Bull. Natl. Mus. Nat. Sci., Ser. A, Suppl. 5, pp. 101–108, February 21, 2011

A New Species of the Squat Lobster Genus Munida (Decapoda:
Anomura: Munididae) from the North Pacific off Japan
Tomoyuki Komai
Natural History Museum and Institute, Chiba, 955–2 Aoba-cho, Chuo-ku, Chiba 260–8682, Japan
E-mail: komai@chiba-muse.or.jp

Abstract A new species of the squat lobster genus Munida Leach, M. ampliantennulata, is described and illustrated on the basis of two specimens from the Iwaki Seamount, off northeastern
Honshu, Japan, at a depth of 1744 m. It closely resembles M. magniantenulata Baba and Türkay
and M. subcaeca Bouvier, but the different structure of the basal segment of the antennular peduncle readily distinguishes the new species from the two relatives. This new species is the nineth of
the genus occurring at the bathyal depths greater than 1500 m worldwide.
Key words : Crustacea, Decapoda, Anomura, Munididae, Munida, new species, North Pacific,
Japan.

During a 2009 research cruise of the RV Soyomaru of the National Research Institute of Fisheries Science, Fisheries Research Agency, the bathyal to abyssal slope on the Iwaki Seamount, located nearly to the Japan Trench, east of
Fukushima Prefecture, was sampled using asmall beam trawl (benthos net). This data presents the first records of the marine fauna of thisseamount. Among the small collection of decapod crustaceans, two specimens of galatheid lobsters were found. Detailed examination has revealed that these specimens represent an undescribed species of Munida Leach, 1820. In thisstudy, this new species is described and illustrated under the name M. ampliantennulata. It appears closest to M. magniantennulata Baba andTürkay, 1992 known from the Lau Basin and off
Queensland, Australia, and M. subcaeca Bouvier,
1922 from the Atlantic, both known from depths
greater than 1000 m. Differentiating characters
between the new species and the two relatives are
discussed.
The type specimens are deposited in the Natural History Museum and Institute, Chiba (CBM)and the National Museum of Nature and Science,
Tokyo (NSMT). The measurement provided is
postrostral carapace length (CL), measured inmillimeters from the base of the rostral spine tothe midpoint of the posterior margin of the carapace. Higher classification follows that recently
proposed by Ahyong et al. (2010)
Taxonomic Account
Munida ampliantennulata sp. nov.
[New Japanese name: Kaizan-chu-koshiori-ebi](Figs. 1–3)

Material examined. Holotype: female (cl 7.0mm), Iwaki Seamount, 36°51.8N, 144°48.8E,1744 m, 9 August 2009, benthos net, RV Soyomaru, coll. Keiichi Kakui, CBM-ZC 10020.
Paratype: 1 juvenile (cl 4.0 mm), same data as
holotype, NSMT-Cr 21343.
Description. Holotype. Carapace (excluding
rostrum) (Figs. 1, 2A) 1.2 times longer thanwide. Dorsal surface gently convex transversely;
main transverse striae mostly interrupted; numerous short to moderately short secondary transverse striae present; most ridges and striae without setae. Gastric region slightly elevated, withpair of epigastric spines (these epigastric spines
appearing to arise from short spinulose ridges)
and scattered tiny granules laterally; postrostral

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Fig. 1. Munida ampliantennulata sp. nov., holotype, female (cl 7.0 mm), CBM-ZC 10020. Habitus, dorsal view,
showing coloration in fresh.

carina low, faintly tuberculate, extending frommidlength of rostrum to beyond level of epigastric spines. Cervical groove distinct. No conspicuous spines other than epigastric spines presenton dorsal surface. Anterior part of branchial region between cervical groove and transverse
groove with scattered granules. Frontal margins
very slightly oblique. Lateral margins feebly convex. Anterolateral spines each located at anterolateral angle, relatively small, distinctly posterior
to sinus between rostrum and supraocular spines.
Second marginal spine anterior to cervicalgroove less than 0.3 length of anterolateral spine.
Branchial margins each with 5 small spines, anteriormost spine larger than other spines.
Rostrum (Fig. 2A) spiniform, about 0.3 times
as long as carapace, nearly horizontal in lateralview. Supraocular spines relatively short andstout, slightly diverging anteriorly and veryslightly ascending in lateral view, not overreaching ocular peduncles, about 0.3 length of rostrum.
Pterygostomial flap (Fig. 1B) unarmed anteriorly, lateral face rugose with irregular transverse

New Munida from Japan103

Fig. 2. Munida ampliantennulata sp. nov., holotype, female (cl 7.0 mm), CBM-ZC 10020. A, carapace, abdomen and cephalic appendages, dorsal view (setae omitted); B, left pterygostomial flap, ventrolateral view;C, thoracic sternum, ventral view (setae on left side omitted); D, sixth abdominal somite, telson and left uropod, outer view (spinules on uropod and setae omitted); E, left eye, basal segment of antennular peduncle andantennal peduncle, ventral view; F, left third maxilliped, lateral view (setae omitted); G, left cheliped, dorsal
view. Scale bars: 2 mm for A, G; 1 mm for B–F.

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or obliquely transverse ridges.
Third thoracic sternite (Fig. 2C) about 3.4
times wider than long, slightly wider than anterior width of fourth sternite; anterior margin faintly granulate, without conspicuous median notch.
Fourth to sixth sternites smooth. Seventh sternitesmooth laterally. Transverse ridges nearlysmooth, with row of short setae.
Second abdominal somite (Fig. 2A) with 1 distinct transverse ridge on tergum; anterior ridge
unarmed. Third somite (Fig. 2A) with anteriorand 1 transverse ridges, unarmed anteriorly.
Fourth somite (Fig. 2A) only with anterior ridge,
unarmed. Telson (Fig. 2D) slightly wider thanlong; subdivision incomplete, but median suture
in posterior half clearly delimited.
Eyes (Fig. 2A) small. Cornea shorter than eyestalk, not dilated, corneal width subequal towidth between rostrum and supraocular spine
and 0.14 of carapace length. Eyestalk slightly
narrowed proximally; eyelash absent.
Basal segment of antennular peduncle (Fig.
2A, E) stout, length excluding distal spines about
1.4 of width; distal spines distinctly unequal withmesial spine distinctly shorter than lateral; 2 lateral spines present, distal spine slightly longer
than distolateral spine, proximal spine locatedsubdistally; statocyst lobe inflated, surface rounded.
Antennal peduncle (Fig. 2A, E) moderately
stout, reaching distal corneal margins. First segment with short distomesial spine not reaching
midlength of second segment; distolateral angle
unarmed. Second segment with small spine eachat distomesial and distolateral angles, spines
subequal, distomesial spine not reaching midlength of third segment. Third segment withminute spine at distolateral angle, unnamed on
distomesial angle. Fourth segment unarmed.
Third maxilliped (Fig. 2F) moderately slender.
Ischium distinctly longer than merus, withminute ventrodistal spine, dorsodistal angle unarmed. Merus slightly narrowed distally, ventral
margin with 2 strong, slightly unequal spines,
distal spine slightly smaller than proximal spine
arising at about midlength; dorsodistal marginunarmed. Carpus, propodus and dactylus unarmed; propodus not inflated.
Chelipeds (Figs. 2G, 3A–C) similar, subequalin length, about 2.0 times as long as carapace,
without setae-bearing short ridges on surfaces;
setae non-iridescent. Merus with row of 6 (right)
or 7 (left) spines on dorsal surface laterally(spines increasing in size distally, distalmost
spine much stronger than others and strongly diverging) and 2 spines mesially (spine at distomesial angle strong, second spine subdistal); lateralface with scattered tiny granules and spinulose
tubercles ventrally and with 1 strong spine onventrodistal angle; mesial face with moderately
strong subdistal spine, ventromesial margin with
2 spines (one at distoventral angle and one atabout midlength); ventral surface with scatteredspinules or short spinulose ridges; surfaces with
scattered simple setae and few long stiff setae
distomesially, mesial face with short plumose
setae. Carpus subequal in length to palm; dorsolateral margin with 5 small spines and few spinules (distalmost spine largest), dorsomesial margin with 4 spines (second spine strongest, strongly diverging); lateral face with few spinules or
granules and 1 spine located at about midlength;
mesial face with 1 moderately strong spine at
middle portion; ventral surface with few minutespinulose tubercles and with 1 distal spine. Palm
about 2.7 times longer than wide; dorsal surface
with row of 4 small spines along midline and 1
minute spine at articulation to dactylus, dorsolateral margin with 3 (left) or 4 (right) large spines(distalmost spine on right side located distal tobase of fixed finger), dorsomesial margin alsowith 3 strong spines; mesial face with 1 strong
spine slightly distal to midlength; ventral surface
with few short transverse ridges; fixed finger
straight, terminating in sharp claw, with 1 minutesubdistal tubercle laterally, cutting edge slightly
denticulate; surfaces with scattered short setae
dorsally, sparse long stiff setae laterally andmesially. Dactylus 1.1 times as long as palm, unarmed on dorsal surface, terminating in sharp,
curved claw crossing tip of fixed finger; lateral
margin unarmed, with several long stiff setae;

New Munida from Japan

105

Fig. 3. Munida ampliantennulata sp. nov., holotype, female (cl 7.0 mm), CBM-ZC 10020. A, merus of left cheliped, lateral view (setae omitted); B, same, ventral view; C, carpus of left cheliped, lateral view (setae omitted); D, left second pereopod (first ambulatory leg), lateral view; E, same, dactylus, lateral view (setae omitted); F, left third pereopod (second ambulatory leg), lateral view (setae omitted); G, left fourth pereopod(third ambulatory leg), lateral view (setae omitted). Scale bar: 1 mm for A–D, F, G; 0.5 mm for E.

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cutting edge faintly denticulate in proximal 0.8,
with row of minute teeth in distal 0.2; no hiatus
between dactylus and fixed finger.
Ambulatory legs (second to fourth pereopods)
moderately long and slender, slightly decreasing
in length posteriorly (Fig. 1). Second pereopod(Fig. 3D) about 1.9 times as long as carapace;merus about 0.7 times as long as carapace, about
7.1 times longer than high, dorsal margin withrow of sparse setae and 3 spines and a few spinules, distal spine strongest, ventral margin with 1strong distal spine followed by 3 small spines interspersed with short spinulose ridges, lateralface with scattered short setae; carpus about half
length of propodus, with prominent extensor distal spine, flexor distal margin produced in spine,lateral face with scattered short setae; propodus
unarmed on extensor margin, lateral face with
scattered short setae, flexor margin with row of 4
(left) or 6 (right) movable spines; dactylus (Fig.
3E) about 0.7 times as long as propodus, slightly
curved distally, bearing sparse short to long stiff
setae, flexor margin slightly sinuous, with 10 corneous spines notably decreasing in length proximally. Third pereopod (Fig. 3F) with merus bearing row of 7 spines increasing in size distally on
dorsal margin and row of tiny spines and shortspinulose ridges on ventral margin; carpus with 1
small extensor spine in addition to strong extensor distal spine; propodus with 6 movable spines
on flexor margin; dactylus with 10 corneous
spines on flexor margin. Fourth pereopod (Fig.
3G) reaching to lateral end of cervical groove of
carapace by mero-carpal articulation; merus
about 0.7 length of that of second pereopod, unarmed on dorsal margin, bearing short transverse
ridges on ventral margin; carpus with extensor
distal and flexor distal spines much smaller thanthose of preceding pereopods; propodus with 2(left ) or 5 (right) movable spines on flexor margin; dactylus with 8 movable spinules on flexor
margin.
Fifth pereopod without distinctive features.
Uropodal protopod (Fig. 2D) with 1 small
spine posteriorly.
Paratype. Differing from holotype in the fol-lowing points. Epigastric spines on carapace simple; dorsal striae less clearly delimited. Third
segment of antennal peduncle bearing minutedistolateral and distomesial spinules. Cheliped(only right side preserved) relatively shorter, andarmature and setation relatively weaker. Meri of
ambulatory legs with row of spinules on extensor
margins.
Coloration in fresh (Fig. 1). Body with very
limited pigmentation. Carapace light pink, becoming pale posteriorly. Ocular peduncles andantennal peduncles light pink, antennular peduncles semitransparent with tinge of pink. Cornea
brown. Chelipeds whitish, with tinge of pink on
fingers and spines on meri. Second to fifth pereopods whitish.
Distribution. Known only from the type locality, Iwaki Seamount, Japan, at a depth of 1744 m.
Remarks. Munida ampliantennulata sp. nov.
closely resembles M. magniantennulata known
from the Lau Basin and off Queensland, Australia (depth range 1223–2003 m), and M. subcaeca from the eastern and western Atlantic(depth range 842–1700 m) (Baba et al., 2008).
These three species have five spines on the
branchial margin of the carapace, the small
cornea (the corneal width is equal or less than the
distance between the sinus formed by thesupraocular and rostral spines), the enlarged
basal segment of the antennular peduncle, andthe small distomesial spine on the first segmentof the antennal peduncle, not reaching the midlength of the second segment (Bouvier, 1922;
Chace, 1942; Baba and Türkay, 1992).
The new species differs from both M. magniantennulata and M. subcaeca in the structure of
the basal segment of the antennular peduncle. In
M. ampliantennulata, the statocyst lobe is strongly inflated, and the lateral spines are located moredistally than in the latter two species. For example, the proximal lateral spine is located distinctly distal to the midlength of the basal segment in
the new species, rather than at the midlength in
the latter two species. Furthermore, M. ampliantennulata differs from M. magniantennulata in
the less convex hepatic margin of the carapace,

New Munida from Japanthe absence of a spine on the anterior part of the
branchial region, the possession of two ventral
spines on the merus of the third maxilliped, andthe relatively short palm of the cheliped, which is
subequal in the length to the carpus. In M. magniantennulata, the anterior part of the branchialregion bears one small spine; the merus of thethird maxilliped is armed with three ventral
spines; and the palm of the cheliped is distinctly
longer than carpus (Baba and Türkay, 1992).
From M. subcaeca, M. ampliantennulata is distinguished by having only one pair of epigastricspines on the carapace, instead of two or morepairs in M. subcaeca, and the less oblique frontal
margins of the carapace (Bouvier, 1922; Chace,
1942; Baba and Türkay, 1992). The size and position of the anterior two lateral spines on the
carapace are also different between the two
species. In M. ampliantennulata, the first spine islarger than the second spine, and it is located at
the anterolateral angle of the carapace. In contrast, in M. subcaeca, the two spines are subequal, and the first spine is located on the frontal
margin mesial to the anterolateral angle of thecarapace. Finally, in the new species, the second
spine is located at about the midlength of the hepatic lateral margin, whereas it is distinctly close
to the first spine in M. subcaeca.
De Grave et al. (2009) counted 246 species in
Munida, and subsequent to that publication, five
new species have been recently described byMacpherson (2009). Munida ampliantennulata is
one of the deepest inhabitants in the genus. Other
than the three species mentioned in this paper,
the following five species of Munida are known
to occur in the depths greater than 1500 m: M asprosoma Ahyong and Poore, 2004 (New South
Wales, Vanuatu and Taiwan, 277–1802 m; Baba
et al., 2009); M. curvipes Benedict, 1902 (southeastern Pacific off Chile, 1922 m; Benedict,1902); M. endeavourae Ahyong and Poore, 2007
(off southeastern Australia, Norfolk Ridge andKermadec Ridge, 620–1700 m; Ahyong andPoore, 2004; Ahyong, 2007); M. microphthalma
A. Milne-Edwards, 1880 (Atlantic Ocean,
621–2165 m; Baba et al., 2008); M. tiresias

107

Macpherson, 1994 (New Caledonia and Okinawa
Trough, Japan, 1140–2063 m; Macpherson,
1994; Osawa and Takeda, 2007).
Etymology. The Latin amplus (large) plus
antennula (antennule) plus tus (suffix denoting
possession) refers to the large basal segment of
the antennular peduncle.
Acknowledgments
I deeply thank Mr. Keiichi Kakui (Departmentof Natural History Sciences, Graduate School of
Science, Hokkaido University) for making available the interesting collection from Iwaki
Seamount for study. I also thank Drs. Enrique
Macpherson, Kareen E. Schnabel, and Hironori
Komatsu for reviewing the manuscript and foroffering valuable comments and suggestions for
improvements.
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