Natatolana rusteni, Keable, 2006

Keable, Stephen J., 2006, Taxonomic Revision of Natatolana (Crustacea: Isopoda: Cirolanidae), Records of the Australian Museum 58 (2), pp. 133-244 : 221-224

Natatolana rusteni n.sp.

Figs. 43–44

Type material. HOLOTYPE: 3, 8 mm, AM P47158 . PARATYPES: 576 specimens AM P38672 ; 3, ♀, in BMNH, USNM, ZMUC. Type locality: off Dobroyd Head , Port Jackson, NSW, Australia, 33°48.7'S 151°16.4'E, [baited trap, unknown substrate, probably sediment], 15 m, [S. Keable, D. Townsend, J. Lowry, 3–4 Jul. 1988, Site 30] .

Additional material. New South Wales: ♀, ZMUC CRU122 , near Solitary Islands , 29°57'S 153°22'E, 50 m, 11 Nov. 1951, Galathea stn 544; series of 224 specimens, AM P47159–47165, Port Jackson , 33°48.3–50.3'S 151°15.2–16.6'E, baited trap, sediments, 8–13 m, S. Keable et al., 1988; series of 254 specimens,

AM P47166–47172, off Bate Bay / Port Hacking, 34°07.00'S 151°10.00'E, baited trap, sediments, 25–40 m,AM/The Ecology Lab Pty. Ltd. Pioneer Consultation Project 1991; series of 18 specimens, AM P47173–47184, Botany Bay, 33°58.25–59.31'S 151°09.91– 11.92'S, baited traps, sediments, 5–7 m, S. Keable & R. Springthorpe 1992, AM/ Federal Airports Corporation Consultation Project .

Diagnosis. Interocular furrow: moderately developed, distinct but not extending across the cephalon. Frontal lamina: lateral margins straight, parallel. Antenna: c. 0.23× as long as body, reaching to posterior of pereonite 2. Coxal plates: furrows moderately developed, on all coxae. Pleonite 4: apex broadly rounded. Pleotelson: narrow, length 1.05× basal width; anterodorsal depression absent; anterolateral margins convex; posterolateral margins convex; apex not produced, lateral margins converging smoothly to a point; with 6–7 RS. Pereopods 2–3: propodus without RS on palm. Pereopod 7: basis broad, width 0.63× length; distance between anterior margin and medial carina greater than between posterior margin and medial carina; posterior margin with setae along entire length. Penes: absent. Pleopod 2 appendix masculina: extending beyond tip of endopod, 1.04× length of endopod; margins very slightly curved laterally; slender; apex recurved, bent slightly medially, bluntly rounded. Uropods: exopod short, 0.72× the length of the endopod.

Additional descriptive characters. Based on holotype. Body: length c. 3.48× width. Colour cream in alcohol. In freshly preserved material there is often an orange or red/ brown colouring on the posterolateral margins of pleonite 4. Chromatophores absent. Eyes: with 6 ommatidia in horizontal diameter; with 8 ommatidia in vertical diameter; round; colour red/brown in alcohol. Frontal lamina: length c. 5× basal width; apex expanded, anterior margin angled. Antennule: peduncular article 1 longer than article 2; article 2 with 1 large pappose seta; article 3 long, larger than article 1 or 2 but shorter than their combined lengths. Flagellum 9-articulate. Antenna: peduncular article 4 with 1 penicillate seta and 2 SS on posterolateral margin, several PS at anterodistal angle; article 5 with 2 conspicuous pappose setae at posterodistal angle, 1 penicillate seta and 5 SS at anterodistal angle. Flagellum 12-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 5 SS; medial lobe with 5 SS and 7 PS; middle lobe with 12 SS. Maxilliped: endite with 1 coupling hook, and 3 PS. Pereon: ornamentation consists of 1 weakly developed furrow on lateral margin of pereonite 1 and 1 short, medial furrow on lateral margins of pereonites 4–6; pereonites 1, 4–6 subequal and longest, 2–3 and 7 subequal. Coxae: pereonite 1 and coxae 2–5 with rounded posteroventral corners, coxae 6–7 with increasingly produced, broad, acute posteroventral corners. Pleonite 2: dorsal posterolateral margin subequal with ventral posterolateral margin. Pereopod 7: basis anterior margin slightly convex; medial carina with PS along entire length; posterior margin convex, PS present. Ischium anterior margin with SS (sparse); posterior margin without RS, PS present. Merus posterior margin with 3 RS (and 3 submarginally), 1 SS. Carpus posterior margin with 3 RS (and 2 submarginally), SS absent. Propodus subequal to carpus; posterior margin with 4 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 of pleopods 1–4, only a few setae on pleopod 5. Uropods: endopod lanceolate; medial margin convex, with 3 RS, PS along entire length; apex with 3 RS; lateral margin slightly convex, with 2 RS and 1 penicillate seta, PS on distal two-thirds. Exopod medial margin convex, with 2 RS, PS on distal two-thirds; apex acute, with 2 RS (1 missing on side illustrated but socket present and setae present on other side); lateral margin convex, with 3 RS, PS on distal two thirds.

Variation. One paratype specimen has seven robust setae on the pleotelson margin.

Size. Adults to c. 8 mm.

Etymology. Named after Mr Jim Rusten, former storeman at the Australian Museum, in recognition of his help with boats and other field equipment that made collection of the type specimens possible.

Remarks. Natatolana rusteni is separated from nearly all other species within the genus by its relatively short antennae that have few flagellar articles. This character, in combination with the number of robust setae on the pleotelson and the shape of the pleotelson, identifies this species as distinct. Natatolana kahiba is most similar but has a shorter, less acute pleotelson with four robust setae. Natatolana lilliput n.sp. is also extremely similar but also has a shorter, less acute pleotelson and a complete interocular furrow.

Distribution and ecology. Australia: within and off Port Jackson and Botany Bay, and off Solitary Islands, New South Wales. At depths of 5– 50 m. Scavenger.

Figures

Fig. 43. Natatolana rusteni n.sp., holotype. Scales = 0.2 mm.

Fig. 44. Natatolana rusteni n.sp., holotype. Scales = 0.5 mm, except for MX2 and U = 0.2 mm.