Leipsuropus astericolus Ariyama, 2012, sp. nov.
Creators: name: Ariyama, Hiroyuki
Publisher: name: Zenodo
Year: 2012
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Amphipoda
Podoceridae
Leipsuropus
Leipsuropus astericolus

description: Leipsuropus astericolus sp. nov.
(Figs 1 A, 2–6)
Leipsuropus sp. Kogure et al., 2010: 94, fig. 1A, B.
Material examined. Holotype: female (OMNH-Ar-8941), 3.2 mm, Oki Strait, Sea of Japan, 35°50.29'N, 132°59.00'E – 35°50.31'N, 132°59.21'E (Fig. 1 A), 98 m deep, sandy bottom, attached to the surface of a starfish Henricia regularis, 16 June 2009, coll. Y. Kogure. Paratypes: 2 males (OMNH-Ar-8942, 8943), 4.4, 3.2 mm, and 3 females (OMNH-Ar-8944–8946), 4.6, 3.8, 3.7 mm, same data as holotype.
Description. Female [based on holotype, 3.2 mm (OMNH-Ar-8941), paratype 4.6 mm (OMNH-Ar-8944) for oostegites, and paratype 3.8 mm (OMNH-Ar-8945) for antenna 1 and uropod 3]. Body (Fig. 2 A), head with pair of small projections in front of eyes, 1 forward dorsal projection and 1 small lateral projection on both sides, anteroventral corners acutely pointed; pereonite 1 with 2 upward dorsal projections and 3 lateral projections; pereonite 2 with 1 upward dorsal projection and 2 lateral projections, ventral margins produced laterally; pereonites 3–5 each with 1 backward dorsal projection and 2 lateral projections, ventral margins produced posterolaterally; pereonites 6, 7 completely separated, each with 1 backward dorsal projection and 2 lateral projections, posteroventral corners produced; pleonites 1, 2 each with 1 upward dorsal projection and 1 lateral projection; pleonite 3 bare.
Antenna 1 (Fig. 3 A, A1) with ratio of lengths of peduncular articles 1–3 1:2.0:1.9, ventral surfaces of articles 1–3 bearing many long setae, lateral and medial surfaces with many fine setae, peduncular article 1 with a few penicillate setae on dorsal surface; accessory flagellum minute, with 2 short setae on tip; primary flagellum with 1 long and 1 small articles, article 1 with ventral long setae and lateral and medial fine setae, article 2 bearing many distal setae. Antenna 2 (Fig. 3 B, B1) shorter than antenna 1, ratio of lengths of peduncular articles 3–5 1:2.2:2.4, peduncular articles with ventral long setae and lateral and medial fine setae; flagellum with 1 long and 1 small articles, article 1 with ventral long setae and lateral and medial fine setae, article 2 setose distally.
Mandible (Fig. 3 D, D1, E, E1), each incisor bearing 6 cusps, left lacinia mobilis with 4 cusps, right 5 cusps, accessory blades 3 in left, 2 in right; plate-like structure with pectinate margin situated beside molar; palp article length ratio 1:2.7: 1.8 in left, article 2 setose medially, article 3 with medial setae and long distal setae. Maxilla 1 (Fig. 3 G, G1), outer plate bearing 8 robust setae apically, tip of palp article 2 with 5 (1 lost?) robust setae. Maxilla 2 (Fig. 3 H), medioproximal margin of inner plate with several fine setae. Maxilliped (Fig. 4 A, A1), distal end of inner plate bearing 3 short robust setae, outer plate with 5 setulose setae and 7 robust setae.
Gnathopod 1 (Fig. 4 B, B1–3), coxa acutely pointed anteriorly, lateral surface bearing several fine setae; basis widened distally, anterior and posterior margins with a few setae, lateral and medial surfaces with several fine setae; posterodistal corner of ischium and posterior margins of merus and carpus bearing many long setae; propodus triangular, posterodistal corner with 9 small robust setae, anterodistal corner setose, medial surface bearing setulose and pectinate setae; dactylus short, posterior margin with several denticles. Gnathopod 2 (Fig. 4 C, C1), coxa short, ventral margin hollowed in the middle, gill curved anteriorly; basis widened distally, anterodistal corner acutely projected laterally, lateral and medial surfaces bearing many fine setae; distal end of ischium with small lateral projection; posterodistal end of merus pointed prominently; carpus short, distal margin fringed with short setae; propodus dilated, anterior surface with 5 lateral and 6 medial thick setae, palm defined by small process, with penicillate seta distally and robust seta proximally, lateral surface bearing many fine setae, medial surface bearing many fine setae and several long simple setae; dactylus strongly curved posteriorly.
Pereopod 3 (Fig. 5 A, A1), coxa slightly broader than long, lateral surface with many fine setae; basis anterodistal corner not projected, lateral surface with several fine setae; merus and carpus each with thick seta on anterodistal corner, lateral and medial surfaces with many fine setae, distal end of carpus produced laterally and medially; propodus setose on anterodistal corner, lateral and medial surfaces with many fine setae; dactylus slightly curved. Pereopod 4 (Fig. 5 B, B1) longer than pereopod 3; coxa wide, gill curved anteriorly; basis anterodistal corner projected; merus with 3 thick setae on anterodistal corner; carpus bearing thick seta on anterodistal corner; other parts similar to pereopod 3. Pereopod 5 (Fig. 5 C, C1) longer than pereopod 4; coxa small, lobate, gill curved anteriorly; posterior margins of merus, carpus and propodus with 1+2, 2+3, 1+1+1 thick setae, respectively, posterodistal corner of propodus setose; other parts similar to pereopod 4. Pereopod 6 (Fig. 5 D, D1) much longer than pereopod 5; coxa small, slightly lobed; posterior margins of merus, carpus and propodus with 1+2, 0+3, 0+1+0 thick setae, respectively; other parts similar to pereopod 5. Pereopod 7 (Fig. 5 E, E1) slightly longer than pereopod 6; coxa very small, slightly lobate; basis posterodistal corner not projected; posterior margins of merus, carpus and propodus with 0+1, 1+3, 0+1+0 thick setae, respectively; other parts similar to pereopod 5. Oostegites on coxae 2–4 (Fig. 4 D–F) gradually broader, margins heavily setose.
Pleopod 1 (Fig. 6 D, D1) shortest; peduncle long, asetose, with 6 coupling hooks; outer ramus shorter than inner, outer and inner rami each with 7 articles, article 1 of inner ramus swelled laterally. Pleopod 2 (Fig. 6 E, E1) longer than pleopod 1; peduncle with 5 plumose setae and 6 coupling hooks; outer ramus longer than inner, outer and inner rami each with 8 articles. Pleopod 3 (Fig. 6 F, F1) shorter than pleopod 2; peduncle with 2 setae and 6 coupling hooks; outer ramus with 8 articles. Uropod 1 (Fig. 6 A), peduncle bearing 2 robust setae on dorsolateral surface; outer ramus 1.2 times as long as peduncle, with 2 dorsolateral and 2 terminal robust setae; inner ramus 1.6 times as long as outer ramus, with 3 dorsolateral, 4 dorsomedial and 3 terminal robust setae. Uropod 3 (Fig. 6 B, B1, C) curled, with 5 setae ventrally, distal margin fringed with short setae. Telson (Fig. 6 B, B1) broader than long, round, distal margin with a few setae.
Large male [paratype, 4.4 mm (OMNH-Ar-8942)]. Generally similar to female except for gnathopod 2 and oostegites. Gnathopod 2 (Fig. 6 G, G1, G2) much larger than that of female; coxa narrow, anterior margin truncate, gill long, curved anteriorly; anterodistal corners of basis and ischium acutely projected laterally; posterodistal end of merus slightly pointed; distal margin of carpus with short robust seta; propodus more enlarged, anterior surface with 3 lateral and 10 medial thick setae, posterior margin with 1 wide and 2 triangular processes, posteromedial surface bearing many long simple setae.
Small male [paratype, 3.2 mm (OMNH-Ar-8943)]. Almost similar to female except for spination of body and oostegites. Body (Fig. 6 H), head with 1 blunt dorsal projection, lateral projection absent; pereonite 1 with 2 upward dorsal projections and 2 lateral projections on both sides; pereonite 2 with 1 upward dorsal projection and 1 lateral projection; pereonites 3–7 each with 1 backward dorsal projection and 1 lateral projection; pleonites 1, 2 each with 1 upward dorsal projection and 1 lateral projection; pleonite 3 bare.
Coloration in life. Eyes red, dorsal surface pale orange with bright orange marks; tips of antennae and distal parts of meri, carpi and propodi of pereopods 3–7 white; other parts pale orange (Kogure et al. 2010, fig. 1B).
Ecology. Dwelling on the surface of a starfish Henricia regularis for protection against predators (Kogure et al. 2010).
Etymology. From the Latin aster (= starfish) and colus (= inhabitant), referring to the habitat.
Remarks. This new species has distinct dorsal and lateral projections on the body. Leipsuropus parasiticus do not have such projections, which has only dorsal rugae on pereonites 1–5 (Haswell 1879; Barnard & Drummond 1981; Hughes 2012). Leipsuropus parasiticus is also distinguished from L. astericolus sp. nov. by the following characters (L. astericolus in parentheses): (1) pereonites 6, 7 fused together (not fused), (2) antenna 1 flagellum with 4 articles (2 articles), (3) antenna 2 much longer than antenna 1 (shorter), (4) dactylus of male gnathopod 2 straight (strongly curved), and (5) palm of female gnathopod 2 transverse (oblique). Leipsuropus sinensis has similar dorsal projections to L. astericolus. However, the former differs from the latter in the following features (L. astericolus in parentheses): (1) dorsal projection of head blunt (acute), (2) lateral projections present only on pereonite 7 and pleonites 1, 2 (on head, pereonites 1–7 and pleonites 1, 2), (3) antenna 1 flagellum with 5 articles (2 articles), (4) palm of male gnathopod 2 almost straight (sinuate), and (5) telson with dorsal protuberance (lacking).
description: Published as part of Ariyama, Hiroyuki, 2012, Two new species of the genus Leipsuropus (Crustacea: Amphipoda: Podoceridae) from Japanese and Korean waters, pp. 41-55 in Zootaxa 3485 on pages 42-48, DOI: 10.5281/zenodo.211354