Natatolana flexura, Keable, 2006

Keable, Stephen J., 2006, Taxonomic Revision of Natatolana (Crustacea: Isopoda: Cirolanidae), Records of the Australian Museum 58 (2), pp. 133-244 : 178

Natatolana flexura n.sp.

Figs. 20–22

Type material. HOLOTYPE: 3, 6 mm, AM P47222 . PARATYPES: All off Wollongong, NSW, baited trap, 100 m, P. Freewater, S. Keable & W. Vader, May 1993 ; 35 specimens (mancas and ♀♀), AM P47223, 34°28.15'S 151°02.37'E, 15.5°C, SEAS NSW-778; 433 , 18♀♀, 75 mancas, AM P47224, 34°33.41'S 151°21.35'E, SEAS NSW-796. Type locality: east of Fortescue Bay , north of Hippolyte Rocks, Tasmania, Australia, 43°06.70'S 148°03.45'E, [baited trap], 100 m, [15.8° C, J. Lowry & P. Freewater, 16–17 April 1993, SEAS TAS-355] .

Diagnosis. Interocular furrow: weakly developed, indistinct and not extending across the cephalon. Frontal lamina: lateral margins concave but not medially constricted, narrowing toward apex. Antenna: c. 0.3× as long as body, reaching to posterior of pereonite 2. Coxal plates: furrows strongly developed, on all coxae. Pleonite 4: apex forming a broad acute point. Pleotelson: broad, length 0.82× basal width; anterodorsal depression present; anterolateral margins almost straight and angling posteriorly toward the midline; posterolateral margins convex; apex not produced, lateral margins converging smoothly to a point; with 2 RS. Pereopods 2–3: propodus without RS on palm. Pereopod 7: basis narrow, width 0.4× 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: extending subequal with tip of endopod, 1.07× length of endopod; margins strongly or very strongly curved laterally; broad; apex not at angle to adjacent margins, broadly rounded with a slight depression at tip. Uropods: exopod slightly shorter than endopod, 0.81× the length of the endopod.

Additional descriptive characters. Based on holotype. Body: length c. 2.7× width. Colour translucent white with a yellow tinge in alcohol. Chromatophores present; small; yellow to brown in freshly preserved material, fading completely after a short time in preservative; on all sections of the body but concentrated on posterior segments. Eyes: with 8 ommatidia in horizontal diameter; with 8 ommatidia in vertical diameter; round; colour red in freshly preserved material, turning to tan after a short time in preservative. Frontal lamina: length c. 4× basal width; apex expanded, anterior margin angled. Antennule: peduncular article 1 longer than article 2; article 2 with 1 large pappose seta and 2 SS at posterodistal angle, 1 PS and 1 penicillate seta at anterodistal angle; article 3 long, larger than article 1 or 2 but shorter than their combined lengths. Flagellum 10- articulate. Antenna: peduncular article 4 with 3 SS on medial surface, 2 SS and 1 penicillate seta at anterodistal angle; article 5 with 2 large pappose setae at posterodistal angle. Flagellum 16-articulate. Mandible: setal row with 18 RS. Maxillule: medial lobe with 3 large and 1 smaller robust pappose setae; lateral lobe with 13 RS on distal surface. Maxilla: lateral lobe with 4 SS; medial lobe with 5 SS and 6 PS; middle lobe with 7 long SS on outer row and 2 long SS on inner row. Maxilliped: endite with 1 coupling hook, and 3 PS. Pereon: ornamentation consists of 1 strongly developed furrow on lateral margin of pereonite 1; pereonites 1, 4–5 subequal and longest, 2–3 and 6 subequal and longer than 7. Coxae: pereonite 1, coxae 2–3 posteroventral corners rounded, coxae 4–7 with increasingly produced, broad, acute posteroventral corners. Pleonite 2: dorsal posterolateral margin subequal with ventral posterolateral margin. Pleotelson: posterolateral margins conspicuously serrate. Pereopod 7: basis anterior margin slightly convex; medial carina with SS; posterior margin convex, PS present. Ischium anterior margin with non-RS absent; posterior margin without RS, PS present. Merus posterior margin with 3 RS, non-RS absent. Carpus posterior margin with 3 RS, SS absent. Propodus longer than carpus; posterior margin with 5 RS, SS absent. Penes: forming well separated flattened lobes. Pleopod 2 appendix masculina: arising basally. Pleopods 1–5: exopod suture feebly developed on pleopods 3–5; endopod PS on most of margins of pleopods 1–4, only a few setae on pleopod 5. Uropods: endopod triangular; medial margin convex, with 3 RS, PS along entire length; apex with 2 RS; lateral margin slightly concave with a prominent notch, with 1 RS and 1 prominent penicillate seta in notch, PS along entire length (but absent from distal section of notch). Exopod medial margin convex, with 2 RS, PS along entire length; apex acute, with 2 RS; lateral margin convex, with 4 RS, PS along entire length.

Variation. The paratype males do not have the appendix maculina as strongly curved laterally as in the holotype.

Size. Adults to c. 6 mm.

Etymology. From the Latin “flecto” (to bend or curve) in reference to the shape of the pleopod 2 appendix masculina.

Remarks. Natatolana flexura can be distinguished from all other species in the genus by the presence of an anterodorsal depression on the pleotelson, the low number of robust setae on the margins of the pleotelson and the shape of the lateral margins of the uropod endopod.

Distribution and ecology. Australia: east of Fortescue Bay, north of Hippolyte Rocks, Tasmania; off Wollongong, New South Wales. At depths of 100 m. Scavenger.

Figures

Fig. 20. Natatolana flexura n.sp., holotype. Scales = 0.2 mm.

Fig. 21. Natatolana flexura n.sp., holotype. Scales = 0.5 mm.

Fig. 22. Natatolana flexura n.sp., holotype. Scales = 0.5 mm, except PL2 = 0.2 mm.