Semitaspongia bactriana, de & Bergquist, 2000

de, Steve & Bergquist, Patricia R., 2000, Two new genera and five new species of the “ Cacospongia ” group (Porifera, Demospongiae, Dictyoceratida), Zoosystema 22 (2), pp. 383-400 : 395-397

Semitaspongia bactriana n.sp. ( Fig.7 )

HOLOTYPE.— Poor Knights Islands . 35°28.5’S, 174°44.5’E, VI.1981, NMNZ POR458 (= SDCC/ NZ 145).

ETYMOLOGY.— The specific name of this sponge reflects the humped form of the type specimen, which bears a strong resemblance to the two-humped Bactrian camels, indigenous to the Mongolian region. This central Asian area was once part of an area called Bactria.

DISTRIBUTION.— Only known from the type locality.

DIAGNOSIS

This sponge is a massive low pad, with short, blunt fingers expanding out from the main body. The surface is densely covered with fine conules, some of which have emergent terminal fibres, that are simple or dendritically branched. Groups of very small pores are irregularly dispersed over the sponge surface. Approximately 70-80% of the base is attached to the substratum, with a central area raised up from the substratum. The consistency is moderately soft and compressible. Externally the sponge is brownish purplegrey, fading to cream basally. Internally the sponge is cream. This specimen has a number of bryozoan and hydrozoan epibionts. The holotype is 90 mm long × 35-65 mm wide × 25-35 mm high.

Skeleton

A moderate density, relatively regular skeleton of strongly laminated primary and secondary fibres. Primary fibres are irregularly and axially cored, sometimes heavily and sometimes only lightly, and may form tangled fascicles. Some fibres, seen in section, appear to have a distinct inner and outer region. Secondary fibres are partially cored. It may be difficult to distinguish between primary and secondary fibres, owing to the presence of fascicles. A central pith is visible in primary fibres, though obscured where fibres are cored, and can sometimes be seen extending into secondary fibres. There are patches of foreign sponge spicules embedded in the mesohyl, but these are not distributed regularly. Primary fibres are 146 µm in diameter (58-340 µm, n = 25); secondary fibres are 68 µm in diameter (29-116 µm, n = 14).

Histology

The choanocyte chambers are diplodal and mostly spherical in shape. They are 26 µm in diameter (21-34 µm, n = 30), and some are arranged in single-file rows. There is moderate to heavy collagen deposition, primarily at the surface, but also around the larger canals and canal beds. In all sections, collagen comprises 30-40% of the mesohyl.

REMARKS

The external features of this sponge are reminiscent of Spongia and Cacospongia , though when the internal structure is examined histologically, its affiliations to Scalarispongia n.gen. are clear. This is the only species of Semitaspongia n.gen.

with a lobate form.

Five new species of Semitaspongia n.gen. are described above. A key has been devised to assist in identifying these species, though it should be used alongside the full species descriptions and plates.

1a. Small fistules or turrets ........................................................................................ 2

1b. Without fistules or turrets .................................................................................... 3

2 (1) a. Forms large, soft, fleshy lumps .......................................................... pulvinata

2b. Low, pad-like form ...................................................................................... glebosa

3 (1) a. Regular, compact form, with numerous, very fine conules ................ bactriana

3b. Irregular form ...................................................................................................... 4

4 (3) a. Very irregular, scruffy and somewhat hairy or bristly .......................... incompta

4b. Irregular, but not bristly; dark fibres may be visible through pinacoderm ................ .................................................................................................................... nigrachorda

Figures

FIG. 7. — Semitaspongia bactriana n. sp.; A, side view; B, fibre skeleton; C, detail of fibre skeleton; D, detail of fibre skeleton; E, histological detail, showing clear tracks of choanocyte chambers through a bed of collagen. Scale bars: B, C, 500 µm; D, E, 250 µm.