Paratimea globastrella, Van, Rob W. M., Kaiser, Kirstie L. & Syoc, Robert Van, 2011

Van, Rob W. M., Kaiser, Kirstie L. & Syoc, Robert Van, 2011, Sponges from Clipperton Island, East Pacific, Zootaxa 2839, pp. 1-46 : 9-11

Paratimea globastrella n. sp.

( Figs 4 A–F)

Holotype. ZMA Por. 21202, Clipperton Island, 10°18’N 109°13’W, 9–18 m, coll. K. Kaiser, 14–26 April 1994.

Description. Thinly encrusting in shallow pockets underneath Porites coral rubble ( Fig. 4 A), pale beige in alcohol, surface uneven, microhispid, consistency soft. Lateral size approx. 2 x 1 cm, less than 0.5 mm in thickness.

Skeleton. Megascleres erect on the substrate, united in ill defined bouquets consisting of tylostyles surrounded by centrotylote oxeas, among which large numbers of globular siliceous bodies are arranged ( Fig. 4 B). Little spongin, except at the substrate.

Spicules ( Figs 4 C–F). Megascleres smooth tylostyles and centrotylote oxeas, of variable size but both in a similar size range. Tylostyles ( Fig. 4 C) 129– 349.7 –481 x 4 – 8.1 –12 µm, centrotylote oxeas ( Fig. 4 D) 105– 294.8 – 483 x 3 – 4.6 –7 µm; rare, modified, thick siliceous rods (not shown) of up to 120 x 22 µm are assumed to be derived from the megascleres. Microscleres rounded and irregularly formed spheres, the larger ones ( Fig. 4 E) more or less globular or slightly elliptical with smooth surface, 36– 48.1 –60 µm diameter, smaller ones ( Fig. 4 F) more irregular with knobs, lobes and often irregularly spined, 12– 17.7 –34 µm diameter. They appear to form an almost continous range of shapes from more spined smaller objects to increasingly more regular smooth spheres.

Etymology. The name refers to the round microscleres assumed to be modified asters (see below).

Ecology. In a fringing reef at some depth in a sheltered position underneath coral rubble.

Remarks. The specimen is assigned to the genus Paratimea on account of the spicule complement of tylostyles, centrotylote oxeas and aster(-derived) microscleres. No Paratimea species have been recorded from Pacific waters so far. From the nine species described in the genus (all from the Atlantic Ocean), the new species differs rather strongly in the possession of microscleres that are only assumed to be modified asters. Similar globular modifications of (spher-)asters are known from certain Tethya species (family Tethyidae ), such as T. omanensis Sarà & Bavestrello, 1995 (see also Van Soest & Beglinger 2008: 779) and T. irregularis Sarà & Bavestrello, 1998 . The modification from a spheraster to a siliceous sphere appears to be associated with isolation as T. omanensis and T. irregularis are only known from an inland sinkhole several hundreds of meters from the sea. If the elongate siliceous rods reported above are indeed derivations of the megascleres, then a parallel is found with similar hypersilicified megascleres reported by Van Soest et al. (2007) in Hymeniacidon and Haliclona specimens from inshore waterbodies in The Netherlands. Possibly, the isolated sponge-unfriendly waters of Clipperton created similar conditions for a species of Paratimea causing its originally normal sphaerasters to develop into the present anomalous partly spined spheres.

De Laubenfels (1954b) described Kotimea tethya from the Honolulu Aquarium, an encrusting species with styles of 700 x 14 µm and variably sized spherasters (5–38 µm) with conical rays. If as could be hypothesized the sphere microscleres of Paratimea globastrella n. sp. are environmentally deformed asters, then possibly Kotimea tethya may be a related sponge. Rützler (2002) assigned K. tethya to Timea , likewise an encrusting sponge genus differing from Paratimea in the absence of centrotylote oxeas.

It is possible that Hymedesmia lophastraea Hentschel,1909 from SW Australia is also a member of Hemiasterellidae , and if so, a likely member of the genus Paratimea because of its thinly encrusting habit. This species possesses proper asters with peculiar anthaster-like micromorphology.

Figures

FIGURE 4. Paratimea globastrella n. sp., A. habit of holotype ZMA Por. 21202, B. thick section of skeleton showing dominance of globular silica bodies interpreted as modified asters, C. tylostyles, D. centrotylote oxeas, E. large globular aster, F. smaller globular asters showing various stages of aster-derived lobes and spines.