Trichogypsia alaskensis, Stone, 2017

Stone, Robert P., 2017, Description of a new species of Trichogypsiidae (Porifera, Calcarea) and first record of the genus in the Pacific Ocean, Zootaxa 4312 (2), pp. 394-400 : 397

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

Figures

FIGURE 2. Location of Trichogypsiidae in the North Atlantic Ocean. Trichogypsia incrustans (●) and T. villosa (▲).

FIGURE 3. Trichogypsia alaskensis n. sp.: (A) the two fragments of the holotype. The left fragment shows the upper side of the sponge with (micro-) conules. The left fragment shows the smoother bottom-side of the sponge with still adhering fragments of the substrate. Scale at bottom in mm. (B) Section parallel to the upper surface. Darker spots are conules of the surface constructed by groups of diactines. Scale bar is 100 µm. (C) Section parallel to the bottom side. Diactines are arranged more parallel to the smooth surface. Scale bar is 100 µm. (D) Section perpendicular to the surface. Top right are the diactines constructing the surface conules. Below is the choanosome of the sponge and at the lower left the smooth surface of the bottomside is visible. Scale bar is 100 µm. (E) Section perpendicular to the surface with a better view of the architecture of the surface conules. Scale bar is 100 µm.

FIGURE 4. Trichogypsia alaskensis n. sp.: (A) Scanning electron microscopy photo of a section perpendicular to the surface. On the upper right the surface conules are visible. The smoother bottom-side of the sponge is visible on the lower left. In between the less dense choanosome. Scale bar is 300 µm. (B) Close-up of surface conules. Groups of diactines, building the conules, are visible. Scale bar is 100 µm. (C) Overview of different sizes and forms of calcareous diactines. Surface of diactines can be smooth or spined. Ends of diactines acute or blunt. Scale bar is 90 µm. (D) Different types of diactines, straight or crooked. Scale bar is 50 µm. (E) Diactines. Scale bar is 100 µm. (F) Close-up of surface of diactine. Spines seem to occur in two categories: large and small. Scale bar is 10 µm.