Prethura tuberculata, 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 : 31-34

Taxon classification Animalia Isopoda Santiidae

Prethura tuberculata sp. n. Figs 5, 6

Material examined.

Holotype. ♂ (0.9 mm), 24°20'N, 123°41'E, Amitori Bay, Okinawa, Japan, 19 July 2012, dead coral, 4 m, coll. MS (KMNH IvR 500,733).

Description of the holotype.

Body (Fig. 5A) 2.6 times as long as maximum width, widest at head, with many small black chromatophores. Head 2.3 times as broad as long, broader than pereon, with pair of rounded protuberances dorsally; frontal margin concave; posterior margin slightly convex. Eyes each with 43 ommatidia. Pereonites 1 to 3 increasing in length posteriorly, each with 3 rounded protuberances dorsally; pereonite 4 longer than pereonite 3, without protuberances; pereonite 5 shortest; pereonite 6 slightly longer than pereonite 5; pereonite 7 as long as pereonite 6. Pereonites 1 to 3 increasing in width; pereonite 4 narrower than pereonite 3; pereonite 5 wider than pereonite 4; pereonite 6 narrower than pereonite 5; pereonite 7 narrowest. Pleonite half as long as pereonite 7, without pigmentations and setae dorsally. Pleotelson (Fig. 5A, E) 1.7 times as long as wide, with 3 pairs of short setae laterally and 4 pairs of short setae marginally.

Antennula (Fig. 5B) consisting of 5 articles. Article 1 with many granules, without setae; article 2 broadest, as long as article 1, with many granules, and with 1 simple seta and 1 broom-like seta distomedially and 1 broom-like seta distolaterally; article 3 and 4 subequal in length, without setae; article 5 longest, approx. 3.3 times as long as article 4, with 3 simple setae and 1 aesthetasc apically.

Antenna (Fig. 5C): articles 1 and 2 without setae; article 3 narrower than article 2, with 2 short setae distally; articles 4-6 and flagellar articles broken.

Left mandible (Fig. 6A) incisor with 4 teeth, 4-toothed lacinia mobilis and 3 serrated setae; molar process cylindrical, with one large and four short teeth, and 1 seta distally. Right mandible (Fig. 6B) incisor with 4 teeth and 4 serrate setae; molar process cylindrical, with 1 seta distally.

Maxillula (Fig. 6C): medial lobe with 5 setae apically and some fine setae medially; lateral lobe with 12 setae apically and some fine setae laterally. Maxilla (Fig. 6D) with medial lobe bearing some fine and 7 stout setae medially; two lateral lobes each with 4 stout setae apically.

Maxilliped (Fig. 6E) palp slender, approx. 0.8 times as long as basis: article 1 without setae; articles 2 about twice as long as article 1, with 1 medial seta; article 3 longer than half of article 2, with 1 seta medially and laterally; article 4 longest, with small distomedial lobe bearing 2 long setae; article 5 shortest, with 3 apical setae. Basis quadrate, bearing one simple and two pectinate setae on dorsal ridge, some simple and irregular shaped setae distally, 3 fan-shaped setae submarginally, and 2 coupling hooks medially. Epipod lanceolate, with acute apex. Pereopods broken.

Pleopod 1 (Fig. 6F) about 2.5 times as long as maximum width, without setae. Pleopod 2 (Fig. 6G, H) with broad protopod bearing simple seta apically; protopod with short projection and simple seta laterally; endopod broad, with stout, short stylet; exopod stout. Pleopod 3 (Fig. 6I) protopod as long as width, shorter than endopod; endopod 1.6 times as long as width, with 3 short, plumose setae distally; exopod 0.8 times as broad as endopod, bearing 1 simple seta apically and many fine setae laterally. Pleopod 4 (Fig. 6J) endopod ovate, 2.7 times as long as broad; exopod its tip not surpassing tip of endopod, distally with 1 long slender and some short setae, and laterally with 7 spinulose scales. Pleopod 5 broken.

Uropod (Figs 5D, 6K) 0.2 times as long as pleotelson. Protopod widest at anterior part, narrow posteriorly, with 4 simple setae distally and 3 simple setae laterally; endopod 0.3 times as long as protopod, cylindrical, with 4 broom-like setae apically.

Remarks.

This new species differs from the only congener, Prethura hutchingsae Kensley, 1982, from the Great Barrier Reef, by the following characters (those of Prethura hutchingsae in parentheses): pleopod 1 lacking any setae (with setae); protopod of pleopod 2 with lateral projection (without projection); epipod of maxilliped with acute apex (blunt apex).

Etymology.

From the Latin “tuberculatus”, referring to the lateral projection of the protopod of pleopod 1.