Ulosa pacifica, 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 : 26

Ulosa pacifica n. sp.

( Figs 11 A–C)

Holotype. ZMA Por. 13998, Clipperton Island, 10°18’N 109°13’W, 9–18 m, coll. K. Kaiser, 14–26 April 1994.

Additional specimens examined (not type material). MNHN DCL 4048–A, Jean-Louis Etienne Expédition Clipperton 2005, station 42, 8 m, on dead corals, 31–01–2005, 1 specimen.

MNHN DCL 4059–A, Jean-Louis Etienne Expédition Clipperton 2005, station 1, on dead corals, 6–01–2005, 1 specimen.

Description. Thin transparent to dirty white encrustation underneath coralline algae and found occupying crevices in dead coral. In places the dark red color of the coralline alga on which it grew shines through the transparent skin ( Fig. 11 A). Approx. 10 x 5 mm in lateral size, less than 1 mm in thickness. Surface smooth, faintly irregular. Consistency soft.

Skeleton ( Fig. 11 B). A wispy, loose reticulation of spongin enclosed spicule tracts running parallel with the surface, seen through the skin at low magnification as whitish lines, amber –colored in transmitted light. Although some of the spicule-fibers are clearly thicker and more continuous than the majority of intercrossing and parallel fibers, there is no regular anisotropic reticulation with clear primary and secondary fibers. Spicule-fibers varying in thickness from 8–12 µm in the smallest to 60 µm in the prominent ones. The number of spicules in the fibers is less variable, 3 to 9 spicules per cross section, with the connecting fibers having fewest spicules. Meshes formed by the fibers are irregularly rectangular, 160 – 420 µm wide.

Spicules. Only megascleres, no microscleres. Spicules thin, curved or wavy styles ( Fig. 11 C) and strongylote forms, with one or both ends variably pointed, rounded, stair-stepped or with open-ended axial canals, 273– 331.3 – 384 x 3 – 3.9 –5 µm.

Etymology. Named for its regional occurrence.

Ecology. Under dead coralline rubble in shallow reef environment.

Remarks. In addition to the holotype, several other thin crusts with only styles as spicules were found among the 2005 material. These crusts were so tiny and thin that no structure of the skeleton could be detected and spicules appeared thinner. These crusts were likely incipient specimens of the present species.

The genus Ulosa was earlier reported from the Central Pacific by De Laubenfels (1954a) with Ulosa spongia , a species of similar habit (encrusting), skeleton (spongin reticulation) and spiculation (styles). However, the largest styles of this species are 500 x 5 µm, clearly much larger than those of our new species. The specimen was also larger (10 cm) and thicker (10 mm) than the present material. Ulosa rhoda De Laubenfels, 1957 from Hawaii is ramose and has styles much thicker than those of our specimens (300–400 x 13–15 µm).

The World Porifera Database (Van Soest et al. 2008) assigned the Pacific Protophlitaspongia ada De Laubenfels, 1954a to Ulosa . This is a thinly ramose species with hastate oxeas of less than 100 µm in length, thus quite unlike our species.

The type of Ulosa , U. angulosa ( Lamarck, 1814 as Spongia ) from South Australia is not well characterized as it is only known from Topsent’s (1931) redescription. It is a massive sponge with spongin fiber reticulation containing smaller (125–180 µm) and relatively thicker styles (5 µm).

Figures

FIGURE 11. Ulosa pacifica n. sp., holotype ZMA Por. 13998, A. habit encrusting a piece of dead coral, scale bar = 1 cm, B. light microscopical view of the skeleton, scale bar = 200 µm, C. stylote megasclere with details of various posterior apices.