Megaciella incrustans, Van, Rob W. M., 2009

Van, Rob W. M., 2009, New sciophilous sponges from the Caribbean (Porifera: Demospongiae), Zootaxa 2107, pp. 1-40 : 14-15

Megaciella incrustans n. sp.

( Figs 5 A–E)

Holotype. ZMA Por. 21063, Colombia, Santa Marta area, Cabo de Aguja, 11.309°N - 74.194°W, 8–15 m, 5- 11-1986, coll. M. Rozemeijer & W. Dulfer.

Description. Thinly encrusting patches on barnacles, largest patch approx. 2 x 3 mm, less than 0.5 mm in thickness. Microhispid, soft. Color: brick-red.

Skeleton. Acanthostyles erect on the substrate, in clumps or bouquets, with the larger penetrating the surface. Ectosomal tylotes arranged in bundles fanning out and carrying the surface membrane; scattered tylotes arranged tangentially. Chelae forming a dense mass in the surface membrane.

Spicules. Ectosomal microspined tylotes, acanthostyles in two size categories, palmate isochelae.

Tylotes ( Figs 5 A–B), with elongate, slightly unequal heads, microspined at both ends, 237- 279.9 -309 x 2 - 3.0 -3.5 µm.

Large acanthostyles ( Fig. 5 C) without prominent heads, spined all over but fewer spines toward the pointed end, 129- 215.5 -293 x 6 - 7.7 -10 µm, small acanthostyles ( Figs 5 C–D), similarly shaped, 63- 76.2 - 93 x 3.5- 4.7 -7 µm. The two size categories are not sharply delimited. Palmate isochelae ( Fig. 5 E), rather narrow, but otherwise of quite usual shape, very little size variation, 9- 12.5 -14 µm.

Ecology. Encrusting on and between barnacles, in shallow reef caves, approx. 10 m.

Etymology. The name refers to the thinly encrusting habit.

Remarks. This species is provisionally assigned to Megaciella , a genus predominantly consisting of elaborate coldwater forms, with reticulate skeletons ( Hooper, 2002a). No Megaciella species have been reported from the Central West Atlantic (van Soest et al. 2008, on line). The species would fit more easily in Clathria (Microciona) Bowerbank (1862) , but this is precluded by the microspined tylotes, instead of which it should have had microspined subtylostyles. A remote possibility is that it is an Acarnus lacking both cladotylotes and toxas, which would then be unrecognziable as Acarnus , as some similarity exists with tylotes and isochelae of e.g. Acarnus nicoleae van Soest et al. (1991). Still, many genera in the Microcionina share elaborate reticulate species as well as species with hymedemioid skeletons, such as Clathria Schmidt (1862) , Antho Gray (1867b) , Acarnus Gray (1867b) , or Iophon Gray (1867b) , and the species described here is merely the first such form reported for Megaciella . No matching descriptions are known from the Central West Atlantic.

Figures

FIGURE 5. Megaciella incrustans n. sp., SEM images of spicules (Holotype ZMA Por. 21063). A – B. Ectosomal microspined tylote, and details of apices; C. Large and small acanthostyles; D. Detail of small acanthostyle; E. Palmate isochela.