Natatolana helenae, Keable, 2006

Keable, Stephen J., 2006, Taxonomic Revision of Natatolana (Crustacea: Isopoda: Cirolanidae), Records of the Australian Museum 58 (2), pp. 133-244 : 182-185

Natatolana helenae n.sp.

Figs. 23–24

Type material. HOLOTYPE: 3, 14 mm, QM W18851. Type locality: Gulf of Carpentaria , Australia, 10°41.4'S 141°51.6'E, [grab], 10 m, [CSIRO Southern Surveyor, 29 Nov. 1991, stn 62].

Diagnosis. Interocular furrow: absent. Frontal lamina: lateral margins straight, narrowing anteriorly. Antenna: c. 0.8× as long as body, reaching to posterior of pereonite 6. Coxal plates: furrows moderately developed, on all coxae. Pleonite 2: ventral posterolateral margin not produced. Pleonite 4: apex slightly rounded. Pleotelson: broad, length 0.67× basal width; anterodorsal depression absent; anterolateral margins almost straight and angling posteriorly toward the midline; posterolateral margins straight, contiguous with anterolateral margins; apex truncate with a serrate margin; with 8 RS. Pereopod 2: propodus without RS on palm. Pereopod 3: ischium anterodistal angle produced subequal to pereopod 2, both more produced than pereopod 1 ischium. Propodus without RS on palm. Pereopods 5–7: propodus short and robust on each pereopod. Pereopod 7: basis broad, width 0.61× length; distance between anterior margin and medial carina less than between posterior margin and medial carina; posterior margin with setae completely absent along entire length. Penes: absent. Pleopod 2 appendix masculina: extending beyond tip of endopod, 1.08× length of endopod; margins straight; slender; apex bent laterally slightly, bluntly rounded. Uropods: exopod short, 0.73× the length of the endopod.

Additional descriptive characters. Based on holotype. Body: length c. 2.35× width. Colour cream in alcohol. Chromatophores absent. Eyes: with 9 ommatidia in

horizontal diameter; with 6 ommatidia in vertical diameter; ovate; colour tan in alcohol. Frontal lamina: length c. 3× basal width; apex expanded, anterior margin angled. Antennule: short, just reaching pereonite 1. Peduncular article 1 longer than article 2; article 2 with 1 large pappose seta medially and several penicillate setae on margins; article 3 short, subequal to article 1. Flagellum 10-articulate. Antenna: peduncular article 4 with 4 short SS at posterodistal angle, 1 penicillate and 1 short SS at anterodistal angle; article 5 with 3 pappose setae and 1 SS at posterodistal angle. Flagellum 47-articulate. Mandible: molar RS absent on margins; incisor narrow, with posterior tooth not strongly developed; setal row with 11 RS. Maxillule: medial lobe with 3 large and 1 smaller robust pappose setae (larger setae with serrations), lateral margin with protuberance absent; lateral lobe with 11 RS on distal surface. Maxilla: lateral lobe with 8 SS (2 are uniserrate and 3 are biserrate); medial lobe with 3 SS and 9 PS; middle lobe with 18 SS, 7 of which are serrate. Maxilliped: palp lateral margin with PS on most of the length of articles 2–5; article 5 serrate setae absent. Endite with 2 coupling hooks, and 6 PS. Pereon: ornamentation consists of 1 strongly developed furrow on lateral margin of pereonite 1 and 1 short, medial furrow on lateral margins of pereonites 4–7; pereonite 1 longest, 2–5 subequal, 6–7 progressively shorter. Coxae: pereonite 1, coxae 2–3 with rounded posteroventral corners, coxae 4–6 with increasingly produced, broad, acute posteroventral corners, coxa 7 posterior margin distinctly concave and posteroventral corner produced into a narrow acute point. Pleonite 2: dorsal posterolateral margin clearly projecting posterior to ventral posterolateral margin. Pleonite 3: rounded. Pleotelson: PS restricted to apex. Pereopod 1: propodus posterodistal angle without RS opposing dactylus. Pereopod 7: basis anterior margin slightly convex; medial carina with PS along entire length; posterior margin convex. Ischium broad, width greater than length; anterior margin with SS; posterior margin with 5 RS (and 3 submarginally), PS present. Merus posterior margin with 2 RS (and 1 submarginally), SS present. Carpus posterior margin without RS, SS absent. Propodus subequal to carpus; posterior margin with 2 RS, SS absent. Pleopod 2 appendix masculina: arising sub-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 subcircular; medial margin rounded, with 4 RS, PS along entire length; apex with 3 RS; lateral margin straight for proximal two thirds, convex at distal third, with 5 RS and 1 penicillate seta, PS on distal third. Exopod medial margin convex, with 3 RS, PS on distal three-quarters; apex acute, with 3 RS; lateral margin convex, with 4 RS, PS on distal two-thirds.

Size. Adults to 14 mm.

Etymology. Named after Ms Helen Stoddart, in recognition of the help she has given me in this and other studies.

Remarks. Natatolana helenae is distinguished from all others species in the genus by the truncate, serrate pleotelson. The lack of robust setae on the mandible molar, the presence of plumose setae on the lateral margins of the maxilliped palp, the serrations on the pappose setae of the medial lobe of the maxillule and the absence of a robust seta at the posterodistal angle of the pereopod 1 propodus, are also unique characters within the genus.

Distribution. Australia: known only from Gulf of Carpentaria. In a depth of 10 m.

Figures

Fig. 23. Natatolana helenae n.sp., holotype. Scales = 0.5 mm.

Fig. 24. Natatolana helenae n.sp., holotype. Scales = 0.5 mm.