Natatolana honu, Keable, 2006

Keable, Stephen J., 2006, Taxonomic Revision of Natatolana (Crustacea: Isopoda: Cirolanidae), Records of the Australian Museum 58 (2), pp. 133-244 : 190-193

Natatolana honu n.sp.

Figs. 29–30

Type material. HOLOTYPE: 3, 11 mm, NIWA 18745 . PARATYPES: all off the west coast of the North Island , New Zealand: 3 , 4♀♀, manca, NIWA 18746 , 38°30'S 172°24'E, 1244–1245 m, NIWA E904 ; 533 , 8♀♀, 3 mancas, NIWA 18747 , 35°20'S 172°15'E, 1286–1313 m, NIWA E881 . Type locality: off the west coast of the South Island , New Zealand, 42°23.7'S 169°11.8'E, [anchor-box dredge], sand-silt-clay, 1120 m, [P.K. Probert, 22 Feb. 1982] .

Diagnosis. Eyes: vestigial. Interocular furrow: well developed, extending across the cephalon or weakly developed, indistinct and not extending across the cephalon; smoothly convex. Frontal lamina: lateral margins straight, narrowing anteriorly. Antenna: c. 0.36× as long as body, reaching to posterior of pereonite 3. Coxal plates: furrows variously developed, absent on coxae 2–5, weakly developed on coxae 6–7. Pleonite 4: apex forming a broad acute point. Pleotelson: broad, length 0.98× basal width; anterodorsal depression absent (there is a slight depression but it is not as distinct and abrupt as the depression found in species such as N. pellucida ); anterolateral margins convex; posterolateral margins convex; apex not produced, lateral margins converging smoothly to a point; with 10–14 RS. Pereopod 2: propodus with 1 RS on palm. Pereopod 3: propodus without RS on palm. Pereopod 7: basis narrow, width 0.33× length; distance between anterior margin and medial carina less than between posterior margin and medial carina; posterior margin with setae on distal half. Penes: present. Pleopod 2 appendix masculina: just shorter than endopod, 0.96× length of endopod; margins very strongly curved laterally; slender; apex not at angle to adjacent margins, bluntly rounded. Uropods: endopod lateral margin with prominent excision. Exopod short, 0.77× the length of the endopod.

Additional descriptive characters. Based on holotype. Body: length c. 2.95× width. Colour translucent white in alcohol. Chromatophores absent. Eyes: with c. 6 ommatidia in horizontal diameter; with 6 ommatidia in vertical diameter; round; without pigment, ommatidia indistinct in alcohol. Frontal lamina: length c. 3.75× basal width; apex expanded, anterior margin angled. Antennule: peduncular article 1 longer than article 2; article 2 with 1 large pappose seta; article 3 very long, subequal to or longer than the combined lengths of articles 1 and 2. Flagellum 10- articulate. Antenna: peduncular article 4 with 1 penicillate seta and 2 SS on posterior margin, 3 SS at anterodistal angle; article 5 with 1 pappose, 1 penicillate and 2 SS at posterodistal angle, 4 SS and 1 penicillate seta at anterodistal angle. Flagellum 21-articulate. Mandible: setal row with 15 RS. Maxillule: medial lobe with 3 large robust pappose setae; lateral lobe with 13 RS on distal surface. Maxilla: lateral lobe with 4 SS; medial lobe with 6 SS and 9 PS; middle lobe with 1 medial row of 5 SS, 1 lateral row of 11 SS. Maxilliped: endite with 1 coupling hook, 7 PS and 1 SS. Pereon: ornamentation absent, all pereonites smooth; pereonite 1 longest, 2–6 subequal, 7 shortest. Coxae: pereonite 1, coxae 2–3 with rounded posteroventral corners, coxae 4–7 with increasingly produced, broad, acute posteroventral corners. Pleonite 2: dorsal posterolateral margin clearly projecting posterior to ventral posterolateral margin. Pereopod 7: basis anterior margin straight; medial carina with SS (on distal three quarters); posterior margin convex, SS present. Ischium anterior margin with non-RS absent; posterior margin with 2 RS (submarginal), PS present. Merus posterior margin with 1 RS (submarginal), SS present. Carpus posterior margin with 4 RS, SS present. Propodus longer than carpus; posterior margin with 6 RS, SS absent. Penes: forming well separated flattened lobes. Pleopod 2 appendix masculina: arising basally. Pleopods 1–5: exopod suture strongly developed on pleopods 3–5; endopod PS on most of margins on pleopods 1–4, absent on pleopod 5. Uropods: endopod lanceolate; medial margin convex, with 5 RS, PS along entire length; apex with 2 RS; lateral margin slightly convex with a prominent lateral excision near apex, with 3 RS, 1 conspicuous penicillate seta in excision, PS on distal third (but absent from proximal part of excision). Exopod medial margin convex, with 3 RS, PS on distal three quarters; apex acute, with 2 RS; lateral margin convex, with 6 RS, PS on distal three quarters.

Variation. The holotype has 11 robust setae on the pleotelson. It is difficult to ascertain the usual number of robust setae present on the pleotelson, as these have been rubbed off most of the material available, but it appears to range between 10 and 14. In some specimens, the interocular furrow is indistinct and incomplete.

Size. Adults to 16.5 mm.

Etymology. From the Maori for deep, in reference to the depths the type specimens have been recorded from.

Remarks. Natatolana honu and N. variguberna are the only species of Natatolana with a prominent excision near the apex of the uropod endopod lateral margin. Natatolana honu most noticeably differs from N. variguberna in having vestigial rather than well-developed eyes, coxal furrows only on the posterior coxae, penes in males, and a greater number of robust setae on the pleotelson margins.

Distribution. New Zealand: west coast of North and South islands. At depths of 1120–1313 m.

Figures

Fig. 29. Natatolana honu, n.sp., holotype. Scales = 0.2 mm.

Fig. 30. Natatolana honu, n.sp., holotype. Scales = 0.5 mm.