Growth of juvenile oceanic stage Loggerhead sea turtles: biometry based on geometric morphometrics

• Autor(a) principal: Gonçalves, Inês Filipa Ferreira Vilhena
• Data de Publicação: 2022
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/36940
• topic: Loggerhead Sea turtle; Geometric morphometrics; Allometry; Northeast Atlantic

Several aspects of the life of the loggerhead turtle (Caretta caretta) are unknown, in particular, those referring to the oceanic and juvenile stages. There are some questions about how they growth, how the shape changes and if the growth is allometric or isometric. The study of sea turtles and their allometry is recent and scarce. Differences in shape can help understand development, adaptations, evolutionary diversification, origin, function roles or morphogenesis and growth among species. For quantify this differences, traditional morphometrics was used, but it was fast until realized that it was a weak method with many flaws. These methods suffer a big evolution when the coordinate-based morphometrics started to take place and discover that a shape can be defined with a few points on each specimen, called landmarks. These points resemble between shapes, allowing to do a two- or three-dimensional array and evaluated in total the variation of the landmarks. In this study, the ability to study the growth pattern and the shape of turtles through geometric morphometrics was assessed. In this research 71 photographs of loggerhead sea turtles captured off Funchal were used. The results show a significant allometric variation with the turtle sizes in the carapace shape and flipper shape. Furthermore, there is an evident allometric growth between the flipper and the carapace showing that the growth rate slows down with turtle size. Comparisons with other studies shows some differences in the results for the carapace shape, but coherent results for the flipper shape. This is one of the few studies applying geometric morphometrics to study the loggerhead sea turtle and the only one with the Northeast Atlantic population. Get to know more about the development of turtles and how they growth with age would be important for the protection and conservation of these species.