Gametogênese e dinâmica da reprodução de Anodontites trapesialis (Lamarck) (Unionoida, Mycetopodidae) no lago Baía do Poço, planície de inundação do rio Cuiabá, Mato Grosso, Brasil

Abstract

O ciclo reprodutivo de Anodontites trapesialis foi estudado entre os meses de maio de 1998 a abril de 1999. Análises quantitativas dos elementos celulares revelaram que a espécie é exclusivamente hermafrodita com folículos masculinos e femininos separados. A gametogênese é contínua com picos de maturação e eliminação de gametas durante a estação seca. A ovogênese tem seu período de maturação máxima em abril e maio, momento em que óvulos maduros são observados preenchendo os folículos e gonoductos. A espermatogênese foi reconhecida por uma fase proliferativa com células em desenvolvimento e apresentou seu período de maturação entre abril e julho. Estas células se diferenciaram dando origem às mórulas espermáticas e espermatozóides livres, organizando a série espermática radial. Durante o período de liberação dos gametas, a maioria dos folículos apresentou agregados de espematozóides formando esferas espermáticas as "spermballs", as quais caracterizam a espécie como espermatozeugmata.

Variations on the larval incubation of Anodontites trapesialis (Unionoida, Mycetopodidae): Synergetic effect of the environmental factors and host availability

“…During the whole sampled period, incubated individuals were found with more frequency during November, May, and August; agreeing with Callil and Mansur (2007) who observed A. trapesialis incubated in April and May in the Pantanal. Bonetto and Ezcurra (1962) also found A. trapesialis forbesianus (Lea, 1860) in Argentin, incubated between August and December.…”

“…When this period is compared with Callil and Mansur´s (2007) dates, conformity is noted related to the period in which there is the presence of embryos at the gills (April and May). Furthermore, the period with higher frequency of incubated species found in this work occurs at the onset of the dry season, when water leaves the flood plains and returns to the main channels (May) and in the dry season (August to November), also noted by Callil and Mansur (2007). In this, a relation can be traced between this period of higher maturation and elimination of gametes with the exit of fish from the lakes and flooding of adjacent areas, which are characteristic of the studied region.…”

“…The Unionidae Anodonta Lamarck, 1799 have multiple reproductive peaks in a single period (Heard, 1975) and Glebula rotundata (Lamarck, 1819) also has a cycle of up to three reproductive periods (Parker et al, 1984). As to the reproductive aspects of the A. trapesialis (Lamarck, 1819) (Unionoida) studied on the Pantanal region of the state of Mato Grosso by Callil and Mansur (2007), it is possible to say that the gametogenesis is continuous, however, with trends to the gonadal maturation stage (Silva-Souza et al, 2011). Ovogenesis has its maximum maturation period in April and May, whereas spermatogenesis from April to July.…”

“…This relation was described by Arey (1932) and Murphy (1942) as a nutrition relation between the larvae and the degeneration of the host tissue, which is the source of nutrients during metamorphosis. There is a wide gap of information regarding the hostparasite relationship in unioniods: almost nothing is known about the infection of fish and the parasite-host relation in the Neotropical region (Silva-Souza and Eiras, 2002;Callil and Mansur, 2007) and little is available with this approach in the world (Hoggarth, 1992;Strayer, 2008).…”

“…For all collected specimens (n = 180; 15 per month), height (H, mm), total length (Lt, mm), demibranch length (Ltd, mm) were obtained with a digital caliper. The measures related to the mass as total weight (Wt, g), weight of soft parts (Wb, g), shell weight (Ws, g) (Callil and Mansur, 2007) and weight of demibranch (Wd, g) were obtained with an analytical balance. All individuals had their demibranches examined under the microscope to detect the presence of eggs and larvae.…”