Cerapus nudus, Just, 2009

Just, Jean, 2009, Ischyroceridae *, Zootaxa 2260 (1), pp. 463-486 : 470-471

Cerapus nudus sp. nov.

( Figs 5 , 6 , Pl. 3G)

Type material. Holotype, male, 2.4 mm, AM P70908, Cobia Hole , Lizard Island (14°39'09"S 145°26'51"E), sediment, 17 m, Australian Museum Party, 25 February 2005 (QLD 1672) . Paratypes: 1 subadult female, AM P70810 (QLD 1654) ; 1 juvenile female, AM P70870 (QLD 1654) ; 1 male, 1 female 3.6 mm (illustrated), AM P70834 (QLD 1666) ; 1 juvenile male, 2 tubes, AM P70813 (QLD 1666); 1 damaged female with tube, AM P70783 (QLD 1666) ; 1 male, 1 female, AM P75646 (QLD 1672) .

Type locality. Cobia Hole , Lizard Island, Queensland, Australia (14°39'09"S 145°26'51"E) .

Etymology. The epithet nudus is Latin for naked, alluding to the near complete lack of setae on coxae and pereopods 3–7.

Description. Based on male holotype, 2.4 mm, AM P70908.

Head. R ostrum short, 0.13 x length head, apically subacute; lateral cephalic lobes with distal corner acute, subocular margin deeply recessed. Antenna 1 peduncular article 1 not produced anterodistally and anteromedially, slightly swollen along posterior margin, posterodistal corner not produced; articles 2 and 3 with 5 rows of long setae on posterior margin: flagellum with 4 articles, proximal one the longest, all with many aesthetascs. Antenna 2 as long as 1; flagellum with 3 articles, proximal one as long as remaining 2 combined. Mandible palp article 3 slender, blade-like.

Pereon. Pereonite 1 without lateral keel, without sternal keel. Pereonites 2–3 without sternal keel. Pereonite 5 length 1.7 x depth. Gnathopod 1 coxa not fused to pereonite 1, width 1.3 x depth, without anteroventral lobe; basis length 2.5 x width; carpus, length 1.3 x width, with broad, setose posterior lobe; propodus palm acute, defined by barbed slender setae. Gnathopod 2 carpochelate; coxa not fused to pereonite 2, width 2.3 x depth; basis short, broad, length 2 x width; carpus broad, length 1.1 x width; palm shallowly excavated, anterodistal tooth small, located near articulation with propodus, posterodistal tooth well defined, medium, length 1.3 x width; propodus very broad, slightly curved, length 2.1 x width, without tooth on posterior margin, posterodistal corner smooth, without teeth; dactylus length 0.9 x propodus.

Pereopods 3 and 4 coxa not fused to pereonite, length 2.3 x depth; basis, length twice width, evenly rounded, with slender setae along anterior margin, without denticles along anterior margin; ischium length 2.3 x width; merus long, length 1.6 x width. Pereopod 5 coxa width 1.6 x length, triangular, without patches of small setae; with a few slender setae along ventral margin; merus with anterior lobe extending beyond anterior margin of carpus, posterior lobe with 3 slender setae; propodus with 1 seta on midposterior margin; dactylus short, uncinate with one accessory hook. Pereopods 6 and 7 coxa without setal fringe ventrally, without patches of small setae near margins, coxa 6 triangular, coxa 7 ventrally rounded; basis with at most a single small slender seta on posterior margin; merus width 1.6 x length, dactylus short, uncinate, with one accessory hook.

Pleon. Uropod 1 biramous, peduncle with distoventral corona of cuticular teeth (not shown in Fig. 6 ), length 1.4 x length of outer ramus; outer ramus with 3 lateral slender setae, with large apical robust seta and smaller slender setae; inner ramus 0.6 length of outer ramus, with 1 apical robust seta and 1 slender seta. Uropod 2 uniramous, length of peduncle 4 x width, 3.3 x length of ramus; ramus small, with denticles and single apical seta. Uropod 3 uniramous, peduncle length 1.4 x width; ramus with 4–5 apical curved hooks. Telson length 2.1 x width, deeply cleft, each lobe dorsally with 10 anteriorly directed hooks in 3 rows.

Female (sexually dimorphic characters). Based on paratype, 3.6 mm, AM P70834. Antennae more slender and with fewer aesthetascs than in male, antenna 1 with 3, antenna 2 with 5 flagellar articles, article 1 as long as and more heavily setose than peduncle article 5. Gnathopod 2 similar to 1, but slightly larger. Pereonites 3–5 and coxae successively more elongate than in male; pereonite 4 length 2.7 x depth, coxa width 3.2 length; pereonite 5 length about 3.4 x depth, 2.5 x longer than in male. Coxa 5 enormously enlarged, broadly rounded ventrally, partly infolded under body. Coxa 6 rounded rectangular. Coxa 7 rounded triangular.

Tube. Uniformly fine sediment and detritus.

Habitat. Infaunal sand and rubble dwellers; 17 m.

Remarks. Cerapus nudus sp. nov. differs from congeners in the Indo-Pacific by the distinctive paucity of setae on coxae and pereopods 3–7, and by its slender, elongate antennae, especially in the female. For specific differences from the only other species of Cerapus reported from Lizard Island, C. volucola , see that species below.

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

Figures

FIGURE 5. Cerapus nudus sp. nov., M, holotype, male, 2.4 mm, AM P70908, F, paratype, female, 3.6 mm, AM P70834, Cobia Hole, Lizard Island, Great Barrier Reef. H, dorsal view of head.

FIGURE 6. Cerapus nudus sp. nov., holotype, male, 2.4 mm, AM P70908, except F, paratype, female, 3.6 mm, AM P70834, Cobia Hole, Lizard Island, Great Barrier Reef. Ex lv, exopod lateral view.