Leocratides (Annelida: Hesionidae) from the Pacific Coast of Middle Honshu, Japan, with a description of Leocratides kimuraorum sp. nov.

Abstract

A new species of hesionid polychaetes, Leocratides kimuraorum sp. nov., is described based on material collected from the Shima Peninsula and Sagami Bay (middle Honshu, Japan), as well as museum specimens collected from Sagami Bay, Suruga Bay, and Shirahama. Leocratides kimuraorum sp. nov. is the third species in this genus and can be discriminated from the two congeners, L. filamentosus Ehlers, 1908 and L. ehlersi (Horst, 1921), by i) the length of the antennae, which are as long as palps, ii) the presence of pharyngeal terminal papillae, and iii) the absence of a papillose peristomial membrane. On the other hand, L. filamentosus, originally described from offWestern Sumatra, Indonesia, was also collected from Sagami Bay, and represents a new record of this species for Japanese waters. Partial mitochondrial cytochrome c oxidase subunit I gene sequences from the holotype of L. kimuraorum sp. nov. and newly collected specimen of L. filamentosus are provided for reliable species identification in the future.

Full text

© 2017 e Japanese Society of Systematic Zoology
Species Diversity 22: 133–141
Leocratides (Annelida: Hesionidae) from the Pacic Coast of
Middle Honshu, Japan, with a Description of
Leocratides kimuraorum sp. nov.
Naoto Jimi1,4, Masaatsu Tanaka2,3, and Hiroshi Kajihara1
1 Department of Natural History Sciences, Graduate School of Science, Hokkaido University,
Kita 10 Nishi 8 Kitaku, Sapporo, Hokkaido 060-0810, Japan
E-mail: beniimo7010@gmail.com
2 Department of Biology, Faculty of Science, Toho University,
2-2-1 Funabashi, Chiba 274-8510, Japan
3 Department of Earth and Environmental Sciences, Faculty of Science, Kagoshima University,
1-21-35 Korimoto, Kagoshima 890-0065, Japan
4 Corresponding author
(Received 29 March 2017; Accepted 13 June 2017)
http://zoobank.org/CD308AA8-CCA0-4831-B7CB-3052E946588F
A new species of hesionid polychaetes, Leocratides kimuraorum sp. nov., is described based on material collected from
the Shima Peninsula and Sagami Bay (middle Honshu, Japan), as well as museum specimens collected from Sagami Bay,
Suruga Bay, and Shirahama. Leocratides kimuraorum sp. nov. is the third species in this genus and can be discriminated
from the two congeners, L. lamentosus Ehlers, 1908 and L. ehlersi (Horst, 1921), by i) the length of the antennae, which are
as long as palps, ii) the presence of pharyngeal terminal papillae, and iii) the absence of a papillose peristomial membrane.
On the other hand, L. lamentosus, originally described from o Western Sumatra, Indonesia, was also collected from
Sagami Bay, and represents a new record of this species for Japanese waters. Partial mitochondrial cytochrome c oxidase
subunit I gene sequences from the holotype of L. kimuraorum sp. nov. and newly collected specimen of L. lamentosus are
provided for reliable species identication in the future.
Key Words: Polychaeta, Phyllodocida, DNA barcode, COI, TRV Seisui-maru, JAMBIO, marine invertebrates, hexactinel-
lid sponge, symbiosis, taxonomy.
Introduction
e hesionid polychaete genus Leocratides Ehlers, 1908
consists of two species, L. lamentosus Ehlers, 1908 and L.
ehlersi (Horst, 1921), both of which were originally found
among hexactinellid sponges from sublittoral substrates
in Indonesian waters. e name-bearing types of the rst
species, L. lamentosus, were collected from Aphrocallistes
beatrix Gray, 1858, o Nias Island at 677 m depth (Ehlers
1908). Leocratides lamentosus has also been reported from
Japan (Imajima and Hartman 1964; Imajima 2003, 2005,
2006, 2007), New Caledonia (Rullier 1972), and Egypt (as
L. lamentosa [sic]; Belal and Ghobashy 2012). e second
species, originally described as Leocrates ehlersi and later
combined with Leocratides by Fauvel (1932), was found
among a species of Aphrocallistes Gray, 1858, collected at
a depth of 274 m in Saleh Bay, north coast of Sumbawa,
Indonesia (Horst 1921, 1924; Pettibone 1970). Besides the
records for the type locality, L. ehlersi has also been report-
ed from Sagami Bay of Japan (as Leocratides ehlersi; Hessle
1925), the Andaman Sea (Fauvel 1932, 1953), the Arabian
Sea (Parulekar 1971), and the Red Sea (Fishelson and Rul-
lier 1969; Amoureux et al. 1978).
e taxonomy within Leocratides is contentious. When
Horst (1921) described L. ehlersi, he diagnosed the two Leo-
cratides species as having one (in L. lamentosus) or two (in
L. ehlersi) dorsal jaw plates. Based on examination of the
two syntypes of L. lamentosus, however, Augener (1926)
argued that L. ehlersi should be treated as a junior synonym
of the former which has actually two dorsal jaw plates, in-
stead of one. Later, Pettibone (1970) redescribed the syn-
types of both species in detail and also concluded that they
were synonymous. In contrast, also having examined the
syntypes of the two, Pleijel (1998) restored L. ehlersi as a
distinct species, concluding that the pharyngeal terminal
papillae and the papillose peristomial membrane are both
present in L. lamentosus, but are absent in L. ehlersi. In this
study, we follow the taxonomy of Pleijel (1998), treating L.
lamentosus and L. ehlersi as two distinct species.
While several authors have recorded Leocratides spe-
cies from Japanese waters, the taxonomic identity of the
Japanese taxon (or taxa) requires further scrutiny. Hes-
sle (1925) reported six specimens of hesionids under the
name “Leocrates ehlersi” from Sagami Bay (from 150 m to
600 m depths). Subsequently, Imajima and Hartman (1964)
emended that record to “Leocratides lamentosus” with-
out any explanation. Imajima (2003, 2005, 2006, 2007) also
25 November 2017
DOI: 10.12782/sd.22_133

134 Naoto Jimi et al.
identied a number of hesionid specimens as L. lamento-
sus; these were collected from the Pacic coast of middle
Honshu (around Sagami Bay and Suruga Bay) and South
West Japan (o the Tokara Islands and the Amami Is-
lands), collected at the depth of 74 m to 297 m. Okanishi et
al. (2016) reported “Leocratides sp.” near Shirahama (from
164–169 m depth). As to the Japanese Leocratides species,
however, the diagnostic characters mentioned earlier were
neither explicitly mentioned by Hessle (1925) and Okanishi
et al. (2016) nor clearly illustrated by Imajima (2003, 2005,
2006, 2007), making their taxonomic identity blurred.
NJ obtained specimens of Leocratides during a research
cruise onboard the training and research vessel (TRV)
Seisui-maru (Mie University) o the Shima Peninsula. An-
other specimen of Leocratides was also collected by MT in
Sagami Bay. A close examination in the laboratory revealed
that these specimens are morphologically consistent with
the description and illustration of “L. lamentosus” by Im-
ajima (2003, 2007) and also the illustration of “Leocrates
ehlersi” by Hessle (1925), whereas they do not correspond
with the original descriptions of L. lamentosus and L. ehler-
si (Ehlers 1908; Horst 1921). In this paper, we describe these
specimens along with some of the voucher material exam-
ined in Imajima (2003, 2007) and Okanishi et al. (2016)
as the third member of Leocratides, providing barcode se-
quence of the holotype for the new species to facilitate fu-
ture reliable identication.
In addition to the new species, we also found a number
of specimens of L. lamentosus in the sense of Ehlers (1908)
but not Imajima (2003, 2007) from Sagami Bay. In this
paper, we give a redescription of L. lamentosus based on
these specimens as representing a truly new record for Japa-
nese waters.
Materials and Methods
Fresh specimens were newly collected from Sagami Bay
and o the Shima Peninsula, Japan (Table 1). Some of the
live specimens were photographed onboard with a digital
camera (Nikon D60), then xed in 10% formalin-seawa-
ter or 70% ethanol. Aer preservation, these specimens
were observed with a microscope (Nikon SMZ1500 and
OLYMPUS BX51) and photographed with a digital camera
(Nikon D5200). All the material has been deposited in the
National Museum of Nature and Science, Tsukuba (NSMT).
Additionally, a part of Leocratides specimens investigated in
Imajima (2003, 2007) and Okanishi et al. (2016), which have
been kept in the NSMT, were also examined.
DNA extraction, and sequencing for partial sequences
of mitochondrial cytochrome c oxidase subunit I (COI)
were carried out following the method of Jimi and Fujiwara
(2016). Newly obtained sequences have been deposited in
the DNA Data Bank of Japan.
Systematics
Genus Leocratides Ehlers, 1908
[New Japanese name: hanakago-otohime-gokai-zoku]
Leocratides kimuraorum sp. nov.
[New Japanese name: Kimura-hanakago-otohime-gokai
(previously called “oni-otohime-gokai”)]
(Figs 1, 2)
?Leocrates ehlersi (non Horst, 1921); Hessle 1925: 14–15, g. 3.
Leocratides lamentosus (non Ehlers, 1908); Imajima and
Hartman 1964: 82–83; Imajima 2003: 136–138, g. 80 (in
part); Imajima 2007: 444, g. 138 (in part).
Leocratides sp.; Okanishi et al. 2016: 14.
Material examined. Holotype: NMST-Pol H-622,
29 mm long, 5 mm wide, sex unknown, o Shima Penin-
sula, St. 1, 103–104 m depth, 12 October 2016, collected by
NJ (right parapodium of chaetiger 5 was removed for ob-
servation; it is preserved in 70% ethanol in a 2.0 ml plastic
tube, which is contained in the same glass vial together with
the rest of the body). Paratypes (14 specimens): NSMT-Pol
P-623–624, ve specimens, 11–19 mm long, 2 mm wide, sex
unknown, o Shima Peninsula, St. 1 (NSMT-Pol P-623, four
specimens) and St. 2 (NSMT-Pol P-624, one specimen), 12
October 2016, collected by NJ; NSMT-Pol P-625, one speci-
men, 25 mm long, 4 mm wide, male (sperm present in each
segment’s gonads), Sagami Bay St. 2, 104–111 m depth,
27 April 2016, collected by MT; NSMT-Pol P-626, three
specimens examined by Okanishi et al. (2016), 6–16 mm
long, 2 mm wide, sex unknown, o Shirahama, 164–169 m
depth, 27 May 2015, collected by NJ; NSMT-Pol R 176, two
specimens examined by Imajima (2003, 2007), 21–24 mm
long, 3 mm wide, sex unknown, Sagami Bay, 110–120 m
Table 1. Collection data of Leocratides spp. in this study.
Locality Latitude Longitude Depth (m) Collection date Collected species Contained sponges
Sagami Bay, St. 1 35°07.132′N to
35°07.388′N
139°33.709′E to
139°33.365′E213–255 29 June 2011 Leocratides lamentosus Unknown
Sagami Bay, St. 2 35°07.5787′N to
35°07.5583′N
139°33.7096′E to
139°33.8756′E104–111 27 April 2016 Leocratides kimuraorum
sp. n ov. Hexactinellid sponge
Sagami Bay, St. 3 35°06.929′N to
35°06.631′N
139°33.814′E to
139°33.734′E292–375 15 February 2017 Leocratides lamentosus Aphrocallistes sp.
O Shima Peninsula,
St. 1
34°11.63′N to
34°11.66′N
136°42.56′E to
136°42.69′E103–104 12 October 2016 Leocratides kimuraorum
sp. n ov.
Demosponge and hexacti-
nellid sponge
O Shima Peninsula,
St. 2
34°11.81′N to
34°11.82′N
136°41.80′E to
136°41.95′E107 12 October 2016 Leocratides kimuraorum
sp. n ov.
Demosponge and hexacti-
nellid sponge

Two species of Leocratides from Japan 135
depth, 14 March 1954, collected by the late Emperor Showa;
NSMT-Pol R 968, one specimen examined by Imajima
(2003, 2007), 21 mm long, 3 mm, sex unknown, Sagami Bay,
85–90 m depth, 24 January 1965, collected by the late Em-
peror Showa; NSMT-Pol P-627: one specimen examined by
Imajima (2007), 16 mm long, 3 mm wide, sex unknown, Su-
ruga Bay, 92 m depth, 4 October 1995, collected by the late
Dr. Minoru Imajima (MI); NSMT-Pol P-628: one specimen
examined by Imajima (2007), 24 mm long, 3 mm wide, sex
unknown, Suruga Bay, 86–91 m depth, 8 February 1978, col-
lected by MI.
Sequence. LC258082, COI gene, 630 bp, determined
from the holotype.
Description. Holotype 29 mm long, 5 mm wide in
chaetiger 7 (not including parapodia), 21 segments, 16 chae-
tigers. Body cylindrical, tapered in posterior region (Fig.
1A, B), transparent in life (Fig. 1A) and whitish in ethanol;
dorsal integument annulated, with 15–17 transverse wrin-
kles per segment. Dorsum with numerous, thin, transverse
discontinuous brown lines, extended into lateral cushions,
Fig. 1. Leocratides kimuraorum sp. nov., holotype, NSMT-Pol H-622. A, Live specimen, dorsal view; B, same, ventral view; C, integument
and lateral cushions in chaetigers 4–5, dorsal view; D, prostomium, dorsal view; E, pharynx and peristomium, ventral view, showing facial
tubercle (white arrow), cushion-shaped appendages (black arrows), and dorsal jaw plates (arrowheads); F, pharynx with terminal papillae,
ventral view. Scale of the ruler: A, B, 1 mm. Scale bars: C–F, 1 mm.

136 Naoto Jimi et al.
varying in length, decreasing in size laterally (Fig. 1A, C);
ventrally, black spots of dierent size and shape arranged
along mid-ventral groove, in chaetal lobe regions, two larger
spots better developed along chaetigers 4–15 (Fig. 1B). Pro-
stomium rectangular, slightly wider than long, mid-dorsally
with shallow depression, square in shape from dorsal view
(Fig. 1D). Median antenna cirriform, smooth, tapered, in-
serted in central part of prostomium, extended beyond an-
terior prostomial margin, 1.1 times longer (and thinner)
than lateral antenna, surpassing palpophores. Lateral anten-
nae tapered, smooth, on anterior edge of prostomium. Palps
bi-articulated, 0.9–1 times longer than lateral antennae,
palpophore two times longer than palpostyle, bent laterally,
pointed to body sides, external to antennae (Fig. 1D). Eyes
brownish, two pairs, on mid-lateral part of prostomium; an-
terior pair slightly larger and more separated than posterior
one (Fig. 1D). Facial tubercle present mid-ventrally on pro-
stomium; cushion-shaped appendage present between palps
and tentacular cirri on each side (Fig. 1E); papillose peristo-
mial membrane absent.
Tentacular cirri eight pairs, long, thick; longest one reach-
ing chaetiger 10. Lateral cushions low, barely projected dor-
sally, slightly projected laterally, undivided, with 17–18 lon-
gitudinal wrinkles per side (Fig. 1C).
Parapodia uniform throughout; with chaetal lobes ta-
pered, truncate, as long as wide (Fig. 2A); dorsal cirri with
cirrophores, latter being cylindrical, smooth, about twice
longer than wide (Fig. 2B); cirrostyle very long, whip-like,
smooth basally, annulated medially and distally, longer than
body width (including parapodia). Ventral cirri basally
Fig. 2. Leocratides kimuraorum sp. nov., right parapodium of chaetiger 5, holotype, NSMT-Pol H-622. A, General appearance of parapo-
dium, anterior view; B, cirrophore; C, ventral cirrus; D, acicular lobe, arrow indicating its tip, the base side of photo is the parapodial tip; E,
bundle of neurochaetae; F, blade of neurochaeta. Scale bars: A, 2 mm; B–E, 300 µm; F, 50 µm.

Two species of Leocratides from Japan 137
smooth, rugose medially and distally, surpassing chaetal
lobe, reaching up to half length of neurochaetal bundle (Fig.
2C).
Neuropodial acicula black, tapered; acicular lobe single,
thick, digitate, tapered into a small mucro (Fig. 2D). Neu-
rochaetae about 20 per bundle (Fig. 2E); handle greenish;
blade pale brownish, bidentate, 5 times longer than wide;
with subdistal tooth short, blunt, 0.4 times longer than api-
cal tooth; guard tooth absent (Fig. 2F).
Cirri of prepygidial segment broken; pygidium smooth,
depressed, with paired cirri; anus located dorso-terminally,
with about 10 anal papillae.
Pharynx dissected in holotype, about 20 low cushion-like
terminal papillae present (Fig. 1F); dorsal jaw two plates,
ventral jaw one plate.
Variation. Dorsal transverse lines and ventral black
spots faded in some paratype specimens.
Etymology. e specic name is a noun in the genitive
plural, aer a Japanese marine ecologist Dr. Taeko Kimura
and a malacologist Mr. Shoichi Kimura, who organized the
cruise of the TRV Seisui-maru of Mie University, during
which a part of the type specimens, including the holotype,
of the new species were collected.
Distribution. Pacic coast of middle Honshu, Japan:
85–169 m depth, collected with hexactinellid sponges.
Remarks. Our specimens undoubtedly belong to Leo-
cratides because their body consists of 21 segments, the an-
terior cirri are in eight pairs, the neurochaetae are bidentate,
the palps are bi-articulated, the parapodia are uniramous,
and the jaws are present, all agreeing with the generic di-
agnosis provided by previous researchers (Pettibone 1970;
Pleijel 1998; Rizzo and Salazar-Vallejo 2014; Salazar-Vallejo
2016).
Leocratides kimuraorum sp. nov. diers from L. lamento-
sus in the lateral antennae because they are as long as palps
in L. kimuraorum sp. nov. but shorter than palps in L. la-
mentosus, and there is no papillose peristomial membrane
in L. kimuraorum sp. nov. whereas it is present in L. lamen-
tosus. It can also be distinguished from L. ehlersi by the pha-
ryngeal terminal papillae (present in L. kimuraorum sp. nov.
vs. absent in L. ehlersi) (Horst 1921; Pleijel 1998).
Because we were not able to examine Hessle’s (1925)
voucher material from Misaki, identied as “Leocrates ehler-
si”, its taxonomic identity remains uncertain, inasmuch as
the morphological features illustrated in his gure (Hessle
1925: g. 3) apply both to L. ehlersi and L. kimuraorum sp.
no v.
We examined some of Imajima’s (2003, 2007) voucher
material from Sagami and Suruga Bays and noticed that his
descriptions contain several errors. For instance, Imajima
(2003, 2007) noted that there were two to ve transverse
wrinkles on the dorsal integument in each segment, where-
as there are actually 15–17 wrinkles per segment. When it
comes to the pharyngeal terminal papillae, Imajima (2003,
2007) stated that these were absent, although the papillae
are in fact present in his voucher specimens. erefore, we
can condently regard his material as belonging to L. kimu-
raorum s p. no v.
Leocratides lamentosus Ehlers, 1908
[New Japanese name: hanakago-otohime-gokai]
(Figs 3, 4)
Leocratides lamentosus Ehlers, 1908: 63, pl. 6, gs 8–12;
Pettibone 1970: 230–231, gs 27–28; Pleijel 1998: 112.
?Leocratides lamentosus; Rullier 1972: 58; Imajima 2005:
82; 2006: 351; Belal and Ghobashy 2012: 178 (as L.
lamentosa [sic]).
Material examined. Nine specimens: NMST-Pol 113219,
one specimen, sex unknown, Sagami Bay, St.1, 213–255 m
depth, 29 June 2011, collected by MT (right parapodium of
chaetiger 10 removed for observation; preserved in 70% eth-
anol in a 2.0 ml plastic tube, kept in the same vial together
with the rest of the body); NSMT-Pol 113220, eight speci-
mens, one female and others of unknown sex, Sagami Bay,
St. 3, 292–375 m depth, 15 February 2017, collected by NJ,
MT, HK.
Sequence. LC258083, COI gene, 592 bp, determined
from a specimen of NSMT-Pol 113220.
Description. 14–30 mm long, 2–4 mm wide in chae-
tiger 7 (not including parapodia), 21 segments, 16 chae-
tigers; right parapodium of chaetiger 10 removed for ob-
servation. Body cylindrical, tapered in posterior region,
transparent in live (Fig. 3A, B), whitish in ethanol; dorsal
integument annulated, with 12–17 transverse wrinkles per
segment. Brown lines on dorsal surface absent (Fig. 3A,
C); ventrally with black spots of varying size and shape ar-
ranged along median groove, in some places roughly on
two rows, in chaetigers 5–16; some spots being particularly
larger than others, arranged laterally in pair along line be-
tween parapodia in each segment, especially prominent in
chaetigers 7–11 (Fig. 3B). Prostomium rectangular, longer
than wide, mid-dorsally with shallow depression, square in
shape from dorsal view (Fig. 3D). Median antenna conical,
smooth, in central part of prostomium, not reaching ante-
rior prostomial margin, 1.3 times longer than lateral anten-
nae. Lateral antennae conical, smooth, on anterior edge of
prostomium. Palps bi-articulated, 1.2 times longer than lat-
eral antennae, palpophore four times longer than palpostyle,
ventral to antennae (Fig. 3D). Eyes brownish, two pairs, on
mid-lateral part of prostomium, anterior pair slightly larger
and more separated than posterior one (Fig. 3D). Facial tu-
bercle present mid-ventrally on prostomium; papillose peri-
stomial membrane present (Fig. 3E).
Tentacular cirri eight pairs, long, thick; longest one reach-
ing chaetiger 6. Lateral cushions low, barely projected dor-
sally, slightly projected laterally, undivided, with 7–8 longi-
tudinal wrinkles per one lateral cushion (Fig. 3C).
Parapodia uniform throughout; chaetal lobes cylindrical,
truncate, as long as wide (Fig. 4A); dorsal cirri with cirro-
phores cylindrical, smooth, 1.3 times longer than wide (Fig.
4B); cirrostyle whip-like, smooth, annulated, longer than
body width (without parapodia). Ventral cirri basally ru-
gose, surpassing chaetal lobe, reaching up to half length of
neurochaetal bundle (Fig. 4C).
Neuropodial acicula black, tapered; acicular lobe single,

138 Naoto Jimi et al.
wider basally, tip digitate, long (Fig. 4D). Neurochaetae
about 20 per bundle (Fig. 4E); handle greenish; blade yel-
lowish, bidentate, six times longer than wide; with subdistal
tooth 0.5 times longer than apical tooth; guard absent (Fig.
4F).
Cirri of prepygidial segment broken; pygidium smooth,
depressed, with paired cirri; anus dorso-terminal, with
about eight anal papillae.
Pharynx dissected, about 20 terminal low cushion-like
terminal papillae present (Fig. 3F); dorsal jaw two plates,
ventral jaw one plates.
Conrmed distribution. From Sagami Bay, Japan to
Indonesia, 213–677 m depth, in hexactinellid sponges.
Remarks. Imajima (2003, 2007) reported “Leocratides
lamentosus” from Japanese waters. However, as indicated
above Imajima’s (2003, 2007) specimens from Sagami and
Suruga Bays actually belong to L. kimuraorum sp. nov. Ima-
jima (2005, 2006) also reported “L. lamentosus” from o
Izu-Oshima Island, Sagami Bay, and several other locali-
ties o the Nansei Islands, southwestern Japan, but neither
morphological accounts nor the basis of his identications
were provided. We searched unregistered polychaete collec-
Fig. 3. Leocratides lamentosus Ehlers, 1908. A, B, F; NSMT-Pol 113220, C–E; NSMT-Pol 113219. A, Live specimen inside a fragment of
an Aphrocallistes sp. hexactinellid sponge, dorsal view; B, same specimen, ventral view; C, integument and lateral cushions in chaetigers 2–4,
dorsal view; D, prostomium, dorsal view; E, pharynx and peristomium, ventral view, showing facial tubercle (white arrow) and papillose
peristomial membrane (black arrows); F, pharynx with terminal papillae, ventral view. Scale bars: A, B, 10 mm; C–F, 1 mm.

Two species of Leocratides from Japan 139
tion in NSMT for the voucher specimens that substantiate
Imajima’s (2005, 2006) records of his “L. lamentosus” from
Izu-Oshima Island, Sagami Bay, and the Nansei Islands,
but were not able to locate them. is makes the validity of
these records of “L. lamentosus” rather obscure. us, we
conclude that there has been no reliable distributional re-
cords of L. lamentosus from Japanese waters and this study
represents the rst record of the species for Japan.
Out of the type locality and Japanese waters, Rullier
(1972) and Belal and Ghobashy (2012) also reported “Leo-
cratides lamentosus” from extremely shallow depths (up to
8 m depth) in New Caledonia and Lake Timsah of the Suez
Canal, Egypt, respectively. However, these studies provided
only a brief account or an inadequate illustration and we
consider these records are doubtful.
Discussion
An ecological association of Leocratides with hexactinel-
lid sponges has been indicated because the two previously
known species, L. lamentosus and L. ehlersi, were both found
among Aphrocallistes hexactinellids (e.g., Pettibone 1970; this
study). Our specimens of L. kimuraorum sp. nov. were also
found among sediments which contained fragments of hexac-
tinellid sponges, indicating that Leocratides species are gener-
ally associated with hexactinellids. Because dredging inevita-
bly disturbs natural habitat, future studies aiming to observe
specimens in-situ using a remotely operated vehicle, could
reveal the ecology of Leocratides and the interaction between
the worms and the host hexactinellid sponges.
Fig. 4. Leocratides lamentosus Ehlers, 1908. Right parapodium of chaetiger 10, NSMT-Pol 113219. A, General appearance of parapodium,
posterior view; B, cirrophore; C, ventral cirrus; D, acicular lobe; E, bundle of neurochaetae; F, blade of neurochaeta. Scale bars: A, 1 mm; B–E,
300 µm; F, 100 µm.

140 Naoto Jimi et al.
In this study, we found that the bathymetric distributions
of L. kimuraorum sp. nov. and L. lamentosus seem to be
clearly separated. In Sagami Bay, the two species were ob-
tained almost sympatrically, but L. kimuraorum sp. nov. oc-
curred in shallow waters, around 100–150 m depth, while L.
lamentosus tended to occur in deeper waters, more than
200 m depth (Table 1). Recent studies focused on cryptic di-
versity of polychaetes indicate that depth may play an im-
portant role in speciation (Nygren et al. 2005, 2010; Schüller
2011; Nygren 2014; Oug et al. 2017); this scenario may be
true for Leocratides. Further eorts combining the records
of Leocrates species from various localities are required to
reveal the nature of species distribution.
Acknowledgments
NJ is grateful for all their help in collecting the specimens
to the captain and crew of the TRV Seisui-maru, Dr. Taeko
Kimura, Mr. Shoichi Kimura, and Ms. Haruka Onishi (Mie
University), Mr. Akito Ogawa (e University of Tokyo),
Ms. Luna Yamamori (Kyoto University), and the member of
the Marine Ecology Laboratory and other students of Mie
University who participated the research cruise, Dr. Akira
Asakura (Kyoto University), Dr. Katsumi Miyazaki (Niigata
University), Dr. Masanori Okanishi (Ibaraki University), Dr.
Asuka Sentoku (e University of Queensland), the mem-
ber of the Shirahama Marine Research and crew of the R/V
Janthina (Kyoto University). MT is indebted to Drs. Ter-
uaki Nishikawa (Toho University) and Hiroshi Namikawa
(NSMT) for giving him chance to participate their faunal
survey in Sagami Bay, during which some specimens were
found. We thank Drs. Hiroshi Namikawa and Hironori
Komatsu (NSMT) for loan or searching of specimens under
their care; Messrs. Mamoru Sekifuji, Hisanori Kohtsuka,
and Dr. Akihito Omori (e University of Tokyo), Dr. Hi-
roaki Nakano and Mr. Yasutaka Tsuchiya (University of
Tsukuba), and all the other participants in the 12th Japa-
nese Association for Marine Biology (JAMBIO) Coastal
Organism Joint Survey held at Misaki, for generous help in
collecting additional material; Dr. Kevin Wakeman (Hok-
kaido University) for correcting the English; and Dr. Sergio
I. Salazar-Vallejo and an anonymous reviewer for providing
informative comments. is study was partly supported by
JAMBIO.
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