Summary1. The evolution of fossoriality in Squamata often leads to a phenotypic syndrome involving snake-like body form, relatively low preferred temperature (T P ) and low critical maximum temperatures (CT max ). However, how traits interacted among them and with the environment during the evolution of such syndrome remains poorly understood. 2. We studied this process in ten species of gymnophthalmid lizards from the Brazilian Caatinga representing one full transition from typical lacertoid species to fossorial snake-like (FSL) ones. We tested whether different morphotypes exhibited different burrowing performances in response to heat, and also different T P and CT max . Then, we estimated how changes in burrowing performance would relate to thermoregulation costs in terms of the number of daily hours for which preferred temperatures are available and of risk of overheating. 3. Fossorial snake-like species burrowed deeper, exhibited lower T P but kept very high CT max , comparable to lacertoid species. A better burrowing performance and lower T P allowed increasing the daily amount of time during which T P was accessible within the soil of the study region. In addition, temperatures above CT max of the studied species were present down to 5 cm deep, suggesting that just burrowing does not protect against exposure to extreme temperatures in species that are surface-active during the day (all lacertoids and some FSL). Nonetheless, FSL species active at cool hours of the day exhibited lower CT max than diurnal and syntopic, lacertoid and FSL species. 4. Based on our data and previous literature, we propose a sequential explanation for the acquisition of the fossorial syndrome in Squamata.
The karyotype of the big-headed Amazon River turtle, Peltocephalus dumerilianus, is characterized based on a sample of seven juveniles from Reserva Biológica do Rio Trombetas, Pará State, Brazil (1°30′ S, 56°34′ W). Here we present the first results on GTG and CBG-banding patterns, Ag-NOR staining and FISH, with telomeric and 45S rDNA sequences as probes. A cytogenetic comparison with related Podocnemidae is also provided.
Trichechus manatus and Trichechus inunguis are the two Sirenia species that occur in the Americas. Despite their increasing extinction risk, many aspects of their biology remain understudied, including the repetitive DNA fraction of their genomes. Here we used the sequenced genome of T. manatus and TAREAN to identify satellite DNAs (satDNAs) in this species. We report the first description of TMAsat, a satDNA comprising ~0.87% of the genome, with ~684bp monomers and centromeric localization. In T. inunguis, TMAsat showed similar monomer length, chromosome localization and conserved CENP-B box-like motifs as in T. manatus. We also detected this satDNA in the Dugong dugon and in the now extinct Hydrodamalis gigas genomes. The neighbor-joining tree shows that TMAsat sequences from T. manatus, T. inunguis, D. dugon, and H. gigas lack species-specific clusters, which disagrees with the predictions of concerted evolution. We detected a divergent TMAsat-like homologous sequence in elephants and hyraxes, but not in other mammals, suggesting this sequence was already present in the common ancestor of Paenungulata, and later became a satDNA in the Sirenians. This is the first description of a centromeric satDNA in manatees and will facilitate the inclusion of Sirenia in future studies of centromeres and satDNA biology.
the genus Saimiri is a decades-long taxonomic and phylogenetic puzzle to which cytogenetics has contributed crucial data. All Saimiri species apparently have a diploid number of 2n = 44 but vary in the number of chromosome arms. Repetitive sequences such as satellite DnAs are potentially informative cytogenetic markers because they display high evolutionary rates. our goal is to increase the pertinent karyological data by more fully characterizing satellite DnA sequences in the Saimiri genus. We were able to identify two abundant satellite DNAs, alpha (~340 bp) and CapA (~1,500 bp), from short-read clustering of sequencing datasets from S. boliviensis. The alpha sequences comprise about 1% and the CapA 2.2% of the S. boliviensis genome. We also mapped both satellite DnAs in S. boliviensis, S. sciureus, S. vanzolinii, and S. ustus. The alpha has high interspecific repeat homogeneity and was mapped to the centromeres of all analyzed species. capA is associated with non-pericentromeric heterochromatin and its distribution varies among Saimiri species. We conclude that capA genomic distribution and its pervasiveness across platyrrhini makes it an attractive cytogenetic marker for Saimiri and other new World monkeys. Squirrel monkeys of the genus Saimiri (Cebidae, Platyrrhini) are medium sized neotropical primates inhabiting forest environments of South America. They range from about 10°N to 17°S including the Amazon basin, the Guianas, and coastal zones of Central America 1,2. As for many other New World monkey (NWM) taxa the phylogenetic relationships within the genus Saimiri are still debated 3. Even the number of species is uncertain, historically ranging from one to 16 distinguished species 4-11. In a recent molecular report on mitochondrial D-Loop and cyt b sequences, Alfaro et al. 3 presented a provisional taxonomy of seven Saimiri species and various subspecies: (1) S. boliviensis, (2) S.
Pseudoryzomys simplex, the false rice rat, is a monotypic genus of the Oryzomyini tribe (Sigmodontinae) distributed in part of Bolivia, Paraguay, Argentina and Brazil. Its diploid number has been described as 56 acrocentric chromosomes decreasing in size and no karyotype figure has been depicted. Herein, we present karyotypic data on P. simplex, including chromosome banding and molecular fluorescent in situ hybridization using telomeric sequences and the whole X-chromosome of its sister clade Holochilus brasiliensis (HBR) as probes. A case of remarkable autosomal heteromorphism due to the presence of a whole heterochromatic arm leading to the variability of FN is reported, as well as the occurrence of regions of homology between the X and Y chromosomes (pseudoautosomal regions) after chromosome painting with the HBR X probe on P. simplex metaphases.
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