Natatolana japonensis ( Richardson, 1904 )

Keable, Stephen J., 2006, Taxonomic Revision of Natatolana (Crustacea: Isopoda: Cirolanidae), Records of the Australian Museum 58 (2), pp. 133-244 : 194-195

Natatolana japonensis ( Richardson, 1904)

Synonymy in Keable, 1996a: 8, figs. 1–3. Additional listings and records of this species are those of Nierstrasz (1931, p. 158), Brusca et al. (1995, p. 80), Saito et al. (2000, p. 64), Yu & Li (2001, p. 263), Nunomura (2004, p. 356).

Type material of N. japonensis . Holotype: 3, 18 mm, USNM 29085 (examined). Type locality of N. japonensis: Yokkaichi Light , Japan, [c. 35°02'N 136°40'E].

Type material of N. miyamotoi . Holotype: 3, TSM TOYA Cr- 10793 (not examined) . Allotype: ♀, TSM TOYA Cr-10794 (not examined) . Paratypes: 2, TSM TOYA Cr-10795-10796 (examined). Type locality of N. miyamotoi: Off Iwase , Toyama City , Japan [36°43.6'N 137°14.7'E], 20 m.

Material examined. Listed by Keable (1996a).

Diagnosis. Interocular furrow: well developed, forming a ridge that extends across the cephalon; smoothly convex. Frontal lamina: lateral margins medially constricted. Antenna: c. 0.3–0.46× as long as body, reaching to between the posterior of pereonite 3 and 4. Coxal plates: furrows variously developed, complete but faint on coxae 2–5 and 7, very faint and incomplete or absent on coxa 6. Pleonite 4: apex forming a broad acute point. Pleotelson: broad, length 0.81–0.85× basal width; anterodorsal depression absent; anterolateral margins almost straight and angling posteriorly toward the midline; posterolateral margins straight, markedly angled to anterolateral margins and meeting at an acute angle or convex; apex not produced, lateral margins converging smoothly to a point; with 10–12 RS. Pereopod 2: propodus with 1 RS on palm. Pereopod 3: ischium anterodistal angle produced, but not as produced as on pereopods 1 and 2, similar to pereopod 4. Propodus with 1 RS on palm (and apparently a socket for another 1). Pereopod 7: basis of medium breadth, or broad, width 0.5– 0.56× length; distance between anterior margin and medial carina less than between posterior margin and medial carina; posterior margin with setae on proximal quarter. Penes: absent. Pleopod 2 appendix masculina: extending beyond tip of endopod, 1.04× length of endopod; margins very slightly curved laterally; slender; apex not at angle to adjacent margins, bluntly rounded. Uropods: exopod subequal to endopod, 0.93× the length of the endopod.

Variation. The posterior of the pleotelson appears to become broader as individuals increase in size. Of the material examined one specimen from off Iwase (TSM Cr 10796), 14 mm long, has the posterior margins of the pleotelson less distinctly angled to the anterolateral margins and has a more acute apex than in the holotype of N. japonensis . Another specimen from the same locality (TSM Cr 10795) is, however, 23 mm long and has a pleotelson identical in shape to that of N. japonensis .The holotype (USNM 29085) is the only specimen examined that has 10 robust setae on the pleotelson, other specimens have either 11 or 12.

Size.Adult specimens examined range from 12 mm to 26 mm.

Remarks. Natatolana japonensis was redescribed by Keable (1996). It can most readily be distinguished from other species of Natatolana by the following characters: size and shape of the eyes, length of the antenna, shape of the lateral margins of pleonite 4, shape, size and setation of the pleotelson and uropods and absence of penes.

Distribution. Japan, Korea and China. At depths of 6–439 m ( Iwasa, 1965; Nunomura, 2004).