琉球大学学術リポジトリ
ヤワゲヤドリカニダマシ ( 新称 ) Polyonyx haigae
McNeil, 1968 ( 甲殻亜門 : 十脚目 : 異尾下目 :カニダマシ科 ) の琉球列島からの記録
メタデータ

言語: en
出版者: 琉球大学資料館 (風樹館)
公開日: 2022-09-20
キーワード (Ja):
キーワード (En):作成者: 大澤, 正幸, 藤田, 喜久
メールアドレス:所属:

URL

http://hdl.handle.net/20.500.12000/0002019452

Fauna Ryukyuana

ISSN 2187-6657
https://fauna-ryukyuana.webnode.jp

Polyonyx haigae McNeil, 1968 (Crustacea: Decapoda: Anomura: Porcellanidae)
from the Ryukyu Islands, southwestern Japan1

Masayuki Osawa1 & Yoshihisa Fujita2

Estuary Research Center, Shimane University, 1060 Nishikawatsu-cho, Matsue, Shimane, 690-8504 Japan(osawam@soc.shimane-u.ac.jp)
2
Okinawa Prefectural University of Arts, 1-4 Shuri-Tounokura-cho, Naha, Okinawa, 903-8602 Japan(fujitayo@okigei.ac.jp)

Abstract. Polyonyx haigae McNeil, 1968, a poorly
known species of the porcellanid genus Polyonyx
Stimpson, 1858, is recorded for the first time fromJapanese waters based on material collected from
Oura Bay in Okinawa Island of the Ryukyu Islands,
southwestern Japan. This represents the third recordof the species and extends the distribution range
more northward and eastward than the previous
record from the Nansha Islands in the South China
Sea. The present two specimens occurred as aheterosexual pair in a tube of an unidentified speciesof the polychaete genus Chaetopterus Cuvier, 1830.
This symbiotic habit has been also known for manyof the other species of the P. sinensis group to which
P. haigae belongs.
Introduction
The Ryukyu Archipelago, defined as the entire island
chain between Kyushu main island of southern
Japan and Taiwan, harbors a large variety of coastal
environments, such as estuarine embayments andfringing lagoons as well as exposed coral and rocky
reefs and boulder beaches. Recent studies on infaunaof decapod crustaceans using commercial suction
pumps (yabby pumps) for extraction of specimensfrom sediments have brought many findings of new
species and rarely recorded taxa from the tropicalwestern Pacific, particularly in the Ryukyu Islands(e.g., Komai 2009; Naruse et al. 2009, 2017; Anker
et al. 2015; Komai & Anker 2015; Komai et al.
2015, 2020; Naruse 2015; Osawa et al. 2018; Komai& Fujita 2019). As a part of continuous works on
estuarine porcellanids in the Ryukyus, this article
reports a poorly known species, Polyonyx haigae
McNeil, 1968 from Okinawa Island, as new to theJapanese fauna. The two specimens examined werecollected using a yabby pump from subtidal sandbottom and found as a heterosexual pair living
symbiotically with a buried and tube-dwelling

polychaete of the genus Chaetopterus Cuvier, 1830.
Material and methods
The specimens examined are deposited in the
University Museum, Fujukan, University of the
Ryukyus, Okinawa (RUMF). The morphologicalterminology used in the description follows Osawa& Chan (2010) and Osawa (2015). For the third
maxilliped, the “external” surface is regarded as“lateral” surface when the appendage is opened,
and the use of “dorsal” and “ventral” for respective“extensor” and “flexor” margins, is applied to thedescription (cf. Osawa & Chan 2010: fig. 48a).
Carapace length (cl) was measured from the anterior
median tip of the rostrum to the posteromedianmargin of the carapace. Measurements of thechelipeds were made as follow: carpus length along
the posterior margin and width between the anterior
and posterior margins at its maximum, chela length
along the anterior margin and breadth along thedorsodistal transverse line of the palm, and dactylus
length along the posterior margin. Measurementsof the ambulatory legs were made as follow: merus
length along the dorsal margin and height between
the dorsal and ventral margins at its maximum,
carpus length along the dorsal margin, propodus
length on the lateral midline and height between
the dorsal and ventral margins at its maximum anddactylus length along the dorsal margin (from thedorsopoximal end of the article to the tip of theventral claw).
Taxonomic AccountFamily Porcellanidae Haworth, 1825
Genus Polyonyx Stimpson, 1858
Polyonyx haigae McNeil, 1968
[New Japanese name: Yawage-yadori-kanidamashi](Figs. 1–4)
41

Polyonyx haigae McNeil, 1968: 38, text fig. 2,
pl. 1-fig. 1 (type locality: Linden Bank, northside entrance to Trinity Passage, east of Cairns,
Queensland; 37 fms). — Osawa & McLaughlin
2010: 114 (list).
Polyonyx plumatus Yang & Xu, 1994: 115, fig. 3(type locality: 3°59.81´N, 112°05.16´E, Nansha
Islands, South China Sea; 56 m). — Osawa &McLaughlin 2010: 115 (list).
Material examined. RUMF-ZC 6108, 1 male (cl6.0 mm), 1 ovigerous female (cl 7.0 mm), Oura
Bay, Nago, Okinawa Island, Ryukyu Islands,“Umisaboten” point, depth of 4–5 m, sand, in tube of
Chaetopterus sp., SCUBA diving with yabby pump,coll. Y. Fujita, 13 September 2010.
Description. Carapace (Fig. 1A, B) transversely
hexagonal in general outline of dorsal view, 1.1–1.2
times as broad as long (proportionally broader
in female), broadest on anterior margins. Dorsal
surface moderately convex from side to side, highest
on cardiac region, entirely covered with short, soft
plumose setae, those on lateral branchial regions
longer. Protogastric ridges demarcated, blunt.
Cervical grooves moderately deep. Hepatic margins
gently convex. Branchial margins subparallel,
somewhat constricted on anterior one third tomedian parts; anterior margins strongly convex, thin;posterior margins and adjacent regions with shortand long transverse ridges. Rostrum (Fig. 1A, C)
moderately broad, distinctly reaching beyond anterior
margin of eyes, produced in dorsal view, ventrally
bent toward anterior tip; trilobate in anterior view,
median lobe rounded, overreaching rounded laterallobes, with shallow median longitudinal groove;
dorso-anterior surface with row of moderately longplumose setae. Orbits shallow, supra-orbital margins
slightly concave, lateral orbital angles rounded.

Pterygostomian flaps (Fig. 1F, G) entire, withshort and long longitudinal ridges and moderately
long, soft plumose setae; dorso-anterior marginterminating in narrow rounded tip.
Third thoracic sternite (Fig. 1D) 3.4–3.8 times as
broad as long measured on midline (proportionallybroader in female), with surface somewhat convex
medially; anterior margin gently convex on broad
median margin, with row of moderately long setae;
lateral lobes narrow, produced, each with rounded
apex. Fourth thoracic sternite with anterior marginmoderately concave; surface depressed medially,
with transverse series of short granular ridges
bearing sparse short setae anteriorly.
Telson (Fig. 1E) 1.2–1.4 times broader than long(proportionally broader in female), composed of
7 plates; lateroproximal plates much smaller thanothers; distal plates each longer than broad.
Ocular peduncles (Fig. 1A, F, G) small, short;
dorsal extension on to cornea weak, rounded.
Basal article of antennular peduncles (Fig. 1H)
broader than long; anterior margin convex, slightly
undulate; ventral surface with transverse ridge ofsmall tubercles anteriorly and short rows of small
tubercles medially; ventro-anterior face slightly
concave.
Antennal peduncles (Fig. 1A, F, G) slender,
nearly smooth, bearing sparse short plumose setae on
surfaces. First article comparatively short and broad,
0.6–0.7 length of combined second to fourth articles,
produced forward in lateral view, in contact withlower orbital margin; surface shallowly concave,
bearing sparse minute setae, blunt ridge along
ventral margin; anterior margin tapering, terminatingin subacute apex. Second and third articles roundly
rectangular, third article elongate. Fourth article
short, rounded.
Third maxilliped (Fig. 1I–K) with coxa

Fig. 1. Polyonyx haigae McNeil, 1968. Male, cl 6.0 mm (A, C–L); ovigerous female, cl 7.0 mm (B); RUMF-ZC 6108.
A, carapace and ocular and antennal peduncles, dorsal view (setae drawn only on left side); B, carapace, dorsal view;C, rostrum, dorso-anterior view; D, third and fourth thoracic sternites, ventral view (surface setae drawn only on rightside); E, telson, external view; F, carapace, pterygostomial flap, and ocular and antennal peduncles, right ventral view;G, same, right lateral view; H, basal article of right antennular peduncle, ventral view; I, right third maxilliped, lateralview (for setae, only soft plumose setae drawn); J, same, merus and distal part of ischium, perpendicular lateral view; K,
same, exopod, perpendicular lateral view; L, right gonopod, dorsal view. Plumose setae shown simplified. Scale bars = 1.0mm.
図 1. ヤワゲヤドリカニダマシ ( 新称 ). 雄 , cl 6.0 mm (A, C–L); 抱卵雌 , cl 7.0 mm (B); RUMF-ZC 6108. A, 頭胸甲 ,
眼柄 , および第 2 触角柄 , 背面観 ( 剛毛は左側のみ図示 ); B, 頭胸甲 , 背面観 ; C, 額角 , 前方背面観 ; D, 第 3 および第 4 胸板 , 腹面観 ( 腹面の剛毛は右側のみ図示 ); E, 尾節 , 外面観 ; F, 頭胸甲 , 側甲 , 眼柄 , および第 2 触
角柄 , 右側腹面観 ; G, 同 , 右側側面観 ; H, 右第 1 触角柄の基部節 , 腹面観 ; I, 右第 3 顎脚 , 側面観 ( 剛毛については，軟羽状毛のみ図示 ); J, 同 , 長節および座節の基部 , 垂直側面観 ; K, 同 , 外肢 , 垂直側面観 ; L, 右生殖肢 ,背面観 . 各部の剛毛の内 , 羽状剛毛は単純化して図示 . スケール = 1.0 mm.
42[ 報告 ] 大澤・藤田 : 琉球列島産ヤワゲヤドリカニダマシ ( 新称 ).

Fauna Ryukyuana, 65: 41–51.

[Report] Osawa & Fujita: Polyonyx haigae from the Ryukyus.

43

Fig. 2. Polyonyx haigae McNeil, 1968; male, cl 6.0 mm; RUMF-ZC 6108. Right larger cheliped (first pereopod). A,
entire, dorsal view (surface setae partially drawn); B, same, ventral view; C, ischium and merus, dorsal view; D, carpus,
perpendicular dorsal view; E, chela, perpendicular dorsal view; F, same, anterior view; G, dactylus and fixed finger,
posterior view; H, same, perpendicular ventral view. Plumose setae shown simplified. Scale bar = 1.0 mm.
図 2. ヤワゲヤドリカニダマシ ( 新称 ), 雄 , cl 6.0 mm; RUMF-ZC 6108. 右大鉗脚 ( 第 1 胸脚 ). A, 全体 , 背面観 ( 背面の剛毛は一部を図示 ); B, 同 , 腹面観 ; C, 座節および長節 , 背面観 ; D, 腕節 , 垂直背面観 ; E, 鉗部 , 垂直背面
観 ; F, 同 , 前面観 ; G, 指節および不動指 , 後面観 ; H, 同 , 垂直腹面観 . 各部の剛毛の内 , 羽状剛毛は単純化して図示 . スケール = 1.0 mm.
44[ 報告 ] 大澤・藤田 : 琉球列島産ヤワゲヤドリカニダマシ ( 新称 ).

Fauna Ryukyuana, 65: 41–51.

bearing blunt projection on ventrodistal margin;
distomedian projection with blunt transverse ridge,
not articulated. Basis articulating with ischium,subtriangular. Ischium broad, with ventral margin
strongly convex; lateral surface with short transverse
ridges and longitudinal ridge along dorsal margin;
dorsodistal projection small, blunt. Merus withlaminate, roundly subrectangular lobe laterally onventral margin; lateral surface with short transverse
ridges and longitudinal row of short ridges along
dorsal margin; laterodistal margin with row of longsoft plumose setae. Carpus nearly smooth on lateralsurface, with subtriangular projection on submedianpart of ventral margin. Propodus slender, nearlysmooth on lateral surface. Dactylus moderately long,subtriangular. Merus to dactylus with long plumose
setae on ventral margins. Exopod with proximal
article small, rounded; distal article laminate, robust,reaching distal margin of merus, constricted on
median part; lateral surface bearing sparse longsoft plumose setae and with row of numerous shortridges dorsally; distal flagellum present.
Chelipeds (first pereopods; Figs. 2A–H, 3A–F) unequal in size, degree of unequality stronger inmale, length subequal in female; entire morphology
generally similar between male and female; dorsal
surface covered with short and very short striaeof microscopic granules, striae each bearing row
of short plumose setae; dorso-anterior margin anddorsoposterior surface of meri and dorso-anterior
surface of chela with dense long, soft plumose setae.
Larger cheliped (Fig. 2A–H) with ischium rounded
and bearing row of short ridges on anterior margin.
Merus with rounded transverse crest submedially on
dorsal surface; dorso-anterior margin with narrow,rounded lobe distally, margin slightly crenulate;ventral surface with short transverse striae; ventroanterior margin with row of short ridges of granules,
ventrodistal margin with row of small tubercles.
Carpus 1.8 times as long as broad, broadest on
median part; dorsal surface moderately convex;
dorso-anterior margin entirely with gently convex
lobe, anterior margin of lobe with row of small bluntand subacute denticles, proximal and distal cornersof lobe rounded; dorsodistal margin with large
rounded lobe on posterior part; posterior marginrounded, delimited by row of short transverse ridges;
ventral surface with short transverse striae and sparse
short plumose setae on anteroproximal part; ventroanterior margin slightly concave on distal one third.
Chela 1.4 times as long as carpus, moderately broad,
2.3–2.4 times as long as broad, lying on anterior[Report] Osawa & Fujita: Polyonyx haigae from the Ryukyus.

side; anterior margin nearly straight on medianpart, delimited by row of short ridges of granules
on proximal half and single row of small blunt andsubacute denticles on distal half. Palm somewhat
inflated; dorsal surface convex; dorsoposterior
margin rounded, delimited by row of transverse
ridges; ventral surface strongly convex, with shortridges of microscopic granules on anterodistally,
distoproximal part with scattered plumose setae
extending fixed finger. Fixed finger with small,curved distal claw, weaky recurved dorsally; dorsal
surface flattish; cutting edge with large median tooth,margin composed of row of small blunt and subacutedenticles generally decreasing in size distally.
Dactylus 0.4 length of chela, opening at obliqueangle, with strongly curved distal claw; dorsal
surface convex proximally and flattish distally, withlongitudinal ridge composed of row of small bluntand subacute denticles along posterior margin;
cutting edge strongly concave on distal half, withmoderately large tooth proximally, margin with row
of small blunt denticles generally decreasing in size
distally, some denticles larger; ventral surface withshort plumose setae along cutting edge,
Smaller cheliped (Fig. 3A–F) generally similar
to larger cheliped in shape, but narrower and moresetose, particularly on chela. Carpus 1.8–2.0 times
as long as broad. Chela 3.1–3.4 times as long as
broad (proportionally broader in female); dorsal
surface less convex than in larger cheliped; anterior
margin slightly concave on median part; cutting edgeof fixed finger with large but low tooth medially,
margin with row of small, nearly equally-sizedblunt and subacute denticles; ventral margin of fixed
finger with small blunt subdistal tooth. Dactylus
proportionally longer, 0.5 length of chela, opening at
more strongly oblique angle than in larger cheliped,with slender distal claw; cutting edge nearly straighton proximal half and strongly concave on distal
half, margin with row of small blunt and subacutedenticles greatly decreasing in size on distal half.
Ambulatory legs (second to fourth pereopods,
P2–4; Fig. 3G–M) moderately short, decreasing insize posteriorly (P2 largest), compressed laterally;
meri, carpi, and propodi with rows of long, soft
plumose setae on dorsal and ventral margins;
dactyli with sparse tufts of short plumose setae on
surfaces. Ischia each with weakly calcified part
dorsodistally on mesial surface. Meri 3.0–3.4 (P2),
2.5–2.6 (P3), and 2.2–2.3 (P4) times as long as highin lateral view, highest on median parts; P2 merus
1.1 and 1.5–1.6 times lengths of respective P3 and45

Fig. 3. Polyonyx haigae McNeil, 1968; male, cl 6.0 mm; RUMF-ZC 6108. A, left smaller cheliped, merus to chela,dorsal view (setae not drawn); B, same, chela, perpendicular dorsal view; C, same, chela, anterior view; D, same,
dactylus and fixed finger, posterior view; E, same, fixed finger and distal part of palm, perpendicular ventral view; F,
same, dactylus, perpendicular ventral view; G, right second pereopod, lateral view; H, same, merus, mesial view; I,
same, propodus and dactylus, lateral view; J, same, propodus, ventral view; K, right third pereopod, lateral view (setae
not drawn); L, same, dactylus, lateral view; M, right fourth pereopod, lateral view (setae not drawn). Plumose setae
shown simplified. Scale bars = 1.0 mm.
図 3. ヤワゲヤドリカニダマシ ( 新称 ), 雄 , cl 6.0 mm; RUMF-ZC 6108. A, 左小鉗脚 , 長節 – 鉗部 , 背面観 剛毛は不図示 ); B, 同 , 鉗部 , 垂直背面観 ; C, 同 , 鉗部 , 前面観 ; D, 同 , 指節および不動指 , 後面観 ; E, 同 , 不動指および掌部の末部 , 垂直腹面観 ; F, 同 , 指節 , 垂直腹面観 ; G, 右第 2 胸脚 , 側面観 ; H, 同 , 長節 , 内面観 ; I, 同 ,前節および指節 , 側面観 ; J, 同 , 前節 , 腹面観 ; K, 右第 3 胸脚 , 側面観 ( 剛毛は不図示 ); L, 同 , 指節 , 側面観 ; M,
右第 4 胸脚 , 側面観 ( 剛毛は不図示 ). 各部の剛毛の内 , 羽状剛毛は単純化して図示 . スケール = 1.0 mm.
46[ 報告 ] 大澤・藤田 : 琉球列島産ヤワゲヤドリカニダマシ ( 新称 ).

Fauna Ryukyuana, 65: 41–51.

P4 meri; dorsal margins slightly crenulated, gently
convex; lateral surfaces slightly convex ventrally,
with scattered pits bearing sparse very short setae;
mesial surfaces flattish, with short transverse ridges
of granules bearing short and moderately longsetae on dorsal and ventral parts, dorsodistal parts
weakly calcified; ventral surfaces slightly convex;
ventrodistal margins of lateral and mesial surfaces
rounded. Carpi slender, long (P2 and P3) andmoderately short (P4); P2 carpus 1.2 and 1.6–1.7
times lengths of respective P3 and P4 carpi; dorsal
margins each with row of very short ridges; lateralsurfaces with scattered pits bearing short and very
short setae; mesial surfaces with short granularridges and small pits bearing short and moderately
long setae; ventral margins rounded, with somesmall tubercles distally; dorsodistal and ventrodistal
corners rounded. Propodi 3.5–3.7 (P2), 3.5–3.6 (P3),
and 3.2–3.5 (P4) times as long as high, highest on
median parts; dorsal margins nearly smooth; lateraland mesial surfaces with scattered pits bearing
sparse short setae; mesial surfaces with short
granular ridges and small pits bearing short setae;
ventral surfaces flattish, with irregularly arranged
longitudinal rows of corneous, acute and blunt
spines, numbers of rows decreasing from 3 or 4 to 2
(P2 and P3) or 1 (P4) toward distal end, total numberof spines approximately 30–40; distoventral margin
with 2 corneous spines subequal in size. Dactyli
0.4 lengths of propodi, each terminating in curved,
sharply pointed, bifurcate claws, dorsal claw muchsmaller than ventral claw; ventral margins each with
2 or 3 teeth decreasing in size proximally, each toothwith small corneous spine.
Fifth pereopod slender, chelate; propodus withnumerous short simple setae and 1 or 2 subdistal
hooked setae.
Male with pair of gonopods on second pleomere(Fig. 1L); endopod elongate oval, rounded distally,slightly curled and bearing short setae marginally;
exopod small, elongate oval.
Female with no pleopods on third pleomere, butwith well developed pleopods on fourth and fifth
pleomeres.
Coloration in life. Carapace brown or reddish
brown, with small and large, white blotches on
median brachial, anterior cardiac, and intestinal
regions. Chelipeds also brown or reddish brown on
dorsal surface, with irregular white blotches on carpi
and palms. Ambulatory legs white, with irregular,
small brown blotches. Plumose setae pale brown.
See Fig. 4.
[Report] Osawa & Fujita: Polyonyx haigae from the Ryukyus.

Distribution. Previously only known from
Linden Bank in the Great Barrier Reef, Australia(McNeil 1968), and the Nansha Islands in the South
China Sea (as P. plumatus; Yang & Xu 1994). Now
from Okinawa Island in the central Ryukyu Islands,
southwestern Japan. This is the second record of P.
haigae from the northern hemisphere and extends its
distribution northward and eastward.
Habitat. The holotype of P. haigae and the two
type specimens of P. plumatus were collected frommud or sandy mud at depths of 37 fms (67.7 m)
and 56–57 m, respectively (McNeil, 1968; Yang &Xu, 1994), but their hosts or accompanying animals
were not recorded. The present two specimens from
Okinawa Island were collected from the sand bottomof an embayment area which was much shallower(4–5 m) than in the previous reports. They occurred
as a heterosexual pair (male smaller than female)in a tube of an unidentified species of the genus
Chaetopterus, although the host polychaete and its
parchment tube were not preserved.
Remarks. Yang & Xu (1994) described Polyonyx
plumatus as a new species from the Nansha Islands(Spratly Islands) in the South China Sea, andcompared with only Eulenaios cometes (Walker,
1887) (as Polyonyx). Werding (2001: 109) consideredP. plumatus as a junior synonym of P. haigae,
because the status of the former species was not fully
discussed in the original description and it seemed tobe identical with the latter species. Nevertheless, thecomparison of the illustrations of the holotypes ofP. haigae and P. plumatus shows that the shapes of
the carapace and rostrum are different. The anterior
branchial margin of the carapace is strongly inflated
in P. haigae unlike in P. plumatus. The median lobeof the rostrum is much narrower and more sharply
pointed in P. haigae than in P. plumatus (McNeill
1968: text fig. 2a, b, pl. 1-fig. 1; Yang & Xu 1994:
fig. 3A, B). The specimens examined of Okinawa
Island agree well with the holotype of P. haigae ingeneral morphological aspect and specimen size(carapace length: 6.0–7.0 mm versus 5.3 mm in theholotype) except having a broader and blunt medianrostral lobe, which is rather similar to that of P.
plumatus instead. The difference in the carapace
branchial margins can be related to the growth since
the carapace is much larger in the holotype of P.
haigae than the type material of P. plumatus (5.3mm instead of 3.1–3.6 mm in the carapace length).
Additionally, the dactylus of the ambulatory leg has
two ventral marginal spines and the distal spine issmaller than the proximal spine in the holotype of P.
47

Fig. 4. Polyonyx haigae McNeil, 1968, RUMF-ZC 6108, coloration of fresh specimens, dorsal view. A, male, cl 6.0mm; B, ovigerous female, cl 7.0 mm.
図 4. ヤワゲヤドリカニダマシ ( 新称 ), RUMF-ZC 6108, 新鮮な標本の体色 , 背面観 . A, 雄 , cl 6.0 mm; B, 抱卵雌 ,cl 7.0 mm.
48[ 報告 ] 大澤・藤田 : 琉球列島産ヤワゲヤドリカニダマシ ( 新称 ).

Fauna Ryukyuana, 65: 41–51.

haigae (McNeill 1968: text fig. 2c) unlike the distal
spine is larger in P. plumatus (Yang & Xu 1994:
fig. 3G–I) and the present specimens from Okinawa
Island. In porcellanids, the spines on the ventral
margin of the ambulatory dactylus usually becomelarger towards the tip of the distal claw in general(e.g., Osawa & Chan 2010; Osawa et al. 2018);
those spines illustrated by McNeill (1968) mightshow an abnormal or artificial condition. The present
specimens support that P. haigae and P. plumatus aresynonymous rather than separate species, as notedby Werding (2001).
Polyonyx haigae belongs to the P. sinensis group,
an informal species group of the genus definedby Johnson (1958), characterized particularly byhaving the ambulatory dactyli each with the dorsal
claw much smaller than the ventral claw. Among 19
Indo-West Pacific species of the group (cf. Osawa
2018; Osawa et al. 2018; Werding & Hiller 2019;
Osawa & Sato 2022), P. haigae appears closest
to P. transversus (Haswell, 1882), known only
from Australian coasts in having the following
characters (for morphology of P. transversus, cf.
Haig 1965; Poore 2004): branchial margins ofcarapace subparallel and not strongly convex;
carpus of each cheliped with row of dense, longplumose setae on dorso-anterior margin; meri of
ambulatory legs unarmed on each posterior margin;
and propodi of ambulatory legs with more than
12 spines on each ventral margin. Nevertheless,P. haigae is distinguished from P. transversus by
the carapace being narrower (1.1–1.2 versus about
1.4 times as broad as long) and bearing scatteredplumose setae instead of no setae on the dorsal
surface, the median lobe of the rostrum being
distinctly produced anteriorly in dorsal view (in P.
transversus, the front is transverse, with the median
lobe being very slightly produced), the carpus ofeach cheliped bearing dense plumose setae insteadof at most some setae on the posterior margin, andthe propodi of the ambulatory legs armed with much
more numerous spines on the posterior surfaces.
The original description of P. haigae by McNeill(1968) cites “Lower margin of propodus (of walkinglegs) covered with about four irregular longitudinalrows of very minute spinules, about 16 spinules ineach row”, whereas in P. transversus, “Propodus ofwalking legs with more than 12 spinules along lower
margin” as noted by Haig (1965) and Poore (2004).
The present two specimens from Okinawa Island
have approximately 30–40 acute and blunt corneous
spines on the ventral (lower) surface of each
[Report] Osawa & Fujita: Polyonyx haigae from the Ryukyus.

ambulatory propodus, which are only 50 to 60% of
the numbers of spines described for the holotypeof P. haigae. Nevertheless, P. haigae still has more
numerous spines on the ambulatory propodi than in P.
transversus.
Polyonyx haigae is also similar to P. pedalis
Nobili, 1906 and three related new species, P. heok,
P. kumejima, and P. planus, described by Osawa &Ng (2016) and known from the Ryukyu Islands, ingeneral morphology of the carapace and pereopods.
Among them, P. heok has been recorded from thesubtidal bottom of Oura Bay where the present
material of P. haigae was obtained (Osawa & Ng2016). Both P. haigae and P. heok were collectedfrom inside of tubes of Chaetoprerus species in Oura
Bay, although it is unknown if the host polychaete
species are the same. Polyonyx haigae is readily
distinguished from all four congeners by a carapace
with scattered short plumose setae on the dorsal
surface, the meri of the ambulatory legs without
denticles or spines on the ventral margins, andthe presence of a pair of gonopods on the second
abdominal segment in male. In P. heok, P. kumejima,
P. pedalis, and P. planus, the plumose setae on the
carapace and male gonopods are absent.
Acknowledgements
The field survey in Oura Bay, Okinawa Island, wassupported by a research grant for “Nansei (Ryukyu)
Islands Biodiversity Evaluation Project” from WWF(World Wide Fund for Nature) Japan. We thank Shin
Nishihira (Sedake, Nago City) who kindly supported
the field work in Oura Bay.
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要旨 . 沖縄島の大浦湾から採集された標本に基づき , ヤワゲヤドリカニダマシ ( 新称 ) Polyonyx
haigae McNeil, 1968 を報告し , 詳細に記載した .
沖縄島の標本は , 本種の日本沿岸からの初記録 ,そして西太平洋域からの 3 番目の記録となる .
本種は , ツバサゴカイ属 Chaetopterus の未同定
種の棲管中から雌雄 1 対で得られた . ツバサゴ
カイ属の種との共生は , 本種が属する P. sinensis
種群の他の多くの種においても知られている .
投稿日 : 2021 年 7 月 28 日
受理日 : 2022 年 6 月 29 日
発行日 : 2022 年 9 月 16 日

ヤ ワ ゲ ヤ ド リ カ ニ ダ マ シ ( 新 称 ) Polyonyx
haigae McNeil, 1968 ( 甲殻亜門 : 十脚目 : 異尾
下目 : カニダマシ科 ) の琉球列島からの記録
大澤正幸 1・藤田喜久 2〒 690-8504 島根県松江市西川津町 1060 島根大学エスチュアリー研究センター (osawam@
soc.shimane-u.ac.jp)
2〒 903-8602 沖縄県那覇市首里当蔵町 1-4 沖縄
県立芸術大学 (fujitayo@okigei.ac.jp)
1[Report] Osawa & Fujita: Polyonyx haigae from the Ryukyus.

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