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11 recordsLinked to original sources
PubMed1992

Mitochondrial DNA evolution at a turtle's pace: evidence for low genetic variability and reduced microevolutionary rate in the Testudines.

Evidence is compiled suggesting a slowdown in mean microevolutionary rate for turtle mitochondrial DNA (mtDNA). Within each of six species or species complexes of Testudines, representing six genera and three taxonomic families, sequence divergence estimates derived from restriction assays are consistently lower than expectations based on either (a) the dates of particular geographic barriers with which significant mtDNA genetic clades appear associated or (b) the magnitudes of sequence divergence between mtDNA clades in nonturtle species that otherwise exhibit striking phylogeographic concordance with the genetic partitions in turtles. Magnitudes of the inferred rate slowdowns average eightfold relative to the "conventional" mtDNA clock calibration of 2%/Myr sequence divergence between higher animal lineages. Reasons for the postulated deceleration remain unknown, but two intriguing correlates are (a) the exceptionally long generation length most turtles and (b) turtles' low metabolic rate. Both factors have been suspected of influencing evolutionary rates in the DNA sequences of some other vertebrate groups. Uncertainities about the dates of cladogenetic events in these Testudines leave room for alternatives to the slowdown interpretation, but consistency in the direction of the inferred pattern, across several turtle species and evolutionary settings, suggests the need for caution in acceptance of a universal mtDNA-clock calibration for higher animals.

Animals↗
PubMed1987

On the diversity of sperm basic proteins in the vertebrates: V. Cytochemical and amino acid analysis in Squamata, Testudines, and Crocodylia.

The variability of sperm basic proteins in representatives of three reptilian orders, Squamata, Testudines, and Crocodylia, has been examined by cytochemistry, acid-urea polyacrylamide gel electrophoresis, and amino acid analysis of amidoblack-stained bands. Snakes contain type 3B intermediate sperm basic proteins by cytochemical criteria. Electrophoresis of basic proteins from epididymis chromatin as well as from testis and ductus deferens cell suspensions shows two fast-moving bands in the vicinity of herring protamine. These proteins are triprotamines containing about 27 mol % arginine, along with lysine and histidine. Lizards have type 1 protamines in their sperm nuclei cytochemically and also show a two-banded electrophoretic pattern similar to that of snakes. However, these proteins are triprotamines, similar to those in snakes with 25 mol % arginine. It may be that these are testis-specific proteins of the spermatid stage in lizards since a cytochemical transition can be observed from type 3A intermediate proteins in spermatids of testis to type 1 protamine in mature sperm of ductus deferens. Turtles contain type 3A intermediate sperm basic proteins cytochemically and basic proteins from epididymis chromatin display both a prominent band and a minor band close to, but slightly slower than, the two bands for snakes and lizards. Amino acid analysis of these bands shows that these basic proteins are also triprotamines but with a higher level of arginine, about 48 mol %, than that in snake and lizard sperm proteins. Basic proteins from epididymis chromatin of a single Mississippi alligator show three main bands moving close to the bands of snakes, lizards, and turtles. These proteins have amino acid compositions typical for triprotamines, with 28-39 mol % arginine. The data indicate that the sperm basic proteins of representatives of 25 species in three reptilian orders are very similar, in contrast to the diversity of sperm protein types found in frogs (Kasinsky, Huang, Kwauk, Mann, Sweeney, and Yee: J. Exp. Zool., 203:109-126, '78; Kasinsky, Huang, Mann, Roca, and Subirana: J. Exp. Zool., 234:33-46, '85a). This appears to be part of a macroevolutionary trend from diversity of sperm basic proteins in frogs to relative constancy in reptiles (Kasinsky, Mann, Pickerill, Gutovich, and Byrd, Jr.:J. Cell Biol., 91:1879, '81; Kasinsky, Mann, Lemke, and Huang: In: Chromosomal Proteins and Gene Expression, Plenum Press, New York, pp. 333-352, '85b). We present the hypothesis that one factor for such a trend resides in the fact that fertilization is internal in reptiles but external in anurans.

Amino Acids↗
PubMed1988

The buccopharyngeal mucosa of the turtles (testudines).

Gross and histological examination of all extant families of turtles revealed that the buccopharyngeal mucosa is morphologically highly varied. The tongues of aquatic species have small lingual papillae or lack them entirely, while terrestrial species have tongues with numerous glandular papillae. The pharynx and the esophagus also have papillae in some species. These either facilitate swallowing in which case they are long, pointed, keratinized, and occur commonly in marine turtles, or they are vascular and nonkeratinized, facilitate respiratory gas exchange and are found in the Trionychidae, Dermatemyidae, and Carettochelyidae. The morphology of the buccopharyngeal mucosa of turtles reflects their diet, feeding behavior, habitat, and relationships. Convergence in the morphology of the buccopharyngeal mucosa occurs among families, especially among the Emydidae and other familes of turtles. Intergeneric parallelism is also seen within the Emydidae.

Animals↗
PubMed1991

Coccidian parasites (Apicomplexa: Eimeriidae) of Graptemys caglei and Graptemys versa (Testudines: Emydidae) from Texas.

Nineteen map turtles, Graptemys caglei and Graptemys versa were collected from the Guadalupe and Colorado River watersheds of south-central Texas and examined for coccidial parasites. Thirteen of the 19 turtles (68%), including 11 of 16 (69%) G. caglei and 2 of 3 (67%) G. versa, were infected with at least 1 coccidian. Five Eimeria spp. (E. chrysemydis, E. graptemydos, E. lutotestudinis, E. pseudogeographica, and E. trachemydis) were harbored by G. caglei, and 2 eimerians (E. graptemydos and E. mitraria) infected G. versa. This represents new host records for these previously described coccidians and is the first time parasites have been documented in turtles of both species.

Animals↗
PubMed1990

Three new species of Eimeria (Apicomplexa: Eimeriidae) from Apalone spinifera pallidus (Testudines: Trionychidae) in Texas, with a redescription of E. amydae.

Three new species of Eimeria are described from pallid spiny softshells, Apalone spinifera pallidus, collected in north-central Texas. Oocysts of Eimeria spinifera n. sp. were found in the feces of 3/9 (33%) turtles and are subspheroid, ellipsoid, or pear-shaped, 16.3 x 14.0 (14-19 x 12-18) microns, with a thin, single-layered wall; shape index 1.2 (1.1-1.3). A micropyle is absent, but an oocyst residuum is present; polar granule present in 16% of the oocysts. Sporocysts are elongate-ovoid, 10.3 x 5.2 (8-12 x 5-6) microns, each with a Stieda body bearing short filaments. Oocysts of Eimeria apalone n. sp. were found in 5/9 (56%) turtles and are ellipsoid, elongate pear-shaped, or subspheroid, 16.8 x 13.2 (12-19 x 10-16) microns, with a thin, single-layered wall; shape index 1.3 (1.0-1.5). A micropyle, oocyst residuum, and polar granule are absent. Sporocysts are elongate-ovoid, 11.3 x 6.2 (9-14 x 5-7) microns, each with a prominent Stieda body. Oocysts of Eimeria pallidus n. sp. were found in 4/9 (44%) A. s. pallidus and are spheroid or subspheroid, 23.4 x 21.6 (18-27 x 17-25) microns, with a thin, single-layered wall; shape index 1.1 (1.0-1.3). A micropyle is absent, but an oocyst residuum is present; polar granule present in 20% of the oocysts. Sporocysts are elongate-ovoid, 14.3 x 6.2 (13-17 x 6-7) microns, each with a Stieda body and short filaments. In addition to the new species, 3 previously described eimerians, including Eimeria amydae Roudabush, 1937, which is redescribed, were also found.

Animals↗
PubMed1985

An allometric comparison of the mitochondria of mammalian and reptilian tissues: the implications for the evolution of endothermy.

The effects of body size and phylogeny on metabolic capacities were examined by comparing the mitochondrial capacities of 6 mammalian and 4 reptilian species representing 100-fold body weight ranges. The mammals examined included 3 eutherian, 2 marsupial and a monotreme species and the reptiles 2 saurian, 1 crocodilian and 1 testudine species. The tissues examined were liver, kidney, brain, heart, lung and skeletal muscle. Allometric equations were derived for tissue weights, mitochondrial volume densities, internal mitochondrial membrane surface area densities, tissue mitochondrial membrane surface areas both per gram and per total tissue and summated tissue mitochondrial membrane surface areas. For the mammals and reptiles studied a 100% increase in body size resulted in average increases of 68% in internal organ size and 107% in skeletal muscle mass. Similarly, total organ mitochondrial membrane surface areas increase in mammals and reptiles by an average 54% and for skeletal muscle by an average 96%. These values are similar to increases in standard (54 and 71%) and maximum (73 and 77%) organismal metabolism values found by other authors for mammals and reptiles respectively. Although the allometric exponents (or rates of change with increasing body size) of the mitochondrial parameters in mammals and reptiles are statistically the same, in general the total amount of mitochondrial membrane surface area in the mammalian tissues are four times greater than found in the reptilian tissues.(ABSTRACT TRUNCATED AT 250 WORDS)

Alligators and Crocodiles↗
PubMedDate not supplied

Contributions to the evolutionary study of the liver afferent veins.

The extra- and intrahepatic venous afferent devices have been followed up in their evolution in all the classes of vertebrates and in man. There were studied 319 cases in 19 vertebrate species, in situ by the method of corrosion preparates with acid-resistant plastic materials or radiographies. The extraparenchymal afferent venous device shows an evolution characterized by the maintenance and improvement of the visceral hepatic venous system and by the gradual freeing of somatic parietal afferences, substantiating new anatomical notions like "liver visceralization", "hepatic parietal territories" and allowed the ascertainment of an evolutionary phyletic line of the liver based on the progressive diminution of the hepatic parietal territory. The basic characteristic type of intrahepatic distribution of the portal vein was sketched beginning with the testudine reptiles and was maintained including man. The liver segmentary angioarchitecture appeared already in birds. These findings allowed the homologation of the cleaved liver with the unitary liver of mammals and man as well as the homologation of the hepatic organ of mammals, birds and of some reptiles, and the understanding of the emergence variation of the portal vein ventrocranialis dexter.

Animals↗
PubMed2026

Highly Contiguous Is Not Chromosomally Accurate: Integrated Cytogenetic and Genomic Mapping in Two Turtle Genome.

High-quality genome assemblies are essential for robust research across biological and medical fields. Assembly errors can have far-reaching consequences for downstream analyses, including gene annotation and the inference of synteny. In contrast to the rapid growth of genomic data volume, there is a notable lag in the integration of chromosome-level assemblies with cytogenetic data. We conducted the first direct genome-to-genome comparison, integrating comparative chromosome painting, the alignment of chromosome-specific probes to available genome assemblies, and synteny-based comparison of independent chromosome-level assemblies of the loggerhead sea turtle (Caretta caretta, 2n = 56) and the red-eared slider (Trachemys scripta elegans, 2n = 50). Using two independent sets of flow-sorted chromosome-specific probes in cross-species hybridizations, together with the sequencing and mapping of chromosome-derived DNA libraries, we assigned assembled scaffolds to all physical chromosomes of both species. In C. caretta, chromosomal assignments and genome-wide synteny were fully consistent with the published assembly, except for the reduced sizes of two microchromosome scaffolds, which we attribute to under-representation of repetitive DNA. In contrast, in T. s. elegans, cytogenetic validation of the assemblies revealed a false rearrangement compared to a missed one. Our results show that even highly contiguous vertebrate genome assemblies can misrepresent chromosome structure. When cytogenetic analyses reveal such inaccuracies, updated reference genomes should be generated for widely studied species to enable accurate inference of karyotype evolution and downstream comparative genomic analyses.

FISH↗