Johannesia

Van, Rob W. M., Kaiser, Kirstie L. & Syoc, Robert Van, 2011, Sponges from Clipperton Island, East Pacific, Zootaxa 2839, pp. 1-46 : 27-28

Johannesia sp.

( Figs 12 A–D)

Material examined. MNHN DCL 4042–C, Jean-Louis Etienne Expédition Clipperton 2005, station 18, 55 m, on dead corals, 20–01–2005, 1 specimen.

Description. Sponge forming a thin membrane over seemingly empty spaces underneath dead corals ( Fig. 12 A), largest patch 15 x 10 µm. Surface smooth. Two large rounded apertures are present on the location of a deeper hole which may be caused by damaging of the sponge. Consistency soft, easily damaged.

Skeleton ( Fig. 12 B). Ectosomal skeleton is a tangential arrangement of loose oxeas and tylostyles, forming a detachable skin. There is no clear choanosomal skeletal arrangement of spicules other than loose individual spicules in confusion.

Spicules. Oxeas ( Fig. 12 C), thin, symmetrical, evenly tapering to a sharp point, 384– 419.1 –517 x 6 – 7.7 –9 µm; (sub-)tylostyles ( Fig. 12 D) with distinct but slight tyle, 182– 237.4 –291 x 2 – 3.59 –5.5 µm (tyle 3– 4.2 –6 µm).

Ecology. Encrusting the underside of corals at greater depths (55 m).

Remarks. The material is thin and sparse, and spiculation and skeletal arrangement are insufficient for proper characterization of the species to which it belongs. The combination of oxeas and tylostyles in a halichondroid arrangement is characteristic of the genus Johannesia Gerasimova et al. 2008 . This genus is based on type species Vosmaeria reticulosa Thiele, 1905 from the SE Pacific (Northern Chile and Peru). It is a massive sponge with a halichondroid skeleton with spicules similar in length but clearly thicker: oxeas 200–700 x 4–20 µm and (sub-)tylostyles of 100–400 x 3–15 µm. Another major difference is the presence of spicule tracts, which are entirely lacking in our specimen. Still, it is not impossible that our material is an incipient sponge of this species.

Figures

FIGURE 12. Johannesia sp., undetermined specimen MNHN DCL 4042 – C, A. habit encrusting a dead coral, B. light microscopic overview of spicules, scale bar = 100 µm, C. oxea and detail of apex, D. (sub-) tylostyle and detail of head.