PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON 113(4): 1162-1 172. 2000. Three species of toxic sponges from Cebu, Philippines (Porifera: Demospongiae) G. J. Bakus and G. K. Nishiyama Department of Biological Sciences, University of Southern California, Los Angeles, California 90089-0371 U.S.A. (e-mail:
[email protected]) Abstract. — Three species of sponges toxic to hard corals are described from Mactan Island, Cebu, Philippines. They were most common at depths of 8-12 m, but they occurred between 3 and 32+ m. Plakortis lita forms thick crusts or is subglobular or massive and liver brown. Diods are very densely packed and irregularly distributed. Triods are rare and microrhabds absent. Acervochalina hooperi, new species, forms thin crusts and is dark green. Thick branching spon-gin fibers are embedded with small oxeas. Xestospongia vansoesti, new species, forms thick crusts but can be digitate, and dark green to black. Dense multis-picular tracts contain oxeas. The sponge produces a copious brown mucus. Since 1994 we have been periodically studying the coral reef community and spe-cifically the sponges of Cebu, Central Phil-ippines. Nishiyama (Nishiyama & Bakus 1999) discovered that all three species of sponges described below were releasing al-lomones into the surrounding seawater. These allomones were toxic to some hard corals which suggests that the sponges and hard corals are competing for space. Thus, sponge toxins may play an important role in the structuring of coral reef communities. We are herein describing these species of sponges from our ecological field studies. Materials and Methods Site description. — Our study site is lo-cated approximately 200 m off the Tumbuli Beach Resort on the east coast of Mactan Island near Cebu City (10°17'N, 124°E) (Fig. 1) (Bakus and Nishiyama 1999). Depths surveyed were 3-32 m. The area has a narrow intertidal region followed by seagrasses (principally Thalassia hempri-chii) to a depth of 5-10 m, then a rich coral reef community to a depth of at least 40 m, with the slope becoming steeper beyond a depth of 20 m. The dominant hard corals in the region include Acropora, Pocillopora, Seriatopora, Tubipora, Halomitra, Para-halomitra, Lobophyllia, Symphyllia, Eu-phyllia, Pectinia, Porites, Montipora, Mil-lepora and Fungia (University of San Car-los Marine Biology section 1979). The av-erage current velocity at the study site was 0.09 m/sec although flow rates as high as about 3.9 m/sec (2 knots) occur occasion-ally during shifting tides. Current direction during our June-July studies was from 60° NE or 220-240° SW, depending on the tides. The water temperature was 28-3 1°C although it can get as low as 26°C in Feb-ruary (F. Sotto, pers. comm.). Underwater visibility was 15-30 m. The three species of sponges occurred at depths of 3-32+ m. They were most common at depths of 8-12 m. Sponges were collected in the field by hand, frozen in a — 30°C freezer, and stud-ied later in the laboratory. Scanning elec-tron micrographs (SEM) of spicules were made with a Cambridge 360 SEM. Spicules were measured with a Zeiss Compound Mi-croscope fitted with an ocular micrometer. Sponge skeletons were digitized with a RCA TC 1005 camera connected to a Data Translation 3155 frame grabber board in a
Specimen codes extracted from OCR text.
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