Pseudosuberites nudus Koltun 1964

Pseudosuberites nudus Koltun, 1964

(Fig. 4, Tab. 2)

Pseudosuberites nudus Koltun, 1964: 90, fig. 23, 1976, 192.

Material. 3 fragmentary specimens from station 048-1 (SMF 11781, 11783, 11784), 602.1 m, 70° 23.94' S, 8° 19.14' W, 12.01.2008. Material examined for comparison: BMNH 1963.7.29.75, Holotype, Soviet Antarctic Exped. 1955–1958, Lat. 65° 50.3’ S; Long. 128° 27’ E., “06” 1957, stn. 44A, 320 m, Leningrad reg. no. 6244, det. Koltun, wet specimen.

Description. Massive irregular sponges overgrowing bryozoans. Two specimens (SMF 11783, 11784) were dead when sampled, they mainly consist of skeletal parts, while most of the soft body is missing. The third (SMF 11781) and largest sponge was alive, it has a great amount of soft tissue surrounding the skeleton. Skeleton of thick plumose tracts, splitting towards the surface. Sponge surface smooth with a discrete detachable ectoderm. Ectosomal skeleton forms irregular tangential reticulation. A large amount of foreign material, especially bryozoan colonies, incorporated into the tissue. Color ex situ as well as in ethanol dirty beige-brown, with the exception of one probably dead specimen (SMF 11783), which is dark brown, almost blackish.

Spicules (Tab. 2) large subtylostyles and smaller tylostyles. Subtylostyles (Fig. 4 E–G) are 1200–2025 µm long, maximal diameter 22.5–52.5 µm and tyle diameter 12.5–22.5 µm. Spicules with a relatively thick middle part, often bent, most often about one third from the tyle. Tyles often indistinct, being only slight swellings, cored by a round widening of the central channel, or even completely absent. Tylostyles (Fig. 4 H–K) are 330–1475 µm long, 8.75–27.5 µm in maximal diameter, with tyles 8.75–17.5 µm wide. The tylostyles are generally of the same shape as the subtylostyles, with a less thick middle part and a more distinct tyle. Transitional forms present, differentiation a bit arbitrary.

Remarks. This species seems to be quite rare: the only records so far to our knowledge are Koltun (1964) and Koltun (1976). Thus, we have now given the third record of the species widening its distribution area to the Weddell Sea. The previous records originate from Wilkes Land / Indian Antarctic ocean (Koltun 1964) and “from Enderby Land in the West to Victoria Land in the East” (Koltun 1976). Former specimens were found in depths between 219 and 393 m, whereas our sponges come from a depth of 600 m, but can still be considered shelf species and thus similar to the previous records. The species is quite clear in its characters, the most similarities are found with P. hyalinus, which is easy to distinguish as it has tylostyles smaller than 1100 x 25 µm and no stylote spicules (Ridley & Dendy 1887).