On clutch size and hatching success of the South American turtles Podocnemis expansa (Schweigger, 1812) and P. unifilis Troschel, 1848 (Testudines, Podocnemididae)

Abstract

Data on clutch size and hatching success of P. expansa were gathered for seven beaches traditionally used by the species and re-analyzed statistically by means of regression analysis, of the number of eggs on the number of females (or nests) and of the number of young on the number of eggs. All regressions were linear, passed through the origin and had excellent fits. Average clutch size varied from 75 to 123, and presented geographic differentiation: (i) Rio Orinoco, (ii) Rio Trombetas + Rio Branco and (iii) Rio Juruá + Rio Purus. Average hatching success was ca. 83%. In P. unifilis there was also geographic variation in clutch size, the Iquitos area showing the highest values. Hatching success of P. unifilis was uniformly high: only one sample, from Iquitos, had less than 90% success. The outstanding fit of the clutch size regressions leads one to consider egg volume variability, which was found to be high in both species, in contradiction with current optimal egg size theory.

Ciclo ovárico y jerarquía folicular de Peltocephalus dumerilianus (Testudines: Podocnemididae)

“…Igualmente, por los resultados analizados, teniendo como base el desarrollo folicular, se puede afirmar que P. dumerilianus posee solamente una postura anual, ligada a los ciclos hidrológicos de su hábitat o los denominados pulsos del Río y específicamente en la época de sequía (sioli 1975;Neiff et al 1994;Vanzolini 2003).…”

“…en cuanto a la influencia que poseen los factores ambientales sobre la reproducción de los quelonios acuáticos continentales, se puede establecer que para la región amazónica, el ciclo reproductivo está condicionado de forma representativa por las variaciones que presentan los flujos de los ríos (Vanzolini 2003), lo cual es denominado elasticidad que es el cociente entre la superficie ocupada durante la fase de máximo anegamiento y/o inundación, y la que corresponde al momento de sequía extrema (Neiff et al 1994), en la cual interactúan intercaladamente los denominados pulsos del río (sioli 1975).…”

A Short Review of the International Trade of Wild Tortoises and Freshwater Turtles Across the World and Throughout Two Decades

“…The number of eggs was reported to increase with the size of the female (Escalona 2010), and the sex of the offspring is determined by incubation temperature (Hernández et al, 2010b). Vanzolini (2003) reported hatching success of over 90 per cent of eggs in undisturbed nests.…”

“…considered P. unifilis "not suitable for private husbandry" due to its specific habitat requirements and high mortality in captivity. Escalona (2010) considered habitat destruction as a significant threat, and Vanzolini (2003) noted that the species was sensitive to the damming of rivers for hydroelectric projects.…”

Gonadotrophic, prolactin, corticosterone, and gonadal hormones levels over 15 months in Giant Amazon River Turtles - Podocnemis expansa (Schweigger, 1812) (Testudines: Podocnemididae), in captive conditions

“…The Giant Amazon River Turtle (Podocnemis expansa, Schweigger, 1812b) South America's largest freshwater turtle, has considerable data published concerning clutch size, hatching and nesting behavior and ecology (Vanzolini, 2003;Ferreira Junior and Castro, 2010). Recently, there has been a great interest in the commercialization of Podocnemis expansa, to alleviate the over collection of wild caught turtles.…”