Biologia e anatomia funcional de Donax gemmula Morrison (Bivalvia, Donacidae) do litoral de São Paulo, Brasil

Abstract

. Donax gemmula Morrison, 1971 is a small bivalve occurring on sandy beaches throughout the Southeastern Brazilian coast to Uruguai. Live specimens were collected from Barequeçaba Beach, São Sebastião, State of São Paulo, Brazil. The animal's behaviour was recorded in situ as well as in aquaria, and its functional morphology registered from specimens dissected under stereomicroscope; details of the anatomy were obtained from histological sections. The minute, smooth subglobose shell, and the large, muscular foot provided with a pair of well-developed elevator muscles allow fast burrowing, vital in the disturbed beach environment where the species lives. A vestigial byssal apparatus is present from juvenile through the adult form and this free-living infaunal donacid does not migrate following the rising and ebbing tides. The mantle margins have the middle fold duplicated; besides captate tentacles, the middle folds bear long, filiform, sensory tentacles, the latter restricted to the rear end of the animal. The presence of complete, large, homorhabdic ctenidia; small but very selective labial palps; short and few convoluted intestine, separated from the style sac; and straining tentacles encircling the inhalant aperture reveal the selective suspension feeding habit of the species. KEY WORDS. Mollusca, sandy beaches, selective suspension feeding, Southwestern Atlantic. Morrison, 1971 ocorre em praias arenosas da costa sudeste-sul do Brasil até o Uruguai. Espécimes foram coletados na Praia de Barequeçaba, São Sebastião, Estado de São Paulo, Brasil. O comportamento do animal foi registrado "in situ" e em aquários e a morfologia funcional a partir de espécimes dissecados sob estereomicroscópio; detalhes da anatomia foram obtidos a partir de cortes histológicos. A concha pequena, lisa, subglobosa, e o pé grande, muscular, provido de um par de músculos elevadores bem desenvolvidos, permitem escavação rápida, vital em praias sujeitas à intensa ação de ondas onde a espécie vive. Aparato bissal vestigial ocorre desde a fase juvenil à adulta e este donacídeo de vida livre, infaunal, não migra acompanhando o ritmo das marés. As margens do manto possuem prega mediana duplicada; além de tentáculos captados, as pregas medianas possuem tentáculos sensoriais filiformes, longos, estes últimos restritos à região posterior do animal. A espécie tem hábito alimentar suspensívoro seletivo, o qual é revelado pela presença de ctenídios grandes, completos e homorhábdicos, palpos labiais pequenos e muito seletivos, intestino curto, fracamente sinuoso, separado do saco do estilete cristalino, e tentáculos ramificados formando um crivo em torno da abertura inalante. PALAVRAS CHAVE. Atlântico sudoeste, Mollusca, praias arenosas, suspensívoro seletivo. RESUMO. Donax gemmula

Anatomy of Phyllodina persica (Bivalvia: Tellinidae), and its first occurrence in southeastern Brazilian waters

“…Despite the same pattern of protractor muscles in taxon previously cited, P. persica presents a smaller anteriorposterior elongated protractor muscle insertion area, with more amorphous outline and with low anterior adductor penetration, very similar to the protractor insertion area shape of T. petitiana (Barón & Ciocco, 1997). This protractor shape and anterior adductor penetration degree is similar to other tellinoid families, such as Donacidae (Purchon, 1963;Narchi, 1978;Ansell, 1981;Passos & Domaneschi, 2004;Simone & Dougherty, 2004), Psamobiidae (Pohlo, 1972), Solecurtidae (Bloomer, 1905), and Semelidae (Domaneschi, 1995;Simone & Guimarães, 2008). Thus this character could be a basal one, as suggested by Simone & Wilkinson (2008)."…”

Mantle margin morphogenesis in Nodipecten nodosus (Mollusca: Bivalvia): new insights into the development and the roles of bivalve pallial folds

“…The periostracum is formed in a deep groove between the outer and middle folds, while the shell layers are secreted by the outer mantle epithelium [ 8 , 9 ]. However, exceptions to this three-folded pattern do exist, e.g., four pallial folds have been described for the Veneridae [ 10 – 12 ], duplication in the middle fold may occur in Donacidae [ 13 ], and two pallial folds may be present in some Arcidae, with the outer one being duplicated [ 14 , 15 ].…”

The biology and functional morphology of the high-energy beach dwelling Paphies elongata (Bivalvia: Mactroidea: Mesodesmatidae). Convergence with the surf clams (Donax: Tellinoidea: Donacidae)

“…When the waves wash these bivalves out of the sand, they can dig themselves back in again rapidly . Over 50 species of Donax have been described and the anatomies and behaviours of some of them elucidated in varying degrees of detail, for example, Donax hanleyanus Philippi (Narchi 1978) D. serra (Röding) and D. sordidus Hanley (Ansell 1981), D. trunculus Linnaeus (Moueza andFrenkiel 1974, 1976;Moueza 1976), D. gemmula Morrison (Passos and Domaneschi 2004), D. gouldi Dall (Pohlo 1967), D. venustus Poli and D. semistriatus Poli (Salas-Casanova and Hergueta 1990), D. striatus Linnaeus (Wade 1967), D. denticulatus Linnaeus (Wade 1969), D. fossor Say and D. variabilis Say (Simone and Dougherty 2004), and D. faba Gmelin, D. semigranosus Dunker, D. cuneatus Linnaeus and D. incarnatus Gmelin .…”