Hyalascus giganteus Ijima, 1898

Hyalascus giganteus Ijima, 1898 View in CoL

Figs 23 View Fig , 24 View Fig .

MATERIAL. IORAS 5 /2/3833: RV ‘ Akademik M.A. Lavrentyev’ – 75, ROV ‘ Comanche’, sta. 18, spec. 5-1, 55.4353° N 167.2668° E, 1420 m GoogleMaps .

DESCRIPTION. BODY. The sponge is funnel-like about 400 mm high and 200 mm in maximal diameter (off the oscular margin) and about 100 mm in the diameter at base. Only fragment of the upper part of this sponge was sampled. The collected specimen is presented by damaged thin lamellate wall fragment 2–5 mm in thickness with no prostalia.

SPICULES. MEGASCLERES. Choanosomal spicules are diactins with rough, conically pointed or rounded outer ends, stout shafts or sometimes with a widening in the middle. Large choanosomal diactins are about 17/ 0.06 mm. Small choanosomal diactins are 1–5/ 0.004 –0.022 mm. Hypodermal pentactins have rough or smooth, rounded or conically pointed outer ends. Tangential rays of hypodermal pentactins are 2–3 mm long, proximal ray is 1.6–3.3 mm long, the diameter of these rays is 0.04 mm.

Dermalia are spicules with rough rays and conically pointed outer ends, mostly they are pentactins with a rudimental tubercle at place of the distal ray. Sometimes dermal spicules are hexactins and stauractins, the latter may have 1 or 2 tubercles in place of reduced rays. Dermal pentactins have tangential rays 0.081 –0.137 mm long (n=25, avg: 0.118 mm, std: 0.013 mm), proximal rays are 0.067 –0.141 mm long (n=25, avg: 0.103 mm, std: 0.020 mm). The diameter of these rays is 0.007 –0.009 mm. Dermal stauractins have rays 0.096 –0.192 mm long (n=8, avg: 0.130 mm, std: 0.039 mm). Dermal hexactins have rays usually of equal length 0.081 –0.137 mm long (n=12, avg: 0.116 mm, std: 0.017 mm). Atrial pentactins have tangential rays 0.081 –0.241 mm long (n=25, avg: 0.120 mm, std: 0.029 mm), rays directed inside the body are 0.056 –0.141 mm long (n=25, avg: 0.107 mm, std: 0.018 mm). Atrial stauractins have rays 0.107 –0.185 mm long (n=6, avg: 0.130 mm, std: 0.029 mm). Small atrial hexactins have rays usually of equal length 0.089 –0.118 mm long (n=3, avg: 0.100 mm, std: 0.016 mm).

MICROSCLERES. Various oxyoidal microscleres (i.e., oxyhexasters, oxyhemihexasters, abnormal oxyoidal-asterous forms (oxystarasters, oxyhemistaurasters); oxyhexactins, stauractins; tauactins, diactins and even monactins) and one type of microdiscohexaster were found. Oxyoidal microscleres have secondary rays with short spines direct- ed towards the center of the spicule. The oxyhexasters and oxyhemihexasters with 1–3 secondary rays are 0.068 –0.144 mm in diameter (n=25, avg: 0.100 mm, std: 0.018 mm), the diameter of their primary rosette is 0.005 –0.014 mm (n=25, avg: 0.008 mm, std: 0.022 mm). The oxyhexactins are 0.076 –0.130 mm in diameter (n=25, avg: 0.102 mm, std: 0.013 mm). The microdiscohexasters have 5–10 secondary rays, their diameter is 0.020 –0.036 mm (n=25, avg: 0.028 mm, std: 0.004 mm), the diameter of their primary rosette is 0.004 –0.010 mm (n=25, avg: 0.028 mm, std: 0.004 mm).

REMARKS. Some differences between H. giganteus ( Ijima, 1904) and the newly found specimen are not considered to be important. Dermal spicules are a little smaller in the new specimen, atrial spicules larger, the size parameters of the microscleres generally are a little wider than those described. Variation of oxyoidal microscleres types is larger in the specimen from the Bering Sea. Nevertheless, all of these differences are considered to be an intraspecific variation.

DISTRIBUTION. Pacific side off Japan (Sagami Sea) and Bering Sea — Piip Volcano, at 1420 m depth (depth in the Sagami Sea — unknown) .