Munida pollioculus, Komai, Tomoyuki & Higashiji, Takuo, 2016

Komai, Tomoyuki & Higashiji, Takuo, 2016, New records of the squat lobster genus Munida Leach, 1820 (Crustacea: Decapoda: Anomura: Munididae) from deep-water off Okinawa Islands, Ryukyu Islands, Japan, with description of a new specie, Zootaxa 4109 (5), pp. 542-554: 543-547

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Munida pollioculus

n. sp.

Munida pollioculus  n. sp.

[New Japanese name: Chihiro-chu-koshiori-ebi] ( Figs 1View FIGURE 1, 2View FIGURE 2)

Material examined. Holotype: East of Kunigami Village, Okinawa Island, 26 ° 46.955 ’N, 128 ° 30.941 ’E, 1000 m, 15 September 2005, bait trap, coll. A. Kaneko & T. Higashiji, 1 female (cl 16.9 mm), infested by rhizocephalan, CBM-ZC 11348.

Description. Carapace (excluding rostrum) ( Fig. 1View FIGURE 1 A) 1.2 times as long as wide. Dorsal surface gently convex transversely; main transverse ridges mostly uninterrupted medially; few secondary transverse striae intervening main ridges on anterior part (anterior to cervical groove); most ridges and striae with row of short setae. Gastric region slightly elevated, with 5 pairs of epigastric spines (second pair just behind supraocular spines strongest, 2 lateral pairs obsolescent) plus 1 scale-like median tubercle; postrostral carina low, obsolescent. Cervical groove distinct. Parahepatic, branchial dorsal and postcervical spines present. Anterior part of branchial region between cervical groove and transverse groove with some short, scale-like ridges; posterior part of branchial region with 6 main transverse ridges (excluding posterodorsal ridge) and a few short secondary striae laterally between main ridges. Cardiac region with 3 main transverse ridges. Intestinal region with pair of short striae, but medially without ridges or stria; posterodorsal ridge distinct, slightly convex medially, with 1 secondary stria. Frontal margins slightly oblique. Anterolateral spines each located at anterolateral angle, strong, slightly overreaching level of sinus between rostrum and supraocular spines. Second marginal spine anterior to cervical groove also strong, though distinctly shorter than anterolateral spine. Branchial margins each with 5 small spines decreasing in size posteriorly.

Rostrum ( Fig. 1View FIGURE 1 A) spiniform, about 0.4 times as long as carapace, slightly sinuous in lateral view; lateral margins with minute denticles. Supraocular spines about 0.3 length of rostrum, slightly diverging distally and slightly ascending in lateral view. Inner orbital spine curved laterally, clearly visible in dorsal view.

Pterygostomial flap bluntly pointed anteriorly with minute granules ( Fig. 1View FIGURE 1 E); anterior margin minutely granulate: lateral face rugose with obliquely transverse ridges.

Thoracic sternite 3 ( Fig. 1View FIGURE 1 B) 1.3 times wider than long, distinctly separated from sternite 4, much wider than anterior width of sternite 4; anterior margin faintly granulate, with shallow, V-shaped median notch; anterolateral angles pointed, directed anterolaterally. Sternite 4 with transverse ridge adjacent to anterior margin; ventral surface shallowly concave medially, with paired short scale-like ridge adjacent to midline. Sternites 5–7 smooth. Transverse ridges dividing sternites nearly smooth, with sparse short setae.

Pleomere 2 ( Fig. 1View FIGURE 1 A) with 1 distinct transverse ridge on tergum; anterior ridge with 4 pairs of strong spines. Pleomere 3 ( Fig. 1View FIGURE 1 A) with 1 medially interrupted stria and 1 transverse ridge on tergum, unarmed on anterior ridge. Fourth pleomere with 1 medially interrupted stria and 1 transverse ridge on tergum, anterior ridge, unarmed. Pleura of pleomeres 2–4 each with scale-like or short ridges. Pleomere 5 with 2 transverse ridges on tergum. Pleomere 6 ( Fig. 1View FIGURE 1 C) with 1 laterally interrupted stria anterior to midlength and broadly W-shaped groove on posterior half, otherwise smooth; posterior margin tri-lobed. All ridges or striae on pleomeres with fringe of short setae. Telson ( Fig. 1View FIGURE 1 D) 1.2 times as wide as long, incompletely divided in 7 plates; several scale-like ridges present on posterolateral and posteromesial plates.

Eyes ( Fig. 1View FIGURE 1 A) small. Cornea slightly longer than eyestalk, not dilated, corneal width slightly greater than width between rostrum and supraocular spine and 0.13 cl. Eyestalk widened distally; eyelashes absent.

Basal article of antennular peduncle ( Fig. 1View FIGURE 1 A, E) moderately stout, length excluding distal spines 1.8 of width; distal spines unequal with mesial spine much shorter than lateral; 2 lateral spines present, distal spine located proximal to base of distolateral spine, directed somewhat upward, extending as far as distolateral spine, proximal spine located slightly distal to midlength of article; statocyst lobe weakly inflated, ventral surface rounded, with scattered minute tubercles and tufts of short setae.

Antennal peduncle ( Fig. 1View FIGURE 1 A, E) moderately stout, overreaching distal corneal margins by length of fourth article. First article with moderately long distomesial spine overreaching midlength of second article; distolateral angle unarmed. Second article with distomesial spine reaching distal end of fourth article, distolateral spine much shorter, slightly falling short of distal end of third article; mesial and lateral margins with few minute tubercles. Third article with minute spine at distomesial angle, unarmed on distolateral angle. Fourth article unarmed.

Third maxilliped ( Fig. 2View FIGURE 2 A) moderately slender. Ischium distinctly longer than merus, with tiny ventrodistal spine, extensor distal angle unarmed; lateral surface with some scale-like tubercles. Merus not markedly narrowed distally, flexor margin with 2 greatly unequal spines, distal spine tiny, proximal spine prominent, arising slightly proximal to midlength; extensor distal margin unarmed; extensor margin and lateral face with several small tubercles. Exopod narrowing distally, distinctly overreaching distal margin of merus; lateral surface with minute tubercles.

Cheliped (first pereopod) ( Figs 1View FIGURE 1 F; 2 B, C) about 2.4 times as long as carapace. Merus with row of 8 spines on dorsal surface laterally (spines increasing in size distally, distolateral spine diverging) and 2 prominent spines distomesially (distal spine stronger than distolateral spine); lateral face with numerous scale-like tubercles becoming larger ventrally and with strong spine at ventrodistal angle; mesial face with 3 well-spaced strong spines adjacent to ventral margin (distalmost spine at ventromesial distal angle) and scattered tiny tubercles; ventral surface with scattered tiny to small scale-like tubercles, distal edge of these tubercles usually multidenticulate, bearing short setae. Carpus 1.2 times as long as palm, 2.3 times longer than distal width; dorsolateral margin with 4 spines noticeably increasing in size distally (distalmost spine located at dorsolateral distal angle), dorsomesial margin with 5 spines (second spine strongest, somewhat diverging); lateral face with several scale-like tubercles (distal edges multidenticulate) and 1 small subterminal spine; mesial face with scattered scale-like tubercles and 1 strong subdistal spine; ventral surface also with scattered scale-like tubercles and small spine at ventrodistal angle. Palm 2.6 times longer than wide; dorsal surface with row of 3 moderately strong spines on proximal 0.6 of midline, dorsolateral margin 4 spines increasing in size distally, dorsomesial margin with 3 spines also increasing in size distally, articular condyle with small spine; mesial face without conspicuous spines; surfaces with scale-like tubercles of various size. Fixed finger straight, terminating in sharp claw; lateral margin with 2 small subdistal spines, 1 moderately strong spine somewhat proximal to midlength and row of tiny, low protuberances; cutting edge straight, with row of minute, rounded denticles interspersing tiny triangular teeth. Dactylus 1.1 times as long as palm, without conspicuous spines, terminating in sharp, curved claw crossing tip of fixed finger; mesial margin with row of low tubercles; cutting edge with row of minute, rounded or triangular denticles over entire length, no hiatus between dactylus and fixed finger. Setae primarily plumose (no iridescent setae present), most arising from tubercles or bases of spines, length variable, particularly long and numerous on mesial faces of merus and carpus.

Ambulatory legs (second to fourth pereopods) moderately long and slender, second and third pereopods subequal in length, fourth pereopod shorter than preceding pereopods. Second pereopod ( Fig. 2View FIGURE 2 D), when anteriorly extended, falling slightly short of tip of rostrum by tip of mero-carpal articulation, about twice of carapace length; merus 1.4 times as long as carapace, extensor margin with row of numerous setae and row of 10 (left) or 13 (right) spines noticeably increasing in length distally, flexor margin with 1 strong distolateral spine followed by 3 smaller spines and scale-like tubercles, lateral face with scattered scale-like tubercles and short setae, flexor distal margin with 1 small subterminal spine on mesial side; carpus with prominent extensor distal spine followed by 1 or 2 small spines on extensor margin, flexor distal margin produced in spine, lateral face with weak longitudinal ridge dorsally and few small scale-like tubercles ventrally; propodus with sparse tufts or individual long setae on extensor margin, lateral surface with some low, scale-like tubercles ventrally; mesial surface with row of numerous plumose setae adjacent to extensor margin, flexor margin with row of 9 (left) or 10 (right) evenly spaced movable spines, all but distalmost spine arising from low protuberances, distalmost spine supported by contiguous acute fixed spine, ventromesial distal margin with 1 movable spine; dactylus ( Fig. 2View FIGURE 2 E) 0.6 times as long as propodus and 5 times longer than greatest width, slightly curved distally, bearing sparse short to long stiff setae, flexor margin mostly straight, with 9 or 10 slender corneous spinules, increasing in length distally, along entire length and 1 very slender subterminal spinule contiguous with unguis. Third pereopod ( Fig. 2View FIGURE 2 F) similar to second pereopod, though shorter; merus bearing row of 8 (right) or 10 (left) spines on extensor margin, flexor margin with 1 moderately strong distolateral spine followed by 3 or 4 smaller spine and scale-like tubercles or ridges; carpus with 2 spines on extensor margin; propodus with 8 or 9 movable spines on flexor margin; dactylus with 9 spinules on flexor margin (except for subterminal contiguous spinule). Fourth pereopod ( Fig. 2View FIGURE 2 G) falling short of anterolateral angle of carapace by mero-carpal articulation; merus 0.8 length of that of second pereopod, extensor margin with small distal spine and some tiny spines or spinulose tubercles proximally, flexor margin with strong distolateral spine following by 1 small spine and scale-like ridges or tubercles, flexor mesial margin with 1 small subdistal spine; carpus with extensor distal spine and flexor distal spine, distinctly smaller than those of preceding pereopods; propodus with 6 or 7 movable spines on flexor margin; dactylus with 9 corneous spinules on flexor margin.

Merus of fifth pereopod slightly rugose on lateral surface.

Uropodal exopod with row of minute movable spinules on nearly straight lateral margin, distal margin truncate, also with row of closely spaced movable spinules; outer surface with sets of 1–4 minute movable spinules laterally. Endopod ( Fig. 1View FIGURE 1 D) with row of scale-like tubercles and distal row of minute movable spinules distally, extending onto truncate distal margin; outer surface with scale-like ridges or tubercles, each bearing 1–4 minute movable spines on distal edge. Uropodal protopod ( Fig. 1View FIGURE 1 D) with small spine on inner distal margin.

Coloration in life. Not known.

Distribution. Known only from the type locality, off Okinawa Island, at depth of 1000 m.

Remarks. The present new species resembles closely M. clevai  and M. microps  , sharing many diagnostic characters, e.g., (1) branchial margin bearing five spines, (2) pleomere 2 with row of spines on anterior ridge while pleomere 3 unarmed, (3) no granules on thoracic sternites 6 and 7, (4) eye small, (5) basal article of antennular peduncle with distomesial spine much shorter than distolateral spine, (6) distomesial spine of second article of antennal peduncle reaching distal end of fourth article, (7) fixed finger of cheliped armed with one or more spines on lateral margin in addition to subterminal spines, and (8) dactylus of second pereopod with accessory spines along entire length of flexor margin. Munida microps  has been recorded from rather wide areas in the Indo-West Pacific (e.g., Alcock 1894, 1901; Kemp & Sewell 1912; Tirmizi 1966; Macpherson 1994, 1996, 1997; Macpherson & de Saint Laurent 2002; Macpherson 2004; Baba 2005), but some workers pointed out possibilities of misidentifications in literature or the presence of closely related species under the name ( Macpherson 1994; Ahyong & Poore 2004; Baba 2005). Therefore, we refer to Baba (2005: 116), who examined a topotypic specimen from the Andaman Sea, for comparison. The new species differs from M. clevai  and M. microps  in the absence of a proximal spine on the mesial margin of the cheliped dactylus and the clearly stouter dactylus of the second pereopod (5 times as long as wide versus 10 times as long) ( Baba 2005; Macpherson 2009). Furthermore, the frontal margin of the carapace is more strongly oblique in M. clevai  (cf. Macpherson 2009, fig. 2 A) than in the new species (cf. Fig. 1View FIGURE 1 A) and M. microps  . The fixed finger of the cheliped has two or three spines in M. microps  , instead of only one relatively strong spine in M. pollioculus  n. sp. and M. clevai  .

The new species is also substantially similar to M. endeavourae Ahyong & Poore, 2004  known from southeastern Australia, Tasmania, Norfolk Ridge, Kermadec Ridge and Bay of Plenty, New Zealand ( Ahyong & Poore 2004; Ahyong 2007; with M. grieveae Vereshchaka, 2005  as a junior subjective synonym) in the small eyes, armature and ornamentation of the carapace, pleon, antennae and pereopods. Munida endeavourae  was actually misidentified with M. microps  by Haig (1973) ( Ahyong & Poore 2004). Nevertheless, Munida pollioculus  n. sp. differs from M. endeavourae  in many characters, such as relatively stout basal article of antennular peduncle, the shorter distomesial spine on the second article of the antennal peduncle (reaching to the distal end of the fourth article of the antennal peduncle versus clearly overreaching it), the presence of a proximal spine on the cheliped dactylus and the presence of a single strong spine on the lateral margin of the fixed finger of the cheliped, instead of two small spines M. endeavourae  . The cheliped palm seems to have more numerous spines in M. endeavourae  (cf. Ahyong & Poore 2004: fig. 5 e) than in M. pollioculus  n. sp. (cf. Fig. 1View FIGURE 1 F).

Etymology. From the Latin pollus (= small) and oculus (= eye), referring to the small eye in this new species. Used as a noun in apposition.