Desmanthus incrustans (Topsent,1889)

(Fig. 2 A-F; Table 1)

Aciculites incrustans Topsent, 1889: 32.

Desmanthus incrustans – Kobluk & Van Soest 1989: 1212.

HOLOTYPE. — Banc de Campêche. Caribbean Mexico, Bonaire, all from reef cavities, 12-30 m, 1984, coll. D. R. Kobluk (MNHN DT 1853) (ZMA POR8491, 8492, 8493).

* Possibly a complex of several closely similar species.

DISTRIBUTION. — Caribbean (Banc Campêche, Bonaire), apparently also in the Mediterranean and the Indian and Pacific Oceans, but these records need critical re-examination. From Table 2 containing spicule sizes reported for various records of the species, it is clear that these are longer and more robust in samples described outside the Caribbean. Kobluk & Van Soest (1989) suggested the Indian Ocean specimens could be Desmanthus topsenti, rather than D. incrustans. Pulitzer-Finali’s (1996) from Papua New Guinea is probably referable to D. rhabdophorus in view of the large rhabdomes of desmas II figured by this author.

ECOLOGY. — In deep-reef habitats and caves, 12- 30 m.

DESCRIPTION

Thinly encrusting, following the contours of the substrate, thickness usually less than 1 mm, lateral size 2 × 1 cm. Pale or darker yellow in colour. Surface strongly hispid due to the numerous projecting styles (Fig. 2A). In between the styles piercing the surface, there are occasional low protrusions of rhabdomes of desmas II (see black arrows in Fig. 2A and detail in Fig. 2B).

Skeleton

The usual arrangement of basal desmas upon which single styles are erected. Desmas II, distinguished primarily on their more robust shape, appear to have a peripheral position in accordance with those of the species described above. Desmas I make up the layer at the base.

Spicules

Desmas I with thinly branched cladi (Fig. 2E), dimensions: 100-140 µm. Desmas II (Fig. 2 C-D), slightly smaller but more robust, mostly with a vestigial rhabdome only, dimensions: 70-120 µm, with rhabdome 10-30 µm. Styles (Fig. 2F) curved at the base, dimension: 300-400 µm in length in the type, 340-510 × 3.5-8 µm in Bonaire specimens.

REMARKS

Several specimens were examined, including a slide from the type and specimens from Bonaire. The rhabdomes of the desmas II are clearly present although considerably shorter than those of the species described above. Nevertheless, both desma types are recognizable and appear to be arranged similarly as in the previously described specimens. This constitutes the main evidence for the synonymy of Desmanthus and Lophacanthus.