Acanthascus (Staurocalyptus) Ijima, 1897

Acanthascus (Staurocalyptus) Ijima, 1897 Acanthascus (Staurocalyptus) tylotus Reiswig et Stone, 2013

Figs 7 View Fig , 8 View Fig ; Suppl. Tab. 6.

MATERIAL. IORAS 5 /2/3807, 3832: RV ‘ Akademik M.A. Lavrentyev’ – 75, ROV ‘ Comanche’, sta. 9, spec. 3-1 and 3-2 correspondingly, 55.4253° N 167.2754° E, 783 m. GoogleMaps IORAS 5 /2/3834: RV ‘ Akademik M.A. Lavrentyev’ – 75, ROV ‘ Comanche’, sta. 9, spec. 1-1, 55.4282° N 167.2775° E, 984 m. GoogleMaps

DESCRIPTION. BODY. All specimens have smooth but verrucose dermal surface (the bigger specimen has more verrucose surface). The specimen IORAS 5/2/3832 is saccular, it is about 200 mm high, 150 mm in diameter of the body and osculum, the walls are about 10–15 mm in thickness. From the specimen IORAS 5/2/3807 it was taken a fragment. It is also strongly destroyed being presented by fragments of the wall about 10–15 mm in thickness. The specimen IORAS 5/2/3834 is funnel-like and about 300 mm high, about 400 mm in diameter, the walls are 30–40 mm in diameter (a fragment of this specimen was sampled). The material in the collection was strongly destroyed during the fixation and transportation.

SPICULES. MEGASCLERES. Choanosomal spicules are diactins with conically pointed, rough outer ends.

Dermalia and atrialia are similar to each other with the only exception — dermal spicules have a row of transitional forms to hypodermal pentactins and hexactins with orthotropal tangential rays, while the atrial spicules are restricted by forms with short rays. Typical dermal spicules as well as atrial ones have short rays with rounded outer ends and with rough shafts. Dermal spicules include pentactins, stauractins,paratetractins and diactins, however most of these spicules are hexactins with equal rays or rays of different length. The dermal hexactins have rays 0.044–0.407/ 0.008–0.022 mm. The dermal diactins with a widening in the middle or four rudimental tubercles have rays 0.067 –0.407 mm long. Some dermal hexactins and pentactins have one extremely long ray, 3 times or more the length of the other rays, which is directed inside the body. This ray is equal in shape to the tangential ones when it is relatively small, or they are rough at base only. The biggest of such spicules, which could be called real hypodermal pentactins and hexactins, have rays smooth at base and rough, conically pointed or rounded outer ends. The rare hypodermal hexactins have rays directed outside the body 0.019 –0.322 mm long, tangetial rays are 0.063 –0.874 mm long, the ray directed inside the body is 0.33–2.59 mm long, the diameter of these rays is 0.03–0.06 mm. Atrial hexactins have rays 0.048–0.248/ 0.008–0.026 mm. Atrial stauractins have rays 0.141 –0.178 mm long. Atrial tauactins have rays 0.081 –0.344 mm long.

MICROSCLERES. Discoidal microscleres of two types: discoctasters and spherical discohexasters. The discoctasters have very short part of the common (fused) part of secondary ray, they seem to appear nearly immediately from the spherical central part, the secondary rays 2–16 in number (usually about 10) are distributed in widened, out curved tufts, their discs are not symmetrical (tendency to floricoidal type).The discohexasters are 0.040 –0.097 mm in diameter; their ‘primary’ rosette is 0.007 – 0.022 mm in diameter. The spherical discohexasters are 0.015 –0.032 mm in diameter; their “primary” rosette is 0.004 –0.009 mm in diameter. Oxyoidal microscleres with smooth rays are generally present- ed by oxyhexactins, rare oxyhemihexasters with one primary ray branching in two units, and rare stauractins and tauactins. The diameter of oxyoidal microscleres is 0.036 –0.191 mm.

REMARKS. Specific similarities between the described material of A. (Staurocalyptus) tylotus and the newly found specimens consist in the identity of the spicule construction and size of specific discoctasters, the domination of oxyhexactins among oxiodal microscleres and hexactins as dermal and atrial spicules which often have rays of different length and conically pointed outer ends of choanosomal diactins. The differences are also important: the presence of spherical discohexasters in both new specimens; numerous transitional forms between dermal spicules and hypodermal pentactins and hexactins. Our material might be distinguished as a separate subspecies but the similarities, especially those related to discoctasters, do not seem to allow distinguishing them at the specific level.

DISTRIBUTION.Bering Sea, 155–984 m depth.