Natatolana pellucida ( Tattersall, 1921 )

Keable, Stephen J., 2006, Taxonomic Revision of Natatolana (Crustacea: Isopoda: Cirolanidae), Records of the Australian Museum 58 (2), pp. 133-244 : 213-214

Natatolana pellucida ( Tattersall, 1921)

Cirolana pellucida Tattersall, 1921: 206 , pl. II figs. 4–10.– Nierstrasz, 1931: 158.– Hurley, 1957: 11.– 1961: 267.

Natatolana pellucida .– Bruce, 1981: 958.– 1986: 76, figs. 49, 50.– Brusca et al., 1995: 82.– Bruce et al., 2002: 152.

Type material. Syntypes: 3, 7.5 mm, 2♀♀, 11.3, 12.0 mm, BMNH 1921.11.29.22-24 (measurements of Bruce (1986), examined and newly measured here as—undissected female, 11 mm, partially dissected 3, 9.5 mm and fully dissected female, 12 mm); many specimens, BMNH 1921.11.29.25-44. All examined. Type locality: off Three Kings Island, New Zealand [c. 34°14'S 172°12'E, British Antarctic ( Terra Nova) Expedition Station 130], surface .

Material examined. Queensland: series from off East Fitzroy Reef, AM P47619 –47622; 29, 23°34.92'S 152°11.76'E, 58 m, 16–17 Jun. 1993, SEAS QLD-952; 1, 23°32.53'S 152°16.45'E, 105 m, 16–17 Jun. 1993, SEAS QLD-956; 8, 23°32.16'S 152°17.98'E, 203 m, 16–17 Jun. 1993 SEAS QLD-959; 7, due east of Mooloolaba , 26°36.21'S 153°34.90'E, 116 m, 2–3 Aug. 1994, SEAS QLD-1126.

Diagnosis. Interocular furrow: moderately developed, distinct but not extending across the cephalon. Frontal lamina: lateral margins straight, narrowing anteriorly. Antenna: c. 0.3× as long as body, reaching to between the posterior of pereonite 2 and half way along pereonite 3. Coxal plates: furrows strongly developed, on all coxae. Pleonite 4: apex forming a broad acute point. Pleotelson: broad, length 0.8× basal width; anterodorsal depression present; anterolateral margins convex; posterolateral margins convex; apex produced into a small point; with 8– 12 RS. Pereopods 1–6: males with conspicuous elongated RS subequal to propodus on the merus of pereopods 1–3 and extending from the carpus to dactylus of pereopods 4– 6. Pereopods 2–3: propodus without RS on palm. Pereopod 7: basis of medium breadth ( Bruce (1986) describes it and illustrates it (from a topotype male) as relatively narrow. In the syntype female examined here it is broader), width 0.48– 0.53× length; distance between anterior margin and medial carina less than between posterior margin and medial carina; posterior margin with sparse setae along entire length. Penes: present. Pleopod 2 appendix masculina: extending beyond tip of endopod, 1.06× length of endopod; slender; margins sinuate; apex recurved, bent slightly medially, acute. Uropods: exopod slightly shorter than endopod, 0.87× the length of the endopod.

Variation. There is a variation in the number of robust setae found on the pleotelson margins. For the syntypes Tattersall (1921) describes and illustrates 12 robust setae while Bruce (1986) describes and illustrates only 10. In BMNH 1921.11.29.22-24 the undissected female syntype has 11 robust setae, the male has nine (and appears damaged on side with only three) and the fully dissected female has 10. In a subsample of ten syntype specimens from BMNH 1921.11.29.22-24, 30% had 10 robust setae, 60% had 11 and 10% had 12. The material from off East Fitzroy Reef, Australia (AM P47619–47622) consistently had only eight robust setae on the margins of the pleotelson. Male syntype specimens in BMNH 1921.11.29.22-24, 25-44, have conspicuously elongated robust setae on the merus of pereopods 4–6 but do not have the elongated robust setae on the merus of pereopods 1–3 that are illustrated by Bruce (1986) from Australian material.

Sexual dimorphism. Females lack the conspicuously elongated robust setae present on the merus of pereopods 1–3 and on the carpus of pereopods 4–6 of adult males.

Size. Largest female 12.0 mm, largest male 8.7 mm, largest manca 5.1 mm, smallest adult female 4.1 mm.

Remarks. Natatolana pellucida is most readily distinguished from similar species by details of the pleotelson and uropods, presence of well-developed eyes, rounded posteroventral margins of pereonite 1 and coxa 2 and relatively short propodus of pereopod 5. This species is most similar to N. galathea but has a relatively narrow pleotelson and uropod endopod compared to it.

Distribution and ecology. Australia: Moreton Bay north to Gladstone Queensland, New South Wales, Bass Strait, Tasmania. New Zealand, Campbell Island. Recorded from surface plankton to a depth of 450 m. Scavenger.