Social and environmental influences on egg size evolution in frogs

The reproductive strategies of frogs are highly diverse, but analysis of these strategies in a phylogenetic context has lagged behind other taxa. Here we investigate associations between aspects of parental care and egg size in a phylogenetic context. We obtained data on egg size and parental care strategies in various species of frogs from the scientific literature. We developed a phylogenetic supertree of frogs by combining the results of multiple phylogenetic analyses using matrix representation parsimony. We used phylogenetic pairwise comparisons to investigate the correlation between various forms of parental care and egg size across the order Anura. We also investigated correlations between tadpole carnivory and egg size, and phytotelm breeding and egg size. We also investigated the association of egg size with several environmental factors. Parental care, male parental care, direct development, stream breeding and montane breeding habitats were all associated with large egg size. Female care (in species with trophic egg feeding), carnivory, use of small pools (phytotelmata) and use of temporary pools were not associated with egg size.     

Molecular phylogeny of the family Dicroglossidae (Amphibia: Anura) inferred from complete mitochondrial genomes

The fork-tongued frogs, members of the amphibian Order Anura, belong to the family Dicroglossidae and are one of the most diverse groups of Anuran frogs; however, their taxonomy and phylogeny remain controversial. In the present study, sixteen dicroglossine mitochondrial genomes representing nine dicroglossine genera and 23 other neobatrachian taxa, were used to reconstruct the phylogenetic relationships of the family Dicroglossidae using different partitioned maximum likelihood and partitioned Bayesian inference methods at both the nucleotide and amino acid levels. The sampled fork-tongued frogs form a strongly supported monophyletic group that is the sister taxon to another well-supported clade that includes representatives of the families Ranidae, Rhacophoridae, and Mantellidae. The monophyly of the subfamily Occidozyginae and Dicroglossinae was revealed with strong supports, and two major clades were supported within Dicroglossinae. The sister-group relationship between the genera Limnonectes and the tribe Paini was supported. In addition, a sister-group relationships between Fejervarya and Euphlyctis + Hoplobatrachus, between Quasipaa and Yerana, and between Feirana and Nanorana are well supported. Estimates of divergence times revealed the divergence of Dicroglossidae during the Late Upper Cretaceous to the Early Eocene, and diversification of the major dicroglossine genera from the Early Eocene to the Middle Miocene.     

Differential Evolution of Advertisement Call Traits in Dart-Poison Frogs (Anura: Dendrobatidae)

The ability to recognise and discriminate between heterospecific and conspecific individuals plays an essential role in mate choice, reproductive isolation and thus species diversification. Many animals discriminate based on advertisement calls, whose evolution may be driven by a variety of forces such as natural selection, sexual selection or stochastic processes. The relative importance of stochastic processes acting on a given trait is usually correlated with its phylogenetic signal. Mate-recognition signals are complex traits composed of multiple features that could potentially respond independently to evolutionary forces. The advertisement call of anurans is used in species recognition and mate choice. In this study, we estimate the phylogenetic signal for body size and a suite of traits describing the male advertisement call from dart-poison frogs (Anura: Dendrobatidae). We found a surprisingly high phylogenetic signal for all call traits. In addition, call traits varied in their degree of phylogenetic signal, suggesting that evolutionary forces have been acting differently on different traits. Pulse duration showed the strongest phylogenetic signal. Peak frequency and body size were correlated and presented high phylogenetic signal indicating that the evolution of one trait may be driving or constraining the other. Since most variation in call traits can be explained by the phylogenetic history of the species, we cannot reject the hypothesis that stochastic processes account for significant evolutionary divergence in frog calls.     

Archaeobatrachian paraphyly and pangaean diversification of crown-group frogs

Current models for the early diversification of living frogs inferred from morphological, ontogenetic, or DNA sequence data invoke very different scenarios of character evolution and biogeography. To explore central controversies on the phylogeny of Anura, we analyzed nearly 4000 base pairs of mitochondrial and nuclear DNA for the major frog lineages. Likelihood-based analyses of this data set are congruent with morphological evidence in supporting a paraphyletic arrangement of archaeobatrachian frogs, with an (Ascaphus + Leiopelma) clade as the sister-group of all other living anurans. The stability of this outcome is reinforced by screening for phylogenetic bias resulting from site-specific rate variation, homoplasy, or the obligatory use of distantly related outgroups. Twenty-one alternative branching and rooting hypotheses were evaluated using a nonparametric multicomparison test and parametric bootstrapping. Relaxed molecular clock estimates situate the emergence of crown-group anurans in the Triassic, approximately 55 million years prior to their first appearance in the fossil record. The existence of at least four extant frog lineages on the supercontinent Pangaea before its breakup gains support from the estimation that three early splits between Laurasia- and Gondwana-associated families coincide with the initial rifting of these landmasses. This observation outlines the potential significance of this breakup event in the formation of separate Mesozoic faunal assemblages in both hemispheres.     

The Ultrastructure of the Spermatozoa of Three Species of Myobatrachid Frogs (Anura,Amphibia) with Phylogenetic Considerations

Comparison of the spermatozoa of three genera of limnodynastines (Myobatrachidae: Anura) with those of 42 other species of frogs (in 11 families) previously examined allows the following phylogenetic inferences. The bufonoid neobatrachians (corresponding with the Arcifera of some classifications) form a monophyletic assemblage which is characterized by the possession, unique for the Anura, of a conical perforatorium; the rod-like perforatorium, which is plesiomorphic for tetrapods, is absent. Of the taxa investigated, the myobatrachids appear to be the sister-group of the remaining bufonoids, here termed eubufonoids (leptodactylids, rhinodermatids, hylids, and bufonids). The spermatozoa of the myobatrachids Limnodynastes, Neobatrachus, and Mixophyes are very similar to each other despite extremely varied fertilization biology. Symplesiomorphies for the Anura which they exhibit include the conical acrosome with subacrosomal material, the elongate, cylindrical nucleus, single flagellum and, paralleling this, an undulating membrane which is supported by a longitudinal element, the axial (major) fibre, the latter being accompanied in the midpiece by mitochondria. A myobatrachid synapomorphy appears to be the presence of a periaxial sheath enclosing the axial fibre of the flagellum. Forward extension of the axial fibre into the centriolar fossa in myobatrachids is seen elsewhere only exceptionally (in the bufonid Nectophrynoides). Bufonids, and most other eubufonoids including leptodactylids, differ apomorphically from Limnodynastes, and Neobatrachus in location of the mitochondria at the axonemal end (and in a collar) rather than the axial fibre end of the undulating membrane. In Mixophyes, mitochondria surround the nuclear-axonemal junction in a cytoplasmic droplet and are probably shed with this at maturity.     

Phylogenetic relationships of discoglossid frogs (Amphibia:Anura:Discoglossidae) based on complete mitochondrial genomes and nuclear genes

The complete nucleotide sequence of the mitochondrial (mt) genome was determined for three species of discoglossid frogs (Amphibia:Anura:Discoglossidae), representing three of the four recognized genera: Alytes obstetricans, Bombina orientalis, and Discoglossus galganoi. The organization and size of these newly determined mt genomes are similar to those previously reported for other vertebrates. Phylogenetic analyses (maximum likelihood, Bayesian inference, minimum evolution, and maximum parsimony) of mt protein-coding genes at the amino acid level were performed in combination with already published mt genome sequence data of three species of Neobatrachia, one of Pipoidea, and four of Caudata. Phylogenetic analyses based on the deduced amino acid sequences of all mt protein-coding genes arrived at the same topology. The monophyly of Discoglossidae is strongly supported. Within the Discoglossidae, Alytes is consistently recovered as sister group of Discoglossus, to the exclusion of Bombina. The three species representing Neobatrachia exhibited extremely long branches irrespective of the phylogenetic inference method used, and hence their relative position with respect to Discoglossidae and Xenopus may be artefactual due to a severe long branch attraction effect. To further investigate the phylogenetic intrarelationships of discoglossids, nucleotide sequences of four nuclear protein-coding genes (CXCR4, RAG1, RAG2, and Rhodopsin) with sequences available for the three discoglossid genera and Xenopus were retrieved from GenBank, and together with a concatenated nucleotide sequence data set containing all mt protein-coding genes except ND6 were subjected to separate and combined phylogenetic analyses. In all cases, a sister group relationship between Alytes and Discoglossus was recovered with high statistical support.     

A Model for Taxonomic Work on Homoxenous Coccidia: Redescription, Host Specificity, and Molecular Phylogeny of Eimeria ranae Dobell, 1909, with a Review of Anuran-Host Eimeria (Apicomplexa: Eimeriorina)

ABSTRACT. We attempt to extend knowledge of anuran Eimeria , and to provide a model for a complex approach to studies on coccidia. New host and geographic records of coccidia in European Anura are provided. In the second part, Eimeria ranae Dobell, 1909 is redescribed from European terrestrial frogs of the genus Rana based on light microscopic and ultrastructural data on both exogenous and endogenous developmental stages, host specificity, and molecular phylogenetic data. Results of experimental transmissions show for the first time that the host specificity of E. ranae is restricted to the genus Rana and that isolates from tadpoles and adults are conspecific. Disappearance of infection during metamorphosis was confirmed experimentally, suggesting that infections in adults result from reinfections. Poikilotherm-host Eimeria species possessing a Stieda body (SB) are for the first time included in a molecular phylogenetic analysis. Eimeria ranae and Eimeria arnyi from a colubrid snake form together a well-supported clade, basal to other SB-bearing coccidia. The other analysed reptile–host eimerians, Eimeria tropidura and Choleoeimeria sp., which possess bivalved sporocysts and lack a SB, represent a distinct basal lineage of the eimeriid clade. The third part of the article reviews anuran-host Eimeria . Three distinct oocyst morphotypes, apparently correlating with the character of endogenous development, are recognized and characterized among anuran eimeriids.     

Complete nucleotide sequences and gene organization of mitochondrial genome of Bufo gargarizans

The complete mitochondrial genome of Bufo gargarizans was sequenced using overlapping polymerase chain reaction (PCR) amplicons (GenBank Accession No. DQ275350). The genome is 17,277 base pairs in length, containing 13 protein-coding genes (ATP6, ATP8, COI-III, ND1-6, ND4L, Cyt b), 2 ribosomal RNAs (12S rRNA and 16S rRNA), 22 transfer RNAs and a putative control region. We analyzed the sequence using bioinformatics methods comparing the obtained mtDNA sequence with other toads and frogs. Based on the concatenated nucleotide sequences of protein-coding genes, we constructed a phylogenetic tree with maximum likelihood (ML) and maximum parsimony (MP) methods and discussed the phylogenetic relationships among 11 species of Anura.     

Phylogenetic patterns of diversification in a clade of Neotropical frogs (Anura: Aromobatidae: Mannophryne)

We used partial sequences of mitochondrial 16S and cytochrome oxidase I genes to perform a phylogenetic study of collared frogs (Anura: Aromobatidae: Mannophryne ), a genus endemic to Venezuela and the islands of Trinidad and Tobago. We analysed 1.2 kb from 13 of the 15 described species of Mannophryne . Maximum parsimony, maximum likelihood and Bayesian analyses support the monophyly of Mannophryne . Mannophryne consists of three deeply differentiated clades that split from each other in a relatively short period of time. The diversification of Mannophryne occurred well before the glacial-interglacial periods of the Quaternary. Our data support the taxonomic validity of M. olmonae , a species endemic to Tobago Island. Mannophryne olmonae is more closely related to the continental species Mannophryne riveroi than to the Trinidad island endemic Mannophryne trinitatis . As in most tropical clades of frogs, molecular evidence indicates that species richness in Mannophryne is largely underestimated and, consequently, current priorities for conservation are inadequate.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 97 , 185–199.     

How much fruit do fruit-eating frogs eat? An investigation on the diet of Xenohyla truncata (Lissamphibia: Anura: Hylidae)

This paper presents the results of a 22-month survey and the examination of the intestinal content of 356 specimens of Xenohyla truncata (Anura: Hylidae) from Restinga de Maricá, Rio de Janeiro, Brazil. Our results confirm prior observations that fruits are intrinsic to the diet of these frogs. In addition, these new data increase our understanding of the relationship between frogs and the plants they feed upon. Plant consumption follows availability of fruits in the area, indicating that the diversity of fruits consumed by the frogs does not represent choice, but rather plant phenology and fruit availability.     

The larval hyobranchial apparatus of discoglossoid frogs: its structure and bearing on the systematics of the Anura (Amphibia: Anura)

The morphology of the larval hyobranchial apparatus of discoglossoid frog species representing the genera Ascaphus, Alytes, Bombina, and Discoglossus is described and the resulting characters were analysed cladistically. Seven species representing seven major lineages of frogs were included in the cladistic analysis of characters. Several changes in the terminology of the musculature are introduced, and a new interpretation of the subarcualis-muscle system is presented. The phylogenetic analysis suggest that the hyobranchial apparatus was substantially altered in the lineages leading to and within the Pipanura. This notably involved fusion, reduction and loss of skeletal structures and muscles, and splitting of certain muscles into muscle groups. The result confirm previous hypotheses based on the study of adults: discoglossoid species retain the most numlerous plesiomorphic characters among extant ianurans. The larval hyobranchial apparatus is in many features structrually similar to that of urodeles. Many of their character states were most likely present in the most recent common ancestor of all living forgs. The cladistic analysis of 31 characters of ithe larval hyobranchial apparatus supports major clades: Anura, Bombinanura, Pipanura, and Pelobatoidea + Neobatrachia. The cladiostic analysis and interpretation of larval characters is in part compatible with phylogenetic hypotheses based on characters of adults and rRNA sequences, but is in conflict with the Mesobatrachia and Archaeobatrachia concepts of other authors.     

Recovering phylogenetic signal from frog mating calls

Goicoechea, N., De La Riva, I. & Padial, J. M. (2010). Recovering phylogenetic signal from frog mating calls. —Zoologica Scripta, 39, 411–154. Few studies have tried to analyse the phylogenetic information contained in frog mating calls. While some of those studies suggest that sexual selection deletes any phylogenetic signal, others indicate that frog calls do retain phylogenetic informative characters. Discordant results can be the outcome of disparate rates of character evolution and evolutionary plasticity of call characters in different groups of frogs, but also the result of applying different coding methods. No study to date has compared the relative performance of different coding methods in detecting phylogenetic signal in calls, hampering thus potential consilience between previous results. In this study, we analyse the strength of phylogenetic signal in 10 mating call characters of 11 related species of frogs belonging to three genera of Andean and Amazonian frogs (Anura: Terrarana: Strabomantidae). We use six quantitative characters (number of notes per call, note length, call length, number of pulses per note, fundamental frequency and dominant frequency) and four qualitative ones (presence/absence of: pseudopulses, frequency modulation in notes, amplitude modulation in notes and amplitude modulation in pulses). We code quantitative characters using four different coding and scaling methods: (i) gap‐coding, (ii) fixed‐scale, (iii) step‐matrix gap‐weighting with between‐characters scaling, and (iv) step‐matrix gap‐weighting with between‐states scaling. All four coding methods indicate that frog calls contain phylogenetic information. These results suggest that divergent selection on frog mating calls may not always be strong enough to eliminate phylogenetic signal. However, coding methods strongly affect the amount of recoverable information. Step‐matrix gap‐weighting with between‐characters scaling and gap‐coding are suggested as the best methods available for coding quantitative characters of frog calls. Also, our results indicate that the arbitrariness in selecting character states and the method for scaling transitions weights, rather than the number of character states, is what potentially biases phylogenetic analyses with quantitative characters.     

重金属污染对蛙蟾类毒性的研究进展

基于近20年的大量相关资料,综述了重金属对蛙蟾类毒性影响方面的研究,介绍了实验动物和实验方法,综合了重金属对蛙蟾类在形态、器官、组织、细胞和分子水平上毒害的主要表现,从重金属致毒过程、环境因素、物种、发育、重金属积累、联合毒性等角度初步分析了重金属对蛙蟾毒性大小的影响因素和毒性作用的主要机理,归纳了蛙蟾的几种抗毒/解毒/避毒反应,对开展进一步的研究提出建议.     

The evolution of jumping in frogs: Morphological evidence for the basal anuran locomotor condition and the radiation of locomotor systems in crown group anurans

Our understanding of the evolution of frog locomotion follows from the work of Emerson in which anurans are proposed to possess one of three different iliosacral configurations: 1) a lateral‐bending system found in walking and hopping frogs; 2) a fore‐aft sliding mechanism found in several locomotor modes; and 3) a sagittal‐hinge‐type pelvis posited to be related to long‐distance jumping performance. The most basal living (Ascaphus) and fossil (Prosalirus) frogs are described as sagittal‐hinge pelvic types, and it has been proposed that long‐distance jumping with a sagittal‐hinge pelvis arose early in frog evolution. We revisited osteological traits of the pelvic region to conduct a phylogenetic analysis of the relationships between pelvic systems and locomotor modes in frogs. Using two of Emerson's diagnostic traits from the sacrum and ilium and two new traits from the urostyle, we resampled the taxa originally studied by Emerson and key paleotaxa and conducted an analysis of ancestral‐character state evolution in relation to locomotor mode. We present a new pattern for the evolution of pelvic systems and locomotor modes in frogs. Character analysis shows that the lateral‐bender, walker/hopper condition is both basal and generally conserved across the Anura. Long‐distance jumping frogs do not appear until well within the Neobatrachia. The sagittal‐hinge morphology is correlated with long‐distance jumping in terrestrial frogs; however, it evolved convergently multiple times in crown group anurans with the same four pelvic traits described herein. Arboreal jumping has appeared in multiple crown lineages as well, but with divergent patterns of evolution involving each of the three pelvic types. The fore‐aft slider morph appears independently in three different locomotor modes and, thus, is a more complex system than previously thought. Finally, it appears that the advent of a bicondylar sacro‐urostylic articulation was originally related to providing axial rigidity to lateral‐bending behaviors rather than sagittal bending. J. Morphol., 2011. © 2010 Wiley‐Liss, Inc.     

凹耳臭蛙胚胎发育及其分类学意义(英文)

通过人工受精的方法获得的凹耳臭蛙(Odorrana tormota)的早期胚胎及胚后幼体的发育过程,根据胚胎发育过程中的形态及生理特征变化规律进行分期。把凹耳臭蛙的发育过程分成两个阶段:1)早期胚胎发育阶段,即从蛙卵受精到鳃盖完成期,在18～23℃水温下,凹耳臭蛙早期胚胎发育阶段历时324h;2)蝌蚪发育阶段,即从鳃盖完成期结束到尾部被完全吸收,本阶段在20～24℃水温条件下历时1207h。凹耳臭蛙蝌蚪未发现腹吸盘特征,从形态特征上支持了分子系统分类学将之从湍蛙属划出的观点。实验中发现,多数胚胎在8细胞期为纬裂,16细胞期为经裂,同时有小部分胚胎(1.5%)在8细胞期为经裂,16细胞期为纬裂。该文进一步讨论了影响卵裂率、孵化率、发育速度,以及生态适应的因素。     

The evolution of development: two portraits of skull ossification in pipoid frogs

Abstract.— Development creates morphology, and the study of developmental processes has repeatedly shed light on patterns of morphological evolution. However, development itself evolves as well, often concomitantly with changes in life history or in morphology. In this paper, two approaches are used to examine the evolution of skull development in pipoid frogs. Pipoids have highly unusual morphologies and life histories compared to other frogs, and their development also proves to be remarkable. First, a phylogenetic examination of skull bone ossification sequences reveals that jaw ossification occurs significantly earlier in pipoids than in other frogs; this represents a reversal to the primitive vertebrate condition. Early jaw ossification in pipoids is hypothesized to result from the absence of certain larval specializations possessed by other frogs, combined with unusual larval feeding behaviors. Second, thin-plate spline morphometric studies of ontogenetic shape change reveal important differences between pipoid skull development and that of other frogs. In the course of frog evolution, there has been a shift away from salamander-like patterns of ontogenetic shape change. The pipoids represent the culmination of this trend, and their morphologies are highly derived in numerous respects. This study represents the first detailed examination of the evolution of skull development in a diverse vertebrate clade within a phylogenetic framework. It is also the first study to examine ossification sequences across vertebrates, and the first to use thin-plate spline morphometrics to quantitatively describe ontogenetic trajectories.     

Serous cutaneous glands in the paludiculine frog Physalaemus biligonigerus (Anura, Leptodactylidae): patterns of cytodifferentiation and secretory activity in premetamorphic specimens

The development of serous cutaneous glands is described in tadpoles of the leptodactylid frog Physalaemus biligonigerus , with attention to the cytodifferentiation processes of the secretory unit (adenomere). Secretory differentiation causes the adenomere to assume the structure of a syncytium and triggers biosynthesis of the serous product (poison), consisting of granules with peculiar repeating substructure. The secretory granules resemble glomerular-like aggregates of randomly orientated tubular subunits. This complex substructure derives from the rearrangement of the dense, compact material released by the Golgi apparatus in the form of small, membrane-bounded particles. Both early and advanced features of P. biligonigerus poison closely resemble those found during serous gland development in the Italian treefrog Hyla intermedia . The similar aspects described during serous biosynthesis in these leptodactylid and hylid frogs suggest they are phylogenetically informative. On the other hand, the peculiar features of their poisons may reflect the differential patternings of their secretory repertories along the divergent phylogenetic paths, which led these frogs to be currently included in different families.     

Patterns of endemism and species richness in Malagasy cophyline frogs support a key role of mountainous areas for speciation

Cophyline narrow-mouthed frogs (Anura: Microhylidae) are a diverse endemic radiation of Madagascar. Cophylines contain a high proportion of range restricted species and constitute a good model system to understand patterns of evolutionary diversification in tropical ecosystems. We combine spatial and phylogenetic analyses for a near-complete taxon sample to test competing explanations for patterns of species richness (SR) and endemism. Our reconstruction of the phylogeny of cophylines indicates the presence of 22 new species and several instances of nonmonophyly. We found a strong historical signal in current cophyline ranges indicating a high degree of spatial niche conservatism in clade diversification, with clades occurring in the North of Madagascar constituting the most derived in the phylogeny. We identified six positively correlated centers of SR and endemism that can neither be explained by stochastic models such as elevational or latitudinal mid-domain effect, nor by low-elevation river catchments. Instead, the locations of these centers in areas spanning a high altitudinal range in combination with specific climatic parameters support a key role of mountainous areas for speciation of these anurans, although we cannot exclude an influence of habitat loss due to human impact. High conservation priority is ascribed to these areas.     

Evolutionary reorganizations of ontogenesis in related frog species of the family Myobatrachidae

Literary data on the comparative embryology of Australian endemic frogs of the family Myobatrachidae have been considered. Six main types of development have been recognized, the important criteria for which are egg size, the site of embryo and tadpole development (in water or on land), the character of larval nutrition (exotrophic or endotrophic), the occurrence of direct development, brooding, etc. An attention has been also paid to the character of the early cleavage process in the embryos of various species. The peculiarities of ontogeny in Myobatrachidae are compared with those in representatives of other families in the order Anura. The perspectives of some further embryological studies of this Australian frog family have been out-lined.