Acryptolaria crassicaulis (Allman, 1888) (Figs 6; 30; Table 7)

Cryptolaria crassicaulis Allman, 1888: lvii, lxvii, lxviii, 41, pl. 19, figs 3, 3a.

Acryptolaria crassicaulis – Peña Cantero et al. 2007: 245-247, figs 6, 15D, 17E, tab. VI.

MATERIAL EXAMINED. — NW New Caledonia. MUSORSTOM 4, stn CP 172, 19°1.2’S, 163°16.0’E, 275-330 m, 17.IX.1985, 2 stems 35 and 15 mm high (MNHN-Hy.2009-0190). Loyalty Islands. BIOCAL 1, stn DW 08, 20°34.351’- 20° 35.092’S, 166°53.904’- 166°54.051’E, 435 m, 12.VIII.1985, 1 stem c. 19 mm high (MNHN-Hy.2009-0191). BIOGEOCAL, stn DW 307, 20°35.38’- 20°35.32’S, 166°55.25’- 166°55.33’E, 470-480 m, 1.V.1987, 1 fragment c. 7 mm long (MNCN 2.03/413). MUSORSTOM 6, stn DW 473, 21°08.80’S, 167°55.30’E, 236 m, 22.II.1989, a few stems up to 15 mm high (RMNH-Coel. no. 31504).

ECOLOGY AND DISTRIBUTION. — The only reliable record of Acryptolaria crassicaulis is from off Ascension Island (07°54’20’’N, 14°28’20’’W), where it was found at a depth of 756 m on volcanic sand (Allman 1888). Our material was collected at depths between 236 and 480 m at the Loyalty Islands and in New Caledonian waters.

DESCRIPTION

Polysiphonic stems up to 35 mm high. Branching frequent, irregular but usually in one plane; branches in a distinct zigzag pattern (Fig. 6), up to third-order branches have been observed. Anastomoses may be present.

Hydrothecae alternate and more or less in one plane (Fig. 6), tubular, almost cylindrical in the free part; diameter smoothly decreasing basally at adnate part; minimum diameter at base (Fig. 6). Hydrotheca gently curved outwards in distal half. Adcauline wall adnate with internode over almost two-thirds of its length (adnate/free ratio 1.5). Adcauline wall convex, though becoming straight at basal third. Abcauline wall concave, though straight at basal part. Hydrothecal aperture circular, directed outwards, almost parallel to long axis of internode (Fig. 6). Rim even, sometimes with numerous short renovations.

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

Coppinia not observed.

REMARKS

Our material differs from the type material in having shorter stems and smaller hydrothecae (cf. Peña Cantero et al. 2007: table VI). However, it agrees with it in the size of the nematocysts (15.2 × 5.0 µm in the type material), the general appearance of the colony, the zigzag structure of the branches and the shape of the hydrothecae. The differences in the size of the hydrothecae are here considered to be of less importance taking into account the extremely large dimensional variation of this character found in other species studied (e.g., A. angulata).

Our material resembles A. conferta in the zigzag arrangement of the branches, as well as in the shape of the hydrothecae, but is distinctly different in the size of the nematocysts (cf. Table 31).