Sadayoshia acamar, Macpherson, Enrique & Baba, Keiji, 2012

Macpherson, Enrique & Baba, Keiji, 2012, The squat lobsters of the genus Sadayoshia Baba, 1969 (Crustacea: Decapoda: Anomura: Munididae): new records including six new species from the Pacific Ocean, Zootaxa 3589, pp. 30-48 : 31-34

Sadayoshia acamar n. sp.

( Figs. 1 , 7 A)

Sadayoshia lipkei Macpherson & Baba 2010: 436 (in part, specimens from Chesterfield Islands and some from New Caledonia).

Material examined. Holotype: Chesterfield Islands. CHALCAL 1984, Stn DC45, 20º48.93'S, 158º30.21'S, 50 m, 23 July 1984: ov. Ƥ 5.1 mm (MNHN-IU-2010-5377).

Paratypes: New Caledonia. Grotte Merlet, 20–30 m, 19–21 January 1993: 2 3 4.7–5.0 mm, 1 Ƥ 3.1 mm (MNHN-IU-2010-5383).

Chesterfield Islands. CHALCAL 1984, Stn DC45, 20º48.93'S, 158º30.21'S, 50 m, 23 July 1984: 2 ov. Ƥ 5.0– 5.1 mm (MNHN-IU-2010-5378, MNHN-IU-2010-5379).—Stn DC51, 21º13.21'S, 158º42.50'E, 55 m, 24 July 1984: 8 3 3.5–5.4 mm, 1 ov. Ƥ 4.7 mm, 1 Ƥ 4.0 mm (MNHN-IU-2010-5380, MNHN-IU-2010-5381).

Etymology. The name acamar refers to one of the stars of the southern hemisphere (constellation Eridanus). The name is considered as a substantive in apposition.

Description. Carapace: Slightly longer than broad; dorsal surface nearly horizontal from anterior to posterior; anterior cervical groove distinct. Dorsal surface with 4 pairs of epigastric spines, 1 parahepatic, 1 anterior branchial and 1 postcervical spine on each side; ridges with numerous short uniramous and some scattered long iridescent setae. Gastric region with 6 transverse ridges: first uninterrupted, second interrupted into 3 or 4 more or less scalelike ridges, third uninterrupted, fourth medially interrupted, fifth and sixth uninterrupted but short. Mid-transverse ridge uninterrupted, preceded by cervical groove. Posterior branchial region laterally with 5 ridges (excluding midtransverse ridge and posteriormost transverse ridges directly anterior to posterior margin of carapace). Lateral margins slightly or moderately convex, with 7 spines: first anterolateral and well developed; second smaller than first, situated at midlength between anterolateral spine and anterior cervical groove; third to fifth on anterior branchial margin, and sixth and seventh on posterior branchial margin. Rostrum 1.3 times as long as broad, length 0.6 that of carapace, rostral spine about 5.0 times longer than wide (measured at sinus between rostral and anterior lateral spines); dorsal surface convex from side to side, horizontal in profile; lateral margin with 2 spines. Pterygostomian flap rugose with sparse small ridges, ending in acute point.

Sternum: Sternal plastron as long as broad, lateral limits divergent posteriorly. Sternite 3 2.3 times as broad as long, anterior margin strongly convex, with small median notch. Sternite 4 1.9 times as long as and 2.7 times broader than preceding sternite, 3.3 times broader than long; surface with 2 medially interrupted, setiferous transverse ridges. Following sternites with 1 or 2 minute ridges. Lateral parts of sternite 7 without granules.

Abdomen: Somite 2 unarmed; somites 2–4 each with 2 uninterrupted transverse ridges and 1 additional interrupted transverse ridge between; ridges with numerous short setae and some scatteredlong iridescent setae.

Eyes: Ocular peduncles 1.2 times longer than broad; cornea moderately dilated, maximum corneal diameter about 0.4 times distance between bases of anterolateral spines; eyelashes short, not reaching midlength of cornea.

Antennule: Article 1 with 4 distal spines: mesial and medioventral spines clearly smaller than others, lateral largest; lateral margin with accesory small spine proximal to distolateral spine; ventral surface with a few short scales.

Antenna: Article 1 with distomesial spine reaching distal margin of article 2. Article 2 with distolateral spine terminating in midlength of article 3 and longer than distomesial spine. Article 3 with distomesial spine usually small, sometimes absent. Article 4 unarmed.

Mxp3: Ischium with small distal spine on flexor margin, extensor margin bluntly produced distally; crista dentata with 26–30 denticles. Merus subequal in length to ischium; flexor margin with 2 well-developed spines of subequal size, terminally unarmed or with small spine (in a few specimens); extensor margin unarmed. Carpus unarmed.

P1: 1.9 times carapace length, relatively stout, with sparse long uniramous iridiscent setae along lateral and mesial margins of merus, palm and fingers; dorsal and ventral surfaces of palm and fingers with scattered short setae. Merus 0.7 times length of carapace, 2.5 times length of carpus, with strong distal spines on dorsal and mesial margins, and a few small spines on dorsal surface. Carpus 0.6 times as long as palm, and 0.7 times as long as broad; dorsal surface with a few small spines; mesial margin with 2–3 well-developed spines. Palm 1.1 times longer than broad; with dorsolateral and mesial rows of spines continued on to fingers; dorsal surface with scattered small spines. Fingers as long as palm, distally spooned; 1 or 2 small spines on dorsal proximal part of movable finger.

P2–4: Somewhat compressed mesiolaterally, sparsely with long uniramous and iridescent setae, and short plumose setae. Meri successively shorter posteriorly; P2 merus 0.8 times carapace length, more than 3.5 times as long as broad, 1.6 times longer than P2 propodus; P3 merus more than 3.5 times as long as broad, 1.4 times length of P3 propodus; P4 merus 3.5 times as long as broad, 1.2 times length of P4 propodus; dorsal margins with row of proximally diminishing spines on P2 and P3, unarmed on P4; ventrolateral margins with strong terminal spine followed by proximally diminshing prominences; dorsolateral surfaces unarmed on P2–4, with 2 spines on P4. Carpi extensor margins with 3–4 spines on P2 and P3, 2 spines on P4, distalmost largest; flexor margins with distal spine; 0–2 small spines on lateral surface. Propodi 3.5–4.0 times as long as broad; extensor margins with 2 or 3 proximal spines, lateral surface with 1 or 2 proximal spines; flexor margins with 7–10 slender movable spines. Dactyli subequal in length, 0.6–0.8 times length of propodi, ending in incurved, strong, sharp spine; flexor margins with 6 seta-like movable spines, each arising from very low tooth.

Remarks. Sadayoshia acamar belongs to a group of species having the antennular article 1 with a lateral marginal spine (= accessory spine) proximal to the distolateral spine and no spine mesial to the anterolateral spine of the carapace. The group contains three species: S. miyakei Baba, 1969 , S. lipkei Mapherson & Baba, 2010 and the present new species. Sadayoshia miyakei can be easily distinguished from the other two species by lacking instead of possessing the postcervical spine on each side of the carapace.

Sadayoshia acamar and S. lipkei can be distinguished by the number of spines along the flexor margin of Mxp3 merus: 3 three spines in S. lipkei and 2 two in S. acamar . However, the median spine can be very small in some specimens of S. lipkei , and a third small distal spine can be observed in a few specimens of S. acamar . Furthermore, P2–4 are slightly more slender in S. acamar than in S. lipkei . For instance, the P2–3 meri are 3.2–3.3 times as long as broad in S. lipkei , instead of being more than 3.5 times longer as in the new species.

Distribution. New Caledonia, and Chesterfield Islands, at 20– 55 m.

Figures

FIGURE 1. Sadayoshia acamar n. sp., holotype, ovigerous female, 5.1 mm, Chesterfield Islands, CHALCAL 1984, Stn DC 45 (MNHN-IU- 2010 - 5377). A, carapace and abdomen, dorsal view; B, sternal plastron, sternites 3 and 4; C, left cephalic region, showing antennular and antennal peduncles, ventral view; D, right Mxp 3, lateral view; E, right P 1, dorsal view; F, right P 2, lateral view; G, right P 3, lateral view; H, right P 4, lateral view. Scale: A, E – H = 1 mm; B – D = 0.5 mm.

FIGURE 7. Rostrum, dorsal view. A, Sadayoshia acamar n. sp., ovigerous female, 5.0 mm, Chesterfield Islands, CHALCAL 1984, Stn DC 45 (MNHN-IU- 2010 - 5378). B, S. actaea n. sp., holotype, female, 3.2 mm, Lifou Island. LIFOU, Stn 1467 (MNHN-IU- 2010 - 5372). C,. S. adaro n. sp., ovigerous female, 3.9 mm, Solomon Islands. SALOMON 1, Stn DW 1744 (MNHN-IU- 2010 - 5376). D, S. aludra n. sp., ovigerous female, 9.1 mm, Chesterfield Islands. CORAIL 2, Stn DW 106 (MNHN-IU- 2010 - 5353). E, S. moorei n. sp., holotype, ovigerous female, 4.1 mm, French Polynesia, Society Islands (UF 16050) F, S. savali n. sp., ovigerous female, 5.4 mm, Lifou Island, Stn 1450. Scale = 1 mm.