Spongia (Spongia) sweeti ( Kirkpatrick, 1900 )

Van, Rob W. M., Kaiser, Kirstie L. & Syoc, Robert Van, 2011, Sponges from Clipperton Island, East Pacific, Zootaxa 2839, pp. 1-46 : 33-34

Spongia (Spongia) sweeti ( Kirkpatrick, 1900)

( Figs 15 A–D)

Polyfibrospongia sweeti Kirkpatrick, 1900: 359 , pl. XV figs 2a–c.

? Spongia virgultosa sensu Desqueyroux-Faúndez 1990 : (not: Euspongia virgultosa Schmidt, 1868 )

Material examined. ZMA Por. 13987, Clipperton Island Expedition 1994, 10 °18’N 109°13’W, 9–18 m, coll. K. Kaiser, 14–26 April 1994, 1 specimen ( Fig. 15 A).

ZMA Por. 13989, same data, 1 specimen.

ZMA Por. 13990, same data, 1 specimen.

ZMA Por. 13991, same data, 1 specimen.

CASIZ 180256 (see below under Clathrina passionensis n. sp.).

MNHN DCL 4045–B, Jean-Louis Etienne Expédition Clipperton 2005, station 13, 32 m, on dead corals, 18– 01–2005, 5 specimens.

MNHN DCL 4048–C, Jean-Louis Etienne Expédition Clipperton 2005, station 42, 8 m, on dead corals, 31–01– 2005, 10 specimens.

MNHN DCL 4048–D, Jean-Louis Etienne Expédition Clipperton 2005, station 42, 8 m, on dead corals, 31–01– 2005, 6 specimens ( Fig. 15 B).

MNHN DCL 4050–B, Jean-Louis Etienne Expédition Clipperton 2005, station 42, 8 m, on dead corals, 31–01– 2005, 3 specimens.

MNHN DCL 4051, Jean-Louis Etienne Expédition Clipperton 2005, station 43, 8 m, on dead corals, 31–01– 2005, 1 specimen.

MNHN DCL 4052–B, Jean-Louis Etienne Expédition Clipperton 2005, station 42, 8 m, on dead corals, 6–01– 2005, 5 specimens.

MNHN DCL 4053–E, Jean-Louis Etienne Expédition Clipperton 2005, station and depth not recorded, on dead corals, 2 specimens.

Description. Repent ramose ( Figs 15 A–B), with thin irregular branches sometimes anastomosing into low growing masses; surface irregular, finely conulose, with frequent fistular outgrowths. Several individuals have ingrown hydroids. Size up to 4 cm long, individual branches 0.4–0.5 cm in diameter. Color pale beige (alcohol).

Skeleton. Ectosome bears a thin sand coat ( Fig. 15 C), which appears more or less continuous. The fiber skeleton ( Fig. 15 D) is typical Spongia -like with a predominance of uncored secondary fibers of uniform diameter throughout the sponge, 10–30 µm. Meshes variable in size, 50–200 µm. Primary fibers cored by sand grains, lying at 700–1000 µm distance, their diameter is 35–90 µm. They are readily recognized near the surface ( Fig. 15 D) but become rarer inwards. The surface fistules are characteristically supported by fascicles of primary fibres ( Fig. 15 E).

Soft tissue. As evidenced by histology choanocyte chambers are uniformly sized and rounded, diameter 24–33 µm. The center areas of many fistules are occupied by numerous embryos in various stages of development, largest embryos 400 µm in diameter.

Ecology and distribution. Encrusting dead corals in shallow reef environment down to 32 m; known from Île Clipperton and Funfuti, Tuvalu.

Remarks. The shape of the new species is similar to the sponge described as Polyfibrospongia sweeti by Kirkpatrick, 1900 from Funafuti, Tuvalu, Central Pacific, which was assigned to Carteriospongia by Bergquist (1980). Although she did not explain this assignment, it is likely she based this on the structure of the ectosomal skeleton with a reticulation of prominent primary fibers. Also, Kirkpatrick likened P. sweeti to Polyfibrospongia flabellifera Bowerbank, 1877 which is a Carteriospongia . The drawing of Kirkpatrick’s sponge is essentially like our own in dimensions and in the reticulated pattern of primary fibers in the walls of the fistules ( Fig. 15 E). Kirkpatrick’s specimen had much longer fistules, and that appears to be the only difference with our material. Kirkpatrick’s (1900) description of the skeleton is misleading where he emphasized bundles of secondary fibers, which occur only in the walls of the fistules. In the main body, the secondary fibers form a continuous anastomosing mass which is characteristic for the genus Spongia . The drawing of his Fig. 2a is, in fact, a good representation of the secondary fiber arrangement.

This species is assigned to the subgenus Spongia because the secondary fibers are of uniform thickness. The species has an uncommon shape and size for a member of the genus Spongia which is predominantly massive, globular or flabellate, in any case usually much larger and more elaborate. The sponge described as Spongia virgultosa by Desqueyroux-Faúndez (1990) from Easter Island is similar in shape and size to our material and the overall skeletal features are also like our specimen with the exception of the finer surface network recorded by Desqueyroux-Faúndez. It is unlikely that the Mediterranean species Spongia virgultosa ( Schmidt, 1868 as Euspongia ), although likewise unusual in being low-growing and possesssing fistular outgrowths, would occur in the Indo- Pacific. Thus, regardless whether the Easter Island sponge is the same species as ours, the present material clearly belongs to a so far unnamed species. There are no further Spongia species recorded from Pacific waters with similar habit.

Figures

FIGURE 15. Spongia (Spongia) sweeti (Kirkpatrick, 1900), A. specimen ZMA Por. 13987, scale bar = 1 cm, B. sample MNHN DCL 4048 – D with diversity of forms, C. light microscopic view of cross section showing light incomplete surface armour of sand grains, scale bar = 1 cm, D. light microscopic view of peripheral choanosomal skeleton with cored primary fibers and dense mass of secondary fibers, scale bar = 100 µm, E. light microscopic view of a longitudinal section through a fistule to show characteristic parallel primary fiber system, scale bar = 100 µm.

FIGURE 2. A. Plakinastrella clippertonensis n. sp. habit of holotype, MNHN DCL 4042 – A. B – D. Oscarella carmela Muricy & Pearse, 2004, B. habit of specimen MNHN DCL 4050 – A, C – D. Oscarella carmela Muricy & Pearse, 2004, C. histological cross section showing basal lacunae and embryos, D. detail of the same showing choanocyte chambers separated by peripheral grooves.