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"Chelus fimbriata."
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Matamatas Chelus spp. (Testudines, Chelidae) have a remarkable evolutionary history of sex chromosomes with a long-term stable XY microchromosome system
The genus
Chelus
, commonly known as Matamata is one of the most emblematic and remarkable species among the Neotropical chelids. It is an Amazonian species with an extensive distribution throughout Negro/Orinoco and Amazonas River basins. Currently, two species are formally recognized:
Chelus orinocensis
and
Chelus fimbriata
and although it is still classified as \"Least Concern\" in the IUCN, the Matamatas are very appreciated and illegally sold in the international pet trade. Regardless, little is known regarding many aspects of its natural history. Chromosomal features for
Chelus
, for instance, are meagre and practically restricted to the description of the diploid number (2n = 50) for
Chelus fimbriata
, and its sex determining strategies are yet to be fully investigated. Here, we examined the karyotype of
Chelus fimbriata
and the newly described
Chelus orinocensis
, applying an extensive conventional and molecular cytogenetic approach. This allowed us to identify a genetic sex determining mechanism with a micro XY sex chromosome system in both species, a system that was likely present in their most common recent ancestor
Chelus colombiana
. Furthermore, the XY system found in
Chelus orinocensis
and
Chelus fimbriata
, as seen in other chelid species, recruited several repeat motifs, possibly prior to the split of South America and Australasian lineages, indicating that such system indeed dates back to the earliest lineages of Chelid species.
Journal Article
Mercury biomagnification in the food chain of a piscivorous turtle species (Testudines: Chelidae: Chelus fimbriata) in the Central Amazon, Brazil
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.
Journal Article
Distribution of Chelus fimbriata and Chelus orinocensis (Testudines: Chelidae)
The matamatas (Chelus fimbriata and the recently described Chelus orinocensis) are the largest species in the family Chelidae, easily identified by their distinct morphological characteristics. The matamatas have a wide distribution in South America, occurring in Bolivia, Brazil, Colombia, Ecuador, Guyana, French Guiana, Peru, and Venezuela, as well as Trinidad and Tobago. However, there are many gaps in the knowledge of its distribution. The objective of this study was to present new records of occurrence for the C. fimbriata species complex and describe the area of distribution. We compiled data from published papers, databases in museums and other scientific collections, and research institutes and conservation organizations. From these data we mapped the species distribution, considering 3 types of river drainages based on water color in the Amazon Basin. We added 182 new records in Brazil, Venezuela, Colombia, Bolivia, and Peru, demonstrating that the C. fimbriata species complex has a wide distribution, totaling 6,907,551 km2 across all 3 river types. Most records were concentrated in areas lower than 200 m above sea level.
Journal Article
The complete mitochondrial genome sequences of Chelodina rugosa and Chelus fimbriata (Pleurodira: Chelidae): implications of a common absence of initiation sites (OL) in pleurodiran turtles
Within the order Testudines, while phylogenetic analyses have been performed on the suborder Cryptodira with complete mitochondrial genomes (mitogenomes), mitogenomic information from another important suborder Pleurodira has been inadequate. In the present study, complete mitochondrial DNA (mtDNA) sequences of two chelid turtles
Chelodina rugosa
and
Chelus fimbriata
were firstly determined, the lengths of which were 16,582 and 16,661 bp respectively. As the typical vertebrate mitogenome, both mtDNAs consist of 13 protein coding genes, 2 ribosomal RNAs (rRNAs), 22 transfer RNAs (tRNAs), and a long noncoding region (control region, CR). However, the initiation sites for light-strand replication (O
L
), which has been identified in all reported Cryptodire mitogenomes, were not found in the putative position of the two chelid turtles and African helmeted turtle
Pelomedusa subrufa.
The results suggested that the absence of mitogenomic initiation sites (O
L
) could be a characteristic of Pleurodira. Phylogenetic relationships of chelid turtles and other turtles were reconstructed using the reported mitogenomes. Both maximum likelihood (ML) and Bayesian inference (BI) analyses suggested the monophyly of Pleurodira and Cryptodira as well as a sister group relationship between the two chelid turtles with strong statistical support. This phylogenetic framework was also utilized to estimate divergence dates among lineages using relaxed-clock methods combined with fossil evidence. Divergence estimates revealed that genus
Chelodina
diverged from genus
Chelus
in Late Cretaceous (~83 million years ago (mya)), and the time is consistent with the vicariance of the fragments which was caused by Gondwana split.
Journal Article