Acanthascus (Rhabdocalyptus) Schulze, 1886

Acanthascus (Rhabdocalyptus) Schulze, 1886 Acanthascus (Rhabdocalyptus) borealis Okada, 1932

Fig. 5 View Fig ; Suppl. Tab. 3.

MATERIAL. IORAS 5 /2/3827: RV ‘ Akademik M.A. Lavrentyev’ – 75, ROV ‘ Comanche’, sta. 18, spec. 3-1, 55.4382° N 167.2652° E, 1569 m GoogleMaps . IORAS 5 /2/3808; 3814: RV ‘ Akademik M.A. Lavrentyev’ – 75, ROV ‘ Comanche’, sta. 9, spec. 2-5 and 2-2 correspondingly, 55°28′58.8″ N 167°15′30.6″ E, 2849 m GoogleMaps .

DESCRIPTION. BODY. The biggest specimen is IORAS 5/2/3827: 160 mm high, 60 mm in maximal diameter (close to the osculum); walls are 2–6 mm thick. Prostalia oscularia are diactins which protrude up to 20 mm over the osculum, prostalia lateralia are hypodermal pentactins which make a dense cover up to 15 mm above the dermal surface. Other specimens are smaller: IORAS 5/2/3814: 60 mm high, 20 mm in diameter in the middle and 15 mm in diameter of the osculum, the walls are 1–1.5 mm thick; IORAS 5/2/3808: 50 mm high, 25 mm in diameter in the middle and 20 mm in diameter of the osculum, the walls are 2–3 mm thick. Prostalia in the small specimens is smaller: oscularia diactins protrude up to 15–20 mm, prostalia lateralia of hypoderropal) spiny pentactins irregularly distributed and protruding 1–4 mm over the dermal surface.

REMARKS. The newly found specimen has spicules size parameter different from those of the type specimen described by Okada (1932) (see the Suppl. Tab. 4). The long ray of atrial hexactins (directed into the atrial cavity) in the new specimen is notably longer then those in previouse descriptions; discoctasters are of a single type and their minimal size is less than that in the type specimen and larger than the minimal size of this type of microsclere in a specimen described by Koltun (1967). The discoctasters in the new specimen are notably larger than the same type of discoctasters in the initial description, microdiscohexasters are absent and oxyoidal microscleres reach larger sizes. Nevertheless most spicule parameters of this new specimen correspond to A. (Rhabdocalyptus) heteraster much more then to other species of the subgenus and it seem more reasonable to expand the spicule parameters in the previous species then to create a new one.

DISTRIBUTION. Bering Sea , off Pacific coast of Canada, 445–2849 m depth .