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Phylogenetic relationships in the Ranidae. Independent origin of direct development in the genera Philautus and Taylorana.

Phylogenetic relationships within a group of Ranidae were studied, particularly between the genera Philautus and Taylorana, to determine whether their original reproductive mode (direct development) appeared independently. To study these relationships, we used the DNA sequences of the 5' end of the gene coding for mitochondrial ribosome small subunit in 28 species. Parsimony analysis resulted in two equiparsimonious trees, 867 steps long (CI = 0.382; RI = 0.429). Data saturation was studied and we applied weighting (weight of 5 for transversions and 1 for transitions) to enhance the phylogenetic information. The tree we obtained (2,212 steps long, CI = 0.408; RI = 0.482) is best supported and allows us to determine clearly that direct development has appeared independently in Philautus and Taylorana. In addition, it is confirmed that the genus Rana sensu lato is heterogeneous. The genera Occidozyga and Phrynoglossus form a clade basal to all the group but this position is not supported. The inclusion of the Rhacophorinae in the Ranidae is confirmed. Finally, this study confirms that the relationships within the group Tomopterna sensu Boulenger, 1918 should be re-evaluated.

Animals↗

Islet hormones from the African bullfrog Pyxicephalus adspersus (Anura:Ranidae): structural characterization and phylogenetic implications.

The African bullfrog Pyxicephalus adspersus is generally classified along with frogs of the genus Rana in the subfamily Raninae of the family Ranidae but precise phylogenetic relationships between species are unclear. Pancreatic polypeptide (PP), insulin, and glucagon-like peptide (GLP-1) were isolated from an extract of P. adspersus pancreas and characterized structurally. A comparison of the amino acid sequence of Pyxicephalus PP (APSEPQHPGG(10)QATPEQLAQY(20)YSDLYQYITF(30)ITRPRF++ +. NH(2)) with those of the known amphibian PP molecules in a maximum parsimony analysis generates a single phylogenetic tree in which Pyxicephalus is the sister to the clade comprising the members of the genus Rana. The three orders of living amphibians form discrete clades with the representative of the Gymnophiona appearing as sister to the Caudata-Anura. In contrast, Pyxicephalus insulin (A chain, GIVEQCCHSA(10)CSLYDLENYC(20)N; B-chain, LANQHLCGSH(10)LVEALYMVCG(20)ERGFFYYPKS(30)) and and GLP-1 (HAEGTFTSDM(10)TSYLEEKAAK(20)EFVDWLIKGR(30)PK) resemble more closely the corresponding peptides from the cane toad Bufo marinus than the peptides from any species of Rana. Cladistic analysis based upon the amino acid sequences of insulin produced a polyphyletic assemblage with the Gymnophiona nesting within an unresolved clade containing the non-ranid frogs. The data support the assertion that the amino acid sequence of PP, but not those of the other islet hormones, is of value as a molecular marker for inferring phylogenetic relationships between early tetrapod species.

Amino Acid Sequence↗

Morphology of the caudal spinal cord in Rana (Ranidae) and Xenopus (Pipidae) tadpoles.

Using a variety of neuroanatomical and histological techniques, we compare the spinal cord and peripheral nerve distribution in the tails of larvae from Xenopus laevis and three species of Rana. The relatively large, postsacral spinal cord of Xenopus contains abundant motoneurons and their axons. Spinal nerves exit from the spinal cord in a regular array, one nerve per myotome, from the cervical region to near the end of the tail. Somata of motoneurons innervating caudal myotomes are found along the entire length of the tail. In contrast, the caudal cord of Rana is reduced to a filum terminale consisting of little more than an ependymal tube; spinal nerves to all caudal myotomes leave the cord in the sacral region and reach their motor targets via a cauda equina and caudal plexus. Motoneuron cell bodies innervating caudal myotomes are found only in the sacral region. The Rana larval pattern is similar to that of adult frogs and mammals, whereas the Xenopus larval pattern is more like that of salamanders and reptiles. These gross neuroanatomical differences are not due to differences in the size or developmental stage of the tadpoles, but instead are associated with differences in the swimming behavior of the larvae. The presence of motoneurons in the caudal spinal cord of Xenopus may provide local intermyotomal control within the tail; the elongated topography of the cord appears to permit finer, rostral-to-caudal regulation of neuromuscular activity. The Rana spinal cord, on the other hand--with motoneurons clustered anteriorly--may produce concurrent firing of adjacent ipsilateral myotomes, but at the expense of fine intermyotomal regulation. The fact that nerves in the tail of Xenopus enter and exit from the spinal cord locally, as opposed to far anteriorly as in Rana, means that for tadpoles of the same size, reflex arc lengths are many times shorter in Xenopus.

Animals↗

Limb regenerative capacity of four species of Japanese frogs of the families Hylidae and Ranidae.

The regenerative capacity of limbs was investigated by amputation of limbs at the zeugopodium in postmetamorphic froglets and adults of various sizes in four species of Japanese frogs, all of which showed some regeneration at these ages. In Hyla arborea japonica and Rana brevipoda porosa most young froglets regenerated their limbs well; however, the rate of regeneration decreased with the age of amputation, and the limb became nonregenerative in adults. Limbs of adults in Rana rugosa and R. japonica, on the other hand, exhibited good regeneration. All of the regenerates in the four species were heteromorphic, consisting histologically of well-developed cartilaginous rods surrounded by connective tissue and skin. Limited development of muscle was apparent in regenerates of the three ranid species. The relations between body size, innervation of limbs, and regenerative capacity are discussed.

Animals↗

Functional stages in the interrenal cells of Rana perezi (Anura: Ranidae).

The electron density of the lipid droplets and mitochondrial matrix of the interrenal cells of Rana perezi differs during the year. This makes it possible to characterize the different stages of interrenal cell activity. A droplet/mitochondria index, based on their relative size, may provide an indicator of cellular activity.

Adrenal Glands↗

Histology of the esophagus of the adult frog Rana perezi (Anura: Ranidae).

Study of the esophageal microscopic morphology of adult Rana perezi by light and electron microscopy discloses some large folds throughout the esophagus that are in themselves ringed. Glandular ostia open in the furrows of the luminal surface. The esophageal wall is made up of a connective adventitia rich in melanocytes, a muscular tunica, a connective and glandular subepithelial layer, and a pseudostratified ciliated epithelium. This epithelium basically consists of ciliated, goblet, basal, microvillous-apex, and migratory cells. Two types of goblet cells are distinguished with regard to the granular ultrastructure. The microvillous-apex cell has not been found in other amphibians. It shows a very differentiated morphology with a high number of mitochondria. The basal cells give the epithelium a pseudostratified morphology, and they have a proliferative function. Glands are branched and drain through an excretory duct that has a monolayered mucosecreting epithelium. The glandular units are formed by two principal types of cells: mucosecretory and serous.

Animals↗

Chondrocranial development in larval Rana sylvatica (Anura: Ranidae): morphometric analysis of cranial allometry and ontogenetic shape change.

This study provides baseline quantitative data on the morphological development of the chondrocranium in a larval anuran. Both linear and geometric morphometric methods are used to quantitatively analyze size-related shape change in a complete developmental series of larvae of the wood frog, Rana sylvatica. The null hypothesis of isometry was rejected in all geometric morphometric and most linear morphometric analyses. Reduced major axis regressions of 11 linear chondrocranial measurements on size indicate a mixture of allometric and isometric scaling. Measurements in the otic and oral regions tend to scale with negative allometry and those associated with the palatoquadrate and muscular process scale with isometry or positive allometry. Geometric morphometric analyses, based on a set of 11 chondrocranial landmarks, include linear regression of relative warp scores and multivariate regression of partial warp scores and uniform components on log centroid size. Body size explains about one-quarter to one-third of the total shape variation found in the sample. Areas of regional shape transformation (e.g., palatoquadrate, otic region, trabecular horns) are identified by thin-plate spline deformation grids and are concordant with linear morphometric results. Thus, the anuran chondrocranium is not a static structure during premetamorphic stages and allometric patterns generally follow scaling predictions for tetrapod cranial development. Potential implications regarding larval functional morphology, cranial development, and chondrocranial evolution in anurans are discussed.

Animals↗

Structural differences between XX and ZW sex lampbrush chromosomes in Rana rugosa females (Anura: Ranidae).

In this study we investigated the morphology and pairing behavior of sex lampbrush chromosomes of XX and ZW females of Rana rugosa from five localities in Japan. Whereas lampbrush chromosomes of XX females from Hiroshima and Isehara had subterminally located centromeres and showed remarkable similarity, those of XX females from Hamakita had the centromeres in the middle. Analysis of landmark configurations revealed that chromosome Xq of Hamakita females closely resembled a part of Xq of Hiroshima and Isehara females, whereas Xp of Hamakita females was inverted compared with the other part of Xq of Hiroshima and Isehara females. Z chromosomes from Kanazawa and Niigata closely resembled the Hiroshima X, whereas the W closely resembled the Hamakita X. XX pairings from Hiroshima, Isehara, and Hamakita were found to be joined by one to four chiasmata at various points all along the axis in both the short and long arms, whereas chromosomal pairs from Kanazawa and Niigata showed only one chiasma between Zp and the distal region of Wq. From these findings we conclude that (1) both the W and the Hamakita X must have evolved from the more primitive Hiroshima and Isehara X chromosomes by a series of pericentric inversions; and (2) females distributed in Hamakita possess two X chromosomes similar to the W, suggesting that either sex-determining or sex-modifying genes on the Hamakita X are clearly different from those on the Kanazawa and Niigata W chromosome.

Animals↗

Opposite effects of cooling on twitch contractions of skeletal muscle isolated from tropical toads (Leptodactylidae) and northern frogs (Ranidae).

Cooling increases the twitch force of frog skeletal muscle (Rana temporaria; Rana pipiens), but decreases the twitch force of tropical toad muscle (Leptodactylus insularis). Action potentials and intramembranous charge movement in frog and toad fibers were slowed identically by cooling. Cooling increased the integral of twitch Ca2+ detected by aequorin in frog fibers (1.4-fold), while also decreasing the peak and slowing the rate of decay. Conversely, cooling decreased the integral (0.6-fold) and the peak of twitch Ca2+ in toad fibers, without affecting the rate of decay. The difference in entire Ca2+ transients may account for cold-induced twitch potentiation in frogs and twitch paralysis in toads. In sustained contractions of toad fibers, cooling markedly decreased maximum force caused by: (i) tetanic stimulation, (ii) two-microelectrode voltage clamp steps, (iii) high [K+], or (iv) caffeine. Maximum force in sustained contractions was decreased moderately by cooling frog fibers. Rapid rewarming and simultaneous removal of high [K+] or caffeine during a sustained contraction, caused toad muscle force to rise towards the value corresponding to the warm temperature. This did not occur after removing high [K+] or caffeine from toad fibers kept in the cold. Transmission electron micrographs showed no relevant structural differences. Parvalbumins are thought to promote relaxation of frog muscle in the cold. The unique parvalbumin isoforms in toad muscle apparently lack this property.

Animals↗

Evidence for two successive pericentric inversions in sex lampbrush chromosomes of Rana rugosa (Anura: Ranidae).

The objective of this study was to clarify the course of inversions by which a ZW sex chromosome dimorphism has become established in Rana rugosa. Fortunately, R. rugosa preserves three different forms of sex chromosomes in the several isolated populations. In both males and females, the homomorphic sex chromosomes from Hiroshima were closely similar to Z, while those from Isehara were slightly different from the Z. Females from Hirosaki demonstrated heteromorphic sex chromosomes. In this study, the configuration and pairing behavior of sex lampbrush chromosomes were examined in the female offspring produced from a cross between a female from Hiroshima and a male from Isehara, as well as the female offspring of a female from Hirosaki and the male from Isehara. For the sex lampbrush chromosomes from Hiroshima and Isehara, chiasmata were exclusively formed between the distal regions of the long arms of one sex chromosome and the terminal regions of the short arms of the other. As a result, landmarks arranged in reverse order were observed in the achiasmatic regions of these chromosomes. For the sex lampbrush chromosomes from Isehara and Hirosaki, on the other hand, chiasma formation was mainly confined to the lower half of the chromosomes corresponding to the long arms, and the landmarks in the achiasmatic regions of these chromosomes were disposed in the opposite direction to each other. These results seem to indicate that in the primitive sex chromosomes of the Hiroshima type two pericentric inversions occurred, leading to the differentiation of the W chromosomes. This is the first report to substantiate the process of sex chromosome differentiation experimentally.

Animals↗

Electrophoretic and morphometric evidence for two species of the genus Rana (Amphibia, Ranidae) and some aspects of their variabilities.

Frogs of two species, genus Rana, R. mascareniensis and R. levantina from northern Egypt, were examined using electrophoresis for 15 presumptive loci and measuring of 11 morphological characters, employing discriminate and principle component analysis. Electrophoretic and morphometric data showed clear interspecific differences. Using serum and tissue electrophoresis all individuals of R. mascareniensis had no intraspecific variabilities but R. levantina showed some intraspecific variabilities.

Alleles↗

Evidence for heteromorphic sex chromosomes in males of Rana tagoi and Rana sakuraii in Nishitama district of Tokyo (Anura: Ranidae).

Karyotypes of the Tago brown frog Rana tagoi and stream Tago brown frog Rana sakuraii from a mountain region in the Nishitama district in Tokyo were examined by conventional Giemsa staining, C-banding and late replication (LR)-banding. Chromosome number was 2n = 26 in all cases. The 26 chromosomes consisted of five (1-5) pairs of large chromosomes and eight (6-13) pairs of small chromosomes. Chromosome 10 had a secondary constriction on the long arm. In all frogs, on chromosome pair 8, the XX/XY type sex chromosome was present. C-banding analysis indicated that, in R. sakuraii, neither the X nor Y chromosome possessed interstitial C-bands but each had centromere staining, while in R. tagoi, an interstitial C-band was present on the long arm of the X chromosome. The Y chromosome had no interstitial C-band. LR-banding analysis demonstrated the X and Y chromosomes to have a LR-band on the short arm and two LR-bands, each on the long arm, and the bands on both species to be essentially the same. Heteromorphic sex chromosomes in males of R. sakuraii and R. tagoi were identified for the first time in this study.

Animals↗

Phylogeography and conservation genetics of the Columbia spotted frog (Rana luteiventris; Amphibia, Ranidae).

The Columbia spotted frog (Rana luteiventris) has a widespread distribution in western Canada and the western US, although the southern reach of its range is highly fragmented into several isolated populations. Threats from various factors have raised concerns regarding the long-term survival of many small, isolated populations. Here, we report a study designed to determine the phylogeographic and conservation genetic parameters of R. luteiventris in the western US. Mitochondrial DNA (mtDNA) sequences were examined for phylogeographic structuring using phylogenetic reconstruction methods, coupled with networking and nested clade analyses. These methods permitted a distinction to be made between historic and demographic forces acting to generate geographical patterning of genetic variation. Phylogenetic analysis revealed four geographically correlated monophyletic clades. Three of these clades correspond to well-defined, nonoverlapping geographical locations in the fragmented portion of the range. The other is comprised of all samples collected from the contiguous range and includes one isolate from northern Wyoming. Networking and nested clade analyses confirmed these results and revealed that historical processes, such as range expansion and vicariance, rather than recurrent gene flow are likely responsible for observed patterns of genetic variation. A measure of genetic variation (theta = 4N(e)mu) revealed that R. luteiventris populations in Utah have a relatively low amount of genetic variation compared with populations in the continuous portion of the range.

Animals↗