Natatolana amplocula Bruce, 1986

Keable, Stephen J., 2006, Taxonomic Revision of Natatolana (Crustacea: Isopoda: Cirolanidae), Records of the Australian Museum 58 (2), pp. 133-244 : 150-151

Natatolana amplocula Bruce, 1986

Natatolana amplocula Bruce, 1986: 74 , fig. 48.– Brusca et al., 1995: 79.– Bruce et al., 2002: 149.

Cirolana albicaudata .– Richardson, 1910: 5 [mis-identification, not N. albicaudata Stebbing, 1900 ].

Type material. Holotype: female, 13.2 mm, ZMUC CRU1691 (examined). Type locality: south of Kei Islands , 5°34'S 132°26'E.

Material examined. Philippines: 333, USNM 40959 , Tomindao Island anchorage, electric light, Albatross Expedition, 26 Feb. 1908 [reported by Richardson (1910)]; 533, 7♀♀ , USNM 40988 , Java Island anchorage, electric light, Albatross Expedition, 14 Dec. 1908 [reported by Richardson (1910)]; 3♀♀ , ZMUC CRU118 , Tubajon Bay, Dinagat, 10°20'N 125°32'E, corals, 40 m, 16 Jul. 1951, Galathea Station 414 . Indonesia: 3, ZMUC CRU128 , Banda Sea , 6°37'N 122°24'E, planktonic, 3April 1929, Dana stn 3684; 57 , ZMUC CRU127 , off Java, 6°41.5'S 105°19.5'E, planktonic-surface, 3 Sep. 1929, Dana stn 3808 . Australia, Northern Territory: 3, NTM Cr 005812, New Year Island , 10°55'S 133°01'E, 5m. Queensland: 3, ♀ , manca, AM P47471, Shadwell Reef, 11°27.66'S 143°46.63'E, nightlight, surface over 20 m depth, H. Larson, J. Leis, M. McGrouther, 12 Jan. 1993, QLD-646; series from west of Carter Reef , 14°33'S 145°35'E, surface over 30 m (neuston and vertical tows), J. Leis & party, RV Sunbird, 4–7 Mar. 1983: 233, 4♀♀ , AM P47472; 2♀♀ , 3 mancas, AM P47473; 3, 5♀♀ , AM P47474; ♀ , AM P47475; ♀ , QM W18911, Lizard Island, 14°40'S 145°28'E, N. Preston, 12 Nov. 1986, stn 1; 3, AM P47476, off East Fitzroy Reef , 23°34.92'S 152°11.76'E, 58 m, 16–17 Jun. 1993, SEAS QLD-952. Western Australia: 533, ♀ , NMV J37011 , North- West Shelf between Port Hedland and Dampier, 18°45'S 118°24'E, trawl, 142 m, G.C.B. Poore & H.M. Lew-Ton, 5 Jun. 1983. Southwest Pacific Ocean: 2♀♀ , AM P47477, Elizabeth Reef, Tasman Sea, 29°55'S 159°05'E, hand net at surface, attracted to light at night, A. Gill & J.K. Lowry on RV Flamingo Bay , 12 Dec. 1987, site 42; 3, ♀ , AM P41150, Taupo Seamount, Tasman Sea , 33°16.85'S 156°09.15'E, limestone and sand bottom, 244 m, 1.2 m sled, J.K. Lowry et al. on RV Franklin, 2 May 1989, FRO589-8; 3, damaged specimen , MNHN, New Caledonia, 19°07'S 163°22'E, 200 m, MUSORSTOM 4, 14 Sep. 1985, stn 0151; 3 , MNHN, Chesterfield Islands , 22°47.7'S 159°23.7'E, 360–390 m, MUSORSTOM 5, 11 Oct. 1986, stn 0299; ♀ , 2 mancas, NMNZ, Raoul Island, Kermadec Islands , 28°50'S 177°48'E, plankton net at surface over 268–332 m, RV James Cook, 17 Jun. 1976 .

Diagnosis. Interocular furrow: well developed, extending across the cephalon; smoothly convex. Frontal lamina: lateral margins straight, narrowing posteriorly. Antenna: c. 0.4× as long as body, reaching to between the posterior of pereonite 3 and posterior of pereonite 4. Coxal plates: furrows strongly developed, on coxae 2–7. Pleonite 4: apex forming a broad acute point. Pleotelson: broad, length 0.74× basal width; anterodorsal depression absent; anterolateral margins convex; posterolateral margins broadly rounded; apex produced into a small point; with 6–12 RS. Pereopod 2: propodus with 2 RS on palm. Pereopod 3: propodus with 2 RS on palm. Pereopod 7: basis broad, width 0.6× length; distance between anterior margin and medial carina less than between posterior margin and medial carina; posterior margin with setae completely absent along entire length. Penes: absent. Pleopod 2 appendix masculina: just shorter than endopod, 0.85–0.95× length of endopod; slender; margins bent slightly medially; apex not at angle to adjacent margins, bluntly rounded. Uropods: exopod short, 0.73× the length of the endopod; lateral margin convex.

Variation. The number of robust setae on the pleotelson is most often 8 but may range between 6 and 12 (6 in the holotype and specimens from Lizard Island, Queensland; eight in specimens from the Philippines [ USNM 40988 ], Carter Reef and Shadwell Reef, Queensland; 10 in specimens from the Philippines [ USNM 40959 ], Taupo Seamount and New Caledonia; 12 in specimens from northwestern Australia and the southwest Pacific [ Elizabeth Reef , Raoul Island and Chesterfield Islands ]. Indistinct tubercles are present on the dorsal surface of pereonites 1 and 3 in males from off Java, Indonesia, New Year Island , NT, Carter Reef and east Fitzroy Reef , Queensland , New Caledonia and Taupo Seamount. The antennae reach the posterior of pereonite 4 in the material from Carter Reef and Elizabeth Reef whereas in other material they extend approximately half way along pereonite 3.

Sexual dimorphism. Males may develop indistinct tubercles on the dorsal surface of pereonites 1 and 3.

Size. Adults to 13.2 mm.

Remarks. Natatolana amplocula is most similar to N. albicaudata (see remarks for that species) and N. curta . Natatolana curta was described from a single specimen and has not been subsequently collected. The uropod endopod is less rounded in the holotype of N. amplocula , than in the holotype of N. curta but the specimen of N. curta is larger and may have had the distal lateral margins somewhat worn down. Other differences of the holotype of N. curta to that of N. amplocula follow with the state for N. amplocula in parentheses: interocular furrow incomplete (complete); dorsal posterolateral margin of pleonite 2 produced posterior to ventral posterolateral margin (subequal), 11 robust setae on the pleotelson margin (six); indistinct tubercles on the dorsal surface of pereonites 1 and 3 (absent—but this appears to be a sexually dimorphic character found only in mature males and the holotype of N. amplocula is female).

The specimens reported here are only tentatively identified as Natatolana amplocula because of the difficulties in differentiating this species as noted above. None of the specimens examined were as large as the holotype of N. curta and none had the uropod endopod as strongly rounded. In other respects, all of the material examined appeared to be intermediate between N. amplocula and N. curta because: all specimens have a complete interocular furrow; the number of robust setae on the pleotelson varies between 6–12; and the dorsal posterolateral margin of pleonite 2 is produced posterior to the ventral posterolateral margin. Furthermore, the holotype of N. curta is a male and has indistinct tubercles on the dorsal surface of pereonites 1 and 3. In a number of samples examined here, similar tubercles were found on male specimens but never females. Because of the limited type material of N. amplocula the significance of these tubercles is unclear.

Distribution. Philippines, Indonesia, northwestern and northeastern Australia, southern Pacific Ocean as far west as the Kermadec Islands and as far south asTaupo Seamount. Recorded from surface plankton to a depth of 441 m.