Thermal acclimation of locomotor performance in tadpoles of the frog Limnodynastes peronii

Previous analyses of thermal acclimation of locomotor performance in amphibians have only examined the adult life history stage and indicate that the locomotor system is unable to undergo acclimatory changes to temperature. In this study, we examined the ability of tadpoles of the striped marsh frog (Limnodynastes peronii) to acclimate their locomotor system by exposing them to either 10 °C or 24 °C for 6 weeks and testing their burst swimming performance at 10, 24, and 34 °C. At the test temperature of 10 °C, maximum velocity (U_max) of the 10 °C-acclimated tadpoles was 47% greater and maximum acceleration (A_max) 53% greater than the 24 °C-acclimated animals. At 24 °C, U_max was 16% greater in the 10 °C-acclimation group, while there was no significant difference in A_max or the time taken to reach U_max (T-U_max). At 34 °C, there was no difference between the acclimation groups in either U_max or A_max, however T-U_max was 36% faster in the 24 °C-acclimation group. This is the first study to report an amphibian (larva or adult) possessing the capacity to compensate for cool temperatures by thermal acclimation of locomotor performance. To determine whether acclimation period affected the magnitude of the acclimatory response, we also acclimated tadpoles of L. peronii to 10 °C for 8 months and compared their swimming performance with tadpoles acclimated to 10 °C for 6 weeks. At the test temperatures of 24 °C and 34 °C, U_max and A_max were significantly slower in the tadpoles acclimated to 10 °C for 8 months. At 10 °C, T-U_max was 40% faster in the 8-month group, while there were no differences in either U_max or A_max. Although locomotor performance was enhanced at 10 °C by a longer acclimation period, this was at the expense of performance at higher temperatures. Accepted: 25 June 1999     

Tooth replacement in adult Xenopus laevis (Amphibia: Anura)

To determine the time scale of tooth replacement in adult Xenopus laevis (Daudin), three large females of similar size were kept in aquaria at 25 °C for ten weeks. They were anaesthetized twice weekly with MS 222 and impressions of their upper jaws were taken using thin sheets of dental gold-casting wax. Because the erupted tips of the teeth were small (100 μm), the impressions were enlarged by projection so that the presence or absence of a tooth at each locus in the jaw could be recorded. Each half of each animal's jaw was analysed separately and a statistical analysis of the records yielded results for the duration of the Replacement Cycle and Functional Life of the teeth. The range of the median Replacement Cycle time between specimens was 910–1,010h, that of the Functional Life 580–700 h and that of the Gap Period (the time over which loci were unoccupied by functional teeth) 230–420 h. A tentative time scale for the complete tooth development cycle (from tooth germ initiation to complete resorption) was calculated by extrapolation from the results and ranged from 59.07 to 71.29 days.     

Hypoxia induces surfacing behaviour in brown-striped frog (Limnodynastes peronii) larvae

In their natural habitat, brown-striped frog (Limnodynastes peronii) larvae periodically swim rapidly from the bottom of their ponds to the water surface and then immediately dive to the bottom again. This behaviour is presumably related to air-breathing. We examined the behavioural and metabolic responses to aquatic hypoxia in L. pernoii larvae. Gas filled lungs were found in all free-swimming larval stages of L. peronii, but air-breathing occurred infrequently in normoxic water. The frequency of air-breathing at 30°C increased rapidly in hypoxic water when oxygen partial pressure (P_o2) fell below 10 kPa. Only a slight increase was observed at similar oxygen partial pressures at 20°C. The critical oxygen tension at 30°C was about 7kPa, below which, aquatic breathing larvae become metabolic oxygen conformers. In natural habitats where surfacing behaviour was observed, temperatures during summer months frequently exceed 25°C and some ponds become extremely hypoxic (po₂ < 3.0 kPa); therefore air-breathing appears to be the only way in which these larvae can maintain a fully aerobic metabolism.     

Experimental infection of striped marshfrog tadpoles (Limnodynastes peronii) by Ichthyophthirius multifiliis.

Ichthyophthirius multifiliis, or white spot, is a well known and widely distributed parasite of freshwater fish. However, it is not know whether it can infect other aquatic vertebrates such as amphibians. This study uses a series of laboratory-based experiments to demonstrate that I. multifiliis can infect the tadpole stage of an amphibian, the striped marshfrog (Limnodynastes peronii) of Eastern Australia. The tadpoles did not appear to develop ichthyophthiriasis at low parasite levels (200 parasites per tadpole), but at high parasite levels (2,000 parasites per tadpole) 100% of the tadpoles developed ichthyophthiriasis. This is the first time that it has been demonstrated that I. multifiliis can infect a nonpiscine vertebrate host.     

A molecular phylogeny for the frog genus Limnodynastes (Anura: myobatrachidae)

Members of the genus Limnodynastes are a prominent and widespread feature of the Australian frog fauna. Yet despite their potential to be informative about biogeographic history and mechanisms of speciation, the relationships among these taxa are not well known. We investigated phylogenetic relationships within the genus Limnodynastes via sequencing of mitochondrial (mt)DNA from current members of the genus Limnodynastes and the monotypic genus Megistolotis. a 450-bp fragment of the 16S rRNA gene and a 370-bp fragment of the protein-coding gene ND4 were used to infer a molecular phylogeny. We revise traditional species groupings and now recognize four species groups within Limnodynastes: the L. ornatus group (L. ornatus and L. spenceri), the L. peronii group (L. peronii, L. tasmaniensis, L. fletcheri, the L. depressus), the L. salmini group (L. salmini, L. convexiusculus, and L. lignarius), and the L. dorsalis group (L. dorsalis, L. terraereginae, L. dumerilii and L. interioris). The L. ornatus species group forms a highly distinctive clade that is a sister group to the other Limnodynastes groups. Pending broader phylogenetic studies it could be removed from the genus Limnodynastes. Our results concur with previous suggestions that Megistolotis lignarius is nested within Limnodynastes, and we therefore reclassify this species as Limnodynastes lignarius. Furthermore, specimens identified as L. depressus form a mtDNA lineage distinct from other species in the genus, confirming the validity of the species. Specimens of species from the L. dorsalis group (L. dorsalis, L. dumerilii, L. interioris, and L. terraereginae) are closely related such that L. dumerilii is paraphyletic with two other species. Finally, our study provides broad support for previous phylogenies based on microcomplement fixation.     

A subordinal classification of frogs (Amphibia: Anura)

Two new anuran suborders, based on two states of the trigeminofacial ganglion character complex are proposed. A subsidiary character is the presence or absence of free ribs in extant taxa. These new suborders are more clades (sister groups) than sequential levels of organization. Discoglossoidei, retaining separate trigeminal and facial ganglia and free ribs, encompasses only Leiopelmatidae and Discoglossidae, although by definition it would include the common ancestor of both lineages. Ranoidei have the trigeminal and facial ganglia fused and extant taxa lack free ribs. This group includes all other frogs.
Only the superfamiliesPelobatoidea and Pipoidea are reallocated by the new arrangement. The former are now regarded as representing the ranoidean stem group. Both laival and adult morphology show that pipoids are highly derived rather than primitive frogs, and their trigeminofacial systems show that they are ranoideans rather than discoglossoideans. They presumably are ultimately derived from pelobatoids, but the known taxa are too specialized for direct derivation and there must have been an intermediate group with pipoid tadpoles but without extreme specializations for either fossorial or aquatic life.     

Key to the Known Tadpoles (Amphibia: Anura) of Costa Rica

We present a key to distinguish among the described tadpoles of Costa Rican frogs and toads, summarize the reproductive modes present in this group, and present a bibliography of the published illustrations of those tadpoles.     

Cranial features of dendrobatid larvae (Amphibia: Anura: Dendrobatidae)

The larval neurocranium and visceral arches of seven dendrobatid species representing four genera are described, based on cleared-and-stained and serially sectioned specimens. A variety of characters is shared by all seven species. Larval features do not substantiate the assumption of close ranoid affinities of the Dendrobatidae. Instead dendrobatid larvae share features such as the special quadripartite cartilago suprarostralis, the lack of the larval processus oticus, the presence of three foramina acustica, and the lack of a foramen perilymphaticum accessorius with many bufonoid larvae. The first of these characters is unique to bufonids, hylids, dendrobatids, and some New World leptodactylids; the other characters also occur in pelobatids and are presumably plesiomorphic for the Neobatrachia. The free proximal ends of Ceratobranchialia II and III are an autapomorphy of the Dendrobatidae supporting the monophyly of the family. Some features of the cranium are paedomorphic: low cartilago orbitalis, lack of connection between cartilage orbitalis and otic capsule (most species), and vestigal taeniae tecti. New anatomical terms are introduced. © 1995 Wiley-Liss, Inc.     

Biochemical acclimation of metabolic enzymes in response to lowered temperature in tadpoles of Limnodynastes peronii

We measured the rate at which the metabolic enzymes lactate dehydrogenase (LDH), citrate synthase (CS), and cytochrome c oxidase (CCO) acclimate in the response to lowered temperature in the axial muscle of tadpoles of Limnodynastes peronii (Anura: Myobatrachidae) over 6 weeks. In addition, we measured growth rates of the tadpoles kept at both temperatures and examined the activities of these enzymes in the liver tissue of the control group and cold-acclimated group at the end of the experiment. We found that LDH acclimates in axial muscle; the differences between the control and cold-acclimated group became apparent after 21 days. After 42 days, the activity of LDH in axial muscle in the cold-acclimated group was 30% greater than the control group. Growth rates were maintained at 0.7 mm/week within both treatments despite the 10 degrees C difference in temperature between experimental groups. Both LDH and CS were increased in activity in the liver (5 and 1.3 times greater, respectively, in the cold-acclimated group). The thermal sensitivity (Q(10)) of LDH was between 20 and 30 degrees C in the cold-acclimated group (1.2+/-0.01) when compared to the control group (1.6+/-0.15). The rate at which acclimation in this species occurs is appropriate for seasonal changes in temperature, and these animals may not be able to respond to a rapid drop in temperature.     

Allozyme Variation among Populations of Rana pirica (Amphibia: Anura)

Genetic variation of Rana pirica , an east Asian brown frog of the R. temporaria group, was elucidated by analysing 140 specimens from 11 populations from Hokkaido and Sakhalin, both locating near the eastern coasts of the Asian continent, and 12 specimens of R. ornativentris from Honshu, Japan mainland, as an outgroup, through horizontal starch gel electrophoresis. Rana pirica shows relatively low genetic differentiation, and high genetic affinities are found between Hokkaido and Sakhalin populations. Populations from these islands are morphologically somewhat differentiated but should be regarded as conspecific. Degree of genetic divergence among populations of amphibian species from Hokkaido, including R. pirica , is not so extensive as that reported for species from Japan mainland and relatively recent formation of amphibian fauna in Hokkaido is suggested.     

Isopods failed to acclimate their thermal sensitivity of locomotor performance during predictable or stochastic cooling

Most organisms experience environments that vary continuously over time, yet researchers generally study phenotypic responses to abrupt and sustained changes in environmental conditions. Gradual environmental changes, whether predictable or stochastic, might affect organisms differently than do abrupt changes. To explore this possibility, we exposed terrestrial isopods (Porcellio scaber) collected from a highly seasonal environment to four thermal treatments: (1) a constant 20°C; (2) a constant 10°C; (3) a steady decline from 20° to 10°C; and (4) a stochastic decline from 20° to 10°C that mimicked natural conditions during autumn. After 45 days, we measured thermal sensitivities of running speed and thermal tolerances (critical thermal maximum and chill-coma recovery time). Contrary to our expectation, thermal treatments did not affect the thermal sensitivity of locomotion; isopods from all treatments ran fastest at 33° to 34°C and achieved more than 80% of their maximal speed over a range of 10° to 11°C. Isopods exposed to a stochastic decline in temperature tolerated cold the best, and isopods exposed to a constant temperature of 20°C tolerated cold the worst. No significant variation in heat tolerance was observed among groups. Therefore, thermal sensitivity and heat tolerance failed to acclimate to any type of thermal change, whereas cold tolerance acclimated more during stochastic change than it did during abrupt change.     

Structural diversity of nuptial pads in Phyllomedusinae (Amphibia: Anura: Hylidae)

We studied the morphological variation of the nuptial pads using light microscopy and scanning electron microscopy (SEM) in 26 species of phyllomedusines (Anura: Hylidae), representing the five currently recognized genera. All phyllomedusines have single nuptial pads with dark colored epidermal projections (EPs). Spine‐shaped EPs occur in Cruziohyla calcarifer, Phrynomedusa appendiculata and in one species of Phasmahyla. The other species have roundish EPs. The density of the EPs on the pad is variable. Species in the Phyllomedusa hypochondrialis Group have EPs with a density that varies between 764 ± 58/mm² and 923 ± 160/mm². In all other studied species (including the Phyllomedusa burmeisteri and Phyllomedusa perinesos groups, Phyllomedusa camba, Phyllomedusa boliviana, Phyllomedusa sauvagii, Phyllomedusa bicolor, and Phyllomedusa tomopterna) the density of EPs varies between 108 ± 20/mm² and 552 ± 97/mm². Pores were observed with SEM in C. calcarifer, Agalychnis lemur, Agalychnis moreletii, but its presence is confirmed through histological sections on several other species. Its visibility using SEM seems to be related with the level of separation between adjacent EPs. The pores in the four studied species of Agalychnis are shown with SEM and histological sections to have a characteristic epidermal rim, that is absent in the otherphyllomedusines. Unlike most previous reports on breeding glands, those of phyllomedusines are alcian blue positive, indicating the presence of acidic mucosubstances on its secretions. J. Morphol. 2012. © 2012 Wiley Periodicals, Inc.     

A New Species of Rhacophorus(Amphibia: Anura: Rhacophoridae)from Vietnam

We describe a new species of Rhacophorus based on two adult specimens collected from Hoa Binh Province, northern Vietnam. Rhacophorus hoabinhensis sp. nov. is distinguishable from its congeners on the basis of a combination of the following morphological characters: size small(SVL 31.1–32.5 mm in males); head slightly longer than wide; vomerine teeth absent; snout short(SNL/SVL 0.16); dorsal skin smooth; forearm and tarsus with dermal fringes; dermal appendage at vent present; webbing formula on fingers Ⅰ12/3-12/3 Ⅱ1-2 Ⅲ1-1 Ⅳ and on toes Ⅰ3/4-1 Ⅱ1/2-1Ⅲ1/2-1 Ⅳ1-1/2Ⅳ; dorsal surface grey yellow with brown spots; lower jaw region dark grey, throat, chest and belly cream; anterior and posterior thighs, as well as ventral surface of tibia orange. The interspecific uncorrected genetic distances(16 S rRNA gene) between the new species from Hoa Binh and other analyzed congeners varied from 9.8% to 17.4%. In the phylogenetic analyses, the new species revealed to be a representative of Rhacophorus and was nested within the R. hoanglienensis-orlovi species group.     

Ultrastructure of Spermiogenesis in Hyla japonica (Anura,Amphibia)

Spermiogenesis in Hyla japonica was examined using transmission electron microscopy. Features which have not been reported previously during spermiogenesis of anurans include: (1) the neck of pericentriolar material is well developed, (2) the perforatorium contains many microtubules, (3) the tail is composed of axoneme and axial rod, but has no undulating membrane. Such a structure has not been described in amphibians, although it occurs in fish and mammals, and (4) the modified microtubules have one to two long projections. So far they have not been observed in any species except Gerris and Aphyosemion. With the exception of the above characteristics, the spermatozoa of Hyla japonica are remarkably similar to those of Bufo sp.     

Evolution of reproduction in the Rhacophoridae (Amphibia, Anura)

Rhacophorid treefrogs have different reproductive modes: some go through a tadpole stage and some have direct development, and the adults of some species produce foam nests. Philautus is the only genus characterized by direct development. The production of foam nests has been reported in the genera Polypedates, Rhacophorus, Chiromantis and Chirixalus. Recent molecular studies did not provide a robust hypothesis concerning the origin of these reproductive modes in the Rhacophoridae. In order to better understand the evolution of these reproductive modes, we tried to clarify relationships within this group, using DNA sequencing. Our data set consists in a large number of new sequences (1676 base pairs corresponding to threee genes) for five outgroup ranoids and 48 Rhacophoridae, including 16 undescribed species from Sri Lanka and southern India, and all homologous data available in Genbank. After the inclusion of Philautus from India, our data show that the separation of Philautus into clades does not coincide with their geographic distribution. Our data point to the existence of a clade, including the genera Rhacophorus, Polypedates, Chiromantis and Chirixalus, which confirms the results of Wilkinson et al. (2002) and suggests that the ability to produce foam nests has emerged only once in the Rhacophoridae, as already stated by these authors.     

中国西部地区绿蟾蜍的分类研究

对中国西部（新疆和西藏）原定名为绿蟾蜍Ｂｕｆｏｖｉｒｉｄｉｓ的２７个居群进行了开矿学比较研究,同时与产于邻近地区的Ｂｕｆｏｄａｎａｔｅｎｓｉｓ（土库曼）、Ｂ．ｌｏａｔａｓｔｉｉ和Ｂ．ｓｔｏｍａｔｉｃｕｓ（克什米尔）的３种蟾蜍标本或原始描述作了对比。我们赞同Ｂｏｒｋｉｎ等（１９８８）的研究结果,并将产中地原定名为．ｖｉｒｉｄｉｓ中四倍体的各居群统归为Ｂ．ｄａｎａｔｅｎｓｉｓ。同时将才原各居群分为４个