Natatolana albicaudata ( Stebbing, 1900 )

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

Natatolana albicaudata ( Stebbing, 1900)

Cirolana albicaudata Stebbing, 1900: 631 , pl. lxviiB.– Nierstrasz, 1931: 152.

Cirolana albicaudata var. japonica Thielemann, 1910: 8 , figs. 1–4.– Nierstrasz, 1931: 152.

Cirolana albicauda japonica .– Iwasa, 1965: 14, 18.

Natatolana albicaudata .– Bruce, 1981: 958.– 1986: 71, figs. 46, 47.–1995a: 409 figs. 19F,G.– Brusca et al., 1995: 79.– Kensley, 2001: 230.– Bruce et al., 2002: 148.

Natatolana albicaudata japonica .– Saito et al., 2000: 64.

Not Cirolana albicaudata .– Barnard, 1936: 152, fig. 2a–c [misidentification = Natatolana insignis Hobbins & Jones, 1993 ].

Not Cirolana albicaudata .– Richardson, 1910: 5 [mis-identification = Natatolana amplocula Bruce, 1986 ].

Type material. Syntypes: 433, 3.8–5.3 mm, 2♀♀, 3.9, 4.2 mm, 5 mancas, 2.0– 3.8 mm, BMNH 1906.4.19:44-54 (examined). Type locality: Barawon , Blanche Bay, New Britain [ Papua New Guinea, c. 6°S 150°E] .

Material examined. Queensland: series from Lizard Island , Qld., 14°40'S 145°28'E, N. Preston: manca, QM W18917, 30 Dec. 1986 ; ♀, QM W18912, 9 Nov. 1987 , stn 2; manca, QM W18913, 4 Dec. 1987 , stn 2; manca, QM W18910, 30 Oct. 1987 , stn 1. New Caledonia: ♀, ZMUC CRU137 , 23°32'S 167°36'E, surface, Dana Station 3604, 24 Nov. 1928 .

Diagnosis. Interocular furrow: well developed, extending across the cephalon; smoothly convex. Frontal lamina: lateral margins straight, parallel. Antenna: c. 0.4× as long as body, reaching to between the posterior of pereonite 2 and 4 (In the original description it is illustrated as extending to posterior of pereonite 4 and described as about half the length of the body. This agrees with the syntype specimens examined here. The redescription of Bruce [1986] states that it extends to the anterior of pereonite 3 but is variable and may extend to pereonite 5). Coxal plates: furrows strongly developed, on coxae 2–7. Pleonite 4: apex forming a broad acute point. Pleotelson: broad, length 0.84× basal width; anterodorsal depression absent; anterolateral margins convex; posterolateral margins convex; apex not produced, lateral margins converging smoothly to a point; with 7–10 RS (the original description and figures indicate 8, Bruce’s (1986) redescription gives 9 or 10 and his figures show 7). Pereopod 2: propodus with 2 RS on palm. Pereopod 3: propodus with 1 RS on palm. Pereopods 5–7: propodus long, on pereopod 5 greatly elongate, 2× that of pereopod 7. 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, 0.94× length of endopod; slender; margins very slightly curved laterally; apex not at angle to adjacent margins, bluntly rounded. Uropods: exopod short, 0.78× the length of the endopod.

Size. The largest syntype specimen is 5.3 mm, Bruce (1986) recorded specimens to 8.9 mm.

Remarks. Bruce (1986, p.53, 74) noted that Natatolana albicaudata , N. amplocula and N. curta share a number of similarities but that N. albicaudata can be distinguished from all other species in the genus by a combination of characters. These include having chromatophores, conspicuously elongated dactyls, a slender propodus on pereopods 4–6, and other characters dealing with the frontal lamina, pereopods, pleotelson and uropods, coxal furrowing and pleon shape that were not elaborated on. Both N. curta and N. amplocula were originally known only from single specimens. Comparison of the types and additional specimens of all three species indicates that the characters used by Bruce (1986) to differentiate them are difficult to apply. Type specimens of N. albicaudata , however, differ from those of N. amplocula and N. curta most noticeably in having a less rounded uropod endopod and pleotelson. It also appears to be a smaller species in which indistinct tubercles do not form on the dorsal surface of the pereonites of males and has fewer robust setae on the uropod exopod. Further collections of N. albicaudata , N. amplocula and N. curta from their type localities would help confirm this, especially as the type material of N. albicaudata is in poor condition, and Bruce (1986) indicated that in material he identified, which is larger than the type material, the apices of the pleotelson and uropods are far more distinctly rounded.

Richardson (1910) identified material from the Philippines as both Natatolana albicaudata and N. curta but did not indicate differences between these species. Examination of the material Richardson identified as N. albicaudata indicates it is most similar to N. amplocula .

The specimens reported here from Lizard Island and New Caledonia are only tentatively identified because of the difficulties in differentiating this species (noted above) and because the material consists of a limited series of females and juveniles.

Distribution and ecology. Records are restricted here to Japan ( Thielemann, 1910; Iwasa, 1965), northwestern and northeastern Australia ( Bruce, 1986), Indonesia ( Nierstrasz, 1931), Papua New Guinea ( Stebbing, 1900; Bruce, 1995a), and New Caledonia. This range is tentative given the similarities with N. amplocula and N. curta . Hayward et al. (1999, 2001) report N. albicaudata from New Zealand but Bruce (2003) considered this a probable misidentification. From surface plankton to a depth of 250 m ( Thielemann, 1910).

Natatolana albicaudata is not a scavenger. Bruce (1995a) has briefly discussed the ecology of this species, noting that it has not been collected in Madang Lagoon using baited traps but does occur there. It has also been collected from coral rock and rubble rather than particulate substrata.