Navegando por Autor "Ândrade, Marcelo"

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Artigo
Mercury biomagnification in the food chain of a piscivorous turtle species (Testudines: Chelidae: Chelus fimbriata) in the Central Amazon, Brazil
(2024-05-03) Cunha, Fábio Andrew G; Forsberg, Bruce R; Vogt, Richard C; Domingos, Fabíola X V; Marshall, Bruce G; Brito, Brendson C; Sousa, Otávio P de; Kasper, Daniele; Santos, Ana Laura P; Ândrade, Marcelo
Due to their natural history and ecological attributes, turtles are excellent organisms for studies of heavy metal contamination. Turtles have a large geographical distribution, occupy different aquatic habitats, and occupy various trophic levels. The present study investigated mercury bioaccumulation in the carnivorous chelonian Chelus fimbriata (Matamata turtle) and Hg biomagnification in relation to its aquatic food chain in the middle Rio Negro, AM-Brazil. Tissue samples of muscle, carapace and claws were collected from 26 C. fimbriata individuals, as well as collections of autotrophic energy sources found in the turtle's aquatic habitat area. The samples were collected in February-March/2014 and analyzed for THg concentrations and carbon (δ13C) and nitrogen (δ15N) stable isotopes. The highest THg levels were found in claws (3780 ng.g-1), carapace (3622 ng.g-1) and muscle (403 ng.g-1), which were found to be significantly different [F(2.73) = 49.02 p < 0.01]. However, THg concentrations in muscle tissue were below the consumption threshold indicated by the WHO and Brazilian Health Ministry. The average δ13C and δ15N values in Matamata samples were -31.7‰ and 11.9‰, respectively. The principal energy source sustaining the food chain of C. fimbriata was found to be terrestrial shrubs, with smaller contributions from emergent aquatic herbaceous plants and algae, while δ15N values showed its trophic position to be two levels above the autotrophic energy sources. There was a positive correlation between THg and turtle size, while a significant relationship was found between THg and δ15N, showing strong biomagnification in the food chain of C. fimbriata: y = 0.21x + 0.46; r2 = 0.45; p < 0.001, for which the slope presented a value of 0.21.
Artigo
USE OF KNOWN INDIVIDUAL MARKING IN RESEARCH AND MONITORING OF FRESHWATER TURTLE POPULATIONS
(ResearchGate, 2024) Cunha, Fabio; Ândrade, Marcelo
The marking or tagging of turtles is a widely used to facilitate the monitoring of population demography, structure, and conservation of species. Even though they are used in many studies of turtle demography, the available methods are not very efficient, except for microchips (Passive Intergraded Transponder/PIT tags); however, the latter is too expensive to be used on a large scale. Here we present a viable, cost-effective tagging alternative that uses a durable plastic cattle tag and pin. Turtles in the genus Podocnemis were tagged in the Lower-Amazon region, west of the state of Pará, Amazon, Brazil. This method is highly recommended for future work on monitoring and population structure of large species of freshwater turtles. In addition to feasibility, it can be used in the form of citizen science, as the information can be obtained by laypeople and taken to researchers and conservationists. Resumen El marcado o marcaje de tortugas es un método ampliamente utilizado para facilitar el seguimiento de la demografía y estructura de las poblaciones y la conservación de las especies. Aunque se utilizan en muchos estudios de demografía de tortugas, los métodos disponibles no son muy eficaces, excepto los microchips (Passive Intergraded Transponder/PIT tags); sin embargo, estos últimos son demasiado caros para ser utilizados a gran escala. Aquí presentamos una alternativa de marcado viable y rentable que utiliza una marca de plástico duradera para ganado y un alfiler. Se marcaron tortugas del género Podocnemis en la región del Bajo Amazonas, al oeste del estado de Pará, Amazonas, Brasil. Este método es muy recomendable para futuros trabajos de seguimiento y estructura poblacional de grandes especies de tortugas dulceacuícolas. Además de su viabilidad, puede utilizarse en forma de ciencia ciudadana, ya que la información puede ser obtenida por profanos y llevada a investigadores y conservacionistas.