Pleurocope iriomotensis, Shimomura, Michitaka & Naruse, Tohru, 2015

Shimomura, Michitaka & Naruse, Tohru, 2015, Two new species of Asellota (Crustacea, Isopoda) from coral reefs on Iriomote Island, Okinawa, Japan, ZooKeys 520, pp. 27-40 : 30

Taxon classification Animalia Isopoda Pleurocopidae

Pleurocope iriomotensis sp. n. Figs 2, 3, 4

Material examined.

Holotype. ♂ (0.9 mm), 24°20'N, 123°41'E, Amitori Bay, Okinawa, Japan, 19 July 2012, dead coral, 25 m, coll. TN (KMNH IvR 500,729).

Paratypes. 3♂♂ (0.5-0.9 mm), Amitori Bay, Okinawa, Japan, 19 July 2012, dead coral, 4 m, coll. MS (KMNH IvR 500,730-500,732).

Description of the holotype.

Body (Fig. 2) 1.6 times as long as maximum width (including spine-like processes), widest at pereonite 3, with many small granules on dorsum, without dorsal setae. Head (including eyestalks) 2.4 times as broad as long, head without eyestalks 1.2 times as broad as long, broader than pereonite 1; frontal and posterior margins of head convex. Eyes each with 2 ommatidia; eyestalks slender, long, reaching near distal end of article 1 of antenna 1. Pereonites 1 and 5-7 laterally rounded, without lateral spine-like processes; pereonites 2 and 3 with pair of long lateral spine-like processes bearing 2 or 3 robust setae; lateral spine-like processes of pereonites 2 and 3 reaching to tip of second article of antennula in length; pereonite 4 with pair of short lateral spine-like processes bearing single robust seta and 2 short teeth distally; lateral spine-like processes of pereonite 4 half as long as ones of pereonite 3. Pereonite 1 shortest; pereonite 2 three times as long as pereonite 1; pereonites 3 and 4 longest, subequal in length; pereonite 5 0.7 times as long as pereonite 4, pereonites 5-7 subequal in length. Pereonites 1 to 3 increasing in width; pereonite 4 narrower than pereonites 3; pereonites 4 to 7 decreasing in width. Coxal plates dorsally visible on pereonites 5-7, laterally with spine-like process and 2 robust setae. Pleotelson (Fig. 2) approx. 2.2 times as long as wide, widest at anterior one seventh, tapering to sharply rounded apex, with 12 robust setae distally.

Antennula (Fig. 3A) consisting of 6 articles. Article 1 longest and broadest, twice broader than eyestalks, with 1 long and 1 short simple setae laterodistally; article 2 nearly 0.8 times as long as article 1, distally with 1 short and 2 long, stout simple setae and 1 broom-like seta; article 3 about half as long as article 2, without setae; article 4 approx. 0.6 times as long as article 3, without setae; article 5 approx. 1.8 times as long as article 4, with 1 aesthetasc distally; article 6 shortest, with 1 long simple seta and 1 aesthetasc apically.

Antenna (Fig. 3B): peduncle consisting of 4 short and 2 long articles, and flagellum of 7 short articles. Articles 1 and 2 subquadrate, without setae; article 3 with a simple seta laterodistally and 4 simple setae on lateral protrusion; article 4 as long as articles 1 and 2 combined, without setae; article 5 longer than article 4, with single simple seta medially and laterally; article 6 as long as article 5, with 2 simple setae distomedially and 2 broom-like setae laterodistally; flagellum as long as peduncular articles 4-6 together, flagellar articles 1-6 each with 0, 1, 0, 2, 2 and 0 simple setae distally; flagellar article 7 with 2 simple setae and 1 aesthetasc.

Maxillula (Fig. 3E) with medial lobe short, lacking setae; lateral lobe with 7 setae distally. Maxilla (Fig. 3F) with medial lobe bearing some fine and 2 stout setae on margin; lateral 2 lobes each with 2 stout setae apically.

Maxilliped (Fig. 3G) palp slender, twice as long as basis: article 1 shortest, without setae; articles 2 to 4 subequal in length, each with single distal seta; article 5 narrowest, with a short seta medially and 2 stout setae apically; basis quadrate with broad endite bearing 2 simple setae distally and 1 coupling hook medially; epipod crenulated laterally, 2.6 times as long as width, 1.5 times as long as basis.

Pereopod 1 (Fig. 3H): basis 0.8 as long as ischium, with 1 dorsal seta; ischium the longest article, with short tooth and 2 long setae dorsally; merus pentagonal, with a ventral and a dorsal seta; carpus trapezoidal, as long as merus, with distoventral tapering projection terminating with 1 stout seta and 1 slender setae ventrally; propodus ovate, 2.3 times as long as width, with 1 proximoventral and 1 distodorsal small setae; dactylus as long as propodus, with 1 triangulate tooth and 1 short seta ventrally and 2 setae subapically, unguis half as long as dactylus and 1 slender seta apically.

Pereopod 2 (Fig. 3I) shorter than pereopods 3-7; basis with 1 distoventral seta; ischium 2.1 times as long as basis, dorsally with 2 robust setae; merus shorter than half length of ischium, with 2 simple setae ventrally and 1 robust seta dorsally; carpus longer than merus, with 2 robust setae ventrally and 1 simple seta dorsodistally; propodus as long as ischium, ventrally with 3 robust unequally bifid setae and 1 fringed scale on distal third, and with 2 simple and 1 robust seta dorsally; dactylus slender, 3.1 times as long as width, with 1 simple seta, 1 stout unguis and 1 accessory claw apically, and with 2 simple setae subapically. Pereopods 3-7 (Figs 3 J–K, 4 A–C) subequal in shape and slightly increasing in length posteriorly; bases with 1 ventrodistal seta; ischia longer than bases, with 1-2 simple ventrally and 1-2 robust setae dorsally; meri less shorter than half length of ischia, with 2 setae ventrally and 1-2 robust setae dorsally; carpi longer than meri, with 1-2 simple and 2 robust setae ventrally and 0-1 simple and 0-1 robust setae dorsally; propodi longer than ischia, with 3 robust setae ventrally and 2-3 robust and 1 broom-like seta dorsally; dactyli with 2 simple setae, 1 stout unguis and 1 short accessory claw apically and 2 simple setae subapically.

Pleopod 1 (Fig. 4D) about 3.4 times as long as maximum width, tapering to apex, apically with 3 pairs of short setae. Pleopod 2 (Fig. 4E, F): protopod 3 times as long as wide, bearing long seta apically; apical seta 1.2 times as long as protopod; endopod surpassing tip of protopod, with slender, long second article; second article 1.2 times as long as protopod; exopod narrower than endopod first article. Pleopod 3 (Fig. 4G): endopod 4.7 times as long as width, bearing 3 stout plumose setae distally; exopod 0.9 times as long as endopod, bearing 2 simple setae apically.

Uropod (Fig. 2) half as long as pleotelson. Protopod wide posteriorly, with 3 robust setae distally; exopod as long as protopod, with 2 robust setae distally; endopod slightly shorter than exopod, with 3 broom-like and 2 robust setae distally.

Description of the paratypes.

Body (Fig. 4H) flattened, without spines and projections on dorsum. Left mandible (Fig. 3C) incisor 4 conical, directed anteriorly, without setae and teeth; lacinia mobilis with 3 teeth. Right mandible (Fig. 3D) incisor with 2 teeth apically, without setae.

Female.

Not known.

Remarks.

Pleurocope iriomotensis sp. n. can be identified by the following combination of characters: pereonite 1 lacking lateral spine-like processes; pereonites 2-4 and coxal plates of pereonites 5-7 each with lateral spine-like process; pleotelson twice as long longer as wide; flagellum of antenna consisting of 7 articles. Pereonite 1 without a spine-like process links the new species to Pleurocope floridensis Hooker, 1985, from the Gulf of Mexico and to Pleurocope dasyura Walker, 1901, from the Gulf of Naples, Italy. Pleurocope iriomotensis is distinguished from Pleurocope floridensis by the following characters (those of Pleurocope floridensis in parentheses): pereonite 4 and coxal plate of pereonite 7 with spine-like process (without spine-like process); eyestalks not reaching to second article of antennula (surpassing second article of antennula); fifth article of antennula with 1 aesthetasc (with 2 aesthetascs); ischium of pereopod 1 with dorsal projection (without dorsal projection); pleopod 1 apically with 3 pairs of short setae (apically with 5 pairs of short setae). Pleurocope dasyura differs from the new species in having pereonite 4 and coxal plate of pereonite 7 without spine-like processes, pereon with 6 long dorsal setae, antenna with long projection, and pleopod 1 apically with 4 pairs of short setae.

Etymology.

The species is named after the type locality.