Natatolana pilula ( Barnard, 1955 )

Keable, Stephen J., 2006, Taxonomic Revision of Natatolana (Crustacea: Isopoda: Cirolanidae), Records of the Australian Museum 58 (2), pp. 133-244 : 214

Natatolana pilula ( Barnard, 1955)

Figs. 38–40

Cirolana pilula Barnard, 1955: 54 , fig. 26a–c.– Kensley, 1975: 39.– 1978: 69, fig. 28H.

Natatolana pilula .– Bruce 1981: 958.– 1986: 8, 222.– Brusca et al., 1995: 82.– Kensley, 2001: 230.

Type material. Syntypes: 3 specimens, SAM A-43144. According to Barnard (1955) “including male but no ovigerous female”. All examined. The material registered as the types has been largely dismembered. One specimen (including pereonites 2–7, pleon and pleotelson), however, has ooestegites and developing embryos. The remaining specimens cannot be sexed. The pleopod 2 with the appendix masculina figured by Barnard (1955) is not present. None of the type material is in good enough condition to use for a full redescription. Type locality: False Bay, South Africa, 34°17'06"S 18°39'02"E and 34°12'08"S 18°36'05"E, 46– 62 m.

Material examined. South Africa: 3, 10 mm, SAM-A14532, False Bay , 34°12.5'S 18°37'E, 15 May 1961, Sta No: FAL 414V .

Diagnosis. Interocular furrow: well developed, extending across the cephalon; smoothly convex. Frontal lamina: lateral margins straight, parallel. Antenna: c. 0.2× as long as body, reaching to just posterior of pereonite 1. Coxal plates: furrows variously developed, strong but incomplete on coxae 2–4, complete on coxae 5–7. Pleonite 4: apex broadly rounded. Pleotelson: broad, length 0.67× basal width; anterodorsal depression absent; anterolateral margins convex; posterolateral margins broadly rounded; apex truncate; RS absent. Pereopods 2–3: propodus without RS on palm. Pereopods 5–7: propodus short and robust on each pereopod. Pereopod 7: basis broad, width 0.58× length; distance between anterior margin and medial carina less than between posterior margin and medial carina; posterior margin with setae along entire length. Penes: absent. Pleopod 2 appendix masculina: extending subequal with tip of endopod, 0.99× length of endopod; margins straight or sinuate; slender; apex bent laterally slightly, serrulate with a minute digitiform process. Uropods: exopod slightly shorter than endopod, 0.8× the length of the endopod.

Additional descriptive characters. Body: length c. 2.5× width. Colour cream to white in alcohol. Chromatophores absent. Cephalon: submarginal cephalic furrow moderately developed, does not run entire length of anterior margin. Eyes: with 7 ommatidia in horizontal diameter; with 9 ommatidia in vertical diameter; ovate; colour deep red 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; 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 long SS projecting from posterolateral margin; article 5 with 2 conspicuous pappose setae at posterodistal angle. Flagellum 15-articulate. Mandible: setal row with 13 RS. Maxillule: medial lobe with 3 large robust pappose setae; lateral lobe with 13 RS on distal surface. Maxilla: lateral lobe with 6 SS; medial lobe with 5 SS and 6 PS; middle lobe with 15 SS. Maxilliped: endite with 2 coupling hooks, and 5 PS. Pereon: ornamentation consists of 1 strongly developed furrow on the lateral margins of pereonite 1 and 1 weakly developed furrow on lateral margins of pereonites 2– 7; pereonite 1 longest, 2–5 subequal, 6–7 progressively shorter. Coxae: pereonite 1, coxae 2–4 with rounded posteroventral corners, coxa 5 with a short square corner, coxae 6 and 7 with broad, acute, posteroventral corners. Pleonites: 1 concealed by pereonite 7, 2–5 visible. Pleonite 2: not produced. Pleonite 3: subacute. Pleotelson: PS restricted to apex. Pereopod 7: basis anterior margin straight; medial carina with PS along entire length; posterior margin convex, posterior margin SS present. Ischium anterior margin with non-RS absent; posterior margin with 2 RS (submarginal), PS present. Merus posterior margin with 8 RS, SS present. Carpus posterior margin with 1 RS, SS absent. Propodus subequal to carpus; posterior margin with 3 RS, SS present. Pleopod 2 appendix masculina: arising basally. Pleopods 1–5: exopod suture absent 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 3 RS, PS along entire length; apex with 3 RS; lateral margin straight, with 1 RS, PS on distal three-quarters. Exopod medial margin convex, with 1 RS, PS present on distal half; apex rounded, with 3 RS; lateral margin convex, with 2 RS, PS on distal quarter.

Size. 10–11 mm ( Barnard, 1955; Kensley, 1978; this study).

Remarks. The material examined matches the original description and illustrations of Natatolana pilula by Barnard (1955) except that chromatophores are absent, whereas the original description mentions pinkish or greyish speckles.

The following characters are most useful in distinguishing Natatolana pilula from other species within the genus; the short antenna, the shape of the posterolateral margins of pleonites 3 and 4, the shape and setation of the pleotelson and uropods; and the morphology of the appendix masculina apex.

Distribution. South Africa: Lambert’s Bay to Natal.At depths of 18–66 m ( Barnard, 1955; Kensley, 1978; Bruce, 1986).

Figures

Fig. 38. Natatolana pilula, male SAM A-14532. Scales for MD, MP = 0.5 mm, for MX1, MX2 = 0.2 mm, for A1, A2 = 0.5 mm.

Fig. 39. Natatolana pilula, male SAM A-14532. Scales = 0.5 mm.

Fig. 40. Natatolana pilula, male SAM A-14532. Scales = 0.5 mm.