Clathria (Thalysias) minuta

Zea, Sven, Rodríguez, Angélica & Martínez, Ana María, 2014, Taxonomy of Clathria (Thalysias) (Demospongiae: Poecilosclerida: Microcionidae) from the Colombian Caribbean, with description of three new species, Zootaxa 3835 (4), pp. 401-436 : 417-420

Clathria (Thalysias) minuta (van Soest, 1984)

Figures 9 , 10 ; plate 2 figures A, B

Synonymy in Hooper (1996: 410), Muricy et al. (2011: 147) and Valderrama and Zea (2013: 366). In addition: Clathria (Thalysias) minuta ; van Soest et al. 2013: 335, fig. 30 (illustration of type material). Clathria minutus ; Alcolado 2002: 64.

? Rhaphidophlus cf. minutus; Kobluk and van Soest 1989: 1216.

Material examined. Holotype (as Rhaphidophlus minutus ), ZMA POR.4796, Curaçao, 300 m off Hilton Hotel, on dead coral Meandrina , 33 m, coll. R.W.M. van Soest, 13 Dec. 1980 (tissue slides). Santa Marta: INV-POR 1217 (Morro, reef terrace, on dead coral, 14–15 m, 26 Jan. 1988), INV-POR 1218 (Punta de Betín, littoral overhanging rock, 8 m, 27 Mar. 2012), Bahía de Santa Marta, coll. S. Zea. Gulf of Urabá: INV-POR 0 548 (material of Valderrama & Zea, 2013), Sapzurro, in crack within a flat of coral Siderastrea siderea , 2–3 m, coll. S. Zea, 29 Sept. 1995.

Shape, color and consistency. Very thin encrustations extending over several square centimeters; smooth, subdermal canals or oscules only slightly evident in some specimens. Color red to scarlet red. Consistency soft (specimens are too thin to be categorized).

Skeleton. Pinacoderm supported by brushes of small auxiliary subtylostyles, sometimes very densely arranged. In a basal plate of sponging there are numerous, erect accessory acanthostyles. There are scattered basal thick principal styles, usually solitary, which are continued upwards by expanding tracts-brushes of choanosomal to subectosomal auxiliary subtylostyles, and then by the ectosomal brushes. Spicules (Table 1): (1) long, somewhat curved, basal principal styles, with slightly to strongly rugose and spiny heads, sometimes deformed down to the neck; ends slightly telescopic, 275– 394.7 –522 µm by 6.7– 9.5 –11.9 µm. (2) Straight auxiliary subtylostyles with smooth to slightly microspined heads; two size categories by spatial location: large, choanosomal to subectosomal ones, 299– 333.9 –389 µm by 2.9– 3.8 –5.2 µm, small, ectosomal ones, 143– 223.3 –280 µm by 1.4– 2.4 –4.8 µm. (3) Slightly curved, slender, echinating accessory acanthostyles, spined all over and often without a distinct apical engrossment of spines; wide range of sizes, 67– 101.7 –176 µm by 4.3– 5.2 –7.1 µm. (4) Thin, wing-shaped toxa with much curved ends, 55– 66.9 –103 µm. (5) Narrow, palmate isochelae, 16.1– 17.5 –19.6 µm.

Distribution and ecology. From Valderrama & Zea (2013) and additions: Bahamas, Cuba (also Alcolado 2002), Curaçao, Colombia (Gulf of Urabá, Santa Marta), Brazil [northeast (Fernando de Noronha Archipelago) to southeastern Brazil (Arraial do Cabo)]. A report from Tropical West Africa (van Soest 1993) was recently described as new, vis. Clathria (Thalysias) minutoides van Soest et al., 2013. It inhabits littoral rocks and coral reefs (shallow to deep, recorded down to 33 m).

Remarks. Our specimens from Santa Marta concur with the type material (also compared with a SEM spicule plate kindly sent by R.W.M. van Soest, pictured in van Soest et al. 2013: fig. 30). This species can be separated from other thinly encrusting, red to orange to scarlet Greater Caribbean Clathria by the presence of acanthostyles in a wide range of sizes (perhaps in two distinct categories). From the various spicule combinations, C. minuta seems rather similar to C. (Microciona) campecheae Hooper, 1996 [new name for Greater Caribbean C. affinis ( Topsent, 1889) (see also van Soest 1984), preoccupied by C. affinis Carter, 1880 from the Indian Ocean (see Hooper 1996)], especially in the similarly sized and shaped toxa. The latter species can be distinguished by having a single category of larger etosomal tylostyles and the acanthostyles not reaching such large sizes. We have not yet found C. campecheae in Colombian waters, although it has been listed as C. affinis from Santa Marta by Rozemeijer & Dulfer (1987) and Aerts & van Soest (1987), whose material was identified by R.W.M. van Soest himself. van Soest et al. (2013) described sister species Clathria (Thalysias) minutoides from NW Africa, distinguished from C. minuta by having the apices of the toxa finely spined.

The record of Rhaphidophlus cf. minutus by Kobluk & van Soest (1989) from Bonaire caves needs to be confirmed as these authors mentioned that their specimen differs from the type in the shape of the toxa, being straight-angled instead of softly to deeply curved. Brazilian records of Clathria (Thalysias) minuta (listed in Muricy et al. 2011: 147) are all from checklists. In contrast to Santa Marta material, Bahamas specimen had distinct star pattern of the canal system and oscules (see Zea et al. 2009).

Figures

FIGURE 9. Clathria (Thalysias) minuta. Schematic drawing of spicule types (A) and skeleton (B). (a) Choanosomal principal styles, (b) choanosomal and subectosomal auxiliary subtylostyle, (c) ectosomal auxiliary subtylostyle, (d) echinating accessory acanthostyles, (e) wing-shaped toxa with recurved ends, (f) palmate chela, (g) section perpendicular to the surface.

FIGURE 10. Clathria (Thalysias) minuta. SEM micrographs of spicules of a specimen from Santa Marta. (a) Choanosomal principal style, (b) ectosomal auxiliary subtylostyle (larger choanosomal and subectosomal ones were not found in the SEM preparation), (c) echinating accessory acanthostyles, (d) wing-shaped toxa, (e) palmate chelae.