Crateromorpha (Neopsacas) krinovi subsp. discoli Menshenina, Tabachnick & Janussen, 2007, sp.nov.

Crateromorpha (Neopsacas) krinovi discoli, sp.nov. (Fig. 5, 6, 7; Tab. 2)

Material examined

Holotype: SMF 10331, R.V. ‘Sonne’, DISCOL 2, 1989, trawl 5, 7° 1.2‘–8.7’ S, 88° 23.0 ‘–22.3’ W (S of Galapagos), depth 4196 m.

Other studied material: USNM 1096678, R.V. ‘Eltanin’, 33, sta. 2166, 14.4.1968, 70° 6’–8’ S, 119° 44’– 38’ W (Antarctic, Amundsen Sea), depth 3553–3575 m.

Description

Body: General shape is the same as in other species of this subgenus. Body is 25 mm long, about 20 mm in diameter, the walls are thin about 1 mm in thickness, the atrial cavity is large. Peduncle is tubular, 75 mm long (broken at the base) 1.5–2 mm in diameter; fragments of a broken peduncle which probably belongs to same specimen are also present in the sample collected from this station. Other specimen is 30 mm long, about 18x 30 mm in diameter, the walls are about 5 mm in thickness; atrial cavity is small, about 10 mm deep and 5–6 mm in diameter. Peduncle is tubular, 90 mm long (broken at the base) 2.5–5 mm in diameter.

Spicules: Choanosomal spicules of the holotype are diactins measuring 0.9–1.7/ 0.011–0.017 mm with a widening or four rudimental tubercles in the middle and rounded, smooth outer ends. In the holotype, hypodermal spicules are pentactins with spines near the spicule centre, the outer ends are smooth and rounded, few hexactins possess short (about 0.1 mm) distal ray. Tangential rays of hypodermal pentactins are 0.205–0.342 mm long, proximal ray is 0.783–1.102 mm long, their diameter is 0.03–0.05 mm. In the USNM 1096678 specimen, about half of hypodermal spicules are pentactins and half are hexactins. The spicule measurements are given in Tab. 2. Dermalia and atrialia are spiny spicules, mostly diactins, rarely stauractins and monactins. The diactins usually have four or several large spines in the middle. Dermal diactins have rays 0.030–0.155 mm long. Atrial diactins have rays 0.033–0.133 mm long. The diameter of the rays of dermal and atrial diactins is 0.004–0.012 mm.

Microscleres are represented by a succession of spiny discoidal spicules varying from discohexactins to discodiactins, their rays are 0.033–0.144/ 0.002–0.006 mm. Among these spicules discopentactins (60–62%) prevail, the others are: discohexactins (2–16%), discostauractins and discoparatetractins (19–30%); discotauactins (4–5%) and discodiactins (1%). In pentactins the four rays forming the cross are slightly bent away from the unpaired ray. An occasional hemidiscohexaster has 9 rays 0.070 mm long with primary rays 0.011 mm long.

Remarks

The USNM 1096678 specimen cannot be considered as paratype of C. (Neopsacas) krinovi because of the distant geographical origins of these two specimens. Furthermore, some differences in the composition of spicules are observed: in the Antarctic specimen about a half of hypodermal spicules are hexactins, while in the holotype hypodermalia are mainly pentactins.

Etymology

The subspecies is named after the German research expedition ‘DISCOL’.