Natatolana bulba Bruce, 1986

Keable, Stephen J., 2006, Taxonomic Revision of Natatolana (Crustacea: Isopoda: Cirolanidae), Records of the Australian Museum 58 (2), pp. 133-244 : 158-161

Natatolana bulba Bruce, 1986

Natatolana bulba Bruce, 1986: 108 , fig. 75.–Springthorpe & Lowry, 1994: 41.– Brusca et al., 1995: 80.– Bruce et al., 2002: 150.

Type material. Holotype: 3, 9.5 mm, AM P32174 . Paratypes: AM E4843. All examined. Type locality: off North West Island , Capricorn Group, Southern Great Barrier Reef, Queensland, Australia, 23°17.5'S 151°42'E, 40 m.

Material examined. Queensland: series from off Flynn Reef: 3, AM P47632, 16°41.32'S 146°18.26'E, 100 m, 6–7 Jun. 1993, SEAS QLD-920; 4, AM P47633, 16°40.82'S 146°18.81'E, 200 m, 7–8 Jun. 1993, SEAS QLD-940; series from off East Fitzroy Reef; 22, AM P47634, 23°32.53'S 152°16.45'E, 105 m, 16–17 Jun. 1993, SEAS QLD-956; 3, AM P47635, 23°30.46'S 152°21.32'E, 300 m, 16–17 Jun. 1993, SEAS QLD-960; 9, AM P47636, due east of Mooloolaba , 26°39.13'S 153°18.88'E, 51 m, 2–3 Aug. 1994, SEAS QLD-1122 . New South Wales: series from northeast and east of Coffs Harbour; 21, AM P47637, 30°15.86'S 153°21.90'E, 92.7 m, 11–12 Aug. 1993, SEAS NSW-870; 6, AM P47638, 30°17.49'S 153°13.90'E, 45.4 m, 11–12 Aug. 1993, SEAS NSW-873; 62, AM P47639, 30°15.75'S 153°21.98'E, 98 m, 12–13 Aug. 1993, SEAS NSW-885; 19, AM P47641, 30°12.97'S 153°29.23'E, 400 m, 8–9 Sep. 1994, SEAS NSW- 994; many, AM P47640, 1.7 km east of Ramsgate, Botany Bay , 33°59.1'S 151°9.95'E, baited trap, 5 m, S. Keable & R. Springthorpe, 7–8 April 1992, FACSCAV-30; 6, AM P47642, Parriwi Point, Port Jackson , 33°48.5'S 151°14.8'E, baited trap, sediment, 8 m, S. Keable & J. Lowry, 23–24 Sep. 1988, site 49; 66, AM P47643, off Wollongong, 34°32.53'S 151°17.07'E, 400 m, 6–7 May 1993, SEAS NSW-787 . Tasmania: series from east of Fortescue Bay ; 25, AM P47645, 43°07.77'S 145°59.47'E, baited trap, 50 m, 17–18 April 1993, SEAS TAS-368; 8, AM P47648, 43°08.96'S 145°15.36'E, 1000 m, 17–18 April 1993, SEAS TAS- 383; 10, AM P38833, 43°07.77'S 145°59.47'E, 50 m, 8–9 April 1994, SEAS TAS-386; 56, AM P47647, about 80 m outside Hannants Bight, north side of Cape Sorell , 42°11.5'S 145°11'E, sand and detritus, 18 m, J. Lowry & S. Keable, 26–27 April 1991, TAS-277 .

Diagnosis. Interocular furrow: moderately developed, distinct but not extending across the cephalon or well developed, extending across the cephalon; smoothly convex. Frontal lamina: lateral margins medially constricted. Antenna: c. 0.25–0.3× as long as body, reaching to between the posterior of pereonite 2 and 3. Coxal plates: furrows moderately developed, on all coxae. Pleonite 4: apex forming a broad acute point. Pleotelson: broad, length 0.9 basal width; anterodorsal depression absent; anterolateral margins convex; posterolateral margins convex; apex produced into a small point; with 4–6 RS (4 in types). Pereopods 1–6: males with RS on the merus of pereopods 1–3, and carpus of pereopods 4–6, shorter than the propodus. Pereopods 2–3: propodus without RS on palm. Pereopod 7: basis broad, width 0.6× 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: just shorter than endopod; margins very slightly curved laterally; slender; apex recurved, bent slightly medially, bluntly rounded. Uropods: exopod short, 0.75× the length of the endopod; lateral margin without RS.

Variation. All material noted here is tentatively identified as Natatolana bulba . Some of the material examined from Queensland ( Flynn Reef : AM P47632, AM P47633; Fitzroy Reef : AM P47635), New South Wales ( Botany Bay : AM P47641; Wollongong : AM P47643) and eastern Tasmania ( AM P47648) have a narrower apex to the uropod endopod than the type specimens. Of these, those from Fitzroy Reef, Queensland ( AM P47635) and Botany Bay , New South Wales ( AM P47641) also have a complete interocular furrow. Specimens from Wollongong, New South Wales ( AM P47643), however, have a narrow apex to the uropod endopod and a complete or an incomplete interocular furrow. Specimens from eastern Tasmania ( AM P38833) have the apex of the uropod endopod intermediate between those of the type specimens and those from Wollongong, New South Wales ( AM P47643). Specimens from New South Wales ( Port Jackson : AM P47642), eastern Tasmania ( AM P47645) and western Tasmania ( AM P47647) have the antennae reaching to the posterior of pereonite 2, not pereonite 3 as in the types. The sample from Mooloolaba, Queensland ( AM P47636), however, contains specimens with antennae that reach to the posterior of pereonite 2 and also some in which the antennae reach to the posterior of pereonite 3. In the material from western Tasmania ( AM P47647) there are a few specimens with five or six robust setae on the pleotelson rather than the usual four .

Size. Adults from 9.5 mm (male from type material) to 12.9 mm (♀ from type material) ( Bruce, 1986). Specimens examined here from AM P47643 to c. 16 mm .

Remarks. Natatolana bulba is extremely similar to N. kahiba , comparison of their type specimens revealed only two characters to differentiate them: the number of robust setae on the uropod exopod lateral margin (none in N. bulba ; two or three in N. kahiba ); and the relative lengths of the antennae (in N. bulba reaching to the posterior of pereonite 3, 0.3–0.35× as long as the body with c. 18 flagellar articles; in N. kahiba reaching between pereonite 1 and 2, 0.2–0.25× as long as the body, with 12–15 flagella articles). Specimens without robust setae on the uropod exopod lateral margin but with short antennae corresponding to those found in N. kahiba were identified as N. bulba as noted in “variation”. Allozyme analysis comparing specimens with this morphology, with that of N. kahiba , shows that recognition of separate species is warranted ( Keable, 1996b).

The most distinctive feature of Natatolana bulba is the lack of robust setae on the lateral margin of the uropod exopod. Similar species recorded here, which may also lack these setae, include N. arrama , N. nammuldi and N. wowine . These species can be most readily separated from N. bulba by the shapes of the frontal lamina, appendix masculina, posterolateral margins of pleonite 4, and the uropods and the number of robust setae on the pleotelson.

Using the key provided by Bruce (1986) Natatolana bulba can only be reached if it is assumed in couplet 21 that it has six or more robust setae on the pleotelson, whereas the type specimens only have four.

Distribution and ecology. Australia: Queensland, New South Wales, and Tasmania. At depths of 5–1000 m. Scavenger.