Forcepia (Leptolabis) microlabis, Van, Rob W. M., 2009

Van, Rob W. M., 2009, New sciophilous sponges from the Caribbean (Porifera: Demospongiae), Zootaxa 2107, pp. 1-40 : 27-29

Forcepia (Leptolabis) microlabis n. sp.

( Figs. 11 A–K)

Holotype. ZMA Por. 21069, Curaçao, Blauwbaai, 12.131°N - 68.987°W, under rubble, 35 m, 1989, coll. E. Meesters & P. Willemsen #B18B8.

Description. Thinly encrusting, englobing and consolidating a few small pieces of coarse coral sediment, under big rubble blocks. Surface faintly hispid. Color brown. The holotype now consists of 5 pieces, each less than 1 cm 2, and the total surface area in all is a few mm2. The encrustations of this species are thoroughly mixed in with two other encrusting sponge species, Rhabderemia minutula Carter (1876) and Timea unistellata sensu Pulitzer-Finali (1986) , the spicules of which appear as contamination in the spicule preparations.

Skeleton. Due to the mix-up with other sponge species, the details of the skeleton are not easy to ascertain; thin tylotes and large sigmas are found in the surface membrane, the acanthostyles, forcipes, small sigmas and chelae occur in the interior, the former in hymedesmioid fashion.

Spicules. Tylotes, acanthostyles in two not sharply delimited size categories, sigmas in two size categories, forcipes in two size categories, chelae in two size categories.

Tylotes ( Figs 11 A–B) thin, somewhat flexuous, with elongate more or less equal-shaped tyles at both ends, 172- 188.6 -209 x 2.5- 2.6 -3 µm.

Large acanthostyles ( Fig. 11 C), head barely differentiated from the shaft, 152- 160.5 -171 x 5 - 6.7 -9 µm; small acanthostyles ( Fig. 11 D), similar in shape to large acanthostyles, 75- 83.9 - 90 x 4 - 5.2 -6 µm.

Forcipes in two distinct sizes and shapes, the larger ( Figs 11 E–F) rather peculiar with long heavily spined legs which due the narrow space between them tend to become entangled, which causes them to look as if the legs are fused at their ends, the whole spicule rather flexuous, 66- 87.4 -106 µm. Small forcipes ( Fig. 11 G) of common horseshoe shape, but so tiny and feeble that they were only observed in light microsopic preparations after they were first detected in the SEM, coarsely spined, 6- 6.8 -8 (legs approx. 0.5 m in thickness).

Large sigmas ( Fig. 11 H), robust, evenly curved, 102- 113 .0-123 µm; small sigmas ( Fig. 11 I), more variable in shape, including S-shaped forms, often with sharply pointed endings, 27- 31.9 -39 µm.

Large arcuate chelae ( Fig. 11 J) with fairly short alae and curved shaft, 21- 30.3 -32 µm, small arcuate chelae ( Fig. 11 K) with larger alae, 11- 12.9 -16 µm.

Ecology. Consolidating coarse coral sediment under rubble in deeper reef parts (35 m).

Etymology. The name refers to the tiny forceps category found in this species.

Remarks. This is the second Forcepia (Leptolabis) species recorded from the Central West Atlantic. Previously, Forcepia (Leptolabis) vermicola Lehnert & van Soest, 1996 (as Forcepia (Trachyforcepia) ), was recorded in deep reefs (88.4 m) at the north coast of Jamaica. We take this opportunity to report its occurrence in reef caves at 10 m depth off the coast of Curaçao, collected by S. Scheffers (ZMA Por. 16597). The two species differ clearly in the presence of sigmas (absent in F. (L.) vermicola ) and the shape and diversity of the forcipes (a single category of forceps with flaring legs in F. (L.) vermicola ). Elsewhere, species of this subgenus occur off the coasts of the North Eastern Atlantic, in deep water off the Azores, and off the coast of West Australia (van Soest, 2002; van Soest et al. 2008, online). The new species stands out among these species by the peculiar heavily spined flexuous forceps, combined with the tiny normal forceps. The tiny forceps is shared only with F. (L.) luciensis , and this species also has forcipes with long spines like our new species, but these are curled into a tight ball rather than stretched out as in F. (L.) microlabis n. sp. Most of the species of this subgenus possess sigmas (the type species, F. (L.) l u c i e n s i s ( Topsent, 1888) excluded), and most are either from sciophilous or deep sea habitats. Species of the subgenus Forcepia also may have tiny forceps, e.g. Californian F. (F.) h a r t m a n i Lee, 2001 with forceps of 5–11 µm, so this is not an exclusive feature of Leptolabis .

The species of the Central West Atlantic assigned to Forcepia s.l. are keyed out below.

Figures

FIGURE 11. Forcepia (Leptolabis) microlabis n. sp., SEM images of spicules (Holotype ZMA Por. 21069). A – B. Tylote and detail of one of the apices; C. Large acanthostyle category; D. Small acanthostyle category; E – F. Entangled large forceps and detail of curved part; G. Microforceps; H – I. Large and small sigma categories; J – K. Large and small arcuate chela categories.