Sistemática e ecologia de espécies de Omalonyx (Mollusca, Gastropoda, Succineidae) no estado do Rio Grande do Sul

• Ano de defesa: 2007
• Autor(a) principal: Arruda, Janine Oliveira
• Orientador(a): Thomé, José Willibaldo
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Pontifícia Universidade Católica do Rio Grande do Sul; Porto Alegre
• Palavras-chave em Português: ZOOLOGIA; MOLUSCOS - RIO GRANDE DO SUL; GASTRÓPODES
• Link de acesso: http://hdl.handle.net/10923/5339

The revalidation of the species Omalonyx convexa (Martens, 1868), its distribution in the Rio Grande do Sul state, as well as its ecology are presented in this work. The specimens of O. convexa presented a variation of the tegument coloring which comprehended from milky white to dark gray, almost black, passing through orange, beige and gray. The shell presented itself covered by the mantle in different proportions, however, it was not completely covered on any of the specimens. The animals were found in lentic water environments and flooded terrains, on macrophytes of the species Eicchornia crassipes, Salvinia auriculata, Pistia stratiotis, in vegetations adjacent to swamp banks and under artificial objects such as canvases, cardboards and styrofoam. A neotype is proposed for the type-species of the genus O. unguis (d´Orbigny, 1835), once it does not present any designated nominotypical material. Regarding the pallial cavity of the family Succineidae, it is observed that the primary ureter initiates at the kidney, near the pericardium, and runs transversely until the rectum. The secondary ureter follows a short distance along the rectum, and then it borders the edge of the mantle passing by the pneumostome, and proceeds to the anterior region of the pallial cavity. Next, the secondary ureter folds with an 180o angle and becomes determined as the tertiary ureter, which follows on the direction of the pneumostome and opens in a position immediately anterior to the respiratory orifice, on its right side, by the excretory pore, which allows their classification among the Heterurethra. The value of the Omalonyx shell in the species diagnosis of the genus was examined. For this purpose, 218 shells from 13 different populations were measured, belonging to three species of Omalonyx. Two Canonical Discriminant Analysis were made: the first considered the population of each locality as a distinct group; for the second, the grouping was made by species. The population groups resulted as highly heterogeneous and only 54. 1% of the groups were correctly classified. The second analysis presented a correction percentage of 94%, with highly significant results, demonstrating that shell measurements can aid in the species determination of this genus. The characters of the reproductive system, the morphology of the tentacles and the position of the genital pore in the holotype of Omalonyx (Neohyalimax) brasiliensis (Simroth, 1896) and Omalonyx s. s. were investigated and discussed. The synonymization of Neohyalimax with Omalonyx is proposed, the former becoming a junior synonym. Omalonyx brasiliensis (Simroth, 1896) remains a valid species, based solely on the holotype.