Coelosphaera (Histodermion) kigushimkada Lehnert & Stone, 2015, n. sp.

Coelosphaera (Histodermion) kigushimkada n. sp.

(Figs. 10 & 11, Table 4)

Material examined. Holotype (ZSM 20150388) and paratype (ZSM 20150389), collected by Brian Knoth with a research survey bottom trawl (haul #15) from the FV Ocean Explorer; 13 June 2012, 265 m depth, 11 km west of Cape Kigushimkada, Umnak Island, eastern Aleutian Islands, Bering Sea (53°07.0560' N, 168°58.4400' W). Water temperature = 3.7°C. Complete specimens in ethanol.

Description. Habitus: A globular, golden-yellow sponge with a surface covered with thin, flattened fistules. Two specimens were collected, the larger (holotype) measures 6–6.4 cm in diameter and 4.8 cm in height, the smaller (paratype) with a maximum diameter of 4.4 cm attains a height of 2.3 cm (Fig. 10 A). Long fistules are 4–7 cm in length, 1.5–3 mm in diameter and are separated at distances of about 2–3 mm. Shorter fistules are recognisable in between long fistules starting from below 1 mm with intermediate lengths up to long fistules. We assume the growth of new fistules between existing ones as the surface of the sponge is spreading during growth. The largest fistules sometimes branch or might be the result of coalescing fistules. Consistency is resilient and elastic.

Skeletal structure: Typical of the genus the sponge is hollow, bladder-like with a thick, parchment-like ectosomal membrane. The ectosomal skin is packed with isochelae (Fig. 10 B) and tornotes (Fig. 10 C) without orientation. The choanosome consists of an irregular reticulation of vague tracts (Fig. 10 D) and single spicules where all spicule categories of this species may occur.

Spicules: Ectosomal (aniso-) tornotes are 415–622 x 8–11 µm (Figs. 11 A & B), choanosomal acanthostyles are 291–596 x 19–34 µm (Figs. 11 A & B). Microscleres are robust, arcuate isochelae, 38–46 µm (Fig. 11 C).

Discussion. Assignment to the genus Coelosphaera is without doubt because this is a hollow sponge with a parchment-like skin possessing fistules. As spiculation includes acanthostyles the subgenus Histodermion is the only option available. This is the first record of a species from the subgenus Histodermion from the Indo-Pacific region. The WPD lists only two species for the subgenus Histodermion: Coelosphaera (Histodermion) cryosi (Boury-Esnault, Pansini & Uriz, 1994) and C. (H.) dividuum (Topsent, 1927). C. (H.) cryosi is known only from the Mediterranean Sea and is much smaller (5 x 2 mm), has a different color (white in preservative), has shorter and thinner acanthostyles, has two categories of isochelae and two size categories of sigmas. C. (H.) dividuum is known only from the Azores in the North Atlantic Ocean and is an encrusting, soft and fragile species. Ectosomal tylotes to strongylotes are centrotylote and generally longer, acanthostyles are longer and thinner, and arcuate isochelae are of a broader size range.

Etymology. named after the type locality near Cape Kigushimkada.