A report of Mustaquimsthenelais (Sigalionidae: Polychaeta) from the Andaman Sea and Japanese waters

Abstract

Mustaquimsthenelais heterochela (Horst, 1917) from the Andaman Sea,
southwestern Thailand and M. dendropapillata Wehe, 2007 from Tanabe Bay, Japan are
described. The latter species is a new record from Japanese waters

Full text

เอกสารวิชาการฉบับที่ ๘/๒๕๕๑
Technical Paper no. 8/2008
รายงานไสเดือนทะเลสกุล Mustaquimsthenelais (SIGALIONIDAE: POLYCHAETA)
จากทะเลอันดามัน และนานน้ําญี่ปุน
A REPORT OF Mustaquimsthenelais (SIGALIONIDAE: POLYCHAETA)
FROM THE ANDAMAN SEA AND JAPANESE WATERS
โดย
จรัสศรี อางตันญา
Charatsee Aungtonya
สถาบันวิจัยและพัฒนาทรัพยากรทางทะเล ชายฝงทะเล Phuket Marine Biological Center
และปาชายเลน
กรมทรัพยากรทางทะเลและชายฝง Department of Marine and Coastal Resources
กระทรวงทรัพยากรธรรมชาติและสิ่งแวดลอม Ministry of Natural Resources and Environment

เอกสารวิชาการฉบับที่ ๘/๒๕๕๑
Technical Paper no. 8/2008
รายงานไสเดือนทะเลสกุล Mustaquimsthenelais (SIGALIONIDAE: POLYCHAETA)
จากทะเลอันดามัน และนานน้ําญี่ปุน
A REPORT OF Mustaquimsthenelais (SIGALIONIDAE: POLYCHAETA)
FROM THE ANDAMAN SEA AND JAPANESE WATERS
โดย
จรัสศรี อางตันญา
Charatsee Aungtonya
สถาบันวิจัยและพัฒนาทรัพยากรทางทะเล ชายฝงทะเล และปาชายเลน Phuket Marine Biological Center
ตู ป.ณ. ๖๐ อ. เมือง จ. ภูเก็ต ๘๓๐๐๐ P.O. Box 60, Phuket 83000
โทร. (๐๗๖) ๓๙๑๑๒๖ , ๓๙๑๑๒๘ Tel. (076) 391126, 391128
๒๕๕๑ 2008

i
สารบาญ
หนา
บทคัดยอ
1
ABSTRACT 2
INTRODUCTION 3
MATERIALS AND METHODS 3
TAXONOMY
Genus Mustaquimsthenelais Wehe, 2007 4
Mustaquimsthenelais dendropapillata Wehe, 2007 6
Mustaquimsthenelais heterochela (Horst, 1917) 10
ACKNOWLEDGEMENTS 13
REFERENCES 14

ii
สารบาญตาราง
Table หนา
1 Comparison of characters of known species of Mustaquimsthenelais
adapted from Pettibone (1971), Wehe (2007), and this study 13

iii
สารบาญภาพ
Figure หนา
1 Mustaquimsthenelais dendropapillata (SMBL Inv-10001): A. anterior end,
dorsal view; B. Close-up of A, showing prostomium; C. Outer lateral
margin of elytron, with branched papillae; D. Ventral surface and ventral
cirri; E. Parapodium from anterior segment, arrow indicates branched
papilla at medial base of ventral cirrus; F–G. SEM micrographs on heterocheliger.
Scales = 100 µm (F) and 20 µm (G). Abbreviations: au, auricle; ct, ctenidium;
antenna; man, lan, lateral median antenna; pa, palp; vc, ventral cirrus;
and vcp, papilla at medial base of ventral cirrus. 7
2 Mustaquimsthenelais dendropapillata (SMBL Inv-10001): A. Anterior
end, dorsal view, B. Parapodium of segment 27, posterior view; C. Anterior
view of same; D. Close-up of ventral cirrus, with branched medial papilla;
E–M. Neurochaetae from same; N, R. Left elytron from segment 4 and 48,
position of scar indicated; P. Left elytron from anterior segment; O, Q, S.
Enlargement of single papilla showing details of papilla. Scales = 1.0 mm
(A–C, N, P, R) and 0.1 mm (D–M, Q), and 0.05 mm (O, S).
Abbreviations: au, auricle; bk, basal knob on ventral cirrus;
ct, ctenidium; dtcr, dorsal tentacular crest; lan, lateral antenna;
man, median antenna; pa, palp; vc, ventral cirrus; and vcp, papilla
at medial base of ventral cirrus. 8
3 Mustaquimsthenelais heterochela (PMBC 20379): A. Parapodium of
segment 14, posterior view; B. Anterior view of same; C–E, G–H.
Neurochaetae (compound falcigers) from same; F. Upper neurochaeta
(simple, spinous capillary) from same; I, M. Left elytron from anterior
and posterior segments, position of scar indicated; K. Left elytron
from segment 38; J, L, N. Enlargement of papillae on elytral margin.
Scales = 1.0 mm (A–B, I, K, M), 0.1 mm (C–H, L, N), and 0.05 mm (J).
Abbreviations: bk, basal knob on ventral cirrus; vc, ventral
cirrus; vcp, papillae at medial base of ventral cirrus. 12

รายงานไสเดือนทะเลสกุล Mustaquimsthenelais (SIGALIONIDAE: POLYCHAETA)
จากทะเลอันดามัน และนานน้ําญี่ปุน
จรัสศรี อางตันญา
สถาบันวิจัยและพัฒนาทรัพยากรทางทะเล ชายฝงทะเล และปาชายเลน ตู ปณ. ๖๐ อ. เมือง จ. ภูเก็ต ๘๓๐๐๐
บทคัดยอ
รายงานฉบับนี้ไดบรรยายลักษณะของไสเดือนทะเล Mustaquimsthenelais heterochela
(Horst, 1917) จากทะเลอันดามันบริเวณภาคใตฝงตะวันตกของประเทศไทย และลักษณะของไสเดือนทะเล
M. dendropapillata Wehe, 2007 จากอาวทานาเบะ ประเทศญี่ปุน ซึ่งเปนรายงานการพบครั้งแรกของ
ไสเดือนทะเลชนิดดังกลาวจากนานน้ําญี่ปุน
คําสําคัญ: Sigalionidae, Mustaquimsthenelais, ทะเลอันดามัน, ประเทศไทย, อาวทานาเบะ, ประเทศ
ญี่ปุน

2
A REPORT OF Mustaquimsthenelais (SIGALIONIDAE: POLYCHAETA)
FROM THE ANDAMAN SEA AND JAPANESE WATERS
Charatsee Aungtonya
Phuket Marine Biological Center, P.O. Box 60, Phuket 83000, Thailand
ABSTRACT
Mustaquimsthenelais heterochela (Horst, 1917) from the Andaman Sea,
southwestern Thailand and M. dendropapillata Wehe, 2007 from Tanabe Bay, Japan are
described. The latter species is a new record from Japanese waters.
Key words: Sigalionidae, Mustaquimsthenelais, Andaman Sea, Thailand, Tanabe Bay, Japan

3
INTRODUCTION
Mustaquimsthenelais was erected by Wehe (2007). This genus is characterized by
having neurochaetae of the heterocheliger type (i.e., falcigerous with a greatly elongated inner
tooth) and elytra with long simple or arborescent branched marginal papillae. Willeysthenelais
heterochela was transferred to this genus, which thus consists of 2 species: M. heterochela
and M. dendropapillata. The type species, M. dendropapillata Wehe, 2007, was described
based solely on the holotype (from the Arabian Sea), as was M. heterochela (from Sanana
Bay, E. Sulawesi, Indonesia).
The Andaman Sea is a marginal sea of the northeastern Indian Ocean, and covers
an area of about 800,000 km2. Sigalionid polychaetes from the Andaman Sea off southwestern
Thailand were preliminarily studied by Aungtonya (2002), who recorded 9 species
representing 9 genera from the BIOSHELF Project. Other published reports of sigalionids
from the Andaman Sea are by Tampi and Rangarajan (1964) for the Andaman Islands group,
India, in which only one species was recorded, and by Phasuk (1992) based on material from
the Fifth Thai-Danish Expedition off southwestern Thailand in 1966, in which about 12
species were recorded, but without descriptions and discussions. In addition to these species,
Labiosthenolepis andamanensis was described by Aungtonya (2007).
Sigalionids have been reported from Japanese waters by Moore (1903), Izuka
(1912), Okuda (1937, 1938, 1939), Inaba (1963), Imajima and Hartman (1964), Imajima
(1967, 2001, 2003, 2005, 2006), and Aungtonya (2007). About 24 species have been
recognized, of which five new species were described from Japan, i.e., Sigalion lituus
Imajima, 2005, S. shimodaensis Imajima, 2006, S. tanseimaruae Imajima, 2006,
Heteropelogenia japonica Imajima, 2006, and Labiosthenolepis andamanensis Aungtonya
(2007).
The aims of this study are to describe and illustrate Mustaquimsthenelais species
from the Andaman Sea and from Tanabe Bay, Japan, and to present a key for the
identification of these species.
MATERIALS AND METHODS
Examinations were carried out using a Nikon SMZ-U stereo microscope and a
Nikon E600 compound microscope. A camera lucida was routinely used to facilitate drawing.
The specimens were stained with Shirlastain (Petersen, 1998). Body width was measured at

4
segment 10–15. The maximum number of segments was counted. Parapodia were removed
from the left side of the body and illustrated in posterior and anterior views. Neurochaetae
were illustrated from the same parapodia. Elytra were also removed from the left side and
illustrated in dorsal view. Parapodium for the SEM study, was fixed in 1–2% osmium
tetroxide in filtered seawater for about an hour, rinsed, and stored in distilled water,
transferred to ethanol, freeze dried, sputter coated with platinum, and examined in a Hitachi
S-4300.
Morphological terms are used in accordance with Aungtonya (2003). The
specimens are deposited in the Reference Collection at the Phuket Marine Biological Center
(PMBC), Thailand and Seto Marine Biological Laboratory (SMBL), Kyoto University, Japan.
TAXONOMY
Family Sigalionidae Kinberg, 1856
Genus Mustaquimsthenelais Wehe, 2007
Mustaquimsthenelais Wehe, 2007: 77.
Type species. Mustaquimsthenelais dendropapillata Wehe, 2007: 78–82, figs. 10–12 (by
original designation).
Diagnosis. Prostomium dorsally fused with tentacular parapodia; ceratophore of median
antenna stout, cylindrical, with large lateral auricles; lateral antennae fused with inner dorsal
sides of tentacular parapodia, without ceratophore. Dorsal tentacular crests present. Inner
tentacular lobes present, with median ciliated ridge. Inner palpal sheath present, outer
sheath indistinct. Facial tubercle absent. Lateral lips of mouth without paired ctenidia.
Segment 2 with ventral buccal cirri. Segment 3 with dorsal tubercles, dorsal cirri absent.
Ventral cirri with long papillae at medial base and with outer basal knob. Elytral surface
with microtubercles or papillae, outer lateral margin with papillae. Notopodia with
posterior upper and anterior lower lobes, anterior upper lobe inconspicuous. Ctenidial pads
present between notopodium and dorsal tubercle or elytrophore. Notochaetae simple, coarsely
to finely spinous capillaries. Neuropodia with three groups of chaetae: upper and lower
groups, and single C-shaped group; posterior upper and lower lobes inconspicuous,
fimbriated; anterior upper and lower lobes not distinct. Parapodial stylodes without papillae.
Neurochaetae compound heterocheligers (with inner tooth curved and greatly

5
elongated), normal articulate blade with bifid tip may be present, distal part of stem spinous
or smooth; upper simple spinous capillaries present.
Remarks. Mustaquimsthenelais was introduced by Wehe (2007), characterized by having
compound chaetae that are unique within the family, i.e., bifid heterogomph falcigers with the
two tips widely separated from one another and a greatly elongated inner tooth (termed
‘heterocheliger’ by Wehe (2007). The characters of the genus Mustaquimsthenelais otherwise
resemble those of Willeysthenelais, both having long papillae at the medial base of the ventral
cirri, parapodial stylodes that are not papillated, and compound neurochaetae that are all
falcigerous; similarly, they both lack a pair of ctenidia either on the lateral lips of the mouth
or medial to the ventral cirri of anterior segments. However, in Mustaquimsthenelais the outer
basal knob of the ventral cirrus is not elongate, whereas in Willeysthenelais it is variable. The
degree of papillation on the ventral side of the body should also be considered in
distinguishing the two genera. In Mustaquimsthenelais the ventral surface is smooth, whereas
members of Willeysthenelais, except W. bandaensis, have papillae on the ventral surface.
It should be noted, according to Wehe (2007), that the outer palpal sheaths are
small, the elytral surface has simple or branched papillae and/or microtubercles and the elytral
margin has branched and/or simple papillae.
The characters in bold text in the above diagnosis are particularly important in
recognizing members of this genus, although they are not necessarily autapomorphies of the
genus. It is the combination of these characters that distinguishes Mustaquimsthenelais.
The so-called 'ctenidia' on the dorsal surface of the tentacular parapodia in
Mustaquimsthenelais (as being adopted by both Pettibone (1971) and Wehe (2007)) has
recently been renamed 'dorsal tentacular crests' by Aungtonya (2003).
Key to Mustaquimsthenelais species
(adapted from Pettibone (1971), Wehe (2007), and this study).
– Medial base of ventral cirri with branched papillae, with up to 12 side branches; outer
lateral margin of elytra with a fringe of branched papillae….….……….………………
……………………………………………….…...….. M. dendropapillata Wehe, 2007
– Medial base of ventral cirri with 2–3 simple, long papillae; outer lateral margin of
elytra with simple papillae.….……………………….…. M. heterochela (Horst, 1917)

6
Mustaquimsthenelais dendropapillata Wehe, 2007
Figs. 1A–G, 2A–S
Mustaquimsthenelais dendropapillata Wehe 2007: 78–82, figs. 10–12.
Material examined. SMBL Inv-10001, 1 specimen, Tanabe Bay, Wakayama, Japan,
33°40.87´N, 135°19.72´E, R/V Janthina III, Smith-McIntyre grab, 28 m, coll. Tetsuya Kato,
16 June 2003.
Description. Body about 33 mm long and 5 mm wide including parapodia, with about 52
segments, posterior end lost.
Prostomium dorsally fused with tentacular parapodia; ceratophore of median
antenna stout, cylindrical, with large subtriangular auricles, located on anterior fourth of
prostomium; style of median antenna rather long (Figs. 1A–B, 2A); lateral antennae short,
located on dorsal side of tentacular parapodia, without ceratophore. Eyes and nuchal organs
present. Dorsal tentacular crests present. Inner tentacular lobes with median ciliated ridge.
Segment 2 with ventral buccal cirri. Segment 3 with dorsal tubercles, dorsal cirri absent.
Branchiae present from segment 2. Ventral surface smooth, numerous papillae present on
posterior and ventral surfaces of neuropodia. Ventral cirri with elongate papilla at medial
base, with up to 6 side branches, resembling the gill of a eunicid (Figs. 1D–E, 2B–D); ventral
cirri with outer basal knob, not elongate.
Elytral surface mostly smooth, on anterior segments with microtubercles confined
to anterior and medial regions, on following segments with microtubercles confined to
anterior regions; margin of elytra on anterior segments with long papillae, from about
segment 10 with up to 13 papillae, including branched papillae with up to 8 filaments (Figs.
1C, 2N–S).
Notopodia with posterior upper lobe and anterior lower lobe, anterior upper lobe
inconspicuous. Notochaetae simple, coarsely to finely spinous capillaries. Neuropodia with
inconspicuous posterior upper and lower lobes, fimbriated; without distinct anterior upper
lobe, anterior lower lobe inconspicuous, fimbriated (Fig. 2B–C). Compound neurochaetae in
C-shaped group heterocheligers, stout, with greatly elongated and curved inner distal tooth;
upper group of heterocheligers more slender; normal bidentate falcigers with articulate blade
present in lower group, distal part of stem smooth; a few upper simple spinous capillaries
present (Figs. 1F–G, 2E–M).

7
Figure 1 Mustaquimsthenelais dendropapillata (SMBL Inv-10001): A. anterior end, dorsal
view; B. Close-up of A, showing prostomium; C. Outer lateral margin of elytron, with
branched papillae; D. Ventral surface and ventral cirri; E. Parapodium from anterior segment,
arrow indicates branched papilla at medial base of ventral cirrus; F–G. SEM micrographs on
heterocheliger. Scales = 100 µm (F) and 20 µm (G). Abbreviations: au, auricle; ct, ctenidium;
lan, lateral antenna; man, median antenna; pa, palp; vc, ventral cirrus; and vcp, papilla at
medial base of ventral cirrus.
C
D
A B
E
vc vcp
ct
lan
au
man
pa
G
F

8
Figure 2 Mustaquimsthenelais dendropapillata (SMBL Inv-10001): A. Anterior end, dorsal
view, B. Parapodium of segment 27, posterior view; C. Anterior view of same; D. Close-up of
ventral cirrus, with branched medial papilla; E–M. Neurochaetae from same; N, R. Left
elytron from segment 4 and 48, position of scar indicated; P. Left elytron from anterior
segment; O, Q, S. Enlargement of single papilla showing details of papilla. Scales = 1.0 mm
(A–C, N, P, R) and 0.1 mm (D–M, Q), and 0.05 mm (O, S). Abbreviations: au, auricle; bk,
basal knob on ventral cirrus; ct, ctenidium; dtcr, dorsal tentacular crest; lan, lateral antenna;
man, median antenna; pa, palp; vc, ventral cirrus; and vcp, papilla at medial base of ventral
cirrus.
A
B C
E F
I
H
G J
D
au
K L M
P
Q
man
dtcr
lan
pa
bk
vc
vcp
ct
N
O
R
S

9
Remarks. The characters of the present specimen match quite well with those of M.
dendropapillata, as described and figured by Wehe (2007), and also resemble those of M.
heterochela in particular in having neurochaetae with a greatly elongated inner tooth on the
bifid heterogomph falcigers. However, M. heterochela differs from M. dendropapillata in
having 2–3 long papillae at the medial base of the ventral cirri, papillae along the outer lateral
margin of the elytra that are simple, lacking a fringe of branched papillae, elytra are notched,
and normal bidentate falcigerous neurochatae are absent, whereas in M. dendropapillata most
segments have a papilla at the medial base of the ventral cirri with up to 6–12 side branches
(resembling the gills of some eunicids), the outer lateral margin of the elytra has a fringe of
branched papillae (as similarly found in Sigalion and Euthalenessa), the elytral notch are
absent and normal bidentate falcigerous neurochatae are present (Table 1).
The medial base of ventral cirri in the present specimen has 6 side branches (or
filaments), whereas there are up to 12 branches in the specimen examined by Wehe (2007).
The elytral surface of the present specimen has microtubercles confined to anterior regions
and the papillae on the elytral surface are not branched, suggesting variation in appearance of
these characters as compared to the species account and illustration provided by Wehe (2007:
anterior third to half of the elytral surface densely covered with microtubercles; and
arborescent-branched papillae (with up to 4 filaments per papilla) may be present
submarginally along the outer edge). Furthermore, the elytral margin of the present specimen
has long papillae, with up to 13 branched papillae (up to 8 filaments per papilla), whereas the
illustration in Wehe (2007: Fig. 10b, d) showed 18–28 branched papillae, with up to 11
filaments per papilla. The specimen described by Wehe (2007) has only anterior fragment, the
length is about 53 mm, and the body width at segment 64, including chaetae is 6 mm, which
is not much different compared to the present specimen (5 mm wide including chaetae). The
difference of various characters between the two specimens seems not to be a growth-related
variation. A degree of variation in appearance of similar structure (papillae number and
filament per papilla) is also evident in certain species of Euthalenessa, as mentioned by
Pettibone (1970). In E. oculata, the anterior elytra have branched papillae varied in a range of
7–19, with 2–14 per papilla.
Although Wehe (2007) only mentioned in the diagnosis of the genus
Mustaquimsthenelais and M. dendropapillata that the third segment has no dorsal cirri, but
such character was illustrated in Figure 10a of his publication. However, appendages on
segment III, when present, can either be dorsal tubercles or dorsal cirri (Aungtonya, 2003). In

10
the present specimen, the dorsal tubercles of segment III are present. The illustration of dorsal
cirrus (Wehe, 2007: Fig. 10a) might be erroneous.
Mustaquimsthenelais dendropapillata is recently known only from Pakistan in the
Indian Ocean and Japan in the West Pacific Ocean. Future studies should attempt to collect
more specimens within the vast gap of area.
Distribution. Pakistan (Arabian Sea): intertidal and Japan (Tanabe Bay): at 28 m.
Mustaquimsthenelais heterochela (Horst, 1917)
Fig. 3A–N
Sthenelais heterochela Horst, 1917: 113, pl. 23, figs. 3–6. – Phasuk 1992: 81, part (st. 1027).
Willeysthenelais heterochela. – Pettibone 1971: 23–24, fig. 14.
Material examined. PMBC 20379, 1 specimen, Fifth Thai-Danish Expedition, st. 1027, haul
2, 7º43´N, 98º57´E, Smith-McIntyre grab, 10 m, muddy to clayey sand, 18 Jan 1966.
Description. Specimen posteriorly incomplete, about 80 mm long and 4 mm wide including
parapodia, about 5 mm wide including chaetae, with about 112 segments.
Prostomium dorsally fused with tentacular parapodia; ceratophore of median
antenna stout, cylindrical, with large subtriangular auricles, located on anterior fourth of
prostomium; style of median antenna rather long; lateral antennae short, located on dorsal side
of tentacular parapodia, without ceratophore. Eyes and nuchal organs present. Dorsal
tentacular crests present. Inner tentacular lobes with median ciliated ridge. Palps extend to
segment 8, with prominent inner palpal sheath, outer sheath indistinct. Segment 2 with ventral
buccal cirri. Segment 3 with dorsal tubercles, dorsal cirri absent. Branchiae present from
segment 4. Ventral surface smooth, 1–2 papillae present on posterior and ventral surfaces of
neuropodia. Ventral cirri with 2 long papillae at medial base, beginning at about segment 7;
with outer basal knob, not elongate (Fig. 3A–B).
Elytral surface smooth except for area along anterior borders covered with
microtubercles; margin with long papillae (Fig. 3I–J, Table 1); elytra on middle segments
with lateral notch.
Notopodia with posterior upper lobe and anterior lower lobe, anterior upper lobe
inconspicuous. Notochaetae simple, coarsely to finely spinous capillaries. Neuropodia with

11
inconspicuous posterior upper and lower lobes, fimbriated; without distinct anterior upper
lobe, anterior lower lobe inconspicuous, fimbriated (Fig. 3A–B). Compound neurochaetae in
C-shaped group heterocheligers, with greatly elongated and curved inner distal tooth, stout
with distal part of stem smooth; upper and lower groups of heterocheligers more slender; a
few upper simple spinous capillaries present (Fig. 3C–H).
Remarks. The characters of the present specimen agree well with Mustaquimsthenelais
heterochela as described and figured by Pettibone (1971; as Willeysthenelais heterochela),
based on the holotype, which is 5 mm in width, including chaetae. This species is
characterized by having simple long papillae on the medial base of the ventral cirri and simple
papillae along the elytral margin. Regarding differences between M. heterochela and M.
dendropapillata, see remarks on M. dendropapillata and Table 1.
It should be noted that an elytral notch is present on the middle segments of the
present specimen, whereas it is present on anterior and middle regions according to Pettibone
(1971).
The specimen was identified as Sthenelais heterochela by Phasuk (1992) in a
checklist with information on distribution but without description or comments.
Distribution. Indonesia (Sanana Bay, E. Sulawesi) and Thailand (Andaman Sea); at 10–22 m.

12
Figure 3 Mustaquimsthenelais heterochela (PMBC 20379): A. Parapodium of segment 14,
posterior view; B. Anterior view of same; C–E, G–H. Neurochaetae (compound
falcigers) from same; F. Upper neurochaeta (simple, spinous capillary) from same; I,
M. Left elytron from anterior and posterior segments, position of scar indicated; K.
Left elytron from segment 38; J, L, N. Enlargement of papillae on elytral margin.
Scales = 1.0 mm (A–B, I, K, M), 0.1 mm (C–H, L, N), and 0.05 mm (J).
Abbreviations: bk, basal knob on ventral cirrus; vc, ventral cirrus; vcp, papillae at
medial base of ventral cirrus.
A
C
B
D E F H
G
J
I
bk vc vcp
M
K
L
N

13
Table 1 Comparison of characters of known species of Mustaquimsthenelais adapted from
Pettibone (1971), Wehe (2007), and this study.
Charatcters M. dendropapillata Wehe, 2007 M. heterochela (Horst, 1917)
Elytral surface
elytra with microtubercles confined to anterior
regions, or extended onto anterior third to half;
arborescent-branched papillae may be present
along outer submarginal edge
elytra mostly smooth, with
microtubercles confined to
anterior border regions
Elytral margin
anterior segments with long papillae; following
segments with up to 28 papillae, including
branched papillae (with up to 11 filaments per
papilla)
with numerous long papillae
Elytral notch absent present
Papillae on medial base
of ventral cirri branched papilla, with up to 12 filaments simple long, with up to 3
filaments
Normal bidentate
falcigerous neurochaetae
with articulate blade
present absent
ACKNOWLEDGEMENTS
This study was supported by the Phuket Marine Biological Center (PMBC),
Thailand, the Global Taxonomic Initiative (GTI) and the Natural Geography In Shore Areas
(NaGISA) Project.
I am indebted to Assoc. Prof. Danny Eibye-Jacobsen (Zoological Museum,
Copenhagen University, Denmark), my former Ph.D. supervisor who introduced me to the
study of polychaetes, for his guidance and help in improving this manuscript. I express my
appreciation to Dr. Dieter Fiege (Forschungsinstitut Senckenberg, Frankfurt/Main, Germany)
for providing valuable comments, Mr. Alexander Muir (the Natural History Museum, United
Kingdom) for improving the English. Sincere thanks are given to Dr. Tetsuya Kato, Seto
Marine Biological Laboratory (SMBL), Japan, for inviting me to study the sigalionids of
Tanabe Bay at the SMBL, providing valuable comments on the manuscript, and for his kind
assistance in SEM study at SMBL, and to Dr. Somchai Bussarawit (PMBC) and Prof.
Yoshihisa Shirayama (SMBL) for their encouragement. I am grateful to the staff of the SMBL
for their generous hospitality, assistance and making my visit more pleasant. Thanks also to

14
the staff of the Reference Collection (PMBC) for their kind assistance and Mr. Patirat
Singdum, the PMBC artist, for making the drawings.
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