Alejandro Larriera

Genetic, enzymatic and developmental alterations observed in Caiman latirostris exposed in ovo to pesticide formulations and mixtures in an experiment simulating environmental exposure

In South America, economic interests in last years have produced a constant increase in transgenic soybean cropping, with the corresponding rise in pesticide formulated products. The aim of this study was to determine the effects of pesticides formulations and mixtures on a South American caiman, Caiman latirostris, after in ovo exposure. We conducted a field-like experiment which simulates the environmental exposure that a caiman nest can receive in neighbouring croplands habitats. Experimental groups were Control group, Treatment 1: sprayed with a glyphosate herbicide formulation, and Treatment 2: sprayed with a pesticide mixture of glyphosate, endosulfan and cypermethrin formulations. Results demonstrated genotoxicity, enzymatic and metabolic alterations, as well as growth delay in caimans exposed in ovo to Treatments 1 and 2, showing a higher toxicity for the mixture. Integral evaluation through biomarkers of different biological meaning is highly informative as early indicators of contamination with pesticides and mixtures in this wildlife species.

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.

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.

Effects of in vivo exposure to Roundup® on immune system of Caiman latirostris

Abstract The present study aimed to evaluate the effect of Roundup® (RU, glyphosate-based formulation) on some parameters of the immune system and growth of Caiman latirostris. Seventy-two caimans (20-day-old) from Proyecto Yacaré (Gob. Santa Fe/MUPCN) were used. Two groups were exposed for 2 months to different concentrations of RU (11 or 21 mg/L; taking into account the concentration recommended for its application in the field), while one group was maintained as control. The RU concentration was progressively decreased through the exposure period to simulate glyphosate degradation in water. Animals were measured and weighed at the beginning and end of the experiment, and blood samples taken after exposure to determine total and differential white blood cell (WBC) counts as well as total protein concentration (TPC), and for performing protein electrophoresis. The results showed that, compared against control hosts, there was a decrease in WBC counts, a higher percentage of heterophils, a higher TPC (with a low percentage of F2 protein fraction), and a negative effect on growth in the young caimans exposed to RU. These results demonstrate that in vivo exposure to RU induced alterations in the selected immune parameters, plasma proteins, and growth of caimans, thereby providing relevant information about the effects of this type of pesticide in this important species in the Argentinian wetlands.

Mating system and population analysis of the broad-snouted caiman (Caiman latirostris) using microsatellite markers

The knowledge about reproductive strategies of a species contributes to their conservation. Multiple paternity is a reproductive behavior increasing effective population size, which could increase genetic diversity particularly in populations submitted to bottlenecks events. In Argentina, wild populations of Caiman latirostris are subject of a management plan devoted to their preservation and sustainable utilization based on its commercial interest. This program started in response to the evident numeric reduction of the populations, as a consequence of hunting pressure and habitat modification; it had a remarkable success in population recovery allowing the commercial use of C. latirostris. Data on reproductive behavior of C. latirostris are limited because mating occurs in the water and the information about their genetic diversity is scarce too. Our specific aims were to study the mating system and population genetic structure applying microsatellite markers in twelve C. latirostris families. The obtained results showed highly significant difference among populations and a lack of correspondence between geographical distance and genetic differentiation suggesting that populations of C. latirostris represent unstable metapopulations. In the paternity analysis was detected more than one father in two nests, which could be explained by capacity of storage sperm, proposed in females of a related species. The behavior of multipaternity could contribute to maintain viable populations of C. latirostris, since the maintenance of genetic variability within populations could help increase their capacity to respond to selective pressure. Further studies employing genetic and behavioral framework are needed to better understand the reproductive biology of C. latirostris.

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.

Analysis of the Population Structure of Broad-Snouted Caiman (Caiman latirostris) in Santa Fe, Argentina, Using the RAPD technique

Abstract Caiman latirostris (Broad-Snouted Caiman) is one of two crocodilian species that inhabit Argentina. Wild populations of C. latirostris in Santa Fe Province are under management by Proyecto Yacaré (MAGIC-MUPCN), a program based on a ranching system whose goal is the sustainable use of the species, together with its habitat conservation. We used 233 random amplified polymorphic DNA (RAPD) markers to obtain preliminary data about population structure and genetic variation in four populations of C. latirostris in Santa Fe province, which may be used to provide a genetic framework of conservation units to evaluate, and perhaps to modify, current plans for its sustainable management. Our results suggest low to intermediate levels of mean heterozygosity (H), mean number of alleles per locus (A), and percentage of loci polymorphic (P). Furthermore, the values of Nm and FST seem to show low levels of gene flow and some population subdivision. Distance genetic analysis appears to reveal high similarity between Estancia El Estero, Costa del Salado, and Estero del Paraje 114 populations, and results of analysis of molecular variance indicate that nearly all variation exists within populations rather than among them, implying that a great number of alleles is shared among populations. New samplings and new measurements in parameters such as H, A, and P, should be carried out in future years to confirm the genetic structure and level of population differentiation and to make new decisions about the management plan that has been successful in the recovery and conservation of C. latirostris.