1,721,005 research outputs found
Usefulness of postpygal caudal vertebrae and osteoderms for skeletochronology in the limbless lizard Anguis veronensis Pollini, 1818 (Squamata: Sauria: anguidae).
No full textIn this study the authors tested the usefulness of postpygal caudal vertebra and osteoderms for the assessment of individual age in the limbless lizard Anguis veronensis POLLINI 1818, employing skeletochronological method. The results showed that osteoderm-based skeletochronology was unreliable since within any specimen examined the number of lines of arrested growth (LAG) varies between different osteoderms, and even within osteoderms. On the contrary, the skeletocronology was to some degree applicable to the neural arch of the caudal vertebra, as the LAG number was roughly stable in all neural arch per animal studied. Assuming that one LAG is formed per year, the oldest individual in the present study was 9 years old. However, age underestimation due to bone remodeling that completely destroyed the LAGs cannot be ruled out. Therefore, caution interpretation is required in the skeletochronological age estimation of Anguis if caudal vertebrae are analyzed
Population size, age structure and life expectancy in a Lacerta agilis (Squamata; Lacertidae) population from northwest Italian Alps
No full textAbstract. We studied population size and age structure of the sand lizard Lacerta agilis Linnaeus 1758, from northwest Italian Alps. Twenty-nine (9 males, 15 females, 5 juveniles) and 19 (8 males, 5 females, 6 juveniles) lizards were captured in 2011 and 2012, respectively. Adult population size, estimated by capture-markrecapture, was 54 individuals in 2011 and 39 in 2012. Mean SVL did not significantly differ between males sampled in the two years of the study (mean ± SD, 2011: 67.1 ± 6.6 mm; 2012: 61 ± 8.7 mm). On the contrary, females sampled in 2011 were significantly larger (73 ± 7.2 mm) than females of 2012 (61 ± 7.4 mm). Adult age, assessed by skeletochronology, ranged 2-5 years both in males and females. All juveniles were one-year old. In both years of sampling there was no significant difference in mean age between the sexes. Males were represented mainly by three and four-year old individuals in 2011 and by two-year old individuals in 2012. Females were represented mainly by three -year old individuals in 2011 and by two-year old individuals in 2012. However, age distribution of adults did not differ for each sex as well as between the sexes both in 2011 and 2012. Although our results showed that the examined population of L. agilis has a stable demographic structure, it should be considered seriously vulnerable, because it is relatively isolated from other neighboring populations, has small absolute size and, therefore, may be highly exposed to negative effects of habitat degradation
To Move or not to move: cranial joints in european gekkotans and lacertids, an osteological and histological perspective
No full textLepidosaurs are frequently described as having highly kinetic skulls,and different forms of cranial kinesis have been described as being characteristic of their radiation. The model of amphikinesis proposed by Frazzetta (J Morphol 1962; 111:287???319, which was long considered a synapomorphy of the large suborder Sauria, is now much debated given its uncertain distribution among the various lizard taxa and the lack of data about its morphological correlates. In this article, we analyze the anatomical correlates of different forms of cranial kinesis, with particular regard to the putative saurian amphikinesis, describing the possible diverse skull movements of several species of European gekkotans (Hemidactylus
turcicus, Mediodactylus kotschyi, and Tarentola mauritanica)
and lacertids (Lacerta agilis, L. bilineata, Podarcis muralis, P. siculus, and Teira dugesii). Using serial and whole-mount histology, we found clear differences between gekkotans and lacertids in the structure of several cranial joints underlining the existence of two degrees of intracranial mobility. The lacertid species possess the anatomical features for streptostyly
(quadrate joints) and metakinesis (parietal-supraoccipital and
parabasisphenoid-pterygoid joints) and lack the anatomical correlates for mesokinesis (mobility of frontal-parietal and palatine-pterygoid joints) and amphikinesis (coupled mesokinesis, metakinesis, and streptostyly). In contrast, geckos present all the anatomical correlates for amphikinesis as described by the traditional quadratic crank model. Finally, we present a comprehensive summary of the different forms of squamate cranial kinesis, advancing two alternative hypotheses about the evolutionary origin of amphikinesis
The herpetofauna of Parco Regionale Area Vulcanica di Roccamonfina e Foce del Garigliano (Campania, Souther Italy)
No full textThe aim of this work is to provide a check-list of the amphibians and reptiles of the Regional Park of the Volcanic Area of Roccamonfina and Foce del Garigliano” (PRAVRFG, Campania, Southern Italy) and surrounding areas, integrating the few bibliographic data with new records coming from field research and from Citizen Science. So far, seven species of amphibians and 15 of reptiles have been found in the study area. Overall, a rather rich herpetological diversity was observed in the PRAVRFG. In particular, reptiles represent approximately 71% of the species present in Campania and 26.8% of the species present in Italy. Furthermore, this work provides new chorological data on the herpetofauna living in the north-western sector of Campania.This check list, although preliminary, represents an indispensable starting point for the identifica-tion of any critical issues of the Park’s herpetofauna and its management
A preliminary survey on the gross morphology and histology of cranial joints in Tarentola mauritanica and Podarcis siculus
No full textAbbiamo esaminato cinque articolazioni craniche (quadrato-articolare, quadrato-pterigoide, epipterigoide-pterigoide,
basisfenoide-pterigoide e fronto-parietale) in Tarentola mauritanica e Podarcis siculus mediante il metodo della doppia colorazione Alcian blu – Alizarina rossa e attraverso
sezioni istologiche. In entrambe le specie quadrato-articolare, epipterigoide-pterigoide e basisfenoide-pterigoide sono risultate tipiche articolazioni sinoviali mentre frontoparietale
e quadrato-pterigoide sono risultate sindesmosi. Inoltre, la sutura frontoparietale è lineare in T. mauritanica ma altamente interdigitata in P. siculus. Un’attenta integrazione fra l’anatomia macroscopica e l’analisi istologica è indispensabile per
interpretare correttamente la struttura e la funzione delle articolazioni craniali nei differenti taxa di Vertebrati
Chromosome Diversity and Evolution of the Endemic Malagasy Velvet Geckos of the Genus Blaesodactylus (Reptilia, Gekkonidae)
Full text link: We performed a molecular and phylogenetic analysis and a comparative cytogenetic study with standard karyotyping, silver staining (Ag-NOR) and sequential C-banding + Giemsa, + fluorochromes on several Blaesodactylus samples. The phylogenetic inference retrieved two main clades, the first comprises B. victori, B. microtuberculatus and B. boivini, while the second includes B. sakalava, B. antongilensis and B. ambonihazo. The available samples of B. sakalava form two different clades (here named B. sakalava clade A and clade B), which probably deserve a taxonomic re-evaluation. We found a karyological variability in Blaesodactylus in terms of chromosome number (2n = 40-42), morphology, location of NORs, and heterochromatin distribution pattern. Blaesodactylus antongilensis and B. sakalava clade A and B showed a karyotype of 2n = 40 mostly telocentric chromosomes. Pairs 1 and 6 were metacentric in B. sakalava clade A and B, while pair 1 was composed of subtelocentric/submetacentric elements in B. antongilensis. In contrast, B. boivini displayed a karyotype with 2n = 42 only telocentric chromosomes. NORs were on the first chromosome pair in B. boivini, and on the second pair in B. antongilensis. Adding our data to those available from the literature on evolutionarily related species, we highlight that the chromosome diversification in the genus probably proceeded towards a progressive reduction in the chromosome number and the formation of metacentric elements
A skeletochronological estimate of age and growth in a large riparian frog from Madagascar (Anura, Mantellidae, Mantidactylus)
Full text linkWe characterized the body size (as snout-vent length), age, sexual size dimorphism, and growth rate in a population of one of the larger riparian frog from Madagascar (Mantidactylus grandidieri) from a rainforest patch close to Vevembe, SE Madagascar. We identified a significant female-biased sexual size dimorphism. Age was estimated using phalangeal skeletochronology and was significantly higher in females than in males. Modal age class turned out to be 4 years in both sexes but a large percentage of adult females (75%) fell in the 5–6 years-old classes, while no male exceeded 4 years. We here report M. grandidieri as a medium-long-lived anuran species. Von Bertalanffy's model showed similar growth trajectories between the sexes although the growth coefficient in females (k = 0.335) was slightly but not significantly higher than in males (k = 0.329)
First Insights on the Karyotype Diversification of the Endemic Malagasy Leaf-Toed Geckos (Squamata: Gekkonidae: Uroplatus)
Full text linkSIMPLE SUMMARY: The geckos of the genus Uroplatus include peculiar endemic species to Madagascar. Even though they have been the subject of several morphological and molecular studies, karyological analyses have been performed only on U. phantasticus, leaving the chromosomal diversity of the genus completely unexplored. In this study, we performed a preliminary molecular analysis and a comparative cytogenetic study providing the first karyotype description of eight species of Uroplatus and an assessment of their karyological variability. We found chromosome diversity in the species studied in terms of total chromosome number (2n = 34–38), localization of loci of Nucleolar Organizer Regions (NORs) (alternatively on the 2nd, 6th, 10th or 16th pair), heterochromatin composition and occurrence of heteromorphic sex chromosome pairs. Adding our newly generated data to those available from the literature, we show that in the genus Uroplatus, as well as in a larger group of phylogenetically related gecko genera, chromosome diversification mainly occurred toward a reduction in the chromosome number by means of chromosome fusions and translocation of NOR-bearing chromosomes. We also hypothesize that the diversification of sex chromosome systems occurred independently in different genera. ABSTRACT: We provide here the first karyotype description of eight Uroplatus species and a characterization of their chromosomal diversity. We performed a molecular taxonomic assessment of several Uroplatus samples using the mitochondrial 12S marker and a comparative cytogenetic analysis with standard karyotyping, silver staining (Ag-NOR) and sequential C-banding + Giemsa, +Chromomycin A3 (CMA(3)), +4′,6-diamidino-2-phenylindole (DAPI). We found chromosomal variability in terms of chromosome number (2n = 34–38), heterochromatin composition and number and localization of loci or Nucleolar Organizer Regions (NORs) (alternatively on the 2nd, 6th, 10th or 16th pair). Chromosome morphology is almost constant, with karyotypes composed of acrocentric chromosomes, gradually decreasing in length. C-banding evidenced a general low content of heterochromatin, mostly localized on pericentromeric and telomeric regions. Centromeric bands varied among the species studied, resulting in CMA(3) positive and DAPI negative or positive to both fluorochromes. We also provide evidence of a first putative heteromorphic sex chromosome system in the genus. In fact, in U. alluaudi the 10th pair was highly heteromorphic, with a metacentric, largely heterochromatic W chromosome, which was much bigger than the Z. We propose an evolutionary scenario of chromosome reduction from 2n = 38 to 2n = 34, by means of translocations of microchromosomes on larger chromosomes (often involving the NOR-bearing microchromosomes). Adding our data to those available from the literature, we show that similar processes characterized the evolutionary radiation of a larger gecko clade. Finally, we hypothesize that sex chromosome diversification occurred independently in different genera
Evolutionary and Genomic Diversity of True Polyploidy in Tetrapods
Full text linkTrue polyploid organisms have more than two chromosome sets in their somatic and germline cells. Polyploidy is a major evolutionary force and has played a significant role in the early genomic evolution of plants, different invertebrate taxa, chordates, and teleosts. However, the contribution of polyploidy to the generation of new genomic, ecological, and species diversity in tetrapods has traditionally been underestimated. Indeed, polyploidy represents an important pathway of genomic evolution, occurring in most higher-taxa tetrapods and displaying a variety of different forms, genomic configurations, and biological implications. Herein, we report and discuss the available information on the different origins and evolutionary and ecological significance of true polyploidy in tetrapods. Among the main tetrapod lineages, modern amphibians have an unparalleled diversity of polyploids and, until recently, they were considered to be the only vertebrates with closely related diploid and polyploid bisexual species or populations. In reptiles, polyploidy was thought to be restricted to squamates and associated with parthenogenesis. In birds and mammals, true polyploidy has generally been considered absent (non-tolerated). These views are being changed due to an accumulation of new data, and the impact as well as the different evolutionary and ecological implications of polyploidy in tetrapods, deserve a broader evaluation
Karyological analyses of Pseudhymenochirus merlini and Hymenochirusboettgeri provide new insights into the chromosome evolution in theanuran family Pipidae
No full texttKaryological studies continue to clarify the evolutionary history of many taxa. We report here on thefirst chromosome survey of the frog Pseudhymenochirus merlini (Pipidae) in comparison with the relatedspecies Hymenochirus boettgeri.In addition to the 2n = 20 regular (A) chromosomes (eight metacentric and two subtelocentric pairs),H. boettgeri has an accessory B chromosome in about half of the scored karyotypes (2n = 21). P. merlinishowed a karyotype of 2n = 20 chromosomes, differing from the set of A chromosomes of H. boettgeri bythree inversions.Other differences are in the location of the nucleolus organizer regions (NORs), on the 10th chromosomepair in P. merlini instead of the 4th pair in H. boettgeri. Heterochromatin is less abundant in P. merlini, andlocalized in centromeric and telomeric regions of all chromosomes. The patterns in H. boettgeri resemblethose of another pipid species, Silurana tropicalis, as to chromosome number (2n = 20), morphology, andG-banding patterns. We propose that these characteristics are symplesiomorphic in Pipidae, allowing usto present a scenario for the chromosome evolution in this family. Our results identify a third mecha-nism of increase in chromosome numbers among pipid frog species, the addition of B chromosomes inHymenochirus, besides the known processes of polyploidization in Xenopus/Silurana, and centric fissionin Pipa
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