Neocirolana taylori, Bruce & Hughes, 2020

Bruce, Niel L. & Hughes, Lauren, 2020, A new species of Neocirolana Hale, 1925 (Crustacea: Isopoda: Cirolanidae) collected during the Royal Society Expedition to Aldabra 1967 - 69, western Indian Ocean, Journal of Natural History 54 (21 - 22), pp. 1395-1407 : 1398-1403

Neocirolana taylori sp. nov. Figures 1–5

Material examined

All samples from Aldabra, Seychelles, Indian Ocean.

Holotype. ♂ (7.5 mm), Picard Settlement , Picard Island, 1 December 1967, seaward flats boulder zone, sublittoral fringe, coll. John D. Taylor ( NHM 2018.1273 ).

Paratypes. ♂ (6.2 mm dissected, 3 slides), ♀ (8.0 mm ovig., 7.8 mm non-ovig. [photo NHM UK 2018.1271]), mancas 4.2, 3.7 mm), same data as holotype ( NHM 2018.1275 ) . ♂ (5.5 mm), Anse Mais , 4 December 1967, boulder zone, coll . NFD ( NHM 2018.1274 ) . ♂ (4.9 mm), ♀ (8.9, 8.2 mm, non-ovig.), East Channel , 4 October 1967, seaward reef, coll . John D . Taylor ( NHM 2018.1276 ) . ♂ (5.0 mm), ♀ (7.5 mm, non-ovig), Guest House Settlement , Picard Island, 5 September 1967, boulder zone opposite settlement, coll . John D . Taylor ( NHM 2018.1272 ) .

Description of male. Body widest at pereonite 5, dorsal surfaces smooth, lateral margins weakly ovate. Rostral point present, folded ventrally and posteriorly, in contact with frontal lamina. Eyes separated by about 64% width of head, each eye made up of 6 transverse rows of ommatidia, each row with ~5 ocelli; eye colour black. Pereonite 1 and coxae 2–3 each with posteroventral angle rounded; coxae 5–7 strongly posteriorly produced, with coxae 7 extending to posterior margin of pleonite 5, each with entire oblique carina; posterior margins of pereonites 5–7 smooth. Pleon with pleonite 1 wholly concealed by pereonite 7; pleonites 3–5 posterior margin smooth; posterolateral angles of pleonite 2 not visible, not posteriorly produced; pleonite 3 with posterolateral margins extending clearly beyond posterior margin of pleonite 5, rounded; posterolateral margin of pleonite 4 rounded, clearly extending beyond posterior margin of pleonite 5; pleonite 5 with posterolateral angles overlapped by lateral margins of pleonite 4. Pleotelson 0.7 times as long as anterior width, dorsal surface without longitudinal carina; lateral margins weakly convex, margins smooth, posterior margin evenly rounded, without median point, with 8 RS.

Antennula peduncle articles 1 and 2 entirely fused; articles 3 and 4 1.1 times as long as combined lengths of articles 1 and 2, article 3 2.3 times as long as wide; flagellum with 10 articles, extending to middle of pereonite 1. Antenna peduncle article 4 1.6 times as long as wide, 2.7 times as long as article 3, inferior margin without plumose setae, without short simple setae; article 5 length 1.1 times as long as article 4, 2 times as long as wide, inferior margin without pappose setae; articles 3–5 anterodistal angles with cluster of 3, 7 and 6 setae; antenna flagellum with 17 articles, extending to posterior of pereonite 2.

Frontal lamina pentagonal, ventral surface entirely flat, as wide as long, lateral margins straight, diverging slightly towards anterior, anterior margin acute, without small median point.

Mandible incisor 0.4 proximal mandible width; molar process anterior margin with 12 flat teeth; without proximal cluster of long simple setae; right mandible spine row composed of 7 spines, left with 5 spines; palp article 2 with 13 distolateral setae, palp article 3 with 16 biserrate RS. Maxillula mesial lobe with 3 large and circumplumose RS (relatively slender); lateral lobe with 12 RS (and 1 stiff slender seta). Maxilla lateral lobe with 4 long simple setae; middle lobe with 5 long simple setae; mesial lobe with 7 distal simple setae and 2 proximal simple and plumose setae. Maxilliped palp article 2 mesial margin with 4 slender setae, lateral margin distally without slender setae; article 3 mesial margin with 9 slender setae, lateral margin with 5 slender setae; article 4 mesial margin with 10 slender setae, lateral margin with 2 slender setae; article 5 distal margin 7 setae, lateral margin with 3 setae; endite with 3 long CPS, and 1 coupling seta.

Pereopod 1 basis 2.1 times as long as greatest width, superior distal angle without cluster of acute setae, inferior distal angle with cluster of 2 acute setae; ischium 0.5 times as long as basis, inferior margin with 0 setae, inferior distal margin with 2 RS, superior distal margin with 4 RS; merus inferior margin with 5 molariform RS, set as two groups of 3 + 2, inferior margin with 2 simple setae, inferior distal margin with 1 RS, superior distal angle with 2 setae; carpus inferior margin with 1 acute RS, inferior margin with 1 simple seta; propodus 2.4 times as long as wide, inferior margin with 1 RS, inferior margin without simple setae, inferior distal margin with 1 large RS, superior distal with 2 simple setae; dactylus 0.4 as long as propodus; inferior margins with setal fringe lacking. Pereopod 2 ischium inferior margin without stout, bluntly rounded RS, 4 long acute RS (as 1 + 3), 2 simple setae, superior distal margin with 3 long simple setae. 1 RS; merus inferior margin with 7 stout RS, set as two groups (as 5 + 2), inferior distal margin with 2 stout RS, superior distal margin without stout RS, superior distal margin with 6 acute RS; carpus inferior distal margin with 3 RS; propodus 2.1 as long as wide, without clusters of acute RS; inferior margin with 2 RS; inferodistal margin without long RS; inferodistal margin with 3 simple setae; dactylus 0.5 as long as propodus. Pereopod 3 similar to pereopod 2. Pereopod 6 similar to pereopod 7. Pereopod 7 basis 2.5 times as long as greatest width, superior margin convex, inferior margin with 5 palmate setae; ischium 0.7 as long as basis, inferior margin with 14 RS (4 clusters of 1 + 3 + 6 + 4), superior distal angle with 12 RS, inferior distal angle with 6 RS; merus 0.5 as long as ischium, 2.1 times as long as wide, inferior margin with 6 RS, superior distal angle with 9 RS, inferior distal angle with 8 RS; carpus 0.6 as long as ischium, 1.6 times as long as wide, inferior margin with 5 RS (as 1 + 2), superior distal angle with 13 RS, inferior distal angle with 9 RS; propodus 0.7 as long as ischium, 2.4 times as long as wide, inferior margin with 6 clusters of RS (as 3 clusters of 2), superior distal angle with 4 slender setae, inferior distal angle with 1 RS; dactylus 0.5 as long as propodus.

Penes opening flush with surface of sternite 7, penial openings separated by <2% of sternal width.

Pleopod 1 exopod 1.7 times as long as wide, lateral margin straight, distally broadly rounded, mesial margin strongly convex, with PMS from distal one-third, with 22 PMS; endopod 2.7 times as long as wide, distally subtruncate, lateral margin weakly concave, with PMS on distal margin only, mesial margin with PMS on distal margin only, endopod with 10–12 PMS; peduncle 1.9 times as wide as long; mesial margin with 3 coupling setae. Pleopod 2 exopod with ~34 PMS, endopod with ~5 PMS; appendix masculina with parallel margins, 1.3 times as long as endopod, distally acute, narrowing from distal 14% of length. Pleopod 3 exopod with 38 PMS, endopod with 14 PMS. Pleopod 4 exopod with 36 PMS, endopod with 9 PMS. Pleopod 5 exopod with 30 PMS. Pleopods 2–5 peduncle distolateral margin without prominent acute RS, 3–5 endopods without distomesial serrate scales.

Uropod peduncle ventrolateral margin with 3 RS, lateral margin with one medial short acute RS, posterior lobe about three-quarters as long as endopod; rami extending beyond pleotelson, marginal setae in single tier, apices narrowly rounded. Endopod apically shallowly bifid; lateral margin weakly convex, proximal lateral margin with 1 RS; distal lateral margin with 2 RS, mesial margin weakly convex, with 7 RS. Exopod not extending to end of endopod, 2.6 times as long as greatest width, apically shallowly bifid; lateral margin weakly convex, with 9 RS; mesial margin convex, with 4 RS.

Size. Males 5.0– 7.5 mm (mean 6.05 mm), females 7.5–8.9 mm (mean 8.08 mm).

Remarks. Neocirolana taylori sp. nov. can be identified by the smooth dorsal body surfaces (lacking carinae or nodular ornamentation), ovate and strongly vaulted body, prominent and posteriorly produced coxae on pereonites 5 to 7, the coxae of pereonite 7 overlapping the pleon and extending posteriorly to just beyond pleonite 5; other distinguishing characters include the acute appendix masculina extending well beyond the distal margin of pleopod 2 and the uropodal endopod lateral margin not excised.

Neocirolana taylori sp. nov. aligns with N. obtusata ( Richardson, 1901) and N. tayronae Müller, 1993 , both from the Caribbean region of the tropical western Atlantic, which are similarly without dorsal ornamentation and lacking an excision to the lateral margin of the uropodal endopod. Neocirolana obtusata has moderately produced coxae that are prominent in dorsal view ( Martin and Felder 1984) but coxae 5 to 7 are not as strongly produced as in N. taylori , not reaching to pleonite 5; N. obtusata also has a broadly truncate pleotelson (vs. narrowly rounded in N. taylori ). Neocirolana tayronae has a more elongate and parallel-sided body, with a more broadly rounded pleotelson than N. taylori , and furthermore has more slender pereopods with a notably longer dactylus on all pereopods (e.g. pereopod 1 dactylus 0.7 as long as propodus in N. tayronae vs 0.4 in N. taylori ).

Distribution. Picard Island, Aldabra Atoll; all samples from the reef crest.

Etymology. Named for the noted malacologist John D. Taylor, who collected most of the specimens as a member, and then fieldwork leader, of the research team on the 1967–8 Royal Society Expeditions to Aldabra.

Figures

Figure 1. Neocirolana taylori sp. nov. habitus, paratype, non-ovig. female, 7.8 mm, NHM UK 2018.1271. Scale mm.

Figure 2. Neocirolana taylori sp. nov. habitus, holotype, male, 7.5 mm, NHM UK 2018.1273; Antennaeparatype male, 6.2 mm, NHM UK 2018.1275, Picard Island, Aldabra Atoll, Seychelles. (a) dorsal view, cephalon and anterior pereonites; (b) dorsal view; (c) lateral view; (d) dorsal view, cephalon; (e) frons; (f) antenna; (g) antennula.

Figure 3. Neocirolana taylori sp. nov. paratype male, 6.2 mm, NHM UK 2018.1275, Picard Island, Aldabra Atoll, Seychelles. a, right mandible; b, left mandible; c, maxilliped; d, maxillula; e, maxilla.

Figure 4. Neocirolana taylori sp. nov. paratype male, 6.2 mm, NHM UK 2018.1275, Picard Island, Aldabra Atoll, Seychelles. a–c, pereopods 1, 2 and 7 respectively.

Figure 5. Neocirolana taylori sp. nov. paratype male, 6.2 mm, NHM UK 2018.1275, Picard Island, Aldabra Atoll, Seychelles. a, uropod; b–f, pleopods 5–1 respectively.