Ericthonius tropicalis, Just, 2009

Just, Jean, 2009, Ischyroceridae *, Zootaxa 2260 (1), pp. 463-486 : 481-484

Ericthonius tropicalis sp. nov.

( Figs 12 , 13 )

Type material. Holotype, male, 3.1 mm, AM P71491, Yonge Reef, Half Mile Opening (14°34'19"S 145°36'51"E), among Halimeda opuntia (green coralline algae), 10 m, I. Takeuchi, R. T. Springthorpe & O. Coleman, 5 March 2005 (QLD 1823) . Paratypes (110 specimens in all): 6 small females, AM P75644 (QLD1687); 2 small males , 1 female, AM P70961 (QLD 1687) ; 8 males, 14 females, AM P71392 (QLD 1791) ; 1 female, 3.1 mm (illustrated), 6 males, 11 females, same data as holotype AM P75645 (QLD 1823) ; 3 males, 4 females, AM P71506 (QLD 1823) ; 10 males varying sizes, 6 females some ovigerous, 6 juveniles, AM P71544 (QLD 1823) ; 3 males, 1 female, AM P71517 (QLD 1827) ; 6 females, some ovigerous, AM P71575 (QLD1823) ; 5 males, 16 females, AM P71578 (QLD 1829); 1 ovigerous female, AM P71550 (QLD 1833) .

Type locality. Yonge Reef , Half Mile Opening, Queensland, Australia (14°34'19"S 145°36'51"E) .

Etymology. The epithet denotes the environment where this species was found.

Description. Based on holotype, male, 3.1 mm, AM P71491.

Head. Eyes approximately 1/3 dorsal head length, situated within lateral lobe of head. Antenna 1 peduncular article 1 distinctly shorter than article 3; flagellum distinctly longer than peduncular article 3, with 8 articles, each with a single aesthetasc. Antenna 2 only slightly longer than 1, peduncular articles 4 and 5 with 4–5 irregular rows of setae; flagellum distinctly longer than peduncular article 5, with 7 articles.

Pereon. Coxae 1–4 not setose on margin. Gnathopod 1 distinctly smaller than gnathopod 2; coxa about 0.5 length and width of coxa 2; propodus about 4/5 length of carpus; propodus length 1.5 width, posterior margin deeply rounded in middle. Gnathopod 2 carpochelate; coxa 2 widely separated from and deeper than coxa 1 and 3, rounded, width approximately 1.5 length, with stridulation ridges along ventral margin; basis short, broad, length 1.8 width; carpus with distinct free posterior expansion, with two carpal teeth, posterior margin of carpus with row of short robust setae and associated slender setae; propodus length subequal to carpus, rectangular, posterior margin with low rectangular projection in distal half and small humps more proximally; dactylus slightly shorter than propodus length, without apical tuft of setae. Pereopods 3–4 basis expanded, subovoid; merus weakly expanded. Pereopod 5 coxa with long slender and plumose setae along ventral margin, basis posterodistal corner rounded, not lobed. Pereopod 7 basis broad, length 1.1 width.

Pleon. Uropod 1 peduncle dorsolateral margin with a few slender setae; outer ramus with apical robust setae only, inner ramus with apical robust setae and single robust seta on medial margin. Uropod 2 peduncle dorsolateral margin with a few slender setae, medial margin with single long robust seta distally, rami without lateral or medial setae. Uropod 3 peduncle length 2.5 width, broad proximally, narrowing distally, with 2 dorsolateral slender setae, ramus length approximately twice width, distally cusped. Telson midlength approximately twice greatest width, lateral lobes with 2 or 3 irregular rows of recurving hooks.

Female (sexually dimorphic characters). Based on female, 3.1 mm, AM P75645.Similar to male, except for sexually dimorphic gnathopod 2. Gnathopod 2 coxa width 1.5 length, ventral margin concave, without stridulation ridges. Coxae 3 and 4 wider than in male.

Habitat. Seagrass beds; Halimeda beds; mixed algae on rubble and shallow reefs. 1–10 m depth.

Remarks. Males of Ericthonius tropicalis sp. nov. differ from the following Australian Ericthonius species by having a row of robust setae along the ventral margin of gnathopod 2 carpus: E. brevicarpus , E. forbesii , E. parabrasiliensis sp. nov., E. pugnax and E. rodneyi . It differs from the two Australian Ericthonius species with such a row of robust setae as follows: E. coxacanthus has a long acute projection anteroproximally on coxa 2; E. tacitus lacks long plumose setae on the ventral margin of coxa 5, and uropods 1 and 2 peduncles have rows of robust setae (a few slender setae only in E. tropicalis ). Ericthonius tropicalis appears to differ from all other Ericthonius species by its unusually broad basis of pereopod 7 in relation to its length. Females of E. tropicalis differ from all other Ericthonius species by the squarish coxa 2 having the ventral margin concave.

Distribution. Australia. Queensland: Lizard Island, Great Barrier Reef (current study).

Ericthonius sp.

( Fig. 14 )

Material examined. 1 male, AM P75643 (QLD 1823) .

Remarks. The single male was found in a sample with seven specimens of Ericthonius tropicalis sp. nov., and two specimens of E. pugnax . Ericthonius sp. lacks robust setae along the posterior margin of the carpus, which aligns it with the subgroup of Australian species comprising E. pugnax , E. parabrasiliensis sp. nov., E. forbesii , E. brevicarpus and E. rodneyi . Ericthonius sp. lacks an apical tuft of long setae on gnathopod 2 dactylus ( E. pugnax , E. parabrasiliensis , E. forbesii ) and a posterior lobe on pereopod 5 basis ( E. pugnax ). It further differs from E. parabrasiliensis in the shape of coxa 2. Ericthonius sp. is closest to E. brevicarpus in possessing an anteroproximal projection on coxa 2, the projection being, however, much smaller and more pointed than in the latter species. Ericthonius sp. lacks a posterodistal spine on the merus of gnathopod 2 present in E. brevicarpus . A tuft of very long slender setae emerging from the posterodistal lobe of the merus of pereopods 6 and 7 and distinctly overreaching the carpus seems to be a unique feature of Ericthonius sp.

Ericthonius sp. appears to represent an undescribed species, but the single specimen is damaged and unsuitable for formal description.

Habitat. Among Halimeda opuntia ; 10 m.

Distribution. Australia. Queensland: Lizard Island, Great Barrier Reef (current study).

Figures

FIGURE 12. Ericthonius tropicalis sp. nov., M, holotype, male, 3.1 mm, AM P71491, F, paratype, female, 3.1 mm, AM P75645, Yonge Reef, Lizard Island, Great Barrier Reef.

FIGURE 13. Ericthonius tropicalis sp. nov., holotype, male, 3.1 mm, AM P71491, Yonge Reef, Lizard Island, Great Barrier Reef.

FIGURE 14. Ericthonius sp., male, AM P75643, Yonge Reef, Lizard Island, Great Barrier Reef.