Tridentella katlae, Bruce & Svavarsson, 2018

Bruce, Niel L. & Svavarsson, Jörundur, 2018, Three new species of Tridentella Richardson, 1905 (Isopoda: Cymothoida: Tridentellidae) from New Caledonia, Zootaxa 4399 (1), pp. 101-118 : 108-111

Tridentella katlae sp. nov. Figs 6–9

Holotype: ♀ (non-ovig. 8.0 mm), New Caledonia, Iles Loyaute, Lifou, Baie du Santal, SE Récif Shelter, 20°54.1’S, 167°03.3'E, atelier, 7–19 November 2000, 150 – 200 m, LIFOU 2000, stn DW1648, N.O.“Alis”, (MNHN-IU- 2017-20).

Description: Body 3.0 times as long as greatest width, dorsal surfaces polished in appearance, widest at pereonite 5, lateral margins subparallel. Head smooth, without ornamentation, rostral point absent. Eyes mesially united; occupying 55% of head length, each eye made up of ~10 transverse rows of ommatidia, each row with ~30 ommatidia, eye colour black. Pereon with partial transverse impressed line on pereonites 5–7; pereonite 1 and coxae 2–3 each with posteroventral angle rounded; coxae 5–7 with incomplete oblique carina; posterior margins of pereonites 5–7 smooth. Pleon with pleonite 1 visible in dorsal view; pleonites 3–5 posterior margin with irregular small nodules; posterolateral angles of pleonite 2 forming acute point, not posteriorly produced; pleonite 3 with posterolateral margins not extending to posterior margin of pleonite 4, acute; posterolateral margins of pleonite 4 clearly extending beyond posterior margin of pleonite 5, acute. Pleotelson 0.8 times as long as anterior width, dorsal surface with paired, serrate submedian carinae, third lower median carina; surface with multiple low, blunt nodules; lateral margins weakly convex, prominently serrate; posterior margin weakly serrate, posterior margin truncate, with shallow notch, with small distinct median point; with 0 RS.

Antennula peduncle articles 1 and 2 distinct, articulated; article 2 1.2 times as long as article 1; articles 3 and 4 1.2 times as long as combined lengths of articles 1 and 2; posterodistal angle not produced; flagellum with 12 articles, extending to posterior margin of eye. Antenna peduncle article 4 2.5 times as long as wide, 2.2 times as long as article 3, inferior margin with 1 simple seta, and 1 short simple setae; article 5 1.6 times as long as article 4, 4.7 times as long as wide, inferior margin with 0 pappose setae, anterodistal angle with cluster of 4 short simple setae; extending to posterior of pereonite 2.

Frontal lamina pentagonal, longer than greatest width, lateral margins concave, anterior margins straight, anterior margin forming median point. Maxilliped palp article 2 mesial margin with 2 slender setae, lateral margin distally with 0 slender setae, article 3 mesial margin with 6 slender setae, lateral margin with 1 slender setae, article 4 mesial margin with 5 slender setae, lateral margin with 2 slender setae (article 4 fused to article 5), article 5 distomesial margin with 7 setae, lateral margin with 2 setae; endite extending to distal margin of palp article 4 with 0 long circumplumose setae.

Pereopod 1 basis 3 times as long as greatest width, superior distal angle with cluster of 2 acute simple setae; ischium 0.3 times as long as basis, inferior margin with 3 setae, superior distal margin with 3 RS; merus inferior margin with 3 RS (small, acute), set as two rows, superior distal angle with 1 setae; carpus inferior margin with 1 RS (small, acute, + 1 seta); propodus 2.1 times as long as wide, inferior margin with 0 RS; propodal palm weakly concave; dactylus 0.3 as long as propodus. Pereopod 2 more slender than pereopod 1. Pereopod 2 ischium inferior margin with 0 stout RS (1 acute RS), superior distal margin with 1 RS (+4 setae); merus inferior margin with 3 stout RS (small, acute), set as two groups, superior distal margin with 0 acute RS (2 setae); carpus inferodistal angle with 1 RS. Pereopod 2 propodal palm with 4 RS. Pereopod 3 similar to pereopod 2. Pereopod 6 similar to pereopod 7. Pereopod 7 basis 3.1 times as long as greatest width, superior margin weakly convex (with 6 plumose setae), inferior margin with 0 palmate setae; ischium 0.4 times as long as basis, inferior margin with 2 acute RS, superior distal angle with 3 RS, inferior distal angle with 4 RS; merus 0.9 times as long as ischium, 1.9 times as long as wide, inferior margin with 4 acute RS, superior distal angle with 5 RS, inferior distal angle with 3 RS; carpus 0.8 times as long as ischium, 1.6 times as long as wide, inferior margin with 1 RS, superior distal angle with 8 RS, inferior distal angle with 4 RS; propodus 1 as long as ischium, 3.1 times as long as wide, inferior margin with 2 RS, superior distal angle with 2 slender setae (and 2 acute RS), inferior distal angle with 1 RS.

Pleopod 1 exopod 1.4 times as long as wide, lateral margin weakly convex, distally broadly rounded, mesial margin strongly convex, with PMS from distal one-third, with ~31 PMS; endopod 1.6 times as long as wide, distally broadly rounded, lateral margin weakly concave, with PMS on distal margin only, mesial margin with PMS on distal margin only, endopod with ~17 PMS; peduncle 2.2 times as wide as long; mesial margin with 5 coupling hooks. Pleopod 2 exopod with ~40 PMS, endopod with ~19 PMS.

Uropod peduncle lateral margin with medial short acute robust seta, uropod peduncle posterior lobe about onehalf as long as endopod; rami not extending beyond pleotelson, marginal setae in single tier, apices broadly rounded. Endopod apically not bifid; lateral margin straight, proximal lateral margin with 0 RS; distal lateral margin with 0 RS, mesial margin straight (then convex proximally), with 0 RS. Exopod not extending to end of endopod, 3.1 times as long as greatest width, apically shallowly and equally bifid; lateral margin straight, serrate with 5 teeth and 0 RS; mesial margin sinuate, proximally concave, with 0 RS.

Male: Not known.

Remarks: Tridentella katlae sp. nov. is the only species in the family with eyes that are medially united in dorsal view and occupying most of the head, a character that occurs also in the family Aegidae (see Bruce 2009). This character together with the tri-carinate pleotelson, with serrated lateral margins and the presence of numerous small simple nodules over the pleon and pleotelson serve to identify the species.

Etymology: Named for Katla Magnúsdóttir, the mother-in-law of the second author, a kind and caring person, who passed away during the second authors sabbatical in Australia.

Figures

FIGURE6. Tridentella katlae sp. nov., holotype(female, non-ovig.8.0mm, MNHN-IU-2017-20).A, habitus,dorsal view; B, posterior pereonites, dorsal view; C, habitus, lateral view; D, head, dorsal view; E, frons; F, pleonites; G, pleotelson and uropods; H, pleotelson and uropods, dorsolateral view.

FIGURE 7. Tridentella katlae sp. nov., holotype (female, non-ovig. 8.0 mm, MNHN-IU-2017-20). A, antennula and antenna, in situ; B, maxilliped.

FIGURE 8. Tridentella katlae sp. nov., holotype (female, non-ovig. 8.0 mm, MNHN-IU-2017-20). A, pereopod 1; B, pereopod 2; C, pereopod 6; D, pereopod 7.

FIGURE 9. Tridentella katlae sp. nov., holotype (female, non-ovig. 8.0 mm, MNHN-IU-2017-20). A, pleopod 1; B, pleopod 2; C, uropod.