Forcepia (Forcepia) fistulosa, Van, Rob W. M., 2009

Van, Rob W. M., 2009, New sciophilous sponges from the Caribbean (Porifera: Demospongiae), Zootaxa 2107, pp. 1-40 : 25-27

Forcepia (Forcepia) fistulosa n. sp.

( Figs 10 A–G)

Holotype. ZMA Por. 21070, Colombia, Santa Marta area, Punta Betín, 11.25°N - 74.2167°W, reef crevices, 25 m, 18-02-1991, coll. L. Aerts.

Paratypes. ZMA Por. 21072, Colombia, Cartagena area, Islas del Rosario, Isla Pavitos, 10.2333°N - 75.75°W, 25 m, 27-10-1990, coll. M. Kielman #S155; ZMA Por. 21071, Santa Marta area, El Morro, 11.25°N - 74.2167°W, 25 m, 18-02-1991, coll. M. Kielman #S168.

Description. Hollow fistules ( Fig. 10 G) rising up from a small, encrusting base; fistules single or divided in two or three. Holotype now broken into three fragments. Length of longest single fistule 2.5 cm, diameter 0.4 cm, complex fistules up to 1.2 cm wide. Surface smooth, glistening. Consistency stiff. Color orange in life, pale brown or pale orange in alcohol.

Skeleton. In the outer wall lies a layer of intercrossing single megascleres, carried by occasional choanosomal spicule bundles fanning out beneath the surface membrane.

Spicules. Tylotes, chelae, forcipes, sigmas.

Tylotes ( Figs 10 A–B) with well-developed elongate tyles, robust, usually evenly curved, 294- 391.8 -444 13–14 µm.

Arcuate chelae (Figs C–D) predominantly twisted, but including ‘normal’ ones ( Fig. 10 C) occurring in different quantities in different specimens, 21- 24.6 -27 µm, normal chelae usually slightly smaller.

Forcipes ( Fig. 10 F) robust, all heavily spined, in a large size range but not clearly divisible in size categories (rare in paratype 21071), 29- 58.0 -102 µm.

In the holotype and in paratype 21071, thin, strongly incurved sigmas ( Fig. 10 E) occur rarely, 39–42 µm. It is not certain that these are proper.

Ecology. In shaded parts of the deeper reef (25 m), in crevices, under overhangs and under larger rubble.

Etymology. The name refers to the persistent fistular habit.

Remarks. The specimens were compared with the neotype of F. colonensis Carter (1874) ZMA Por. 0 4564, which on paper would seem very close. The chelae of this species are definitely in two size categories and the larger has the teeth always severely reduced, resembling sigmas at first glance. An unregistered specimen from Colombia (El Morro, 15 m, 20-10-1989, coll. M. Kielman, color light orange, tylotes 450 µm, chelae 21–27, possibly in two categories, forcipes 102–236 µm) considered to belong to Forcepia (Forcepia) colonensis has less pronounced reduced alae in the larger chelae, but other features appear similar. The habit of this specimen is also fistular, whereas the neotype of F. (F.) colonensis is a thin hollow crust. These varying characters are here interpreted as differences of maturity, but nevertheless, the new species approaches F. (F.) colonensis closely and the major difference rests in the presence of the peculiarly twisted chelae.

The new species also is close to F. minima n. sp. resembling it in habit, but in the new species the fistules are much larger than in F. minima n. sp.; tylotes are distinctly larger and thicker (no overlap) and the forcipes are of one type only, whereas those of F. minima are in two categories. Some specimens (holotype and one of the paratypes) bear sigmas, though rare, and these may be proper but vestigial. The chelae are in majority peculiarly twisted, resembling those of F. grandisigmata closely, and as in that species also occur in a normal form. Some specimens have only a low proportion of twisted chelae. Sizes of these chelae are slightly different between F. fistulosa n. sp. (on average smaller) and F. grandisigmata (on average larger). Forcipes are similar in shape and ornamentation in the two, with those of F. f i s t u l o s a n. sp. showing a larger size range. The major difference, however, are the sigmas, which reach very large size (up to 202) in F. grandisigmata as the name implies.

Figures

FIGURE 10. Forcepia (Forcepia) fistulosa n. sp., SEM images of spicules (Holotype ZMA Por. 21070). A – B. Tylote and details of the apices; C. Normal-shaped arcuate isochelae; D. Various types of twisted chelae; E. Sigma; F. Forceps; G. photo of fragmented holotype.