Carlos I. Piña

Effect of Incubation Temperature on Incubation Period, Sex Ratio, Hatching Success, and Survivorship in Caiman latirostris (Crocodylia, Alligatoridae)

Abstract Temperature-dependent sex-determination has been reported for all extant crocodilians. We present information about incubation temperature effects on incubation period, sex ratio, hatching success, and hatchling survivorship during the first year of life for Caiman latirostris. Incubation period was negatively related to temperature. Sex of hatchlings were related to incubation temperature. Only females were produced at 29°C and 31°C, only males were produced at 33°C, and both males and females hatched at 34.5°C. Hatching success and survivorship were unaffected by incubation temperature.

Allometry of Reproduction in Wild Broad-Snouted Caimans (Caiman latirostris)

Abstract We studied 20 nesting female Caiman latirostris and their clutches in Santa Fe Province, Argentina. We regressed clutch and egg parameters and hatchling size with several measurements of female size (ln-transformed) to evaluate the allometry of reproduction in the wild. Larger females produced relatively smaller clutches. Larger females produced larger eggs and hatchlings. Egg width, not length, limits egg size relative to female body size. Future studies should address the relationship between female fecundity and hatchling fitness.

Microsatellite DNA markers applied to detection of multiple paternity in Caiman latirostris in Santa Fe, Argentina

Detecting multiple paternity in wild populations of the broad-snouted caiman (Caiman latirostris) has important implications for conservation efforts. We have applied microsatellite markers to examine genetic variation in C. latirostris and also have provided the first data concerning detection of multiple paternity in wild populations of this species. Blood samples from four nest-guarding C. latirostris females and their hatchlings were obtained from Santa Fe Province, Argentina. Amplified products were analyzed by electrophoresis on 10% polyacrylamide gels and visualized with silver staining. Four out of the eight markers tested reliably amplified and yielded useful data. Using polyacrylamide gels with silver staining provides high enough resolution to obtain individual genotypes. In order to assess the presence or absence of more than two parents in each nest, we used the single locus Minimum Method, and applied Cervus 3.0 and Gerud 2.0 software in parentage analyses. Our results indicate more than one father in at least two families. This behavior could be the consequence of high habitat variability in the area where our population was sampled. The ability to understand mating systems is important for maintaining viable populations of exploited taxa like C. latirostris.

Embryological development of Caiman latirostris (Crocodylia: Alligatoridae).

A standard development embryological series is the primary basis to organize information of any embryological study and is also used to determine the age of eggs and embryos in field conditions. In this article, we calibrate developmental series of the broad‐snouted caiman, Caiman latirostris, against an established series for Alligator mississippiensis. Morphometric measures and extend of the opaque‐shell banding were also related to embryo age. In earlier stages, external morphological features alone can account for embryo age, but we suggest that morphometric measurements should be introduced later in the development. Unlike morphologic and morphometric attributes, the opaque patch was not a useful age predictor. As expected, a close correlation between embryonic development of C. latirostris and A. mississippiensis was observed. genesis 46:401–417, 2008.

The temperature-sensitive period (TSP) during incubation of broad-snouted caiman (Caiman latirostris) eggs

All crocodiles studied to date exhibit temperature-dependent sex determination. During the many weeks from egg laying to hatch there is a period of 10 to 15 d in the middle third of incubation (in the American alligator) during which the sex of the embryo is irreversibly fixed, referred to as the temperature-sensitive period or TSP. In this work we investigated the TSP in Caiman latirostris eggs incubated at female-inducing and male-inducing temperatures (29 ◦ C and 33 ◦ C respectively) by switching eggs from 29 ◦ Ct o 33 ◦ C and vice versa at timed interval throughout incubation. Compared to Alligator mississippiensis the duration of TSP was longer, and the onset of TSP was at an earlier stage of incubation.

Effects of Incubation Temperature on the Size of Caiman latirostris (Crocodylia: Alligatoridae) at Hatching and after One Year

Abstract We investigated the effects of incubation temperature (29°C, 31°C, and 33°C) on total length (TL) and body mass (BM) of Caiman latirostris, a crocodilian with temperature-dependent sex determination (TSD), at hatching (N  =  180) and in a sample of hatchlings (N  =  40) after one year of raising. Size at hatching was strongly clutch-specific. Animals incubated at 31°C (100% females) were larger than at 29°C (100% female) and 33°C (100% males). Absolute growth to one year was higher for females (eggs incubated at 29°C and 31°C) than for males (eggs incubated at 33°C). The possibility that constant 33°C incubation temperature had compromised embryological development cannot be rejected. If so, it confirms that high incubation temperatures can have long-lasting effects on posthatching growth. If not, possible advantages of females growing more rapidly than males are discussed.

Caiman latirostris growth: the effect of a management technique on the supplied temperature

Abstract Temperature and diet affect growth of crocodilians, and it has been suggested that growth depends on the interaction between temperature and food availability. High temperature during digestion increases appetite, gastric contraction frequency and amplitude, and peptic activity. In this paper, we present information about growth of Caiman latirostris in captivity under different thermal treatments. Our goal is to improve growing of caimans and thereby reduce production costs. We grew C. latirostris for 2 months under two different treatments (average temperatures TA=22.24 °C; TB=18.24 °C). Those kept at higher temperature grew faster, producing a 5.2 cm and 100.5 g difference after 60 days of experiment.

Cranial sexual discrimination in hatchling broad-snouted caiman (Caiman latirostris)

Broad-snouted caiman (Caiman latirostris) hatchlings present a consistent sexual dimorphism in their cranium shape and size. Male hatchlings have smaller crania than females. Using multivariate statistical analyses it is possible to discriminate sex in broad- snouted caiman hatchlings by their cranial shape with a reasonable efficiency. The understanding of sexual dimorphism of crocod ilian hatchlings might be possibly improved by experimental approach considering, genetic and phenotypic variables such as incubation temperature and clutch of origin.

Reproductive Allometry of Podocnemis expansa (Testudines: Podocnemididae) in Southern Brazilian Amazon

Abstract Podocnemis expansa is the largest freshwater turtle in South America and exhibits a complex reproductive behavior. Females lay eggs in sandy banks formed during the dry season. Nesting habitat can influence hatching success and sex determination. In some turtle species, female body size is crucial to determine reproductive parameters such as clutch size and shape. In this study, we investigate allometric relationships between female body size and their tracks, and clutch characteristics and nest shape in sandy beaches along the Javaés River, southern Brazilian Amazon. Our results indicate that female body size can be estimated based on tracks. Larger females leave larger foot tracks in the sand and have larger clutch sizes with larger clutch mass than smaller females. Female carapace width and body mass can be considered reliable variables to estimate clutch size and total clutch mass for the species. Larger females should be protected because they can be responsible for most annual clutch production. Resumo Podocnemis expansa é o maior quelônio de água doce da América do Sul, apresentando um comportamento reprodutivo complexo. Essa espécie nidifica em bancos arenosos formados durante as vazantes dos rios da Amazônia. As características do ambiente de nidificação podem influenciar o sucesso reprodutivo e o sexo dos filhotes. Alguns trabalhos já demonstraram que o tamanho corporal da fêmea é determinante para as condições da ninhada (quantidade e tamanho dos ovos) e nas dimensões dos ninhos (profundidade e diâmetro) em algumas espécies de quelônios. O presente estudo investigou as relações alométricas entre o tamanho corpóreo da fêmea, seus rastros, as variáveis da ninhada e a forma dos ninhos em ambiente natural em uma praia do rio Javaés, na Amazônia Brasileira. Foi observado que o tamanho corpóreo da fêmea de P. expansa pode ser estimado em função do seu rastro. Fêmeas maiores deixam rastros maiores na areia, além de produzirem mais ovos (tamanho da ninhada) e com maior massa (massa da ninhada) do que fêmeas menores. A largura da carapaça e a massa da fêmea podem ser consideradas variáveis confiáveis para estimar o tamanho e a massa da ninhada dessa espécie. A proteção de fêmeas de maior tamanho deveria ser priorizada, já que podem ser responsáveis por grande parte da produção anual de ovos.

Allometry of reproduction of Podocnemis expansa in Southern Amazon basin

Podocnemis expansa (giant Amazon freshwater turtle) is the biggest freshwater turtle of South America. Like in other reptiles, the nest of P. expansa is a hole in the sand deep enough to avoid predators and extremes of temperature and humidity. However, nesting habitat selection in reptiles has effects on incubation success and on hatchlings. Female body- size is also related to the size and shape (i.e., form) of the nest, which might in theory be related to the female reproductive success. In this study we established allometric relationships between female body size and nest form. Fieldwork was carried out in nesting beaches of Araguaia and Crixas-Acu Rivers in Southern Amazon basin, Brazil, from September to December 2000. As a result, we can establish that nest form does not affect reproductive success in the species, but female body length is positively related to egg mass and clutch size.