Freshwater sponges (Porifera, Demospongiae) in a benthic filter... 335 Freshwater sponges (Porifera, Demospongiae) in a benthic filter feeding community at the Guanacaste Dry Forest, Costa Rica Cecilia Volkmer-Ribeiro & Vanessa de S. Machado Museu de Ciências Naturais, Fundação Zoobotânica do Rio Grande do Sul, Caixa Postal nº 1188, 90001-970 Porto Alegre, RS. ([email protected]; [email protected]) ABSTRACT. The freshwater sponges Trochospongilla variabilis Bonetto & Ezcurra de Drago (1973), Radiospongilla crateriformis (Potts, 1882), Spongilla cenota Penney & Racek (1968) and Corvoheteromeyenia heterosclera (Ezcurra de Drago, 1974) compose with the sphaerid bivalve Eupera cubensis (Prime, 1865) and several Phylactolaemata bryozoans a benthic filter feeding community living in seasonal lentic and lotic habitats with high Particulate Organic Carbon (POC), low conductivity and acid pH within the Costa Rica Dry Forest biome. The sponge specimens gathered led to the re-description of the four species. KEYWORDS. Freshwater Sponges, Bryozoans, Bivalves, Central America, Dry Forest. RESUMO. Esponjas continentais (Porifera, Demospongiae) em uma comunidade bêntica filtradora na Floresta Decidual de Guanacaste, Costa Rica. As esponjas de água doce Trochospongilla variabilis Bonetto & Ezcurra de Drago (1973), Radiospongilla crateriformis (Potts, 1882), Spongilla cenota Penney & Racek (1968) e Corvoheteromeyenia heterosclera (Ezcurra de Drago, 1974) compõem, com o bivalve esferídeo Eupera cubensis (Prime, 1865) e diversos briozoários Phylactolaemata, uma comunidade bêntica de filtradores em ambientes sazonais lênticos e lóticos com alto Carbono Orgânico Particulado (POC), baixa condutividade e pH ácido no bioma da Floresta Decidual da Costa Rica. Os espécimes de esponjas coligidos conduziram à redescrição das quatro espécies. PALAVRAS-CHAVE. Esponjas continentais, Briozoários, Bivalves, América Central, Floresta Seca. The first record of the occurrence of freshwater Trochospongilla Vejdovsky, 1883 and the species sponges in Central America and the Antilles was made Spongilla cenota Penney & Racek (1968). ROUSH (2000) by MEEK (1908), who assigned Eunapius fragilis (Leidy, published the results of the survey of Bryozoans and 1851) to Guatemala. JONES & RUTZLER (1975) reported the sent the sponge material to the senior author for study. occurrence of Eunapius carteri (Bowerbank, 1863), The results of that study are now offered and contain the Trochospongilla leidii (Bowerbank, 1863) and redescription, with the first Scanning Electron Trochospongilla horrida (Weltner, 1893), to Panamá. Microscopy (SEM) illustrations of S. cenota and the POIRRIER (1977) refered to a personal communication by gemmule structure of C. heterosclera. The paper presents Vincent Resh concerning the occurrence of the first register of species of sponges that compete with Anheteromeyenia ryderi (Potts, 1882) in Belize. POIRRIER Bryozoans and sessile bivalves in a freshwater & TRABANINO (1989), in turn, registered Ephydatia environment. The characteristics are reported of the fluviatilis (Linnaeus, 1759) and Spongilla alba (Carter, habitats occupied by this community of benthic, sessile 1849) in El Salvador; and SMITH (1994), in a survey of and filter-feeding macro-invertebrates in the area. The sponges in the Virgin Islands, detected only E. fluviatilis. common functional adaptations presented by the The latter species was also registered by MURILLO & members of this community are also remarked. MORA (1995) in Costa Rica. BASS & VOLKMER-RIBEIRO (1998) assigned and illustrated Radiospongilla crateriformis MATERIAL AND METHODS (Potts, 1882) in the islands of Barbados and Nevis. More recently, DEBROT & VAN-SOEST (2001) registered The Guanacaste Conservation Area was Corvoheteromeyenia heterosclera (Ezcurra de Drago, established in order to protect the Dry and Deciduous 1974) and S. alba in the islands of the southern Caribbean, Tropical Forest of Costa Rica. The streams originating in and MANCONI & PRONZATO (2005) described this biome are of low order, shallow and slight inclination, Anheteromeyenia cheguevarai in western Cuba and and dry during five or six months of the year. The indicated the occurrence of Ephydatia facunda Weltner description and map of the collecting sites, organized for (1895), R. crateriformis and Radiospongilla sp. on the the samples of bryozoans in the area, carried out between island. 1996 and 1997 are found in ROUSH (2000), together with ROUSH (1999) in announcing the survey of features of the habitats (temperature, pH, conductivity, freshwater Bryozoans which he carried out in the current and Particulate Organic Carbon (POC)). The Guanacaste Conservation Area, in Costa Rica, remarked geographical coordinates of the collection sites were the restriction of their occurrences to the Deciduous furnished by S. A. Roush, in a pers. comm. to the senior Forest Area and the occurrence of freshwater sponges in author. The species of sponges gathered by S. A. Roush the same habitats. He, preliminarily, identified the sponge and the object of the present study, were entrusted to genera Radiospongilla Penney & Racek, 1968, Dosilia the senior author and are thus deposited and catalogued Gray, 1867, Corvomeyenia Weltner, 1913, in the Porifera collection of the Museu de Ciências Iheringia, Sér. Zool., Porto Alegre, 99(4):335-344, 30 de dezembro de 2009 336 VOLKMER-RIBEIRO & MACHADO Naturais of the Fundação Zoobotânica do Rio Grande do (MCN-POR 6995; Fig. 3) on the bark of submerged logs. Sul, Porto Alegre, RS, Brazil (MCN-POR). The specimens Skeleton reticulated, anisotropic, from the base to the of the bivalve were identified by Dr. M. C. D. Mansur at top, with very slender fibers in the spherical specimens. Museu de Ciência e Tecnologia, Pontifícia Universidade Megascleres slender, straight to slightly curved, abruptly Católica do Rio Grande do Sul (PUC), Porto Alegre, and pointed anfioxea with minute straight spines sparsely catalogued in the Malacological Collection of the Museu ditributed along the spicule (Fig. 8). Megascleres length: de Ciências Naturais of the Fundação Zoobotânica do from 239.02 µm to 446.96 μm (average 344.3 μm); width: 7.02 Rio Grande do Sul (MCN-MOL). Preparations of μm to 17.03 μm (average 12.10 μm). Microscleres absent. dissociated spicules of the sponges were obtained Gemmoscleres in one series of slender, straight to sligthly according to VOLKMER-RIBEIRO (1985) and VOLKMER- curved, strongly spined anfistrongyla, the shorter about RIBEIRO & TURCQ (1996), for studies with, respectively, half the length of the longer ones (Figs. 8, 9), with larger light optical and Scanning Electron Microscopy (SEM). incurved spines grouped around the extremities of the The SEM photographs were obtained at the Electron spicule, thus forming small umbonate rotules (Fig. 10). Microscopy Laboratory of Universidade Luterana do Gemmoscleres length: from 79.97 µm to 123.10 μm (average Brasil (ULBRA), in Canoas, Rio Grande do Sul. Fifty 97.71 µm); width: 5.10 µm to 8.23 µm (average 6.83 μm). measurements were made of each spicule category, Gemmules extremely abundant (Figs. 1, 2), distributed from considering all the specimens of each one of the species. the base to the surface, large, pear shapped (Fig. 11), the Digital photographs of representative specimens of each older ones grayish and the new ones whitish. Foraminal of the four sponge species as well as of the bivalves tube long, contained inside the thick pneumatic coat, were also produced. gemmoscleres radially embedded in the pneumatic coat up to the collar which surrounds and surpassess the foraminal RESULTS AND DISCUSSION tube (Figs. 11, 12). Pneumatic coat consisting of a network of irregular and slender spongin fibers, thus producing also The identification of the collection of sponges irregular air cameras (Fig. 13). Outer gemmular coat thin, made by S. A. Roush, revealed the occurrence of gemmular surface crateriform, each crater containing the Trochospongilla variabilis Bonetto & Ezcurra de Drago starlike rotule of a gemmosclere (Fig. 11). (1973), R. crateriformis, S. cenota and C. heterosclera. Remarks. The species occurred with globose, The species were found in lentic and lotic environments yellowish, fragile, spongin rich specimens in lentic of small proportions, restricted to the area of the Pacific environment (MCN-POR 6995; Figs. 1, 2); and grayish, Dry Forest of Costa Rica and characterized by water harder, spicule rich shallow crusts in lotic (MCN-POR temperatures of 23° C, pH 5.5, specific condutivity of 6998; Fig. 3) environments at the Guanacaste Dry Forest. -3 60µS, POC of 810 to 1580 mg.cm (ROUSH, 2000). Together The fragile specimens conform to the description offered with the specimens of some sponges, several individuals by RIOJA (1953) for the ones, obtained from km 286 of the of the sessile bivalve Eupera cubensis (Prime, 1865) road Mexico-Tuxpan. Also, his drawings of the gemmule (Mollusca, Bivalvia, Sphaeridae) were found. Species of structure of R. crateriformis have now been confirmed in Phylactolamatae bryozoans were sampled and identified every detail with SEM illustration. This is the third record by ROUSH (2000) in these environments: Fredericella of R. crateriformis for the Caribbean Region, following browni (Rogick, 1941) and some belonging to Plumatella that of BASS & VOLKMER-RIBEIRO (1998) for Barbados and Lamarck, 1816. Table I shows the places where sponges that of MANCONI & PRONZATO (2005) for Cuba. The occurred alone, with bryozoans or with