Anisomysis (Anisomysis) phuketensis, Moriya, Mitsuyasu, Srinui, Khwanruan & Sawamoto, Shozo, 2015

Moriya, Mitsuyasu, Srinui, Khwanruan & Sawamoto, Shozo, 2015, Two new species of the genus Anisomysis (Anisomysis) (Crustacea, Mysida, Mysidae) from coral reef waters in Thailand, ZooKeys 525, pp. 129-145 : 132-136

Taxon classification Animalia Mysida Mysidae

Anisomysis (Anisomysis) phuketensis sp. n. Figs 5, 6, 7, 8

Type series.

Holotype (NSMT-Cr 24249), adult male (BL, 3.6 mm); allotype (NSMT-Cr 24250), adult female with embryos (BL, 3.9 mm); paratypes (NSMT-Cr 24251), 2 adult males (BL, 3.8, 4.0 mm) and 2 adult females with embryos (BL, 3.2, 3.6, 3.4 mm); Ko Lon, Phuket Is., Thailand, 7°47.01'N, 98°21.30'E; collected with a hand net (mesh size, 0.33 mm; mouth diameter, 30 cm) by skin diving in a coral reef of 2-3 m deep, December 3, 2010 by M. Moriya.

Description.

Body slender (Fig. 5A). Carapace extending anteriorly into obtusely triangular rostrum with bluntly pointed apex, covering bases of antennules (Fig. 5B, C).

Eyes large, cornea occupying half of eye in dorsal view (Fig. 5 A–C). Eyestalk very short, without papilliform process on dorsal surface.

Antennular peduncle more robust in male (Fig. 5B) than that in female (Fig. 5C); first segment shorter than third, armed with two setae at anterolateral corner; second segment shortest. In female (Fig. 5C), first segment armed with single seta at anterolateral corner.

Antennal scale (Fig. 5D) closely near the anterior margin of antennular peduncle in male (Fig. 5B), well beyond anterior margin in female (Fig. 5C); 5.5 times as long as broad in male, 6.1 times as long as broad in female. Antennal peduncle short, not reaching middle of antennal scale in both sexes (Fig. 5D).

Mandibular palp (Fig. 6A) 3-segmented; second segment widened mesially at around mid-length, armed with setae on both margins, without triangular processes; third segment rectangular, 0.5 times as long as second segment, outer margin armed with 5 marginal setae increasing in length distally, distal margin with 5 barbed setae on margin, 1 recurved and barbed seta and 1 long seta at distomedial corner. Maxillule and maxilla as shown in Fig. 6B and C, respectively.

First thoracopodal endopod (Fig. 7A) short and stout, armed with straight, strong terminal claw. Second thoracopodal endopod (Fig. 7B) short; merus as long as carpopropodus, dactylus with strong, curved terminal claw. Third to eighth thoracopodal endopods (Fig. 7 C–H) with undivided carpopropodus in both sexes. Flagelliform part of first and eighth thoracopodal exopods 7-segmented (Fig. 7A, H) and second to seventh 8-segmented (Fig. 7 B–G). Basal plate of eight thoracopodal exopods with rounded outer distal corners.

Abdomen (Fig. 5A) long and slender, sixth somite 1.3 times longer than fifth.

First, second, third, and fifth pleopods of male and all pleopods of female rudimentary. Fourth male pleopod (Fig. 8A) biramous; endopod minute and thin lobe with 4 setae; exopod long, three-segmented, overreaching distal end of telson (Fig. 5A). First segment longer than second and third segments combined; second segment shortest; segment length ratios 3:1:1.5; third segment with two terminal setae, almost equal in length, outer setae slender and naked, inner setae swollen at base and barbed on distal half.

Uropod slender, setose around (Fig. 8B); endopod straight, 1.5 times longer than telson excluding apical spines, no spine in statocyst region; exopod slightly curved outward, 1.1 times as long as endopod.

Telson (Fig. 8B) short, nearly 3/5 length of sixth abdominal somite, 1.2 times longer than broad at base, compressed around distal 1/4, then expanding distally, dis tal margin slightly narrower than base; lateral margin armed with 4-5 short spines; apex of telson concave at the middle with paired spines almost equal in length, apical margin truncate with two long stout spines, outer spine curved inward, slightly shorter than inner straight spine.

Etymology.

The species is named after the type locality.

Remarks.

The most noticeable characteristic of Anisomysis (Anisomysis) phuketensis is the form of the telson. This species resembles Anisomysis (Anisomysis) robustispina Panampunnayil, 1984 and Anisomysis (Anisomysis) truncata Panampunnayil, 1993 in the presence of the peculiar long stout spines on the apical margin of telson. However, Anisomysis (Anisomysis) phuketensis is distinguished from Anisomysis (Anisomysis) robustispina by the following characters: only two long stout spines on telson (three in the latter), the length/width ratio of telson being 1.2 (1.6 in the latter), the length ratio of uropodal endopod to telson being 1.5 (2.3 in the latter). Although the telson of Anisomysis (Anisomysis) truncata is also armed with two pairs of stout apical spines, the outer spines are twice as long as the inner (subequal in Anisomysis (Anisomysis) phuketensis ) and lacks the medial depression with two small spines, which is present in Anisomysis (Anisomysis) phuketensis and Anisomysis (Anisomysis) robustispina .

Distribution.

The type locality and Ko Chueak, Hat Chao Mai National Park, Trang Province, Thailand.