Enameloid/enamel transition through successive tooth replacements in <Emphasis Type="Italic">Pleurodeles waltl</Emphasis> (Lissamphibia,Caudata)

Study of the evolutionary enameloid/enamel transition suffers from discontinuous data in the fossil record, although a developmental enameloid/enamel transition exists in living caudates, salamanders and newts. The timing and manner in which the enameloid/enamel transition is achieved during caudate ontogeny is of great interest, because the caudate situation could reflect events that have occurred during evolution. Using light and transmission electron microscopy, we have monitored the formation of the upper tooth region in six successive teeth of a tooth family (position I) in Pleurodeles waltl from late embryos to young adult. Enameloid has only been identified in embryonic tooth I₁ and in larval teeth I₂ and I₃. A thin layer of enamel is deposited later by ameloblasts on the enameloid surface of these teeth. From post-metamorphic juvenile onwards, teeth are covered with enamel only. The collagen-rich enameloid matrix is deposited by odontoblasts, which subsequently form dentin. Enameloid, like enamel, mineralizes and then matures but ameloblast participation in enameloid matrix deposition has not been established. From tooth I₁ to tooth I₃, the enameloid matrix becomes ever more dense and increasingly comes to resemble the dentin matrix, although it is still subjected to maturation. Our data suggest the absence of an enameloid/enamel transition and, instead, the occurrence of an enameloid/dentin transition, which seems to result from a progressive slowing down of odontoblast activity. As a consequence, the ameloblasts in post-metamorphic teeth appear to synthesize the enamel matrix earlier than in larval teeth.     

中国拟小鲵属(有尾目,小鲵科)一新种记述

在比较和研究拟小鲵属已知物种黄斑拟小鲵、水城拟小鲵后,确定贵州省绥阳县宽阔水所产拟小鲵为1新种,即宽阔水拟小鲵Pseudohynobius kuankuoshuiensis.新种与黄斑拟小鲵近似,但新种体尾背面黄斑近圆形,头长与头宽之比大于1.55,可与之区分.新种与水城拟小鲵P.shuichengensis相似,但新种体尾及四肢背面有黄色斑块,四肢贴体相向时掌、踱部前半不重叠,而极易与之相区别.     

Foraging behaviour in tadpoles of the bronze frog<Emphasis Type="Italic">Rana temporalis</Emphasis>: Experimental evidence for the ideal free distribution

The ability of bronze frogRana temporalis tadpoles (pure or mixed parental lines) to assess the profitability of food habitats and distribute themselves accordingly was tested experimentally using a rectangular choice tank with a non-continuous input design. Food (boiled spinach) was placed at two opposite ends of the choice tank in a desired ratio (1:1, 1:2 or 1:4) to create habitat A and B. The tadpoles in Gosner stage 28–33, pre-starved for 24 h, were introduced in an open ended mesh cylinder placed in the center of the choice tank, held for 4 min (for acclimation) and then released to allow free movement and habitat selection. The number of tadpoles foraging at each habitat was recorded at 10, 15, 20, 25 and 30 min time intervals. The actual suitability,S _i (the food available in a habitat after colonization of tadpoles) of each habitat was obtained from the equationS _i =B _i−f _i (d _i) whereB _i is basic suitability (amount of food provided at each habitat before release of tadpoles),f _i is the rate of depletion of food (lowering effect) with introduction of each tadpole, andd _i is the density of tadpoles in habitati. The expected number of tadpoles at each habitat was derived from the actual suitability. With no food in the choice tank, movement of the tadpoles in the test arena was random indicating no bias towards any end of the choice tank or the procedure. In tests with a 1:1 food ratio, the observed ratio of tadpoles (11.71: 12.28) was comparable with the expected 12:12 ratio. The observed number of tadpoles in the habitats with a 1:2 food ratio was 8.71:15.29 and 7.87:16.13 for pure and mixed parental lines respectively. In both cases, the observed ratios were close to the expected values (7:17). Likewise, in experiments with a 1:4 food ratio, the observed number of tadpoles in the two habitats (10.78:37.22) did not differ significantly from the expected ratio of 7:41. In all tests, the number ofR. temporalis tadpoles matched ideally with habitat profitability (undermatching indexK ≜ 1. The study shows that tadpoles of the bronze frog exhibit an ideal free distribution while foraging regardless of whether they are siblings or non-siblings in a group, which correlates well with their group living strategy in nature.     

Atrial natriuretic peptide (ANP) system in the lung of Rana esculenta

The atrial natriuretic peptide (ANP)-system was examined in Rana esculenta lung with cytochemical and immunocytochemical methods. The results showed a cellular type that synthesizes the hormone and the presence of receptors in various components of the lung. The lung, therefore, produces ANP and at the same time is a target organ for the hormone. ANP may play an important physiological role in pulmonary function and in protecting against pulmonary edema.     

An integrative assessment of the taxonomic status of putative hybrid leopard frogs (Anura: Ranidae) from the Chortís Highlands of Central America,with description of a new species

Integrative taxonomy seeks to approach the complex topic of species diagnosis using independent, complementary lines of evidence. Despite their ubiquity throughout North and Central America, taxonomy of the American leopard frogs (Anura: Ranidae: Rana: subgenus Pantherana) remains largely unresolved, and this is arguably nowhere truer than in the Central American country of Honduras, where there are two nominal species, the taxonomy of which remains unresolved. Leopard frogs from several mountainous areas along the continental divide in Honduras have previously been considered putative hybrids between Rana brownorum and R. cf. forreri, as opposed to two alternate hypotheses: one that they represent a high-altitude eco-morph of a single widespread species that included both lowland forms, or a second that there is an undescribed highland species distinct from either of the recognized lowland forms. We examine this set of hypotheses using three independent lines of evidence. First, we used species distribution modelling to examine potential geographic isolation of the highland form and the two putative parental lowland species, and found strong ecological separation between the highland and lowland forms. Second, mitochondrial and nuclear DNA supports the distinction of the highland form from both putative parental species, with mtDNA data refuting the hypothesis that representatives of either species may represent a matrilineal founder. Morphologically, the highland form is significantly smaller than, and otherwise readily differentiated from, both R. brownorum and R. cf. forreri, as well as all other Rana found in Honduras and adjacent areas. As a result, we formally describe the highland leopard frog as a new species.

http://zoobank.org/urn:lsid:zoobank.org:pub:BE53F587-3618-4433-9651-E495808E5474     

Contribution à l'étude ultrastructurale des cellules interrénales de Salamandra salamandra L. (Amphibien Urodèle)

Summary The interrenal (adrenocortical) cells of spotted Salamanders seriously affected by a mycotic disease for a long period, have a strikingly large dimension. Their nuclei and nucleoli show a marked hypertrophy. The cytoplasm is sometimes completely deprived of liposomes; it is very rich in mitochondria, smooth-surfaced reticular tubules and free ribosomes. Ergastoplasmic cisternae are frequently encountered in the vicinity of the nuclei. The Golgi apparatus is considerably developed. This organisation, which is common to all the cells, characterizes a stage of intense activity of hormonal synthesis, probably induced by high levels of ACTH. Beside these typical features, small dense bodies are particularly abundant at the periphery of the cells. No mitotic division could be seen.In Salamanders which suffer only moderately from the disease, the cells of the central part of the interrenal islets are the only ones to show the characteristics of great activity. On the other hand it can be noted that such cells are the more numerous the more the situation of the islet is cranial. As opposed to this, the cells of the periphery of the islets show only signs of a poor activity.During the extension of the disease, the number of highly active cells increases progressively, probably as a consequence of the activation of the peripheral cells. This activation usually begins with the hypertrophy of the nucleus and the nucleolus. The cytoplasmic modifications (namely the lipid depletion and the apparition of numerous dense bodies in the vicinity of the Golgi apparatus) seem to appear during a second stage only.

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Zusammenfassung Die Interrenalzellen von Feuersalamandern, welche seit längerer Zeit an einer Pilzkrankheit schwer leiden, zeigen einen ungewöhnlich großen Durchmesser. Ihre Zellkerne samt Nukleoli sind überentwickelt. Das Zytoplasma ist hie und da frei von Liposomen, zeigt aber überaus zahlreiche Mitochondrien, glatte Tubuli des endoplasmatischen Retikulums und freie Ribosomen. In der Nähe des Zellkerns trifft man häufig ergastoplasmatische Zisternen an. Der Golgi-Apparat ist stark ausgebildet. Diese Organisation, die man in allen Zellen wiederfindet, deutet auf eine starke Aktivität der Hormonsynthese hin, die wahrscheinlich unter dem Einfluß von hohem und andauerndem ACTH-Gehalt steht. Ferner findet man kleine elektronendichte Körper, vor allem häufig an der Peripherie der Zellen. Mitotische Zellteilungen wurden nicht beobachtet.Bei Salamandern, die von der Erkrankung weniger befallen waren, zeigen nur die inneren Zellen der Interrenalinseln Äquivalente einer starken Aktivität. Sie sind im übrigen desto zahlreicher, je weiter cranial die Interrenalinsel liegt. Die Zellen in der Peripherie dagegen tragen die Merkmale einer schwachen Aktivität.Im Laufe der Krankheit nimmt die Zahl der hochaktiven Zellen fortwährend zu, wahrscheinlich infolge der Aktivierung der Zellen der Peripherie. Diese Aktivierung beginnt mit der Vergrößerung der Zellkerne und Nukleoli. Die zytoplasmatischen Veränderungen, insbesondere das Verschwinden der Liposomen und das Erscheinen von elektronendichten Körpern in der Nachbarschaft des Golgi-Apparates, scheinen in einer zweiten Phase aufzutreten.

     

Development of hearing in vertebrates with special reference to anuran acoustic communication

Amphibians, specially anurans, are excellent model systems for studying acoustic communication. After hatching, anurans exist in two forms; these have two distinct mode of sound perception. Aquatic larvae are perceptive to waterborne sound stimuli; then, following metamorphosis, as terrestrial adults, perceptive to airborne sound stimuli. Added to this, the metamorphosing tadpole presents an equally interesting study as it could recapitulate the events which occurred during the evolution of hearing in vertebrates at the lime of the transition from aquatic to terrestrial life. Metamorphosis entails the loss of a prominent aquatic sensory system—the lateral line system—and the simultaneous gain of another, the inner ear, along with the coevolution of the tympanic middle ear, a basilar papilla and a periotic labyrinth in the inner ear. Another interesting feature is that anurans are believed to be the first terrestrial vertebrates to use vocalization as a part of their reproductive behaviour. Vocal communication plays an important role in behaviour, ranging from territorial defense to reproduction, and calls are classified according to the particular behaviors that they subserve. Adult male anurans produce a species-specific mating call which is used to attract conspecific females dung their mating season, and this call serves as a mechanism in maintaining reproductive isolation from other sympatric species.     

中国蛙科─新种──福建大头蛙（两栖纲：无尾目）

本文对我国各地的大头蛙属Ｌｉｍｎｏｎｅｃｔｅｓ作了进一步研究,认为福建等地标本与Ｌ．ｋｕｈｌｉｉ（ＤｕｍｅｒｉｌｅｔＢｉｂｒｏｎ）有明显区别,被确定为新种,即福建大头蛙Ｌ．ｆｕｊｉａｎｅｎｓｉｓｓｐ．ｎｏｖ．。模式标本保存在中国科学院成都生物研究所。     

On the trophic spectrum of Pelophylax ridibundus (Pallas, 1771) (Amphibia: Anura: Ranidae) in western Iran

Using the stomach flushing technique, a total of 188 specimens of the Marsh Frog, Pelophylax ridibundus, were flushed, of which 129 had at least one food item in the stomach. The diet consisted of Annelida, Mollusca, Arthropoda and Chordata with Arthropoda being the most abundant group. Both diet volume and number of food items per stomach were significantly larger in April than in August. The proportion of frequency of occurrence (FOi%) of food categories did not show a constant food item in flushed materials. Pelophylax ridibundus prefers Diptera, Coleoptera, Amphipoda and Hymenoptera over other food categories. The Index of Relative Importance (IRI) for food categories differs between sexes and seasons. Differences were found in the food volume and the number of food items between seasons, but not between sexes. Prey volume is positively correlated with frog size.     

The evolution of parental investment in caecilian amphibians: a comparative approach

Parental care is widespread among vertebrates and the observed patterns of parental care and investment are extremely diverse. Among amphibians, caecilians (Gymnophiona) exhibit considerable variation in reproductive modes, including both oviparity and viviparity, combined with highly unusual investment strategies (e.g. skin‐feeding and intrauterine feeding). In the present study, current knowledge on the reproductive modes is integrated into an analysis of the evolutionary scenario of parental investment of caecilians. Phylogenetically basal caecilians possessing a biphasic life cycle that includes an aquatic larval stage invest in macrolecithal eggs directly corresponding to size at hatching. Some phylogenetically derived caecilians (i.e. the Teresomata) have a smaller clutch size and show a reduction to either medium‐yolked (mesolecithal) or small‐yolked (microlecithal) eggs. Via alternative pathways of parental investment, such as intrauterine feeding in viviparous taxa and maternal dermatotrophy in oviparous taxa, teresomatan caecilians increase both offspring size and quality. However, more data regarding reproductive biology are needed to obtain a fully resolved understanding of the evolution of reproduction in caecilian amphibians.