Trichogypsia alaskensis Stone 2017, n. sp.

Trichogypsia alaskensis n. sp.

(Figs 3, 4; Table 1)

Material examined. Type material is deposited at the Zoologische Staatssammlung (ZSM) in München, Germany. The holotype (ZSM20170008), growing on the surface of the paratype of Hamacantha (Vomerula) cassanoi (ZSM 20160080), collected by Robert Stone, 7 June 2015, 174 m depth, Fairweather Ground, eastern Gulf of Alaska (58°12.156´N, 138°49.656´W).

Description. The holotype is dried and in two fragments (Fig 3 A), the larger fragment measuring 18 x 11 x 1– 2 mm with attached pieces of the substrate sponge, the smaller is 16 x 6 x 1–2 mm. The color of both pieces is golden brown with some beige spots. The consistency is hard and incompressible. There are no visible oscula. The upper side is microconulose (Figs 3 B, 4A, B), due to abundant and approximately evenly spaced groups of protruding diactines. The bottom-side is smooth (Figs 3 C, 4A), only microhispid, due to relatively short diactines arranged perpendicular to the surface. In the choanosome the diactines are arranged more or less parallel to the plane of the incrustation (Fig 4 A), at the upper surface groups of diactines form small conules of the height of the diactines (Figs 3 D, E, 4B). As the height of the conules is lower than the length of the largest diactines, the conules and also the diactines arranged perpendicular to the surface of the bottom-side contain mostly relatively small diactines. However, larger diactines may also reach into the conules from below. In the choanosome larger diactines are more abundant but, smaller diactines are found as well. Diactines are usually somewhat distorted, irregularly shaped, some spined, some microspined, some completely smooth, and sometimes only partially spined (Figs 4 C-F). They occur in a broad size range, 76–1225 x 5–46 µm, mean values 464 x 18 µm.

Discussion. The World Porifera Database (Van Soest et al. 2017) lists two valid species of Trichogypsia from the Northeast Atlantic Ocean (Fig 2) and we compare the new species to both. Spicule types, spicule arrangement in the sponge and surface characteristics generated from the spicule arrangement are very close to the line drawings of Borojevic et al. (2000) and reproduced by Hooper & Van Soest (2002) for the type species (T. villosa). However, Trichogypsia alaskensis n. sp. has a larger size range of diactines than both congeners and it is much more variable with regard to the surface characteristics of its diactines. While T. villosa has diactines with both ends spined and T. incrustans has diactines with only one end spined, the diactines of T. alaskensis n. sp. are highly variable from smooth to partially spined to completely spined. Trichogypsia alaskensis n. sp. further differs from the two known congeners in the following characteristics:

T. villosa Carter, 1871, Northeast Atlantic Ocean, a greyish or greenish-white colored sponge with “a single vent at one end of the ellipse … furnished internally with a circle of minor vents arranged round the large one” (p. 2). Diactines are seemingly smaller, although Carter provided a mean size only with no size range, and are spined on both ends.

T. incrustans (Haeckel, 1872) (= T. lichenoides), Northeast Atlantic Ocean, a thin, white encrusting sponge with a smooth or almost smooth surface. Diactines are smaller and spined at one end only.

Etymology. Named after the type locality in the Gulf of Alaska.

Species Diactines

T. villosa Carter, 1871) Average 452 x 14, two spined ends

T. incrustans (Haeckel, 1872) 200–300 x 10–15, with few larger ones, one spined end T. alaskensis n. sp. 76–1225 x 5–46, (means 464 x 18), some completely smooth, some with

one or both ends spined