Elasmopus hooheno J. L. Barnard 1970

Elasmopus hooheno J.L. Barnard, 1970

(Figs 5, 6)

Elasmopus hooheno J.L. Barnard, 1970: 121, fig. 70. —J.L. Barnard, 1971: 71, figs 33–35. — Ledoyer, 1972: 217, pls 35, 36. — Ledoyer, 1978: 269. — Ledoyer, 1979a: 161, fig. 10 II. — Ledoyer, 1979b: 69, fig. 40 I. — Ledoyer, 1983: 470, fig. 177. — Berents, 1983: 116, fig. 13. — Ren, 1998: 197, fig. 3. — Lowry & Stoddart, 2003: 178 (catalogue).

Elasmopus rapax. — Sivaprakasam, 1969: 45, fig. 6A.

Not Elasmopus hooheno. — Appadoo & Steele, 1998: 639 (= E. pseudinteger Appadoo & Myers, 2003).

Material examined. 1 male, 6.3 mm, 3 slides AM P78771 (76 LIZ 16 B); 4 unsexed, AM P71466 (QLD 1789); 1 female, 4.0 mm AM P78772 (76 LIZ B); 66 unsexed, AM P30107; 2 unsexed, AM P75720 (QLD 1877); 3 unsexed, AM P75716 (QLD 1947); 1 unsexed, AM P75719 (QLD 1972); 2 unsexed, AM P75718 (QLD 1978); 9 unsexed, AM P75717 (QLD 2006).

Type locality. Kawela Bay, Oahu, Hawaiian Island (~ 21°42'10"N 158°0'40"W).

Description. Based on male, 6.3 mm, AM P30107 (Berents, 1983).

Head. Head eyes ovate; lateral cephalic lobe broad, truncated, anteroventral margin with notch/slit, anteroventral corner rounded. Antenna 1 longer than antenna 2; peduncular article 1 subequal in length to article 2, with 1 robust seta on posterior margin; article 2 longer than article 3; accessory flagellum minute, with 2 articles; flagellum with 13 articles. Antenna 2 peduncular article 4 subequal to article 5; flagellum with 6 articles. Mandible incisor a smooth cutting edge with 2 apicomedial cusps; palp well developed, 3- articulate; article 1 about as long as broad, shorter than article 2, inner margin weakly produced distally; article 2 longer than article 3; article 3 short (2 x as long as broad), strongly falcate, longer than article 1.

Pereon. Gnathopod 1 coxa anteroventral corner slightly produced, rounded, anterior margin straight; merus without posterodistal tooth; carpus about 2 x as long as broad, shorter than propodus, with setae in anterodistal bunches and along posterior margin; propodus palm acute, straight, entire, defined by posterodistal corner, with posterodistal robust setae. Gnathopod 2 coxa posteroventral corner notch absent; basis slender; merus acutely produced distoventrally; carpus compressed, not enclosed by merus and propodus, length 0.75 x breadth; propodus expanded, with slender setae along posterior margin, palm acute, sculptured, about one third length of propodus, with rounded distomedial shelf, with group of 4 robust setae on shelf, with midmedial excavation, palmar margin without robust setae, with 1 subacute or truncate tooth, subpalmar surface smooth, corner defined by posteroventral tooth, without posterodistal robust setae; dactylus reaching end of palm, closing into socket, with 1 seta on anterior margin, without posteroproximal shelf, apically blunt. Pereopod 4 coxa posteroventral lobe slightly developed, with rounded posteromedial corner. Pereopod 5 basis expanded, posterior margin straight, with long slender setae, posteroventral corner broadly rounded; carpus and propodus with few long, slender setae along anterior margin. Pereopod 6 basis posterior margin straight, with long slender setae, posteroventral corner broadly rounded; merus and carpus broadened; carpus and propodus with few long, slender setae along anterior margin; propodus not expanded posterodistally. Pereopod 7 basis posterior margin convex, smooth, with long slender setae, not produced posterodistally, posteroventral corner broadly rounded; merus and carpus broadened; propodus not expanded posterodistally.

Pleon. Pleonites 1–3 dorsally smooth, without setae, spines or carinae. Epimeron 1 posteroventral corner broadly rounded. Epimeron 2 posteroventral corner acute. Epimeron 3 ventral margin smooth, posteroventral margin smooth, posteroventral corner narrowly rounded. Urosomites 1–3 dorsally smooth, without setae, spines or carinae. Uropod 1 peduncle with basofacial robust seta. Uropod 3 rami distally truncated, apical robust setae short and long; inner ramus shorter than outer ramus; inner ramus short (length 1.9 x breadth); outer ramus short, subequal to peduncle, 1-articulate. Telson moderately cleft (30 to 65%), broader than long, short, lobes apically truncated, apical conical extension absent, without dorsal robust setae, each lobe with 2 short and long apical/subapical robust setae, without robust setae on inner and outer margins.

Female (sexually dimorphic characters). Based on female, 4.0 mm, AM P78772. Gnathopod 2 not enclosed by merus and propodus; propodus subrectangular, straight, smooth, without shelf, with sparse robust setae, without teeth along margin, without posteroventral corner, with posterodistal robust setae; apically subacute.

Habitat. Marine, epibenthic, among Sargassum, other algae, rocks and coral rubble and reef rock, intertidal and subtidal.

Remarks. Elasmopus hooheno is a widespread Indo-West Pacific species which ranges from Madagascar in the western Indian Ocean to Hawaii in the north-central Pacific Ocean. The GBR population differs from other populations in having a moderately cleft telson (deeply cleft in the Hawaiian population). In the original description J.L. Barnard (1970) described the mandibular palp as “normally falcate”. The third article of the palp illustrated for the Madagascar population by Ledoyer (1983) is long and weakly falcate, whereas in the GBR population it is short and strongly falcate.

Elasmopus hooheno and E. crenulatus are the only Elasmopus species on the GBR with a shortened inner ramus on uropod 3. Elasmopus hooheno differs from E. crenulatus by the sculptured palm on the male second gnathopod (smooth in E. crenulatus) and smooth posterior margins on the basis of pereopods 6 and 7 (castelloserrate in E. crenulatus).

Distribution. Australia. Queensland: Thursday Island, Torres Strait (current study); Lizard Island (Berents 1983); One Tree Island (current study). Western Australia: Direction Island and Prison Island, Cocos (Keeling) Islands, Indian Ocean (Berents 1983). India. Kilakkarai, Gulf of Mannar (Sivaprakasam 1969). Indonesia. Marsegu Island, Moluccas (Ledoyer 1979a). Madagascar. Tuléar (Ledoyer, 1972, 1979b). Mauritius. (Ledoyer, 1978). South China Sea. Nansha (or Spratly) Islands (Ren 1998). USA. Oahu, Hawaiian Islands (J.L. Barnard 1970).