Acryptolaria minuta Watson 2003

Acryptolaria minuta Watson, 2003 (Figs 18; 30; Table 19)

Acryptolaria minuta Watson, 2003: 163, 164, fig.13A-C. — Peña Cantero et al. 2007: 256-258, figs 11, 16C, tab. XI.

MATERIAL EXAMINED. — Loyalty Islands. MUSORSTOM 6, DW 406, 20°40.65’S, 167°06.80’E, 373 m, 15.II.1989, several stems up to 30 mm high, on hydroid stem (MNHN-Hy.2009-0201). — Stn DW 481, 21°21.85’S, 167°50.30’E, 300 m, 23.II.1989, several stems up to 25 mm high, on sponge (RMHH-Coel. no. 31520).

Norfolk Ridge. BIOCAL 1, stn DW 37, 22°59.990’- 23°00.079’S, 167°15.650’- 167°16.340’E, 350 m, 30.VIII.1985, three stems up to 27 mm high, on gorgonian axis (MNCN 2.03/425).

ECOLOGY AND DISTRIBUTION. — So far Acryptolaria minuta was known only from the Macquarie Island area (52°59.4’- 53°02’S, 159°59’- 159°58.2’E), where it was collected at a depth of 1422 m on a dead primnoid gorgonian (Watson 2003). Our material was found at depths between 300 and 373 m in the Loyalty Islands and Norfolk Ridge areas where it was found epibiotic on a sponge, the axis of a gorgonian and a hydroid stem.

DESCRIPTION

Stems up to 30 mm high. Branching frequent and irregular,approximately in one plane;anastomoses may be present. Branches straight (Fig. 18A, C, D).

Hydrothecae alternately arranged in one plane (Fig. 18A, C, D), tubular, roughly cylindrincal; diameter decreasing at basal part (Fig. 18). Hydrotheca strongly curved outwards; adcauline wall adnate over approximately two-thirds of its length (adnate/free ratio 2.1), convex. Abcauline wall concave, but basally straight. Hydrothecal aperture circular and directed outwards, almost parallel to long axis of branches; rim even, with few renovations (Fig. 18A).

Large nematocysts relatively small and ovoid (Fig. 30).

Coppinia not observed.

REMARKS

Peña Cantero et al. (2007) redescribed the holotype of Acryptolaria minuta composed of scarce material mounted on a slide. As indicated by those authors, Acryptolaria minuta is similar to A. minima in the size of the hydrothecae, though in the former the hydrothecae are larger and thinner, strongly curved outwards and with a much larger portion of the adcauline wall free. Moreover, the nematocysts are much smaller (25.8 × 9.8 Μm in the type material of A. minima). Our material roughly agrees with Watson’s species. The slight difference in the size of the nematocysts (16.7 × 6.3 Μm in the type material) is considered to be less important as Peña Cantero et al. (2007) measured the nematocysts of the holotype of A. minuta in a mounted slide.