Bathydorus sp.

Reiswig, Henry M. & Stone, Robert P., 2013, <strong> New glass sponges (Porifera: Hexactinellida) from deep waters of the central Aleutian Islands, Alaska </ strong>, Zootaxa 3628 (1), pp. 1-64 : 36-39

Bathydorus sp.

( Fig. 18 , Table 9)

Synonymy. Bathydorus sp. Stone et al., 2011: 34.

Material examined. USNM# 1196556 , ROV ' Jason II' from RV ' Roger Revelle', dive J2101, 02 August 2004, 8.6 km SSW of Cape Sasmik, Tanaga Island , Aleutian Islands , Alaska, 51º31.483'N, 177º57.494'W, 494 m, whole specimen attached to cobble, ethanol .

Description. The specimen ( Fig. 18A ) was flattened onto its cobble substrate and slightly damaged during fixation and transport; its dimensions are 11.0 x 8.3 x 2.0 mm. An osculum, 2.6 mm diameter, appears to be present apically but neither an atrial cavity nor atrial spicules could be identified; this is clearly a juvenile specimen. Long, thick prostal diactins project from the deep parenchyma, through the dermal layer, and radiate 5.9–7.9– 9.9 mm from the surface; their distal ends are broken. Hypodermal pentactins are not raised to form a veil but remain under the dermal surface providing support for the dermal spicules and surface ( Fig. 18B ); where these appear slightly raised, their position is ascribed to displacement during flattening of the specimen since dermalia remain above those pentactins.

Megascleres are hypodermal pentactins, dermalia, and both thick prostal and thin parenchymal diactins (spicule dimensions are given in Table 9). Hypodermal pentactins ( Fig. 18C ) are relatively small and thin for Rossellidae ; they are mostly smooth with finely spined or rough ray ends. Dermalia ( Fig. 18D ) are mainly stauractins, with a few diactins, triactins and pentactins (just one seen); they are all entirely sparsely spined and ray ends are bluntly rounded. Diactine and triactine dermalia have the same size and characters as stauractins, but the undeveloped rays are represented by small hemispheric knobs, one on the triactins and 4 on diactins. Larger prostal and parenchymal diactins were subjected to size-frequency analysis which indicated 3 (and perhaps 4) distinct classes on the basis of spicule thickness; we recognize 2 classes of thick prostalia (A: 65–90 µm, Fig. 18E; B : 30–65 µm in thickness, Fig. 18F ) and one class of thin parenchymal diactins (4.7–20.0 µm in thickness, Fig. 18G ). Since very few prostalia were available for measurement, we group the thick prostalia A and B together in Table 9.

unless otherwise indicated).

Microscleres consist of nearly equally abundant hemioxyhexasters (53%) and oxyhexactins (46%), with a very few complete oxyhexasters (1%). Hemioxyhexasters ( Fig. 18H , right and bottom) are thin, with very short, nearly smooth, primary rays, each of which bears 1–2 (rarely 3) long straight rough terminals. The few oxyhexasters have the same size and characters as the hemioxyhexasters. Oxyhexactins ( Fig. 18H left) are similar but all rays are fairly straight and rough, without a basal bulge indicative of the encompassed primary ray.

Remarks. Although this is a juvenile specimen of Bathydorus , it is large enough to express adult spicule types for hypodermalia, prostalia, dermalia, and microscleres; atrialia are probably the last spicules to be developed, and indeed, there are no atrialia found in this specimen. The genus Bathydorus presently contains six recognized species. The character of dermalia being mainly stauractins with few diactins in this specimen excludes it from B. echinus Koltun, 1967 (dermalia mainly pentactins), B. servatus Topsent, 1927 (dermalia as equal numbers of stauractins and diactins), and B. uncifer Schulze, 1899 (equal numbers of stauractins and pentactins). Presence of hypodermal pentactins and straight rays on hemioxyhexasters excludes the new specimen from B. spinosus Schulze, 1886 . The new specimen differs from B. fimbriatus Schulze, 1886 , by the latter's tight bundled terminal rays of its oxyhexasters. It is difficult to conclude that the new specimen cannot belong to B. levis Schulze, 1895 , but while the new specimen has hypodermal tangential rays to nearly 1.4 mm long, these reach only 500 µm in the latter, and rare diactin dermalia have been reported only in B. levis spinosissimus Lendenfeld, 1915 which has much smaller stauractine dermalia. It seems prudent to refrain from assignment of this juvenile Bathydorus to a known species, and to report the specimen as Bathydorus sp. Since this specimen is too small to recognize in video footage, it's local abundance is unknown.

Genus Caulophacus Schulze

Subgenus Caulophacus Schulze

Type species: Caulophacus latus Schulze, 1886

Figures

FIGURE 18. Bathydorus sp., body and spicules. A. Entire specimen teased from cobble. B. Close-up of surface. C. Hypodermal pentactin, whole and magnified ray ends (SEM). D. Dermal stauractin, triactin and diactin, whole and magnified ray ends (SEM). E. Large thick prostal diactin, whole and magnified end (SEM). F. Small thick prostal diactin, whole and magnified ray end (SEM). G. Thin parenchymal diactin, whole and magnified end (SEM). H. Oxyhexactin and hemioxyhexaster, whole and magnified center of the latter (SEM). I. Portion of basidictyonal attachment framework (SEM).