Asbestopluma TOPSENT 1901

ASBESTOPLUMA TOPSENT, 1901

Type species: Cladorhiza pennatula Schmidt, 1875 (by subsequent designation).

Diagnosis, from Hajdu & Vacelet (2002): Cladorhizidae with palmate anisochelae.

ASBESTOPLUMA AGGLUTINANS SP. NOV.

(FIG. 5)

Type material

Holotype: NAUDUR 15-2-1B, 20/12/1993, 18°15.90′S, 113°22.08′W, 2689 m, Muséum National d’Histoire Naturelle, Paris, no. MNHN D JV 82.

Paratype: GARRETT GN 19-07, 31/01/1991, East Pacific Rise, Garrett Segment, 13°22.50′S, 112°16′W, 2680 m, Muséum National d’Histoire Naturelle, Paris, no. MNHN D JV 83.

Etymology

From ‘agglutinare’, Latin, verb: to glue, referring to the collection by the sponge of numerous skeletons of protistans.

Locality and habitat

East Pacific Rise. NAUDUR 15-2, 20/12/1993, 18°15.90′S, 113°22.08′W, 2689 m, on a dead smoker. GARRETT GN 19-07, Garrett Segment, 31/01/1991, 13°22.50′S, 112°16′W, 2680 m, on a basalt fragment.

Description

Two small erect sponges (Fig. 5A), consisting of a somewhat flattened axis 4 cm high and 0.8–1 mm in diameter, smooth on the basal quarter, then with biserially arranged lateral filaments arising perpendicularly to the axis in two opposite series. Filaments frequently broken, up to 5 mm long, cylindrical and 1– 1.5 mm in diameter at the base, abruptly reduced to a thin spicular axis at approximately 0.7 mm from the axis in the holotype, up to 6 mm long in the paratype in which the cylindrical base is generally longer and thinner. No aperture or aquiferous system visible. Colour brown in alcohol.

Skeleton: Main axis of large fusiform styles longitudinally arranged, surrounded by a dense feltwork of small acanthotylostrongyles including sediment and skeletons of radiolarians and foraminiferans. Axis of the lateral filaments made of smaller styles, with a similar feltwork of acanthotylostrongyles and sediment in the thickened base. Fixation base with a cover of thick, more or less flexuous styles or substrongyles tangentially arranged. Microscleres very abundant in the tissue of stem and branches.

Spicules:

1. Styles of the main axis (Fig. 5B, C), straight, fusiform, with a blunt point. Size 1550–2100 × 30–35 µm. 2. Styles (mycalostyles) (Fig. 5D) of the axis of the lateral filaments, straight, moderately fusiform, with an oval head and a short, acerate tip. Size 370–780 × 8.5– 17 µm.

3. Styles or substrongyles (Fig. 5E) found only at the fixation base, generally curved or more or less flexuous, sometimes vermiform, thicker in the middle, with unequal ends. Size 220–535 × 15–42 µm.

4. Acanthotylostrongyles (Fig. 5F, G) forming a feltwork around the main axis and the base of the filaments, straight or more often curved near the head, entirely covered by small spines curved toward the end near the head and toward the head near the end. Head roundish, end abruptly cut. Size 65–165 × 0.8– 2.3 µm.

5. Anisochelae 1 (Fig. 5H). Head with large lateral alae attached to the shaft along approximately twothirds of their length, frontal ala large, ovoid. Shaft feebly curved in the first part, then bearing two small fimbriae near the foot. Foot with two small diverging alae. Size 32–36 µm, shaft diameter 4.1–5 µm.

6. Anisochelae 2 (Fig. 5I, J). Head with large lateral alae attached to the shaft along their whole length. Shaft with a free part short, curved and bearing two small rectangular alae in the first part, then strongly bent and with a large ovoid ala ending in a short point. Size 9.8–10.5 µm, shaft diameter 0.8–1 µm.

7. Sigmancistras (Fig. 5K), with a 90° twisting and acerate points, without notch. Size 23–28 µm, 2.3 µm in maximum width.

Remarks

This species is remarkable in its morphology, with regular thickenings of the basal parts of the lateral filaments, and in the number of skeletons of various foraminiferans and radiolarians included in these thickened parts. This may suggest that protistans are an important part of the diet of the sponge.

The nearest relative of this species among the Asbestopluma spp. of this area appears to be A. biserialis (Ridley & Dendy, 1886), which has been described and reported from the South Pacific. However, A. biserialis does not display the cylindrical thickenings of the base of the filaments, has no coating of spinose microtylostyles, has no vermiform basal spicules and the large anisochelae 1 are absent. The new species more closely resembles the spicule characters of A. pennatula (Schmidt, 1875) and A. quadriserialis Tendal, 1973, from the North Atlantic and Arctic. It differs from these species, which are geographically very distant, in its external shape, larger styles, smaller anisochelae 1, which also show minor differences although their general shape is rather similar, and in the basal vermiform styles, which are rather straight strongyles in the two other species. Asbestopluma quadriserialis also differs in the presence of two sizes of sigmancistras.

Unlike the other sponges described here, this species is represented in the collection by two specimens from relatively distant localities (557 km). It is worth noting that the two specimens show no significant differences, either in morphology or in spicule characters.