ABSTRACT
Abstract Introduction: Morphometrics analysis is an efficient and low-cost technique used in studies of sexual dimorphism in turtles. Kinosternon scorpioides scorpioides, scorpion mud turtle, has a wide phenotypic variation, depending on the area of its occurrence. Objective: The objective of this work was to identify the anatomical sexual difference of K. s. scorpioides, adults and hatchlings, through morphometric analysis; and relate the weights of adult animals to environmental factors (temperature and rainfall) in Marajó Island, Brazil. Methods: The sample collection was carried out from March to September 2018, covering both the rainy season (January to July) and the dry season (August to December). For the biometric analysis, 95 adults and 21 hatchlings were used, in which the length and width of the carapace and plastron, height of the shell, and weight were measured (adults only). For the geometric morphometry analysis, 21 adults and 13 hatchlings were used, in which 27 coordinates of anatomical landmarks were inserted in each image of the carapace and 11 in the plastron. Hatchlings were sexed by histology which was enabled by the identification of the ovaries and testicles. Results: The results showed the existence of dimorphism in adults. The plastron and height were higher in females, which had a more rounded carapace than males. This characteristic may be related to the species' sexual strategy, where males impose copulation. Histologically, it was possible to identify the ovaries and testicles in the hatchlings, but there was no anatomical sexual difference, despite the tendency to differentiate in the analysis of carapace PCA. Conclusions: Sexual dimorphism in K. s. scorpioides may play an important role on its reproductive behavior, which is synchronized with environmental events. This fact suggests that the reproductive strategies of this species would be severely affected by changes in the ecosystem.
Resumen Introducción: La morfometría es una técnica eficiente y de bajo costo, utilizada en estudios de dimorfismo sexual en tortugas, mediante el marcado de puntos anatómicos. Este grupo incluye Kinosternon scorpioides scorpioides, con una amplia variedad fenotípica, dependiendo del área en la que se encuentra presente. Objetivo: Este estudio tuvo como objetivo identificar la diferencia sexual entre K. s. scorpioides, adultos y juveniles, a través del análisis morfométrico; y verificar la relación entre las medidas de peso para adultos y los factores ambientales (temperatura y precipitación) en la isla de Marajó, Brasil. Métodos: La recolecta se realizó de marzo a septiembre de 2018, cubriendo tanto la temporada de lluvias (enero a julio) como la estación seca (agosto a diciembre). Para el análisis biométrico, se utilizaron 95 animales adultos y 21 crías, en los que se midió la longitud y el ancho del caparazón y el plastrón, la altura del casco y el peso en adultos. Para la morfometría geométrica, se utilizaron 21 adultos y 13 juveniles, en los que se identificaron 27 coordenadas de puntos de referencia anatómicos en el caparazón y 11 en el plastrón. Los individuos recién eclosionados fueron sexados por histología de rutina, que permite identificar ovarios y testículos. Resultados: Los datos analizados mostraron que existe dimorfismo sexual en adultos. El plastrón y la altura fueron mayores en las hembras, que tenían un caparazón más redondeado que los machos. Esta característica puede estar relacionada con la estrategia sexual de la especie, donde los machos imponen la cópula. En los juveniles recién eclosionados fue posible identificar histológicamente los ovarios y los testículos, pero no hubo diferencias sexuales en relación con la morfometría corporal, a pesar de la tendencia a diferenciarse en el análisis de PCA de caparazón. Conclusiones: El dimorfismo sexual en K. s. scorpioides puede desempeñar un papel importante en su comportamiento reproductivo, que ocurre en sincronía con los eventos ambientales. Este hecho sugiere que las estrategias reproductivas de esta especie se verían gravemente afectadas por los cambios en el ecosistema.
Subject(s)
Animals , Polymorphism, Genetic , TurtlesABSTRACT
Birth weight is a performance parameter of great zootechnical importance for both meat and dairy production, as well as for breeding animals, mainly due to its relation to survival rate at weaning, and the weight of animals throughout their developmental and growth phases. Therefore, the objective of this work was to establish heritability estimates, as well as phenotypic and genetic trends of birth weight of water buffaloes from State of Pará, Brazil. Descriptive statistics were calculated and the Shapiro-Wilk Normality test was performed with a Statistical Analysis System package. Heritability estimates were established by Bayesian inference. BW was 36.6 kg in average. The statistical model considered sex, year of birth and breed composition of the animals as fixed effects, and animal, maternal and residual as random effects. Direct heritability was platykurtic (flattened) and with higher asymmetry, presenting a bimodal distribution with the first mode close to 0.10, and the second mode close to 0.30; the maternal heritability was trimodal, with peaks very close to 0.15, and another, less evident, close to 0.20. The direct genetic trend of birth weight was negative (-0.03kg year-1) and maternal genetic trend was close to zero (0.001kg ano-1), even though the phenotypic trend had been positive (0.156 kg year-1). There is genetic variability to be addressed in a breeding program, however, very little was done as far as selection for growth of water buffaloes in the State of Pará.
O peso ao nascer constitui característica produtiva de elevada importância zootécnica, devido à sua relação com a taxa de sobrevivência à desmama e com os pesos nas demais fases de desenvolvimento do animal, quer seja para a produção de carne, leite ou em animais que se destinam à reprodução. O objetivo deste trabalho foi obter estimativas de herdabilidade e tendências fenotípicas e genéticas do peso ao nascer, em bubalinos do Estado do Pará, Brasil. Foram calculadas as estatísticas descritivas e realizado o teste de Normalidade de Shapiro-Wilk por meio do pacote estatístico Statistical Analisys System. As estimativas de herdabilidade foram obtidas por inferência Bayesiana. O peso ao nascer apresentou média de 36,6 kg. O modelo de análise considerou como fixos os efeitos de sexo, ano de nascimento e composição racial do animal e como efeitos aleatórios animal, efeito materno e residual. A distribuição da herdabilidade direta apresentou-se platicúrtica (achatada) e com maior assimetria, tendo uma distribuição bimodal com a primeira moda próxima a 0,10 e a segunda próxima a 0,30; a materna apresentou-se trimodal, com picos bem próximos a 0,15 e outro menos evidente próximo a 0,20. A tendência genética direta do peso ao nascer mostrou-se negativa (-0,03kg ano-1) e a tendência genética materna próxima à zero (0,001 kg ano-1), ainda que a tendência fenotípica tenha sido positiva (0,156kg ano-1). Existe variabilidade genética possível de ser trabalhada em um programa de melhoramento, no entanto, pouco foi feito quanto à seleção para crescimento em búfalos no Estado do Pará.