal teeth,
ventrodistal margin rounded; ne scale-
like spinules on unguis of ambulatory
dactyli in transverse lines ..……A. demani
Rostrum with 4-8 dorsal teeth in distal
part of rostrum, ventral margin with
one small subdistal tooth; ne scale-like
spinules on unguis of ambulatory dactyli
in longitudinal lines ...………...A. australis
3. Ambulatory dactyli with corpus-unguis
suture perpendicular to ventral margin;
corpus without accessory tooth; lateral
pair of posterior telson spines as small as
dorsal spines, marginal ...…......A. gravieri
Ambulatory dactyli with corpus-unguis
suture strongly oblique; corpus with
accessory tooth; lateral pair of posterior
./-|   
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telson spines distinctly larger than dor-
sal spines, submarginal ...…….....A. miersi
Anchistus australis Bruce, 1977
(gs. 4A–B, 5, 39E–F)
Anchistus australis f. typica Bruce, 1977a: 56,
gs. 7-9 [type locality: Capre Cay, Swain’s
Reefs. Unavailable under Art. 15.2].
Anchistus australis f. dendricauda Bruce,
1977a: 62, gs. 10 [type locality: West Cay,
Diamond Islets. Unavailable under Art. 15.2].
Anchistus australis Bruce, 1981b: 389, 395, g.
3A; Bruce, 1983a: 43-44; Bruce, 1983b: 892,
g. 10A; Bruce, 1983c: 199 (listed); Bourdon,
1983: 867 (listed); Devaney & Bruce, 1987:
222; Bruce, 1990: 15, 18 (listed); Bruce, 1991a:
258-259, 275; Bruce, 1993: 55; Chace & Bruce,
1993: 71 (listed); Müller, 1993: 7 (listed); Strack,
1993: 53; Fransen, 1994a: 106, g. 1; Bruce &
Coombes, 1995: 106; De Grave, 1999: 126, g. 1;
Li, 2000: 6-7, g. 6 (listed); Hayashi, 2002: 221,
gs. 432a, b, 434a, b, 435a, b; Bruce, 2003b: 210
(listed); Hayashi, 2006: 510; Marin & Savinkin,
2007: table 2 (listed); De Grave & Fransen, 2011:
340 (listed); Fransen & Reijnen, 2012: 47; Hosie
et al., 2015: 283 (listed); Liu, 2020: 312-313.
Material examined. INDONESIA: 1 male
pocl. 5.2mm (photo by M.S.S. Lavaleye 24/22-
24), 1 female pocl. 7.00mm (photo by M.S.S.
Lavaleye 24/22-24) (...41436), stn
.20, Ambon Island, Hitulama, 20.xi.1990,
depth 15 m, -diving, in Tridacna squa-
mosa Lamarck, coll. C.H.J.M. Fransen and J. van
Egmond. – 1 male pocl. 2.14mm, 1 female pocl.
3.83mm, 1 ovigerous female pocl. 2.92mm
(...41437), stn .16, W-side of
Pombo Island, E of Ambon Island, 16.xi.1990,
snorkeling, in T. squamosa, coll. J.C. den
Hartog. – 1 male pocl. 2.99mm, 20 juveniles
pocl. 1.10-1.95mm (...41438), stn
.20, Ambon Island, Hitulama, 20.xi.1990,
depth 15 m, -diving, in large Tridacna
sp. (Ø 39cm), coll. C.H.J.M. Fransen & J. van
Egmond. – 1 female pocl. 4.55mm (.
..41439), Nanaka, 7.ii.1980, in Tridacna
sp., don. . – 1 ovigerous female pocl. 7.5mm
(...53540, GenBank JX185709; -
scanned), stn .12, Ternate, Tanjung Tabam,
0°50’5.1”N 127°23’10”E, 30.x.2009, depth 8 m,
-diving, in T. squamosa, coll. C.H.J.M.
Fransen, fcn. -00044, photo .12.0073-79.
– 1 non ovigerous female pocl. 5.0mm (.
..58048), stn .28,  Kalimantan,
Berau Islands, Maratua Island, N-side, lagoon
near entrance, 02°14’51.0“N 118°37’47.9”E,
17.x.2003, depth 8 m,  diving, in T. squa-
mosa, coll. C.H.J.M. Fransen, lm 16. – 1 oviger-
ous female pocl. 3.5mm, 1 male pocl. 3.0mm
(...27919), stn .28, W Papua,
Raja Ampat Islands, N Batanta, N pulau Yari,
00°46.779’S 130°42.711’E, 28.xi.2007, depth 8
m,  diving, in T. squamosa, coll. C.H.J.M.
Fransen, fcn. 102. MALAYSIA: 1 ovigerous
female pocl. 7.01mm (...41287),
West Malaysia, Tioman Island, Telek Dalam,
in T. squamosa; depth 10 feet, 22.vi.1983, coll.
P. Ng. – 1 ovigerous female pocl. 5.3mm,
with bopyroid on left side under carapace
(...53859; GenBank JX185708),
stn .18, Sabah, Semporna area, Ligitan Isl.,
04°14’06.5”N 118°48’26.5”, 4.xii.2010, depth 5 m,
-diving, in T. squamosa, coll. dive guide
Jerry.
Diagnosis. Rostrum with 4–7 dorsal dis-
tal and 0–1 ventral distal tooth, reaching just
beyond the basal segment of the antennal
peduncle. Sixth abdominal segment with pos-
terior ventral angle rounded. Telson with small
dorsal spines at 0.67 and 0.81 of telson length,
with lateral pair of terminal spines small, sit-
uated next to intermediate spines. Antennal
spine absent. Anterior margin between ventral
orbital angle and antero-lateral angle almost
straight. Basal segment of antennular pedun-
cle with convex lateral margin and distolateral
tooth. Deep slit present between distolateral
spine and lamina of scaphocerite. Stylocerite
acute. Chela of rst pereiopod spatulate,
non-cannulate, with cutting edges laterally
minutely pectinate in distal 2/3rd, medially
-  - |./-
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
 4 A) Anchistus australis Bruce, 1977, ...58048, stn .28, in Tridacna squamosa Lamarck,
1819; B) A. australis, ...53540, stn .12, in T. squamosa; C) Anchistus demani Kemp,
1922, ...42792, stn .792, in Tridacna maxima (Röding, 1798); D) A. demani, .
..58049, stn .07, in T. maxima; E) Anchistus gravieri Kemp, 1922, ...58052,
stn FR15, in Hippopus hippopus (L., 1758); F) Anchistus miersi (De Man, 1888), ...42970,
stn .720, in T. squamosa: G) A. miersi, ...46473,  Sulawesi, in T. squamosa; H)
A. miersi, ...53568, stn .19, in T. squamosa.
  .... 
./-|   
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entire. Dactylus of chela of second pereiopod
with one large triangular acute tooth in prox-
imal half; xed nger with 4–10 small teeth in
proximal half. Palm with oval tympanal organ
on medio-ventrally in proximal part. Dactylus
of pereiopod 3–5 biunguiculate; exor margin
of corpus carinate with small triangular sub-
distal accessory tooth; unguis attened with
ne scale-like spinules in longitudinal lines.
Protopod of uropod rounded.
Remarks. In one Tridacna squamosa spec-
imen with a maximum width of 39cm, one
small male specimen (pocl. 2.99mm) and 20
juveniles (...41438) with cara-
pace lengths between 1.10 and 1.95mm were
found. This indicates that part of one brood
of a female remains in the host. Larval devel-
opment may be somewhat abbreviated and
planktonic larval stages remain in the host
mantle cavity until molting in megalopa and
subsequent juvenile stages. One can assume
that the juveniles leave the host when they
become adults. The smallest specimens
show the rostrum more similar to certain
Periclimenes O.G. Costa, 1844 species. The dor-
sal teeth are spread over the distal half of the
rostrum and a rudiment of an epigastric spine
is present in these youngsters. This implicates
that the dorsal rostral spines ‘move’ forward
after each moult, clustering together in the
distal part in fully grown specimens.
The material corresponds well with the
type description of A. australis f. typica. The
characteristics of A. australis f. dendricauda,
intermediate posterior terminal spines of tel-
son terminating in series of short blunt pro-
cesses, and dorsal rostral margin with eight
teeth, were not encountered. The distolateral
tooth of the basal segment of the antennular
peduncle is more prominent than in the speci-
men gured by Bruce (1977a: g. 7d and e).The
number of teeth in the xed nger of the sec-
ond pereiopods usually is 10 in the adult spec-
imens of the present material. In some, 7 teeth
are present, and in the juveniles, sometimes
even less than 7. Bruce (1977a) noted 4–5 teeth
in the type-series.
Colour (gs. 4A–B). Large dark blue and/or
red-brown dots on carapace, abdomen, perei-
opods, scaphocerite, antennal peduncles and
caudal fan.
Hosts. Recorded from Cardiidae,
Tridacninae: Hippopus hippopus (L., 1758) (De
Grave, 1999; Hayashi, 2006); Tridacna derasa
(Röding) (Bruce, 1977a; Bruce, 1991a; Hayashi,
2002, 2006); Tridacna gigas (L., 1758) (De
Grave, 1999; Hayashi, 2006); Tridacna max-
ima (Röding, 1798) (Hayashi, 2006); Tridacna
squamosa Lamarck, 1819 (Bruce, 1977a, 1981b,
1983a, 1991a, 1993; Strack, 1993; De Grave, 1999;
Hayashi, 2006; Fransen & Reijnen, 2012; Liu,
2020); Tridacna sp. (Bruce, 1983b; Bruce &
Coombes, 1995; Hayashi, 2006).
Distribution. Queensland, Australia (Bruce,
1977a), Great Barrier Reef, Australia (Bruce,
1981b), Port Essington, Australia (Bruce,
1983a); Cobourg Peninsula, Australia (Bruce
& Coombes, 1995); Fiji (Bruce, 1981b); Hainin
Province, China (Liu, 2020); Seram Island,
Indonesia (cf. Bruce, 1983b; Bourdon, 1983);
Ambon Island, Indonesia (Strack, 1993; Fransen,
1994a); Ternate, Indonesia (Fransen & Reijnen,
2012); Sabah, Malaysia (Fransen & Reijnen,
2012); Tre Island, Vietnam (Bruce, 1993); Hansa
Bay, Papua New Guinea (De Grave, 1999); New
Caledonia (cf. Bruce, 1991a); Enewetak Atoll
(Devaney & Bruce, 1987); Japan (Hayashi, 2002,
2006). Now for the rst time recorded from
Tioman island, West Malaysia, and from three
new localities in Indonesia: Raja Ampat; NE
Kalimantan; and Nanaka, Sulawesi.
Anchistus demani Kemp, 1922
(gs. 4C–D, 6–9)
Anchistus demani Kemp, 1922: 256, gs.
86–88 [Type locality: Aberdeen, Port Blair,
Andamans, low tide]; Holthuis, 1952: 13 (listed);
Holthuis, 1953: 56; Bruce, 1967: 568 (listed);
-  - |./-
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
 5 Anchistus australis Bruce, 1977. A-H, L, M) ...41438; I–K) ...41436. A) habitus,
lateral view, B) anterior appendages, lateral view; C) anterior appendages, dorsal view; D) rostrum,
lateral, female, pocl. 7.0mm; E) idem, male, pocl. 5.2mm; F) idem, juvenile male, pocl. 1.1mm;
G) tail fan; H) telson; I) left major second pereiopod; J–K) idem, chela; L) dactylus left third pereiopod,
medial view; M) idem, ventral view. Scale A, I = 4mm; B, C, F, G = 2mm; D, E, H, J, K, M = 1mm;
L = 0.1mm.
  .... 
./-|   
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
Bruce, 1972a: 219 (listed); Hipeau-Jacquotte,
1972b: 9; Hipeau-Jacquotte, 1973a: 104, g. 5;
Bruce, 1974: 200–201; Bruce, 1975a: 150, 162
(listed); Bruce, 1975b: 26 (listed); Bruce, 1976b:
147 (listed); Bruce, 1976c: 22; Bruce, 1976d:
464; Bruce, 1977a: 50; Bruce, 1978a: 119; Bruce,
1978b: 287 (listed); Bruce, 1979a: 232; Bruce,
1981c: 3; Bruce, 1982: 276 (listed); Bruce, 1983b:
892; Bruce, 1983c: 200 (listed); Bruce, 1984:
147 (listed); Bruce, 1990: 15, 18 (listed); Bruce,
1991a: 259–260, 275, g. 22; Bruce, 1993: 57;
Müller, 1993: 8 (listed); Chace & Bruce, 1993:
72 (listed); Britayev & Fachrutdinov, 1994:
124, g. 2A-C; Fransen, 1994a: 107, 110, 111, g.
2d; Fransen, 1994b: 88, pl. 1C; Poupin, 1998: 12;
De Grave, 1999: 132, text-g. 4; Li, 2000: 9 g.
9 (listed); Hayashi, 2002: 225; Bruce, 2003b:
211 (listed); Li et al., 2007: 177, g. 74 (listed);
Marin & Savinkin, 2007: table 2, 3 (listed);
Bruce, 2010a: 63 (listed); De Grave & Fransen,
2011: 340 (listed); Radhakrishnan et al., 2012:
table 1 (listed); Aznar-Cormano et al., 2015:
202 (listed); Samuel et al., 2016: table 1 (listed).
Anchistia cf. demani Rosewater, 1965: 381, 386.
Anchistus deseani – Strack, 1993: 46 [errone-
ous spelling].
Material examined. INDONESIA: 1 oviger-
ous female pocl. 3.81mm (photo by M.S.S.
Lavaleye 8/38a), 1 female pocl. 4.07mm, 1 male
pocl. 2.60mm (...41457), stn .11,
Ambon Island, Nusaniwe, 12.xi.1990, depth 2 m,
snorkeling, found together in one Tridacna sp.,
coll. C.H.J.M. Fransen. – 1 female pocl. 2.21mm
(...41458), stn .16, Pombo
Island E of Ambon Island,  side, 16.xi.1990,
snorkeling, in Tridacna squamosa Lamarck,
coll. J.C. den Hartog. – 1 non ovigerous female
(
R = 3/0
) pocl. 2.5mm (...46481),
 Sulawesi, Spermonde Archipelago,
Kudingareng Keke, S side, depth 3-5 m, snorke-
ling, 26.ix.1994, from Tridacna deresa (Röding)
(Ø 20cm), coll. J.C. den Hartog. – 1 female pocl.
2.7mm with pair of abdominal bopyroids,
rostrum damaged (...46482), stn
.04, N Sulawesi, Selat Lembeh, Pulau
Lembey, Pantai Parigi, 01°28’N 125°14’E, small
fringing reef, gently sloping from beach to 10
m, depth 1-3 m, snorkeling, 15.x.1994, in T. squa-
mosa, coll. J.C. den Hartog. – 1 male 2.1mm
(
R = 2/0
) (...46483), stn .06, N
Sulawesi, Selat Lembeh, Pulau Lembey, Pantai
Parigi, 01°28’N 125°14’E, small fringing reef,
gently sloping from beach to 10 m, depth 1-3 m,
snorkeling, 15.x.1994, in T. squamosa, coll. J.C.
den Hartog. – 1 ovigerous female pocl. 4.0mm
(
R = 2/0
) (...46484), stn .06,
N Sulawesi, Selat Lembeh, Pulau Lembey,
Pantai Parigi, 01°28’N 125°14’E, small fring-
ing reef, gently sloping from beach to 10 m,
depth 1–3 m, snorkeling, 15.x.1994, in Tridacna
maxima (Röding) (Ø 20cm), coll. J.C. den
Hartog. – 1 male pocl. 1.9mm (
R = 2/0
), 1 ovi-
gerous female, pocl. 2.3mm (
R = 3/0
), .
..57965), stn .10,  Kalimantan,
Berau Islands, Samama Island, 02˚07’31.6”N
118˚20’09.7”E, 7.x.2003, depth 5 m,  div-
ing, in Tridacna crocea Lamarck (Ø 10cm), coll.
C.H.J.M. Fransen, lm 2/25-29. PHILIPPINES:
1 male pocl. 2.2mm (
R = 2/0
), 1 female pocl.
4.0mm (
R = 3/0
) (...48351),
stn .11, Cebu Strait, W of Bohol, E side
of Cabilao Island, S of Cambacis, 9°52.92’N
123°47.37’E, patchy reef with algae, 14.xi.1999,
depth 2-5 m, snorkeling, in T. maxima; coll.
J.C. den Hartog. – 1 male pocl. 3.0mm, 1 oviger-
ous female pocl. 4.9mm (...48354;
GenBank OQ600396 (16S)), stn .06, Cebu
Strait, W of Bohol, N side of Cabilao Island,
near Looc, 9°53.49’N 123°46.53’E, 9.xi.1999,
depth 1 m, snorkeling, sandy reef at with
seagrass, in Hippopus hippopus (L.) (Ø 15cm),
coll. J.C. den Hartog. SEYCHELLES: 1 male
pocl. 1.56mm (...42791), - E
stn .754, St Joseph Atoll,  rim, lagoon,
5°24’S 53°19’E, 26.xii.1992, depth 1 m, reef at
at low tide, snorkeling, in Tridacna sp. (Ø
18cm); coll. J.C. den Hartog, photo 17/15 17.
– 1 ovigerous female pocl. 3.44mm, 4 speci-
mens pocl. 1.44, 2.25, 2.94, 3.06mm (.
..42792),  -E stn .792, St François
-  - |./-
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
Atoll, W rim, 7°05’S 52°44’E, 5/6.i.1993, outer
slope down to 27 m depth, scuba diving, in T.?
maxima coll. C.H.J.M. Fransen, photo 33/5 12.
RED SEA: 1 ovigerous female pocl. 3.38mm
(...28583), Sudan, E of Port Sudan,
Wingate reef, 5.ix.1970, on top of reef in shal-
low water, in Tridacna sp., coll. N.V.C. Polunin,
no. 12. – 1 ovigerous female pocl. 4.16mm
(...28584), Egypt, Gulf of Akaba,
Sinai Peninsula, Marsa Murach, 22.viii.1967,
coll. L. Fishelson, no.  2412. – 2 males pocl.
2.79mm and 3.18mm, 1 female pocl. 2.60mm,
1 ovigerous female pocl. 4.81mm (.
..41480), SW of Umm Aabak, near Nocra
Island, in Tridacna sp., 22.iii.1962, depth 0-2 m,
Israel Red Sea Expedition no. E62/1378. – 1 male
pocl. 3.12mm (...41481), Landing
Bay, Entedibir Island, 31.iii.1962, in Tridacna
sp., depth 2 m, Israel Red Sea Expedition no.
E62/1432. – 1 male pocl. 2.79mm (.
..41482), Umm Aabak, 25.iii.1962,
Israel Red Sea Expedition no. E62/2220. – 1
female pocl. 2.73mm (...41483),
no further locality information; 1962, Israel
Red Sea Expedition no. E62/1503. – 2 ovi-
gerous females pocl. 2.0 and 2.5mm, 1 male
pocl. 1.5mm, 1 juvenile pocl. 1.0mm (.
..58049), stn .07, Fsar, 22°13’46.4”N
39°01’44.5”E, 10.xi.2015, depth 12 m, in 3 small
T. maxima, coll. C.H.J.M. Fransen. – 1 ovigerous
female pocl. 2.8mm (...58050),
stn .14, Tahlah, 22°16’25.9”N 39°03’01.1”E,
13.xi.2015, depth 4 m, in small T. crocea, coll.
C.H.J.M. Fransen. MICRONESIA: few spec-
imens (...28934), Palau Group,
Ngemelis, S of Koror, -.iv.1971.
Diagnosis. Rostrum reaching distal end of
basal segment of the antennular peduncle,
distally typically bidentate (seldom only one
tooth present). Antennal spine absent. Ventral
orbital angle slightly produced. Antero-lateral
angle of carapace rounded. Anterior margin
of carapace between orbital ventral angle
and antero-lateral margin straight. Sixth
abdominal segment with posterior ventral
angle rounded. Telson with dorsal spines
minute, at 0.61 and 0.87 of telson length, with
lateral pair of terminal spines small, situated
subdistal to intermediate spines. Basal seg-
ment of antennular peduncle with distolat-
eral angle rounded. Scaphocerite with straight
lateral margin and deep slit between distolat-
eral tooth and lamina. Third maxilliped with
antepenultimate segment slightly broader
than penultimate segment. First pereiopod
with chela spatulate, non-cannulate; lateral
cutting edges minutely pectinate in distal 2/3,
medially entire. Second pereiopods with chela
equal or unequal, dactylus with one large tri-
angular tooth in proximal half; xed nger
with 4–11 small teeth in proximal half; palm
with oval tympanal organ medio-ventrally in
proximal half. Ambulatory pereiopods with
dactylus biunguiculate; accessory tooth blunt
and inconspicuous; dorsal attened surface of
unguis with ne scale-like spinules. Protopod
of uropod rounded.
Remarks. Specimens correspond closely
with previous descriptions. The rst pereio-
pods have minutely pectinate cutting edges
like the other members of the genus. The
species seems close to A. australis in sharing
the absence of an antennal spine, in having
a deep slit between de distolateral tooth and
the lamina of the scaphocerite, and in having
similar ambulatory dactyli.
Colour (gs. 4C–D). The colour pattern is
similar to that of A. miersi, e.g., transparent
with numerous circular dark blue dots over
body, antennae, chela of second pereiopods
and caudal fan. Kemp (1922: 259) noted the
dots to be pale green or red: “Two of the spec-
imens, which were found together in a large
Tridacna, were transparent when alive and
dotted all over with pale green chromato-
phores. The female bore green eggs. The third
specimen also found in Tridacna, was trans-
parent with red chromatophores …”.
./-|   
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 6 Anchistus demani Kemp, 1922. A-G, I, J) ...41457; H) ...41480. A) habitus,
lateral view, ovigerous female pocl. 3.8mm; B) anterior appendages, lateral view, ovigerous female
pocl. 3.8mm; C) idem, dorsal view, ovigerous female pocl. 3.8mm; D) rostrum, female pocl. 4.1mm; E)
idem, ovigerous female pocl. 3.8mm; F) idem, male pocl. 2.6mm; G) left second pereiopod; H, I) idem,
chela; J) right third pereiopod dactylus, medial view. Scale A = 4mm; B, C, G, = 2mm; D-F, H, I, = 1mm.
  .... 
Hosts. Recorded from Cardiidae,
Tridacninae: Tridacna? crocea Lamarck,
1819 (Bruce, 1979a); Tridacna gigas (L., 1758)
(Holthuis, 1953); Tridacna maxima (Röding,
1798) (Bruce, 1974, 1976c, 1976d, 1977a, 1978a;
1993; Britayev & Fachrutdinov, 1994; Poupin,
1998); T.? maxima (Fransen, 1994b); Tridacna
squamosa Lamarck, 1819 (Rosewater, 1961;
Bruce, 1976d; Britayev & Fachrutdinov, 1994);
Tridacna sp. (Holthuis, 1953; Bruce, 1981c;
1983b; 1991a; Fransen, 1994a). Newly reported
from Hippopus hippopus (L., 1758); Tridacna
derasa (Röding, 1798); and conrmed from
T. crocea.
Distribution. Port Blair, Andaman Islands
(Kemp, 1922); Marshall Islands (Holthuis, 1953;
Rosewater, 1961); Gilbert Islands (Holthuis,
1953); Thailand (Rosewater, 1965); Perhantian
Islands, Malaysia (Bruce, 1979a); Zanzibar
and Kenya, East Africa (Bruce, 1976c, 1976d);
Seychelles (Bruce, 1976c; Fransen, 1994b);
Aldabra Island, Comoro Islands (Bruce, 1978a);
Farquhar, Seychelles (Bruce, 1974); Capricorn
group, Australia (Bruce, 1977a); Heron Island,
-  - |./-
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
Australia (Bruce, 1981c); Seram Island,
Indonesia (Bruce, 1983b); Ambon, Indonesia
(Fransen, 1994a); New Caledonia (cf. Bruce,
1991a); Tre Island, Vietnam (Bruce, 1993);
South Vietnam (Britayev & Fachrutdinov,
1994); Tuamotu (Poupin, 1998). Here reported
for the rst time from East Kalimantan and
Sulawesi, Indonesia; the Red Sea; Palau; and
Cebu Strait, the Philippines.
Anchistus gravieri Kemp, 1922
(gs. 4B, 10–15)
Anchistus gravieri Kemp, 1922: 249 (key),
252-255, gs. 82–84 [Type locality: Vanikoro,
Santa Cruz Islands, Polynesia]; Holthuis, 1952:
13 (listed); Bruce, 1967: 568; Bruce, 1972a: 219
(listed); Monod, 1972: 24, gs. 65-86; Hipeau-
Jacquotte, 1972b: 9; Bruce, 1975a: 162; Bruce,
1977a: 47-50, gs. 2, 3; Bruce, 1983c: 200
 7 Anchistus demani Kemp, 1922, ...41457, female pocl. 4.1mm. A) tailfan, dorsal view;
B) distolateral part exopod uropod, dorsal view; C) telson, dorsal view; D) left mandible, ventral view;
E) left maxillula, ventral view. Scale A = 1.25mm; B, 0.125mm; C = 0.25mm; D, E = 0.5mm.
  .... 
./-|   
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
(listed); Bruce, 1990: 15, 18 (listed); Bruce,
1991a: 260, 275, g. 23; Müller, 1993: 9 (listed);
Fransen, 1994a: 107, 111, g. 2a; Li, 2000: 10,
g. 10 (listed); Hayashi, 2002: 225; De Grave &
Fransen, 2011: 340 (listed).
not Anchistus gravieri – McNeill, 1953: 89
(= Polkamenes nobilii (Holthuis, 1952)).
Material examined. VIETNAM: 1 ovigerous
female pocl. 6.9mm (...58051),
Nathrang, entree 1948, st. 870 E. 413, in
Tridacna sp., coll. R. Serène. VANUATU: 1 male
pocl. 3.9mm, 1 female pocl. 4.2mm (.
..58052), stn 15, S Aoré Island, Bruat
Channel, 15°21’56”S 167°5’44”E, 16.ix.2006,
depth 3 m, hand picked, in Hippopus hip-
popus, coll. C.H.J.M. Fransen, fcn. 57, photo
T.-Y. Chan.
Diagnosis. Rostrum reaching end of penul-
timate segment of antennular peduncle,
bent downward, with 2–4 dorsal distal teeth
and one or none ventral tooth. Antennal
spine well developed. Ventral orbital angle
produced. Antero-lateral angle of cara-
pace rounded. Anterior margin of carapace
between ventral orbital angle and antero-
lateral angle straight. Sixth abdominal segment
 8 Anchistus demani Kemp, 1922, ...41457, female pocl. 4.1mm. A) left maxilla, ventral view;
B) left rst maxilliped, ventral view. Scale = 0.5mm.
  .... 
-  - |./-
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
 9 Anchistus demani Kemp, 1922, ...41457, female pocl. 4.1mm. A) left second maxilliped,
ventral view; B) left third maxilliped, ventral view; C) left rst pereiopod, lateral view. Scale A,
B = 0.5mm; C = 1.25mm.
  .... 
./-|   
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
with posterior ventral angle rounded. Telson
with small dorsal spines at 0.61 and 0.79 of tel-
son length, with lateral pair of terminal spines
small, situated next to intermediate spines.
Basal segment of antennular peduncle with or
without distolateral tooth. Stylocerite acute.
Scaphocerite with straight or slightly convex
lateral margin, slit between distolateral tooth
and lamina of moderate depth. First perei-
opods with chela spatulate, not cannulate,
with lateral cutting edges minutely pectinate
in distal 2/3, medially entire. Second pereio-
pods unequal or equal, proximal half of palm
with oval tympanal organ medio-ventrally in
 10 Anchistus gravieri Kemp, 1922, ...58051, Nathrang, ovigerous female, pocl. 6.9mm.
A) habitus, lateral; B) anterior appendages, dorsal view; C) idem, lateral view; D) telson, dorsal view;
E) left second pereiopod; F) idem, chela; G) right third pereiopod dactylus. Scale A = 4mm;
B, C, E = 2mm; D, F = 1mm; G = 0.1mm.
  .... 
-  - |./-
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
proximal part; dactylus with one, sometimes
two, moderate triangular teeth in proximal
half; xed nger with 6–8 small teeth in prox-
imal half. Ambulatory pereiopods with simple
dactyli, not biunguiculate, dorsal attened
surface unguis with ne scale-like spinules.
Protopod of uropod acutely produced.
Remarks. The specimens studied agree
well with former descriptions of the species
(Kemp, 1922; Monod, 1972; Bruce, 1977a, 1991a).
 11 Anchistus gravieri Kemp, 1922, ...58052, Vanuatu (stn FR15). A–C, E) female, pocl.
4.2mm; D, F, G) male, pocl. 3.9mm. A) habitus, lateral view; B) anterior appendages, lateral view;
C, D) idem, dorsal view; E, F) rostrum, lateral view; G) tail fan, dorsal view. Scale A = 4mm;
B-D = 2mm; E-G = 1mm.
  .... 
./-|   
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
Colour (g. 4E). Large dark blue dots on car-
apace, abdomen, pereiopods, scaphocerite,
antennal peduncles and caudal fan.
Host. Recorded from Cardiidae,
Tridacninae: Hippopus hippopus (L., 1758) (cf.
Bruce, 1977a, 1991a); newly recorded from an
unidentied Tridacna.
Distribution. Vanikoro Island, Santa
Cruz Islands, Polynesia (Kemp, 1922); New
Caledonia (Monod, 1972; Bruce, 1991a); Herald
Island, Australia (Bruce, 1977a); Nathrang,
Vietnam (Fransen, 1994a). Now recorded for
the rst time from Vanuatu.
Anchistus miersi (De Man, 1888)
(gs. 4F–G, 16, 39B,D)
Harpilius Miersi De Man, 1888: 274, pl. 17 gs.
6–10 [type locality: Elphinstone Island];?
Whitelegge, 1897: 148.
Coralliocaris nudirostris – Nobili, 1899: 235.
 12 Anchistus gravieri Kemp, 1922, ...58052, Vanuatu (stn FR15), female, pocl. 4.2mm.
A) left mandible, dorsal view; B) left maxillula, dorsal view; C) left maxilla, dorsal view; D) left rst
maxilliped, dorsal view. Scale = 0.5mm.
  .... 
-  - |./-
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
 13 Anchistus gravieri Kemp, 1922, ...58052, Vanuatu (stn FR15), female, pocl. 4.2mm. A) left
second maxilliped, dorsal view; B) left third maxilliped, dorsal view; C) left rst pereiopod, lateral
view; D) right second pereiopod, ventral view; E) idem, chela, medial view. Scale A, B = 0.5mm;
C = 1.25mm; D = 2mm; E = 1mm.
  .... 
./-|   
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
non Anchistus Miersi – Nobili, 1906a: 48; Pérez,
1920: 1027 (both Polkamenes nobilii (Holthuis,
1952)).
Anchistus Miersi – Nobili, 1906b: 63; Nobili,
1907: 359; Holthuis, 1955: 62 (listed).
Marygrande mirabilis Pesta, 1911: 573, gs. 1–5
(partim) [type locality: Samoa]; De Grave,
2001: 129–134, gs. 4–5.
Anchistus miersi – Borradaile, 1898: 387;
Borradaile, 1917: 324; Tattersall, 1921: 391;
Seurat, 1934: 60; Kubo, 1940: 52–54, gs. 18-20
(pro parte); Holthuis, 1952: 110, 111 (full syn-
onymy), g. 45; Holthuis, 1953: 56; Johnson,
1961: 59, 62, 63, 76; Ooishi, 1964: 196 (listed);
Johnson & Liang, 1966: 434; Miyake & Fujino,
1968: 414-415 (pro parte); Bruce, 1972a: 219,
222 photograph (listed); Miyake, 1972: 65,
210 (listed); Bruce, 1973: 136; Bruce, 1975b:
26 (listed); Fujino, 1975: 252-255, g. 1, pl. 1;
Monod, 1976b: 24, gs. 29-36; Bruce, 1976b:
147; Bruce, 1976c: 22; Bruce, 1976d: 464-465;
Bruce, 1976e: 448; Watabe & Tomida, 1977: 46;
Bruce, 1977b: 174-175; Bruce, 1978a: 119; Bruce,
1978b: 279; Bruce, 1979a: 232-233; Johnson,
1979: 31; Bruce, 1982: 267 (listed); Miyake,
1982: 32, pl. 11, g. 6 (listed); Bruce, 1983c: 200
(listed); Bruce & Svoboda, 1983: 36 (listed);
Bruce, 1984: 147 (listed); Vine, 1986: 101 (listed);
Devaney & Bruce, 1987 (listed); Bruce, 1990: 15,
18 (listed); Holthuis, 1993: 130, g. 111; Müller,
1993: 9 (listed); Bruce, 1993: 57, g. 3A; Chace
& Bruce, 1993: 72; Britayev & Fachrutdinov,
1994: 129, g. 3E-F; Fransen, 1994a: 107, 110,
111, g. 2c; Fransen, 1994b: 89, g. 1D; Poupin,
1998: 12 (listed); De Grave, 1999: 132, pl. 1 gs.
d, e; Li, 2000: 11, g. 11 (listed); De Grave, 2001:
129-134, gs. 4–5; Hayashi, 2002: 223, gs. 432i,
j, 434g, h, 435, g, h; Bruce, 2003b: 211 (listed);
Li, 2004: 67; Hayashi, 2006: 510, 512; Marin &
Savinkin, 2007: table 2 (listed); Li et al., 2007:
178, g. 75 (listed); De Grave & Ashelby, 2011:
table 1 (listed); De Grave & Fransen, 2011: 340
(listed); Radhakrishnan et al., 2012: table 1
(listed); Fransen & Reijnen, 2012; Hosie et al.,
2015: 283 (listed); Neo et al., 2015: 877-878, gs.
1, 2; Anker & De Grave, 2016: 407; Samuel et al.,
2016: table 1 (listed).
Anchistus meirsi – Fankboner, 1972: 35–41,
gs. 1-3 [erroneous spelling].
Auchistus miersi – Strack, 1993: 46 [erroneous
spelling].
Ancistus miersi – Ng et al., 1995: 43, g. [erro-
neous spelling].
Material examined. INDONESIA: 2 oviger-
ous females pocl. 4.29, 4.74mm (.
..41389), stn .30, Suli, 29.xi.1990,
depth 1–3 m, snorkeling, in 2 Hippopus hip-
popus (L.) (Ø 15–20cm), coll. H.L. Strack, one
with pinnotherid. – 1 ovigerous female pocl.
3.90mm (photo by M.S.S. Lavaleye 3/4-8)
(...41390), stn .11, Nusaniwe,
12.xi.1990, snorkeling, depth 2 m, in Tridacna
sp., coll. C.H.J.M. Fransen and J.C. den Hartog.
– 1 male pocl. 3.25mm, 1 female pocl. 4.87mm
(...41391), Karimuajawa, Rotenoa,
25.iii.1974, don. . – 1 male pocl. 3.90mm, 1
female pocl. 4.94mm (...41392),
Ambon Island, Ambon Bay, Tantoci, 3.vi.1975,
coll. M.K. Moosa, Banner & Banner, Rumphius
 Expedition, don. , fcn.  133. – 1 oviger-
ous female pocl. 7.47mm (...41393),
Sunda Strait, Panaitan Island, 1983, don. .
– 1 male pocl. 5.00mm, 4 females pocl. 4.74,
4.81, 6.04, 6.30mm (...41394), Java,
Seribu Archipelago, Tikus Island, Goba,
24.x.1974, coll. S. Sidabutan, don. . – 1 male
pocl. 5.19mm, 1 female pocl. 7.47mm (.
..41395), Java, Seribu Archipelago, Tikus
Island, 26.v.1975, in Tridacna sp., don. . – 1
male pocl. 5.84mm, 2 females pocl. 5.84,
5.91mm (...41396), Java, Seribu
Archipelago, Tikus Island, 27.v.1975, in Tridacna
sp., coll. V. Toro, don. . – 4 males pocl. 4.35,
4.74, 5.13, 5.39mm, 3 females pocl. 2.47, 5.71
(with bopyrid under carapace), 7.34mm
(...41397), Java, Seribu Archipelago,
Tikus Island, 28.v.1975, in Tridacna sp., coll. V.
Toro, don. . – 1 male pocl. 5.3mm
-  - |./-
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
 14 Anchistus gravieri Kemp, 1922, ...58052, Vanuatu (stn FR15), female, pocl. 4.2mm.
A) right third pereiopod, lateral view; B) right fourth pereiopod, lateral view; C) left fth pereiopod,
medial view; D) right third pereiopod dactylus, medial view; E) idem, lateral view. Scale A-C = 1.25mm;
D, E = 0.125mm.
  .... 
./-|   
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
 15 Anchistus gravieri Kemp, 1922, ...58052, Vanuatu (stn FR15), female, pocl. 4.2mm. A) right
fourth pereiopod dactylus, lateral view; B) left fth pereiopod dactylus, medial view. Scale = 0.125mm.
  .... 
-  - |./-
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(...58053), Java, Seribu Archi-
pelago, Tikus Island, 25.i.1975, coll. S. Sidabutan,
don. . – 2 females pocl. 4.48, 5.71mm
(...41398), Ambon Island,
Sowahtelu Archipelago, Morela, 03°32’00”S
128°12’30”E, 8.i.1973, coll. M.K. Moosa, don.
, fcn.  324. – 1 ovigerous female pocl.
7.79mm (...41399), E coast of Ajer
Island, 21.iv.1971, 11.00hr., R.V. “Mutiara ”, don.
. – 1 male pocl. 4.87mm, 1 ovigerous
female pocl. 7.14mm (...41400),
Sulawesi, Ujung Pandang, Kayangan Island,
7.vi.1975, coll. M.K. Moosa, Banner & Banner,
Rumphius  Expedition, don. , fcn. 
260. – 1 male pocl. 2.9mm, 1 ovigerous female
pocl. 3.8mm (...46472), SW
Sulawesi, Spermonde Archipelago, Pulau Badi,
 side, 3.x.1994, depth 0.5 m, snorkeling, in
H. hippopus (Ø 20cm), coll. J.C. den Hartog. – 1
male pocl. 3.2mm, 1 ovigerous female pocl.
4.4mm (...46473), SW Sulawesi,
Spermonde Archipelago, Barang Lompo, NW
side, 23.ix.1994, depth 3–5 m, snorkeling, from
Tridacna squamosa Lamarck, coll. J.C. den
Hartog. – 1 male pocl. 2.1mm, 1 ovigerous
female pocl. 2.6mm (...46474), SW
Sulawesi, Spermonde Archipelago, Gusung,
harbour, NE side, 8.x.1994, depth 1–2 m, snor-
keling, from T. squamosa (Ø 10cm) in very tur-
bid water, coll. J.C. den Hartog. – 1 ovigerous
female pocl. 4.9mm (...46475), SW
Sulawesi, Spermonde Archipelago,
Kudingareng Keke, S side, 26.ix.1994, depth 3–5
m, snorkeling, in T. squamosa (Ø 15cm), coll.
J.C. den Hartog. – 1 male pocl. 3.4mm, 1 oviger-
ous female pocl. 4.0mm (...46476),
stn .06, N Sulawesi, Selat Lembeh, Pulau
Lembey, Pantai Parigi, 01°28’N 125°14’E,
15.x.1994, small fringing reef, gently sloping
from beach to 10 m, depth 1-3 m, snorkeling, in
H. hippopus, coll. J.C. den Hartog. – 1 male pocl.
3.3mm (...46477), stn .08, N
Sulawesi, Selat Lembeh, S of Tanjung
Batuangus, channels between lava outows,
01°30’N 125°15’E, 16.x.1994, fragile corals on
slopes, down to muddy bottom, depth 1-3 m,
snorkeling, in T. squamosa (Ø 25cm), coll. I.J.
Smit. – 1 ovigerous female pocl. 3.0mm (.
..46478), stn .13, N Sulawesi, Selat
Lembeh, Air Bajo near Kareko, 01°29’N 125°15’E,
21.x.1994, sandy bay between rocks, N-exposed,
gently sloping bottom, sandy beach to 4 m,
large boulders, depth 0-5 m, snorkeling, in
Tridacna maxima (Röding), coll. I.J. Smit. – 1
male pocl. 3.0mm, 1 non-ovigerous female
pocl. 2.5mm (...46479), stn .22,
N Sulawesi, Selat Lembeh, Pulau Lembeh, near
Batu Riri, 01°28’N 125°14’E, 31.x.1994, small
enclosed bay, from sandy beach, seagrass belt,
depth 2 m, scuba diving, in H. hippopus
20cm), coll. C.H.J.M. Fransen. – 1 male pocl.
2.7mm (...46480), stn .22, N
Sulawesi, Selat Lembeh, Pulau Lembeh, near
Batu Riri, 01°28’N 125°14’E, 31.x.1994, small
enclosed bay, from sandy beach, seagrass belt,
depth 2 m, scuba diving, in H. hippopus
(Ø 15cm), coll. C.H.J.M. Fransen. – 1 male pocl.
3.7mm, 1 female pocl. 6.1mm (.
..47688), stn .28, Moluccas, NW
Seram, Kotania bay, SW of Pulau Marsegu,
03°01’S 128°03’E, 11.xi.1996, depth 20 m, 
diving, in T. squamosa (Ø 40cm) with
Xanthasia sp. or Tridacnatheres sp., coll.
C.H.J.M. Fransen. – 1 non ovigerous female
pocl. 1.9mm (...53568; GenBank
JX185706), stn .19, Halmahera, Tidore, SW
of Tobala, 0°44’56.6”N 127°23’13.5”E, 4.xi.2009,
depth 10 m,  diving, sloping rubble reef,
in small T.? squamosa, coll. C.H.J.M. Fransen,
fcn. CF-00075, photo .19.0101-108. – 1 female
pocl. 6.49mm (..D.204368), Siboga
Expedition stn 78, Borneo Bank, Lumu-lumu
Shoal, 3°24’S 117°36’E, 10/11.vi.1899, shore
exploration, in Tridacna sp., depth 34 m, bot-
tom coral and coral sand (publ. Holthuis, 1952:
110). – 1 male pocl. 2.66mm, 1 ovigerous female
pocl. 3.90mm (...41487), West
Papua, Kameri, Noemfoor, 2.iii.1955, from local
./-|   
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people, in Tridacna sp., leg. L.B. Holthuis no.
714. – 1 ovigerous female pocl. 6.4mm (.
..58030), stn .25, Java Sea, Kepulauan
Seribu (Thousand Islands), of Jakarta, Kotok
Besar Island, NW-side, 5°41’56”S 106°32’23”E,
16.ix.2005, depth 5 m,  diving and snor-
kelling, in T. squamosa, coll. C.H.J.M. Fransen.
– 1 ovigerous female pocl. 3.8mm (.
..58032), stn .23, Java Sea, Kepulauan
Seribu (Thousand Islands), of Jakarta,
15.ix.2005, depth 20 m, in Hyotissa hyotis (L.),
coll. C.H.J.M. Fransen, lm 9. – 1 ovigerous
female, pocl. 3.6mm (...58054),
stn .03, NE Kalimantan, Berau Islands,
Derawan Island, S-side (jetty Derawan Dive
Resort), 02°17’03.3”N 118°14’48.8”E, 13.x.2003,
depth 0-2 m, snorkeling, in H. hippopus, coll.
C.H.J.M. Fransen, lm 10. MALAYSIA: few
specimens (...53798; GenBank
JX185704); stn .40, Semporna, Ribbon Reef,
04°36’10.0”N 118°45’53.6”E, 11.xii.2010, depth 5
m,  diving,? in Tridacna sp., collected by
boatman. – 1 non ovigerous female pocl.
2.0mm (
), 1 ovigerous female pocl.
3.2mm (...53806; GenBank
JX185705), stn .22, Semporna, Bumbun
Island W (channel), 04°27’40.7”N 118°38’09.1”E,
5.xii.2010, depth 3 m,  diving, in H. hip-
popus, coll. C.H.J.M. Fransen. – 1 non ovigerous
female pocl. 1.8mm (...53938;
GenBank JX185707), stn .14, Semporna,
Ligitan Isl., Ligitan 2, 04°09’35.8”N 118°52’22.2”E,
3.xii.2010, depth 5 m, in H. hippopus, coll. B.T.
Reijnen. – 1 male pocl. 2.73mm, 1 female pocl.
4.61mm, 1 ovigerous female pocl. 4.03mm
(...41387), West Malaysia, Tioman
Island, Telok Dalam, 22.i.1983, in T. squamosa,
depth 10 feet, coll. P.K.L. Ng. – 1 male, pocl.
4.55mm; 1 female, pocl. 3.64mm (.
..41388); West Malaysia, Tioman Island,
Tekek Bay, 23.vi.1983, depth 20 feet, in T. squa-
mosa, coll. P.K.L. Ng. MALDIVES: 2 ovigerous
females pocl. 7.79, 8.70mm (.
..15162), Addu Atol, Gan Island,
26.xii.1957, coll. S. Gerlach, Xarifa Expedition.
RED SEA: 1 ovigerous female pocl. 6.10mm
(...41486), Landing Bay, Entedibir
Island, 3.iv.1962, Israel Red Sea Expedition no.
E62/3842. – 1 ovigerous female pocl. 7.27mm
(...41488), Dahab, 10.x.1968, in
Tridacna sp., coll. L. Fishelson, NS 4401. – 1 ovi-
gerous female pocl. 6.04mm (.
..41489), Landing Bay, Entedibir Island,
6.iv.1962, Israel Red Sea Expedition no.
E62/2391. – 1 ovigerous female pocl. 6.62mm
(...41490), Ras-A-Tanrar, 2.vii.1969,
coll. L. Fishelson, NS 5826. SEYCHELLES: 1 ovi-
gerous female pocl. 5.3mm (.
..42793), -E, stn .797, Platte
Island atoll, 05°49’S 55°21’E, 7.i.1993, depth 12
m, lagoon of inner atoll,  diving, in T.?
maxima, coll. C.H.J.M. Fransen. – 1 male pocl.
2.9mm, 1 ovigerous female pocl. 4.0mm
(...42790), -E stn .723, Bird
Island, of N coast 3°42’S 55°12’E, 21xiiI.1992,
depth 7 m, coral reef, near drop-of,  div-
ing, in T. squamosa, coll. C.H.J.M. Fransen.
PHILIPPINES: 1 male pocl. 2.99mm (.
..41386), Mactan Island near Cebu,
Maribago, summer 1979, in Tridacna sp., coll. V.
Storch. CAROLINE ISLANDS: 1 ovigerous
female pocl. 3.38mm (...16511),
Ifaluk, in front of Falarik, 26.ix.1953, depth
0.5–3 m, in H. hippopus, lagoon reef, coll. F.M.
Bayer no. 402, don. . MARSHALL
ISLANDS: 1 ovigerous female pocl. 6.10mm
(...16510), Eniwetok Atoll, N end of
Island, 10.vii.1959, in Tridacna sp., coll. J.S.
Garth, 59–3.
Diagnosis. Rostrum reaching just beyond
basal segment of antennular peduncle, with
3–5 dorsal distal teeth, 0–2 ventral distal
teeth. Antennal spine present. Ventral orbital
angle slightly produced. Antero-lateral angle
rounded. Anterior margin between ventral
orbital angle and antero-lateral angle straight.
Sixth abdominal segment with posterior ven-
tral margin rounded. Telson with small dorsal
-  - |./-
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pairs of spines at 0.63 and 0.79 of telson length,
with lateral pair of terminal spines robust,
placed just behind intermediate pair. Basal seg-
ment of antennular peduncle distally rounded,
or with small distolateral tooth, not overreach-
ing lamina. Scaphocerite with lateral margin
straight, slit between distolateral tooth and
lamina of moderate depth. Chela of rst perei-
opods spatulate, not cannulate, cutting edge
laterally minutely pectinate in distal 2/3, medi-
ally entire. Dactylus of second chela with one
large triangular tooth in proximal half, xed
nger with 5–10 small teeth in proximal half;
palm with oval tympanal organ medio-ven-
trally in proximal part. Ambulatory dactyli
biunguiculate; accessory tooth well developed,
accessory tooth and attened dorsal surface of
unguis with ne scale-like spinules. Protopod
of uropod acutely produced.
Remarks. The material corresponds closely
to published descriptions. The distolateral
tooth of the basal segment of the antennu-
lar peduncle is usually minute or absent. The
position of the lateral pair of terminal spines
of the telson just behind the intermediate pair
is present in all investigated specimens.
The specimens investigated by Kubo (1940)
appear not all belong to this species. The telson
(g. 20G) has the lateral terminal spines not
in the characteristic position just behind the
intermediate spines, but in the lateral position
known of other Anchistus and Polkamenes. As
 16 Anchistus miersi (De Man, 1888). A–D) ...41390, ovigerous female pocl. 3.9mm; E–G)
...41389, ovigerous female pocl. 4.7mm. A) habitus, lateral view; B) anterior appendages,
dorsal view; C) idem, lateral view; D) telson, dorsal view; E) left second pereiopod, ventral view;
F) idem, chela, medial view. Scale A = 4mm; B, C, E = 2mm; D, F = 1mm.
  .... 
./-|   
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Kubo (1940) had specimens from the bivalve
Pteria sp., it is possible that his specimens
belonged to Polkamenes pycnodontae.
The tympanal organ was rst described
and gured for this species by Monod (1976b:
24, g. 33) as: “Le propode des chélipèdes
porte d’un côté, et vers la base, une sorte d’aire
déprimé ovalaire et cette fossette n’est pas un
artefact puisqu’elle existe sur les deux appen-
dices. Je n’ai rien trouvé à ce sujet dans la lit-
térature mai ce détail a certainement dû se
voir déjà remarqué”. This means that Monod
had not encountered such a structure before
and gave no suggestions for its function.
Colour (gs. 4F–H). Transparent with
large blue or red-brown spots over body and
appendages, ova green.
Hosts. Recorded from Cardiidae,
Tridacninae: Hippopus hippopus (L., 1758)
(Holthuis, 1953; Miyake & Fujino, 1968,
Fankboner, 1972; Bruce, 1977b; Fransen, 1994a;
Hayashi, 2002, 2006; Fransen & Reijnen, 2012);
Tridacna crocea Lamarck, 1819 (Miyake &
Fujino, 1968; Hayashi, 2002, 2006); Tridacna
gigas (L., 1758) (Fankboner, 1972; Bruce,
1983b; Hayashi, 2006); Tridacna elongata
Lamark, 1819 (= Tridacna maxima (Röding,
1798))(Ooishi, 1964; De Grave, 1999); T. max-
ima (Kubo, 1940; Bruce, 1976d, 1978a, 1993;
Britayev & Fachrutdinov, 1994; Hayashi, 2002,
2006); T.? maxima (Fransen, 1994b); Tridacna
squamosa Lamarck, 1819 (many records;
Borradaile, 1917; Kubo, 1940; Miyake & Fujino,
1968; Bruce, 1976b, 1976c, 1976d, 1979a, 1993;
Britayev & Fachrutdinov, 1994; Fransen, 1994b;
Ng et al., 1995; Hayashi, 2002, 2006; Neo et
al., 2015); Tridacna? squamosa (Fransen &
Reijnen, 2012); Tridacna sp. (Holthuis, 1952;
Johnson, 1961; Bruce, 1973, 1976e, 1978b, 1979a,
1993; Fujino, 1975; De Grave, 1999; Fransen &
Reijnen, 2012); Tridacna sp. (Li, 2004). Also
recorded from Margaritidae: Pinctada max-
ima (Jameson, 1901) (Kubo, 1940; Miyake &
Fujino, 1968; Hayashi, 2002, 2006); Pinctada
margaritifera (L., 1758) (Seurat, 1934;
Hayashi, 2006); Pinctada fucata (A. Gould,
1850) (Hayashi, 2006, as Pinctada marten-
sii (Dunker, 1880)). From Pinnidae: Pinna
sp. (Nobili, 1906b; Tattersall, 1921; Hayashi,
2002, 2006); Streptopinna saccata (L., 1758)
(Hayashi, 2006). From Pteriidae: Pteria pen-
guin (Röding, 1798) (Kubo, 1940, as Pteria
macroptera (Lamarck, 1819); De Grave, 1999, as
Magnavicula penguin/ Magnavicula bennetti
Iredale, 1939); Pteria sp. (Nobili, 1907 (with
doubt); Hayashi, 2002, 2006).
Distribution. Widely distributed in the
Indo-Pacic, from the Red Sea to Moçambique
and Madagascar to the Gambier Archipelago
in the east. Kenya, Tanganyika and Zanzibar,
East Africa (Bruce, 1976c, 1976d); Red Sea
(Nobili, 1899, 1906b; Tattersall, 1921; Vine,
1986); Persian Gulf (Nobili, 1906a); Comoro
Islands (Bruce, 1978a); Seychelles (Borradaile,
1917; Bruce, 1976b); Egmont, Chagos Islands
(Borradaile, 1917, see also Bruce, 1976b);
Maldives (Borradaile, 1917; Bruce, 1976e,
1993); Madagascar (Bruce, 1978b); Perhentian
Islands, Malaysia (Bruce, 1979a); Sabah,
Malaysia (Fransen & Reijnen, 2012); Penang,
Malaysia (Johnson, 1979); Lumulumu Shoal,
Borneo Bank, Indonesia (Holthuis, 1952);
Anambas, Indonesia (Li, 2004); Ambon,
Indonesia (Holthuis, 1993; Fransen, 1994a);
Tidore, Indonesia (Fransen & Reijnen, 2012);
Singapore (Johnson, 1961, 1979; Anker &
De Grave, 2016; Neo et al., 2015); Tre Island,
Vietnam (Bruce, 1993); Philippines (Chace
& Bruce, 1993); Mergui Archipelago (De
Man, 1888); British New Guinea (= Southern
Papua New Guinea) (Borradaile, 1898);
Queensland, Australia (Bruce, 1977b); Papua
New Guinea (De Grave, 1999); Nouméa, New
Caledonia (Monod, 1976b); Japan (Hayashi,
2002, 2006); Ryukyu Islands, Japan (Fujino,
1975); Marshall Islands (Holthuis, 1953); Palau
(Kubo, 1940); French Polynesia (Nobili, 1907);
Gambier Islands (Seurat, 1934); Funafuti
-  - |./-
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
Atoll (Whitelegge, 1897). Now for the rst
time recorded from the Caroline Islands,
Micronesia; and from the following loca-
tions in Indonesia: Panaitan Island, Seribu,
and the Thousand Islands, Sunda strait; NE
and S Kalimantan; Numfor, West Papua;
SW and N Sulawesi; and NW Seram, the
Mollucas.
Genus Dasella Lebour, 1945
Dasia Lebour, 1938: 650. Type species, by
monotypy: Dasia herdmaniae Lebour, 1938.
Gender: feminine. Invalid junior homonym of
Dasia Gray, 1839 (Reptilia), and Dasia van der
Goot, 1918 [in B. Das, 1918] (Hemiptera).
Dasella Lebour, 1945: 279. Replacement name
for Dasia Lebour, 1938. Type species therefore
Dasia herdmaniae Lebour, 1938.
Diagnosis (emended from Bruce, 1995: 47).
Small sized shrimps of subcylindrical body
form. Rostrum well developed, compressed,
dorsal margin without teeth, ventral margin
with or without minute distal tooth, lateral
carinae feebly developed. Carapace smooth,
glabrous; inferior orbital angle produced,
orbit feebly developed, antennal spine pres-
ent, hepatic spine mobile, supraorbital and
epigastric spines absent, anterolateral margin
rounded, not produced. Abdomen smooth,
glabrous, third segment not posterodorsally
produced, pleura broadly rounded. Telson
with two pairs of large dorsal spines, three
pairs of posterior spines. Eye small, cornea
globular. Antennula with basal segment of
peduncle with distolateral tooth, agella
short, short free ramus reduced. Antenna with
basicerite unarmed, scaphocerite well devel-
oped with small distolateral tooth. Epistome
unarmed. Mandible normal, without palp,
molar process robust, incisor process dentate;
maxillula with feebly bilobed palp, laciniae
moderately broad; maxilla with simple palp,
basal endite broad, bilobed, coxal endite obso-
lete, scaphognathite broad; rst maxilliped
with slender palp, basal endite broad, fused
with coxal endite, exopod well developed,
caridean lobe broad, agellum with numer-
ous plumose setae distally, epipod rectangular
or rounded, without podobranch; third maxil-
liped with endopod slender, ischiomerus and
basis fused, exopod with numerous plumose
setae distally, coxa not medially produced,
with large lateral plate, without arthrobranch.
Fourth thoracic sternite without median pro-
cess. First pereiopods moderately robust, che-
lae with ngers subspatulate, non-cannulate,
cutting edges minutely pectinate. Second
pereiopods well developed, similar, unequal,
ngers simple, unarmed; palm without tym-
panal organ. Ambulatory pereiopods with
dactyli strongly compressed, unguis distinct
with scattered scale-like spinules, corpus
with armed or unarmed distoventral process.
Uropod with protopodite acutely produced,
exopod of uropod with small distolateral
tooth with larger mobile spine medially.
Three species are designated to this genus:
Dasella ansoni Bruce, 1983, Dasella brucei
Berggren, 1990, and Dasella herdmaniae
(Lebour, 1938).
Key to the species of Dasella
1. Propodal spines on pereiopod 3–5 long,
sharp; minute ventral tooth on rostrum
(sometimes absent); length of rostrum
barely about as long as the antennular
peduncle........................................................2
Propodal spines on pereiopod 3–5 long,
club-shaped; no teeth on rostrum; length
of rostrum much shorter than antennu-
lar peduncle.........................D. herdmaniae
2. Large blunt tooth on dactylus of pereio-
pod 3–4 with hooked process....D. ansoni
Large blunt tooth on dactylus of pereio-
pod 3–4 without hooked process...............
............................................................D. brucei
./-|   
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
Dasella ansoni Bruce, 1983
Dasella ansoni Bruce, 1983d: 22, gs. 1–5 [Type
locality: Arafura Sea, 10°58’S 132°10’E, 27 m;
see Bruce & Coombes, 1995]; Berggren, 1990:
558 (listed); Bruce, 1990: 10, 16, 18 (listed);
Müller, 1993: 23 (listed); Holthuis, 1993: 140,
g. 123 (listed); Bruce & Coombes, 1995: 108
(listed); Li, 2000: 41, g. 41 (listed); De Grave &
Fransen, 2011: 348 (listed).
Diagnosis (based on Bruce, 1983d). Small-
sized shrimp. Rostrum barely reaching dis-
tal border of distal segment of antennular
peduncle, slightly depressed, acute, dorsally
thickened, without distinct lateral carinae,
without dorsal teeth, with one acute minute
ventral tooth near tip. Antennal spine present,
small. Hepatic spine well-developed, small,
mobile, below level of than antennal spine.
Inferior orbital angle distinct, produced.
Antero-lateral angle of carapace broadly
rounded, feebly produced. Anterior margin
of carapace between ventral orbital angle and
antero-lateral angle straight. Sixth abdomi-
nal segment with posterolateral angle acute,
posteroventral angle feebly acute. Telson
with large dorsal spines at 0.35 and 0.50 of
telson length, lateral pair of terminal spines
just behind intermediate pair, distal margin
of telson rounded, without median process.
Basal segment of antennular peduncle with
one small distolateral tooth. Scaphocerite
with lateral margin almost straight, slit
between small distolateral tooth and lam-
ina shallow. Chela of rst pereiopods spatu-
late, with cutting edges minutely pectinate
along entire rim. Second pereiopods unequal;
almost straight dactylus barely exceeding
xed nger on both chelae, without teeth on
cutting edges; palm without tympanal organ.
Ambulatory dactyli with large broad dis-
toventral process on exor margin of corpus,
accompanied by small hooked tooth on tip
in third and fourth pereiopods; unguis sim-
ple, acute. Distoventral spines on ambulatory
propodi long, acute.
Colour. Generally transparent; rostrum,
antennular peduncles and chelae of second
pereiopods feebly spotted with small white
dots (Bruce, 1983d).
Hosts. Only known to be associated with
one species of ascidian: Phallusia depressius-
cula (Heller, 1878) (Ascidiidae) (Bruce, 1983d).
Distribution. Only known from its type
locality: Arafura Sea (10°58’S 132°10’E),
Australia (Bruce, 1983d; Bruce & Coombes,
1995).
 17 Dasella herdmaniae (Lebour, 1938) from Herdmania momus (Savigny, 1816). A) ...53924,
stn .52; B) ...53535, stn .10.
  .... 
-  - |./-
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
Dasella brucei Berggren, 1990
Dasella herdmaniae Bruce, 1981a: 50-56, gs.
1–2. (not Dasella herdmaniae (Lebour, 1938)).
Dasella brucei Berggren, 1990: 558 [Type local-
ity: Heron Island, Queensland, Australia, 15
m]; Bruce, 1990: 10, 16, 18 (listed); Müller, 1993:
23 (listed); Li, 2000: 42, g. 42 (listed); Bruce,
2003a: 111, g. 1; De Grave & Fransen, 2011: 348
(listed).
Diagnosis (based on Bruce, 1981a). Small-
sized shrimp. Rostrum exceeding proximal
segment of antennular peduncle, slightly
depressed, acute, dorsally thickened, with-
out distinct lateral carinae, without dorsal
teeth, without or with one acute minute ven-
tral tooth near tip. Antennal spine present,
small. Hepatic spine well-developed, small,
mobile, below level of antennal spine. Inferior
orbital angle distinct, produced. Antero-
lateral angle of carapace broadly rounded,
feebly to strongly produced. Anterior margin
of carapace between ventral orbital angle
and antero-lateral angle somewhat straight.
Sixth abdominal segment with posterolateral
angle acute, posteroventral angle feebly acute.
Telson with large dorsal spines at 0.40 and
0.70 of telson length, lateral pair of terminal
spines just behind intermediate pair, distal
margin of telson with median acute process.
Basal segment of antennular peduncle with
one small distolateral tooth. Scaphocerite
with lateral margin almost straight, slit
between small distolateral tooth and lamina
shallow. Chela of rst pereiopods spatulate,
with cutting edges minutely pectinate along
entire rim. Second pereiopods unequal, with
dactylus barely exceeding xed nger on both
chelae, without teeth on cutting edges; palm
without tympanal organ. Ambulatory dactyli
biunguiculate, with large broad distoventral
process on exor margin of corpus; unguis
simple, acute. Distoventral spines on ambula-
tory propodi long, acute.
Colour. Unknown.
Hosts. Known from two species of ascidi-
ans: Herdmania grandis (Heller, 1878) (Bruce,
2003a) and Herdmania momus (Savigny, 1816)
(Pyuridae) (Bruce, 1981a, 2003a).
Distribution. Three localities of
Queensland, Australia: Heron Island,
Murdock Point (Mooloolaba), and Moreton
Bay (Berggren, 1990; Bruce, 2003a).
Dasella herdmaniae (Lebour, 1938)
(gs. 17–19)
Dasia herdmaniae Lebour, 1938: 650, plate
1 [type locality: Tuticorin, Gulf of Manaar,
Madras, India, associated with ascidian
Herdmania pallida (Heller, 1878) (= Herdmania
momus (Savigny, 1816))].
Dasella herdmaniae – Lebour, 1945: 279;
Holthuis, 1952: 17 (listed); Holthuis, 1955: 68,
g. 4lc, d (listed); Bruce, 1976a: 89; Bruce,
1981a: 50, gs. 1, 2; Bruce, 1981c: 5; Bruce,
1983c: 201 (listed); Berggren, 1990: 554, gs.
1–3; Chace & Bruce, 1993: 78–79; Müller, 1993:
23 (listed); Li, 2000: 42, g. 43 (listed); Bruce,
2010a: 63 (listed); De Grave & Fransen, 2011:
348 (listed); Radhakrishnan et al., 2012: table
1 (listed); Horká et al., 2016: 6, gs. 2-4; Samuel
et al., 2016: table 1 (listed); Chow et al., 2021:
table A.1.
Material examined. INDONESIA: 1 male
pocl. 2.6mm, 1 ovigerous female pocl. 3.8mm
(...49846; GenBank KU170689),
stn .14, Bali, NE-side Pulau Serangan, of
lighthouse, 08°43’17”S 115°15’31”E, 5.iv.2001, 16
m depth,  diving, slowly declining reef
slope, sandy base, in Herdmania momus
(Savigny), translucent, coll. C.H.J.M. Fransen.
– 1 male, pocl. 2.5mm, 1 ovigerous female pocl.
2.5mm, (...58055), stn .05,
Sanur, Penjor Point, 08°41’36”S 115°16’20”E,
1.iv.2001, depth 15 m,  diving, slowly
declining reef slope, sandy base, in H. momus,
translucent with red chromatophores of body
and appendages, coll. C.H.J.M. Fransen, photo
C.H.J.M. Fransen & W. Renema. – 1 male pocl.
./-|   
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
2.2mm, 1 non-ovigerous female pocl. 2.2mm,
(...58056), stn .05, Sanur,
Penjor Point, 08°41’36”S 115°16’20”E, 1.iv.2001,
depth 15 m,  diving, slowly declining
reef slope, sandy base, in H. momus, translu-
cent with red chromatophores over body and
appendages, coll. C.H.J.M. Fransen. – 1 male
pocl. 2.7mm, 1 non-ovigerous female pocl. 1.9,
2.8, 3.5, 3.6 (with bopyroid) mm, (.
..58057), stn .13, NE-side Pulau
Serangan, Loloan Serangan, 08°43’39”S
115°15’13”E, 5.iv.2001, depth 15 m,  div-
ing, slowly declining reef slope, sandy base, in
H. momus, translucent with red chromato-
phores over body and appendages, coll.
C.H.J.M. Fransen. – 1 specimen pocl. 1.1mm
(...58058), stn .12, E-side
Nusa Dua, of Club Med Hotel, N of channel,
08°47’06”S 115°13’57”E, 4.iv.2001, depth 18 m,
slowly declining reef slope, sandy base, in
ascidian, coll. C.H.J.M. Fransen. – 1 ovigerous
female pocl. 4.3mm (...48254),
stn .18, N Sulawesi, Selat Lembeh, near
Tandarusa, Sarena Kecil West, 01°27’N 125°13’E,
24.x.1994, depth 2 m, snorkeling, sandy bank,
from sandy shore to coral covered slope, in
tunicate, coll. J.C. den Hartog. – 1 non oviger-
ous female pocl. 1.8mm (.
..48253), SW Sulawesi, Spermonde
Archipelago, Barang Lompo, NW side,
23.ix.1994, depth 3–5 m,  diving, in
Polycarpa sp. ascidian, coll. C.H.J.M. Fransen.
– 1 ovigerous female pocl. 3.0mm, 1 male pocl.
2.1mm (...48252), SW Sulawesi,
Spermonde Archipelago, Kudingareng Keke,
 side, 28.ix.1994, depth 3–5 m,  div-
ing, in ascidians, coll. C.H.J.M. Fransen. – 1 ovi-
gerous female pocl. 4.6mm, 1 male pocl.
3.1mm, 1 non ovigerous female pocl. 3.5mm, 1
juvenile pocl. 1.6mm (...48251),
SW Sulawesi, Spermonde Archipelago, Pulau
Badi,  side, 3.x.1994, depth 15 m, 
diving, in large solitary milkey white transpar-
ent ascidians, coll. C. Massin. – 1 ovigerous
female pocl. 4.1mm (...48250),
stn .08, N Sulawesi, Selat Lembeh, S of
Tanjung Batuangus, channels between lava
outows, 01°30’N 125°15’E, 25.x.1994, depth
2–5 m, snorkeling, fragile corals on slopes,
down to muddy bottom, coll. J.C. den Hartog.
– 1 ovigerous female pocl. 3.4mm (.
..48249), stn .38, Moluccas, Ambon,
Hitu, E coast, N of Tengah tengah, 8.xii.1990,
depth 10 m,  diving, in ascidian, coll.
C.H.J.M. Fransen. – 1 ovigerous female pocl.
2.5mm (...48248), stn .34,
Moluccas, Ambon, Hitu, Ambon Bay, outer
bay, Rumahtiga, 5.xii.1990, depth 3–5 m,
 diving,? from ascidian, coll. C.H.J.M.
Fransen, photo M.S.S. Lavaleye. – 1 male pocl.
2.9mm (...47589), stn .24,
Moluccas, Ambon, S coast, Seri bay, 03°45’S
128°09’E, 22.xi.1996, depth 15 m,  diving,
in solitary ascidian, H. momus, coll. C.H.J.M.
Fransen. – 1 male pocl. 2.6mm, 1 ovigerous
female pocl. 4.7mm (...47582),
stn .20, Moluccas, Ambon, Ambon bay, N
coast W of Lilibooi, 03°45’S 128°01’E, 20.xi.1996,
depth 30 m,  diving, from large solitary
ascidian af. Phallusia Savigny, coll. C.H.J.M.
Fransen. – 1 male pocl. 2.8mm, 1 female pocl.
4.2mm (...47580), stn .24,
Moluccas, Ambon, S coast, Seri bay, 03°45’S
128°09’E, 22.xi.1996, depth 15 m,  diving,
in H. momus, coll. C.H.J.M. Fransen. – 1 non
ovigerous female pocl. 2.0mm, 1 male pocl.
2.5mm (...47579), stn .32,
Moluccas, Ambon, E coast, close to Cape
Meriam, 03°38’S 128°21’E, 23.xi.1996, depth 10
m,  diving, in solitary ascidian af.
Phallusia, coll. C.H.J.M. Fransen. – 1 male pocl.
2.5mm with pair of abdominal bopyroids, 1
non ovigerous female pocl. 1.8mm (.
..47577), stn .24, Moluccas,
Ambon, S coast, Seri bay, 03°45’S 128°09’E,
22.xi.1996, depth 15 m,  diving, in H.
momus, leg. C.H.J.M. Fransen. – 1 ovigerous
female pocl. 2.4mm (...53535;
GenBank OQ603086 ()), stn .10,
Halmahera, Maitara, Maitara NW, 0°44’32”N
-  - |./-
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
127°21’50.9”E, 29.x.2009, depth 7 m, 
diving, coral reef with sandy patches, corals
and sea fans abundant, in H. cf. momus (Asc.
33), coll. C.H.J.M. Fransen, fcn. -00039,
photo .10.0171-175. – 1 ovigerous female
pocl. 3.0mm, 1 male pocl. 2.6mm (.
..58059), stn .21, Tanjung Ratemu
(S of river), Halmahera mainland, 0°54’24.7”N
127°29’17.7”E, 5.xi.2009, depth 8 m, in ascidian
(Asc 91), coll. A. Gittenberger. – 3 males pocl.
1.6, 1.7 and 2.0mm, 1 non ovigerous female
pocl. 1.4mm (...57964; GenBank
OQ603089 () & OQ600397 (16S)), stn.
.03, NE Sulawesi, Lembeh Strait, E Sarena
Besar, 1°27’34.1634”N 125°14’1.896”E, 31.i.2012,
depth 15 m, in H. momus, coll. C.H.J.M.
Fransen. – 2 ovigerous females pocl. 3.3mm, 1
male pocl. 2.8mm, with abdominal bopyroid),
1 non ovigerous female pocl. 2.8mm (.
..58060), stn .21, NE Sulawesi,
Lembeh Strait, Tanjung Kungkungan,
1°27’58.392”E 125°14’2.2554”E, 10.ii.2012, depth
4 m, in H. momus, coll. C.H.J.M. Fransen. – 3
males pocl. 2.7mm and 2.4 and 2.5mm, 1 ovi-
gerous females pocl. 4.1mm (.
..58061), stn .33, NE Sulawesi,
Lembeh Strait, Tanjung Nanas I, 1°27’39.492”N
125°13’35.7954”E, 17.ii.2012, depth 15 m, each
pair in H. momus, coll. C.H.J.M. Fransen. – few
specimens (...58062), stn .16,
Java Sea, Kepulauan Seribu (Thousand
Islands), of Jakarta, Sepa Island, NW-side,
5°34’32”S 106°34’48”E, 13.ix.2005, unknown
depth,  diving, in ascidian, coll. C.H.J.M.
Fransen. – 1 ovigerous female pocl. 4.4mm
(...54134), stn .19, W Papua,
Raja Ampat Islands, Maya’s mimpi,
00°30.456’S 130°39.919’E, 25.xi.2007, depth 20
m,  diving, in H. momus, coll. J.D.
Thomas. – 1 ovigerous female pocl. 4.0mm
(...58063), stn .26, W Papua,
Raja Ampat Islands, S. Gam, E entrance Besir
Bay, Bun Isl., 00°30.988’S 130°33.812’E,
27.xi.2007, depth 2–12 m, in ascidian?
Polycarpa sp., coll. J.D. Thomas. MALAYSIA: 1
ovigerous female pocl. 3.3mm (.
..53860), stn .37, Sabah, Semporna
area, S Boheydulang Isl., outer reef,
04°35’00.3”N 118°46’39.1”E, 11.xii.2010, depth 7
m,  diving, in H. momus, coll. C.H.J.M.
Fransen. – 1 male pocl. 2.3mm (.
..53870; GenBank OQ603087 ()), stn
.31, Sabah, Semporna area, N Kulapuan
Isl., 04°32’09.6”N 118°50’18.6”E, 9.xii.2010,
depth 20 m,  diving, in H. momus, coll.
C.H.J.M. Fransen. – 1 non ovigerous female
pocl. 4.4mm, 1 ovigerous female pocl. 2.9mm,
1 male pocl. 2.6mm (...53967;
GenBank OQ603088 ()), stn .57,
Sabah, Semporna area, S Larapan Isl. 2,
04°32’51.1”N 118°36’31.3”E, 17.xii.2020, depth 12
m,  diving, in H. momus, coll. C.H.J.M.
Fransen. – 1 non ovigerous female pocl.
2.4mm (...53924; GenBank
KU064966), stn .52, Sabah, Semporna
area, Silumpat Isl., 04°45’58.7”N 118°23’25.6”E,
16.xii.2010, depth 25 m,  diving, in H.
momus, coll. C.H.J.M. Fransen, photo 1263–
1270. MOZAMBIQUE: 1 male pocl. 1.4mm, 1
ovigerous female pocl. 2.3mm (.
..39850), Inhaca Island, 26°S 33°W,
19.i.1990, depth 5 m,  diving, associated
with Pyura stolonifera (Heller), don. M.
Berggren, Kristineberg Marine Biol. Stn.,
Sweden (published by Berggren, M., 1990. J.
Crust. Biol 10(3): 554–558). VANUATU: 1 spec-
imen (...58064), stn FR06, NW
Tutuba Island, 15°19’33”S 167°10’06”E,
13.ix.2006, depth unknown,  diving,
hand picked, in Herdmania sp., fcn. CF35.
Diagnosis (based on Berggren, 1990). Small-
sized shrimp. Rostrum falling short of the
distal segment of the antennular peduncle,
slightly depressed, acute, dorsally thickened,
without distinct lateral carinae, without dor-
sal nor ventral teeth. Antennal spine present,
small. Hepatic spine well-developed, small,
mobile, far below level of antennal spine.
./-|   
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
 18 Dasella herdmaniae (Lebour, 1938). A) ...57964, ovigerous female, pocl. 3.8mm; B–E)
...48249, 1 ovigerous female pocl. 3.4mm. A) habitus, lateral view; B) left mandible,
ventral view; C) left maxillula, ventral view; D) left maxilla, ventral view; E) left rst maxilliped, ventral
view. Scale A = 2mm; B–E = 0.5mm.
  .   ()  ....  (–)
-  - |./-
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via free access

Inferior orbital angle distinct, produced.
Antero-lateral angle of carapace slightly
rounded, slightly produced. Anterior margin
of carapace between ventral orbital angle and
antero-lateral angle straight. Sixth abdomi-
nal segment with posterolateral angle acute,
posteroventral angle feebly acute. Telson with
large dorsal spines at 0.35 and 0.50 of telson
length, lateral pair of terminal spines just
behind intermediate pair, distal margin of tel-
son rounded, without median process. Basal
segment of antennular peduncle with one
small distolateral tooth. Scaphocerite with
lateral margin almost straight, slit between
small distolateral tooth and lamina shallow.
Chela of rst pereiopods spatulate, with cut-
ting edges minutely pectinate along entire rim.
Second pereiopods unequal, almost straight
dactylus barely exceeding xed nger on both
chelae, without teeth on cutting edges, palm
without tympanal organ. Ambulatory dactyli
biunguiculate, with large broad distoventral
process on exor margin of corpus; unguis
simple, acute, minute microstructures pres-
ent on dorsal margin. Distoventral spines on
ambulatory propodi long, club-shaped.
 19 Dasella herdmaniae (Lebour, 1938). ...48249, 1 ovigerous female pocl. 3.4mm. A) left
second maxilliped, ventral view; B) left third maxilliped, ventral view; C) left rst pereiopod, lateral
view; D) right fth pereiopod dactylus, medail view. Scale A, B = 0.5mm; C = 1.25mm; D = 0.1mm.
  .... 
./-|   
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
Colour (g. 17). Whitish/opaque with small
red dots scattered over the carapace, abdo-
men, and chelae of the second pereiopods
(Berggren, 1990).
Hosts. Known from various species of ascid-
ians. Pyuridae: Herdmania momus (Savigny,
1816) (Horká et al., 2016); Herdmania pallida
(Heller, 1878) (Lebour, 1938); Pyura stolonifera
(Heller, 1878) (Berggren, 1990); unidentied
ascidian (Bruce, 1981c). Now recorded for the
rst time from Styelidae: Polycarpa sp. and
Ascidiidae: Phallusia sp.
Distribution. Known from various regions
of the Indo-West Pacic and the Indian Ocean:
Ponta Torres, Inhaca Island (approximately
26°S, 33°W), Mozambique (Berggren, 1990);
Gulf of Mannar, India (Lebour, 1938); Heron
Island, Australia (Bruce, 1981c); Indonesia
(Chow et al., 2021); Bali, Indonesia (Horká et
al., 2016); Sabah, Malaysia (Horká et al., 2016).
Now recorded for the rst time from Vanuatu
(Tutuba Island), and the following new local-
ities in Indonesia: N, SW, and NE Sulawesi;
Ambon, the Mollucas; Halmahera; Seribu
(Thousand Islands); and Raja Ampat, West
Papua.
Genus Ensiger Borradaile, 1915
ZooBank: urn:lsid:zoobank.org:act:012A13F1-
C8A9-4C9F-B4E7-E8B5EE345560
Ensiger Borradaile, 1915: 207. Type species,
being the rst species subsequently placed
in this subgenus, which was described with-
out any nominal species: Anchistia auranti-
aca Dana, 1852 (a junior subjective synonym
of Cancer custos (Forskål, 1775); rst placed in
Ensiger by Borradaile, 1917. The genus is herein
resurrected. Gender: masculine. Etymology:
Borradaile (1915, 1917) did not provide infor-
mation on the derivation of the name. From