Desmanthus levii, Van Soest & Hajdu, 2000

Van Soest, Rob W. M. & Hajdu, Eduardo, 2000, New species of Desmanthus (Porifera, Demospongiae) with a discussion of its ordinal relationships, Zoosystema 22 (2), pp. 299-312 : 304-307

Desmanthus levii n. sp.

( Fig. 1 F-I)

HOLOTYPE. — NW side of Uva Island. W side of bay, Contreras Islands, Gulf of Chiriqui, Pacific coast of Panama, on boulders, 5 m, coll. W. H. de Weerdt, #12-XII-90-1-1 ( ZMA POR13398).

PARATYPE. — NW side of Uva Island. Rocky Point, Contreras Islands, Gulf of Chiriqui, Pacific coast of Panama, on fishing net, 3 m, coll. W. H. de Weerdt, #10-XII-90-1-1 (on verongid) ( ZMA POR13399).

ETYMOLOGY. — Named in honor of Prof. Claude Lévi in recognition of a lifetime devoted to sponge biology. DISTRIBUTION. — Pacific coast of Panama, shallow water, 3- 5 m.

DESCRIPTION

Thin crusts, up to 1 mm in thickness, covering up to 20-25 cm 2 in area (only a few cm 2 were collected). Colour bright orange. Surface smooth, fine-grained, no special markings were noted. Structure compact.

Skeleton

In dehydrated sections ( Fig. 1F ), the surface appears pierced by the numerous curved styles which stand erect between the rhabdomes of desmas II. Some styles may lie loosely, tangentially to the surface. The choanosomal skeleton is composed of a thin basal layer of desmas I with moderate zygosis. On top of this layer is a thick continuous layer or alternatively several layers of desmas II. The upper layer or most proximally situated desmas II have some of the rhabdomes (see arrows in Fig. 1F ) protruding beyond the surface among the styles. All cladomes are facing down.

Spicules

Smooth desmas I ( Fig. 1H ), with thin multiply branched cladi, dimensions: 90-112 × 5-10 µm (n = 12). Smooth, more robust desmas II ( Fig. 1G ), with cladomes strongly concave and strongly tuberculate, dimensions: 94-136 × 12- 20 µm. Rhabdomes conical and fairly straight, mostly smooth, dimensions: 47-141 × 15-23 µm. Smooth, curved, relatively thin styles ( Fig. 1I ), thicker at the base, with sharp points, most often slightly bent on the basal part, dimensions variable but in single size category, dimensions: 136- 460 × 4-12 µm.

REMARKS

This species resembles D. rhabdophorus (Hentschel, 1912 as Lophacanthus ) and D. meandroides n. sp. in many morphological aspects, and it is likely they are closely related. Its specific characters are the distinctly smaller desmas I which are concentrated in an unusually thin layer at the base, and the rhabdomes of desmas II which are on average shorter than those of the other two species. In view of this, it is unlikely that D. levii n. sp. constitutes a disjunct population of either of these.

COMPARISON WITH OTHER SPECIES

OF DESMANTHIDAE

The following species described by previous authors are assigned to the family Desmanthidae . Their spicular characters are presented in Table 2.

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 ).

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 pro- trusions 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 .

Desmanthus topsenti Hentschel, 1912 ( Fig. 2G, H )

HOLOTYPE. — Aru Islands . Stn 77, Merton coll. ( SMF 1560 ).

DISTRIBUTION. — Aru Islands (eastern Indonesia), on rocks at 20 m.

DESCRIPTION

Thinly encrusting, about 0.5 mm thick and 1.7 cm long. Surface hispid. Colour grey or brownish grey in alcohol. Structure compact.

Skeleton

The main skeleton consists of an irregular layer of desmas on which monactinal spicules are erected. Spicules

Desmas which can be separated in basally arranged smaller desmas ( Fig. 2H ), presumably desmas I, with more tuberculate cladi, dimensions: 240-270 × 20 µm, and peripherally arranged more robust desmas ( Fig. 2G ), presumably desmas II, dimensions cladome: 200- 310 × 30-45 µm. They are not clearly separated morphologically and the larger desmas lack a distinct rhabdome. Monactinal spicules are styles and rhabdostyles, variable in form, size and curvature, the smaller sizes tend to be rhabdostyles, dimensions: 224-1000 × 14-31 µm.

REMARKS

Hentschel (1912) states that this species differs from D. incrustans mainly in the absence of clear rhabdomes in the desmas. A syntype specimen from the Senckenberg Museum was re-examined (SMF 1560, from stn 77 of the Merton collection described by Hentschel). The rhabdomes are certainly inconspicuous, but nevertheless there is a clear division in thinner and more robust desmas. So far no other specimens of this species have been recorded, but it is possible that some of the Indian Ocean records of D. incrustans are referable to this species.

Figures

FIG. 1. — A-E, Desmanthus meandroides n. sp.; A, habit of holotype, MNRJ 341, photographed in situ; B, from holotype, partly cleaned section of desma II skeleton showing forest of outward-pointing rhabdomes; C, from holotype, desma II showing prominent rhabdome; D, from holotype, desma I; E, from holotype, style; F-I, Desmanthus levii n. sp.; F, from holotype ZMA 13398, uncleaned section shown sideways. Arrows indicate desma II rhabdomes protruding into the surface membrane among the styles; G, from holotype, desma II showing prominent rhabdome and concave cladome; H, from holotype, desma I; I, from holotype, style (scale bar: bar shared with Fig. 1E = 100 µm). Scale bars: A, 1 cm; B-I, 100 µm.

FIG. 2. — A-F, Desmanthus incrustans; A, overview of uncleaned section of the type specimen, MNHN D.T. 1853 showing styles and rhabdomes of desmas II (arrows) protruding through the organic ectosome; B, detail of Fig. 2A showing the protruding rhabdomes of desmas II; C,Bonaire specimen ZMA 8491, desma II; D, Bonaire specimen ZMA 8491, desma II; E, Bonaire specimen ZMA 8491, desma I; F,Bonaire specimen ZMA 8491, style;G-H, Desmanthus topsenti, from type specimen SMF 1560; G, desma II; H, desma I. Scale bars: A, B, F-H, 100 µm; C-E, 10 µm.