Munidopsis myojinensis, Cubelio, Sherine Sonia, Tsuchida, Shinji, Hendrickx, Michel E., Kado, Ryusuke & Watanabe, Seiichi, 2007

Cubelio, Sherine Sonia, Tsuchida, Shinji, Hendrickx, Michel E., Kado, Ryusuke & Watanabe, Seiichi, 2007, A new species of vent associated Munidopsis (Crustacea: Decapoda: Anomura: Galatheidae) from the Western Pacific, with notes on its genetic identification, Zootaxa 1435, pp. 25-36 : 27-31

Munidopsis myojinensis , n. sp.

( Figs. 2–5 )

Material examined. Type material. Holotype: ovigerous female, 26.11 mm (NSMT-Cr16877), taken by manned submersible, Shinkai 2000 , dive # 2K 1009 and the support ship Natsushima from Myojin Knoll 32°06.29’N, 139° 52.19’ E, 7 May 1998, 1288 m. Allotype: 1 male, 22.05 mm (NSMT-Cr16879), NW Eifuku Seamount, 21°29.24’N, 144°02.48’E, 27 October 2005, 1625 m, dive HD# 492. Other paratypes: 1 male, 20.54 mm ( LACM CR2004 -019.1), NW Eifuku Seamount, 21°29.26’ N, 144°02.50’E, 11 April 2004, 1573 m, R793-33-01; 1 female 24.26 mm ( USNM), NW Eifuku Seamount, 21°29.26’N, 144°02.51’E, 10 April 2004, 1576 m, R792-08-01; 1 female, 22.63 mm (NSMT-Cr16877), Myojin Knoll, 32°06.30’N ,, 139°52.04’E, 29 June 1999, 1340 m, Shinkai 2000 , dive # 2K 1112.

Additional material. Myojin Knoll: 1 female 24.48 mm (JAMSTEC 018307), 32°06.25’N, 139°52.17’E, 4 July 1999, Shinkai 2000 , dive # 2K 1116; 3 females, 27.4 mm, 23.19 mm, 18.75 mm, 1 male, 22.05mm (JAMSTEC 057776–057779), 32°06.21’N, 139°52.17’E, 25 June 2004, 1219 m, Hyper-Dolphin, dive # 312; 2 females, 21.66 mm, 22.54 mm (JAMSTEC 058045–058046), 32°06.21’N, 139°52.17’E, 25 June 2004, 1219 m, Hyper-Dolphin, dive # 312.

Northwest Eifuku Seamount: 2 females, 22.63 mm, 21.22 mm, 2 males, 20.40 mm, 21.79 mm (JAM- STEC 061128 – 061132), 21°29.252’N, 144°02.489’E, 27 October 2005, 1625 m, Hyper-Dolphin, dive # 492; 2 males, 17.95 mm 16.23 mm, 1 female, 17.06 mm (JAMSTEC 061325 – 061327), 21°29.24’N, 144°02.49’E, 27 October 2005, 1625m, Hyper- Dolphin, dive # 492; 1female, 19.30 mm (EMU-7229), 21° 29.26’N, 144°2.50’E, 11 April 2004, 1573 m, R793-33-01; 1 female, 20.25 mm, (EMU-7230), 21°29.26’N, 144°2.52’E, 10 April 2004, 1576 m, R792-08-01; 9 females, 26.20 mm, 22.29 mm, 27.61 mm, 21.71 mm, 17.27 mm, 19.07 mm, 28.77 mm, 21.22 mm, 25.75 mm (JAMSTEC 061241 – 061258), 21°29.252’N, 144°02.52’E, 29 October 2005, 1582 m, Hyper-Dolphin, dive # 494.

Diagnosis. Carapace covered with scale like short ridges; epigastric spine strong and well developed. Frontal margin oblique; antennal spine present, stronger than anterolateral spine. Lateral margin spinous, spine at end of anterior cervical groove long and strong. Rostrum long, triangular, serrated laterally, slightly upturned. Abdominal tergites unarmed; telson composed of 10 plates. Eyestalk immovable, eyespine long, cornea rounded. P1 bearing numerous elevated scaliform ridges and rugosites; fixed finger without denticulate ridge on distolateral surface. P2–4 relatively long and spinous; P2 reaching tip of P1. Epipods absent from pereopods.

Description. Carapace, exclusive of rostrum, distinctly longer than broad moderately convex transversely, anterior and posterior bifurcation of cervical groove distinct. Rostrum 0.21–0.23 times length of remaining carapace, almost horizontal, occasionally slightly upturned distally, moderately triangular with fine serrations on lateral margin, dorsal surface with sparse coarse setae and distinct median longitudinal carina merging into median tubercles on anterior gastric region. Strongly oblique frontal margin sweeping to antennal spine followed by a distinct anterolateral spine, additional 1 or 2 small spine between antennal and anterolateral spine. Gastric region moderately inflated with prominent pair of epigastric spines and adjacent 1 or 2 small spines (sometimes obsolete), followed by scale like setae but tuberculate, elevated rugae bearing sparse short setae. Cardiac region with moderate, transverse elevation preceded and flanked by distinct grooves. Anterior branchial region with strong lateral spine followed by successively diminishing 4 or 5 spines. Posterior branchial region with strong lateral spine, rugosites with tendency to being transversely continuous across central part of cardiac region. Pterygostomian flap with obliquely interrupted rugae, distinct posteriorly, obsolescent anteriorly, anterior margin angular.

Abdomen unarmed, transverse ridge on segments 2 or 3 with sparse short stiff setae, segments 4–6 almost smooth, segment 6 with posteromedian margin almost transverse, distal margin of lateral lobes convex. Telson composed of 10 plates, length width ratio 0.78–0.92, median lateral plate fringed with long stiff setae. Eyes moderate in size, well exposed, cornea cupped within broad based immovable ocular peduncle, strong mesiodorsal eyespine directed anterolaterally and reaching mid length of rostrum.

Basal article of antennular peduncle, exclusive of spines, somewhat longer than broad, dorsolateral inflation bearing tubular process often developed into spines, distolateral spine well developed, distoventral mesial margin scalloped, contiguous with small mesiodorsal spine.

Antennal peduncle having article 1 with flat ventral process ending in acute spine and much smaller distolateral spine, article 2 with short distolateral spine, article 3 unarmed, article 4 with a crenulated scalloped ending.

Third maxilliped having ischium shorter than merus when measured in midlateral line, bearing mesial crest armed with finely uniform evenly spaced corneous tipped spines and distoventral spine. Basis with 2 or 3 corneous spines in line with crest on ischium. Merus with 4 irregular small spines on flexor margin and small spine at disto dorsal corner. Dactylus reaching proximal end of ischium when folded.

Thoracic sternum broadened posteriorly. Sternite 3 forming apposed lobe at either side of mid line, irregularly serrate on margin.

First pereopod (P1) 1.70–1.81 times as long as carapace excluding rostrum, bearing numerous tuberculate, elevated scaliform ridges and rugosites, long plumose setae more dense ventrally along distomesial margin of merus and carpus. Ischium with mesial row of several spines on distal portion and 1 spine on ventral margin, merus with a row of 4 strong spines terminally, preceded by a row of spines dorsally, 2 or 3 spines ventromesially, often irregular tubercles all along merus. Carpus with well-developed acute spine mesially somewhat proximal to junction with palm, followed by a few spines slightly dorsal, 2 distodorsal spines. Propodus spiny, often with 4 distoventral and 2 distolateral spines; ventral surface tuberculate. Fingers longer than palm (up to 1.25 times in females and 1.5 times in males), slightly curved, opposable margins forming spooned shaped cavity; cutting edges closely fitted, with very fine teeth and tuffs of setae; tips close fitted, spooned; fixed finger without denticulate carina on distolateral surface.

Pereopods 2–4 (P2–4) relatively long, P2 almost reaching tip of P1, corresponding segments of respective pereopods nearly equal in length. Merus with dorsal crest bearing row of spines, ventrolateral margin with strong terminal spine followed by small spines or tubercles, mesially and laterally with row of tubercles or scales. Carpus with tuberculate lateral ridge in parallel with row of dorsal marginal spines. Propodus 1.8 times as long as dactylus, more setose on merus and carpus, especially on mesial face, with two longitudinal tuberculate dorsal ridges, dorsomesial ridge often bearing few spines, dorsolateral in line with preceeding segments. Dactylus stout, setose, ending in short, curved, corneous claw preceded by 11–13 successively diminishing teeth on flexor margin, each tooth bearing short stiff setae arising from its base.

Epipods absent from pereopods.

Eggs few, measuring 2.1 x 2.3 mm in diameter.

Etymology. Named after the type locality Myojin Knoll, a noun in the genitive.

Va r ia ti o n. The material we examined indicates that females are larger than males. In females, P2 is slightly longer than P1 (cheliped) and reaches or slightly overreaches the tip of P1 when extended. In males, P2 is about the same length as P1, falling just short of the tip of P1 when extended. The telson is broader in females than in males. Both of the aforementioned variations are sexual dimorphic. The number of gastric spines shows considerable variation. Most specimens (including the holotype), bear a prominent pair of epigastric spines, but in few paratypes, it is accompanied by 1 or 2 obsolete lateral spines. The eyespine is directed anterolaterally in holotype and a few paratypes, and directed forwards in the remainder.

Remarks. Munidopsis myojinensis closely resembles M. starmer in general ornamentation and spination of the body. The eyespine of M. myojinensis almost reaches half of the rostrum and is directed anterolaterally, whereas M. starmer features a much smaller eyespine compared to rostral length, abdominal segment 6 with a rounded, protruding posterolateral flap distinctly overreaching the posteromedian margin and overhanging anterior junction between the telson and uropodal protopod. Munidopsis myojinensis is characterized by transverse abdominal segment 6 without a protruding posterolateral flap. This character links the new species to M. lauensis , but these two species have clearly different spination of the carapace and cheliped. Munidopsis myojinensis is also allied to M. subsquamosa in the carapace spination, but distinguished by the more spinous and tuberculate P1, absence of epipods, and the more strongly curved corneous claws on the dactyli of P2–4.

Distribution. Deep-sea hydrothermal vents viz, Myojin Knoll, 1219–1224 m, in South of Japan and Northwest Eifuku Seamount, 1582–1625 m, in North Mariana Arc.

Molecular analysis. A clear genetic differentiation between M. myojinensis and M. lauensis from different vent sites (i.e., Desmos, Hine Hina, Mariner Sites and Brothers Seamount in the Western Pacific)was obtained ( Fig. 6 ). This is the first report on the genetic identification of vent associated Munidopsis from Western Pacific using a molecular marker, and it shows that both M. myojinensis and M. lauensis form reciprocally monophyletic clusters on the NJ tree. Monophyly of the both species is supported by a high bootstrap proportion (100%) and few or no differences between specimens of the same species obtained from different localities.

Habitat and ecology. Myojin Knoll consists of many small chimneys, 1–3 m height, and a larger chimney of about 20 m height emitting vigorous transparent hydrothermal fluids. The vent site is characterized by a predominance of deep-sea mussels and barnacles. Dense beds of mussel, Bathymodiolus septemdierum Hashimoto & Okutani, 1994 and deep-sea barnacles, Ashinkailepas seepiophila Yamaguchi, Newman & Hashimoto, 2004 and Neoverruca sp. were observed. Alvinocaridid shrimp, Alvinocaris brevitelsonis Kikuchi & Hashimoto, 2000 , bythograeid crab, Austinograea yunohana Takeda, Hashimoto & Ohta, 2000 and few aggregations of sea anemones were also observed in the video footage. There were thick bacterial mats in the substratum. Munidopsis species were seen crawling on the vicinity of the chimneys in the video image ( Fig. 3 c), most among mussels.

The fauna of Northwest Eifuku Seamount was different from that of Myojin Knoll. Substrate was characterized with volcanic rocks with thick bacterial mass. Barnacles abundant in Myojin Knoll were totally absent. Two species of alvinocaridid shrimps, Alvinocaris brevitelsonis and Opaepele loihi Williams & Dobbs, 1995 and a few bythograeid crabs, Austinograea yunohana were observed. Munidopsis were seen either among the deep-sea mussels, mostly seen idle or swiftly swimming back beating their abdomen when some disturbances occur. The density of Munidopsis was higher than that of Myojin Knoll ( Fig. 3 d).

Figures

FIGURE 2. Munidopsis myojinensis holotype female (NSMT-Cr 16877), a, carapace, lateral; b, right P 1, dorsal; c, right P 2, lateral; d, dactylus of P 2, lateral e, thoracic sternum, f, endopod of right third maxilliped; g, posterior part of abdomen and telson; h, left antennal peduncle, ventral view; i, left antennular basal article, ventral. Scales: a, b, c = 3 mm; e, g = 3 mm; d, f, h, i = 1 mm.

FIGURE 3. Munidopsis myojinensis holotype female (NSMT-Cr 16877), a, dorsal view, b, lateral view, c, in-situ photograph of Myojin Knoll sampling site; d, in – situ photograph of Northwest Eifuku Seamount sampling site.

FIGURE 4. Munidopsis myojinensis paratype male (LACM CR 2004 - 019.1); a, carapace, frontal region, dorsal; b, right anterior part of carapace, lateral; c, right P 1, dorsal; d, left P 1, dorsal, with details of merus, ventral; e, thoracic sternum; f, right P 2, lateral; g, right P 5, lateral. Scales = 3 mm.

FIGURE 5. Munidopsis myojinensis paratype male (LACM CR 2004 - 019.1); a, right antennal peduncle, dorsal (right) and ventral (left) views; b, left third maxilliped, ventral, and dorsal view of merus; c, left antennular basal article, ventral; d, telson, dorsal. Scales: a – c = 1 mm; d = 3 mm.

FIGURE 6. Genetic relationships between Munidopsis myojinensis and M. lauensis based on DNA sequences. Munida taenia is the outgroup.