Acryptolaria minima Totton 1930

Acryptolaria cf. minima Totton, 1930 (Figs 17; 30; Table 18)

Acryptolaria minima Totton, 1930: 162, 163, fig. 18a, b. — Ralph 1958: 315, fig. 3e, f. — Peña Cantero et al. 2007: 254-256, figs 10, 16B, 18C, 19B, D, tab. X.

MATERIAL EXAMINED. — Norfolk Ridge. BIOCAL 1, stn DW 36, 23°08.647’- 23°08.900’S, 167°10.994’- 167°11.296’E, 650-680 m, 29.VIII.1985, 3 stems up to 14 mm high (RMNH-Coel. no. 31519). — Stn DW 51, 23°05.273’- 23°05.432’S, 167°44.951’- 167°45.355’E, 700- 680 m, 31.VIII.1985, 2 stems up to 17 mm high on sponge (MNHN-Hy.2009-0200).

ECOLOGY AND DISTRIBUTION. — Acryptolaria minima was previously only known from New Zealand shelf waters, at depths from 20 m (Totton 1930) to 180 m (Ralph 1958), having been reported from off Cape North and Cape Maria van Diemen (Totton 1930) and from Cook Strait (Ralph 1958). Our material was collected in deeper waters, at depths between 650 and 700 m, in the Norfolk Ridge area; it was epibiotic on sponges.

DESCRIPTION

Stems up to 17 mm high. Branching frequent (up to third-order branches present), either irregular or alternate in more or less one plane or in several planes. Branches straight (Fig. 17).

Hydrothecae alternately arranged in approximately one plane (Fig. 17), cylindrical, either with a constant diameter throughout, only decreasing at base, or with slightly decreasing diameter along adnate part (Fig. 17). Hydrotheca smoothly curved outwards; adcauline wall adnate to internode over two-thirds of its length (adnate/free ratio 2.3-2.7). Adcauline wall convex throughout; abcauline wall straight basally and concave in distal half. Hydrothecal aperture circular and directed outwards, frequently parallel to long axis of branches. Rim even, often with short renovations.

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

Coppinia not found.

REMARKS

Peña Cantero et al. (2007) redescribed the holotype of Acryptolaria minima. They characterized this species as having its hydrothecae almost completely adnate to the branches (only one-fifth of the adcauline wall is free), by the shape and size of the hydrothecae and by the size of the nematocysts, as it has the smallest hydrothecae and the largest nematocysts (apart from A. tortugasensis) amongst the known species of Acryptolaria. Our material generally agrees with the type material in size of hydrothecae and nematocysts (cf. Peña Cantero et al. 2007: table X) but differs because in the type material the hydrothecae are less strongly directed outwards, have a shorter free portion of the adcauline wall and the basal part of the abcauline wall is slightly convex. Consequently we have some doubts concerning the proper dessignation of our material. Given the diversity shown by the genus in the area under investigation it would not be surprising if our material belonged to a different species, which owing to the paucity of material cannot be characterized at present.