Cladocroce kiska Lehnert & Stone, 2013, n. sp.

Cladocroce kiska n. sp.

(Fig. 5)

Material examined. Holotype: USNM# 1202120, collected by Jim Stark on 16 July 2012 at 51°46.37´N, 177°27.45´E, 11.1 km SE of Vega Point, Kiska Island, western Aleutian Islands, Alaska, USA, at a depth of 255 m and a water temperature of 4.1°C; paratype: USNM# 1202121, collected by Jay Orr on 4 July 2012 at 51°40.75´N, 177°11.26´W, 4.2 km SW of Cape Chlanak, Kanaga Island, central Aleutian Islands, Alaska, USA, at a depth of 84 m and a water temperature of 4.5°C.

Description. Both specimens are stalked flabellate but lobed and golden brown in color. The lobes are coalesced to some degree. The consistency of both specimens is soft, elastic, compressible and difficult to tear. Circular oscules, 2–5 mm in diameter, with rims slightly raised above the surface are arranged in irregular rows. There are oscules on the upper stalk and on the outside margin of the lobes but not in obvious rows. The holotype has a maximum height of 26 cm, a maximum width of 20 cm, is somewhat planar and consists of two main branches and 7 lobes total (Fig. 5A). The lobes are about 1 cm thick. The stalk is about 2 cm in diameter, 3.5 cm in length, 3.5 cm wide at the holdfast and attached to a pebble (4.5 cm diameter). It widens gradually into a flabellate, folded sponge with a smooth surface. The paratype was partially fragmented upon collection and has a maximum height of 27 cm, a maximum width of 26 cm, is somewhat less planar (almost arborescent) and consists of two main branches with 12 lobes total. The lobes are about 1 cm thick. The stalk is much less obvious, about 4 cm wide at the holdfast and attached to a small cobble. There is no special ectosome developed, ascending paucispicular tracts, 30–50 µm in diameter, terminate in spicule brushes at the microhispid surface which is optically smooth (Fig. 5B). Paucispicular tracts are connected by single spicules. Independent from the reticulation of tracts and single spicules are pauci- to polyspicular tracts running through the sponge (Figs. 5C & D). Spicules are oxeas, 252–343 x 10–18 µm (Fig. 5D) and thin, abundant sigmas 17–25 µm (Fig. 5E).

Discussion. Haplosclerid sponges with co-occurring oxeas and thin sigmas are known from the genera Gelliodes and Hemigellius, both within the family Niphatidae. We dismissed this assignment since all Niphatidae have a three dimensional ectosomal skeleton which is often a somewhat irregular reticulation of pauci- or multispicular fibres or tracts (Van Soest & Hooper, 2002; p. 834) and our specimens have no developed special ectosome. The combination of oxeas and sigmas is also known in Haliclona (Gellius). However, we argue against this position since the choanosomal skeleton of species within the subgenus Gellius is halichondroid in the interior parts. Assignment of the species described here to Cladocroce was made due to the spicule tracts running independently through the reticulation of ascending paucispicular tracts connected by single spicules, a character regarded diagnostic for the genus Cladocroce. As in other species of Cladocroce these spicule tracts can be drawn out of the sponge with a forceps. However, to fit this new species into the genus Cladocroce we have to broaden the definition of the genus to allow sigmas to occur within the genus. These sigmas are not unusual for other genera within the family Chalinidae, as discussed above. Obviously, we have weighted skeletal architecture more heavily than spicule complement in this assignment. Comparing characters of the new species with congeners, it differs in habitus, dimensions of oxeas (compared above with seven species of Cladocroce), and it is the only Cladocroce with sigmas.

The specimens were collected remotely with a research trawl so we did not visually observe the seafloor habitat where the specimens resided. However, the type specimens were attached to a rounded pebble and rounded small cobble, respectively, that would indicate that this species is found on relatively flat habitat consisting of unconsolidated sediments with pebbles and small cobbles and at depths between 84 and 255 m.

Etymology. Cladocroce kiska, named after Kiska Island in the western Aleutian Islands near where the holotype was collected.