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

Cladocroce attu n. sp.

(Fig. 4)

Material examined. Holotype: USNM# 1202119, collected by Jim Stark on 30 July 2012 at 52°49.07´N, 172°06.08´E, 25.7 km WSW of Cape Wrangell, Attu Island, western Aleutian Islands, Alaska, USA, at a depth of 358 m and a water temperature of 3.8°C.

Description. The sponge is funnel-shaped, stalked, and golden brown in color. The sponge was attached to a small cobble (73 mm x 44 mm x 28 mm). The specimen was torn but otherwise is of firm consistency, resilient, and difficult to tear in the direction of the spicule tracts. The specimen has a maximum height of 28 cm while the funnel reaches a maximum diameter of about 25 cm (Fig. 4A). The stalk is almost 3 cm long and has a smooth surface, macroscopically different from the highly porous surfaces of the funnel (Fig. 4B). The stalk is approximately 1 cm in diameter and widens to 1.5 cm at both ends. The inner surface of the funnel is smooth while the outer surface of the funnel is somewhat ribbed and covered with meandering, sometimes branched ridges 1–2 mm in height and 1– 3 mm in width (Fig. 4B). The thickness of the funnel wall is about 3–5 mm and the margin of the funnel is irregular in outline. The specimen harboured several ophiuroid associates. As is usual for the genus, a special ectosome is not developed and the choanosome consists of ascending paucispicular tracts connected by single spicules. Independent pauci- to polyspicular tracts run through the skeleton of this sponge (Figs. 4C, D & E). Spicules are oxeas, 158–183 x 14–16 µm (Fig. 4F).

Discussion. Comparing with the same species as C. infundibulum n. sp. we find that C. reina has only slightly smaller oxeas but these are less than half of the thickness and C. reina is a shallow water species from the Pacific Coast of Mexico. The growth form of C. attu n. sp. looks very much like Isodictya quatsinoensis Lambe, 1892 but, of course, can be easily distinguished by the spicules.

The specimen was collected remotely with a research trawl so we did not visually observe the seafloor habitat where the specimen resided. However, the specimen was attached to a small rounded cobble at a depth of 358 m that would indicate that this species is found on relatively flat habitat consisting of unconsolidated sediments with pebbles and small cobbles.

Etymology. Cladocroce attu is named after Attu Island in the western Aleutian Islands, near the site of collection.

FIGURE 4. Cladocroce attu n. sp. A. holotype, grid marks are 1 cm 2. B. Close-up of basal area showing ridges on the outer surface and smaller circular apertures in between. Grid marks are 1 cm 2. C. Numerous polyspicular tracts running through choanosomal reticulation. Scale bar is 250 µm. D. Polyspicular tracts. Scale bar is 250 µm. E. Close-up of polyspicular tracts. Scale bar is 250 µm. F. SEM photo of oxeas.