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Direct environmental impact and microevolutionary pressure may both shape the phenotype by acting synergistically (cogradient) or antagonistically (countergradient). An experimental approach is therefore needed to determine which environmental challenges are responsible for the observed inter-population variation in a phenotypic trait and if such variation is adaptive. Rana temporaria L. larvae were reared in a factorial experiment, with two temperature regimes (differential of 6°C) and larvae originating from two source populations in Poland: a montane pond in the Babia Góra National Park (elevation 1025 m) and a lowland swamp near Warszawa (elevation 100 m). Populations did not differ in early larval growth rates or in the length of the larval period. In both populations, the early rates of development were higher and the larval period was expectably and substantially shorter at higher temperature. The montane larvae were heavier at metamorphosis than the lowland larvae, but significantly so only at the low temperature treatment. The observed patterns of responses partially conform to the cogradient model of phenotypic variation, in which both environmental and selective effects are mutually enhancing the differentiation of populations.
The life-cycle stages of a new species of Uvulifer, U. iruvettiensis sp. nov. infecting the white-throated kingfisher Halcyon smyrnensis (Linnaeus) in Kerala, India are described. The new species is described in detail, and compared with its related species. The furcocercous cercariae emerged from the planorbid snail Indoplanorbis exustus (Deshayes). Metacercariae were found below the skin of tadpoles of Euphlyctis cyanophlyctis (Schneider). H. smyrnensis became infected when fed on tadpoles containing infective metacercariae. Pre-patent period is 10 days. Successive stages in the development of metacercariae and adults were followed in the laboratory.
Fossil material from the lower Miocene collected in the basin lake of Beşkonak (Turkey) included 19 slabs showing 19 amphibian anuran tadpoles of rather large size, at Gosner stages 36–38. These well preserved specimens show many morphological and skeletal characters. They are here tentatively referred to the genus Pelobates. Two of these tadpoles show an unusual group of black roundish spots in the abdominal region, and a third similar group of spots is present in another slab but we were unable to state if it was associated with a tadpole or not. Several hypotheses can be proposed to account for these structures: artefacts; intestinal content (seeds; inert, bacterial or fungal aggregations; eggs); internal or external parasites; diseases; eggs produced by the tadpole. The latter hypothesis is discussed in detail and is shown to be unlikely for several reasons. However, in the improbable case where these spots would correspond to eggs, this would be the first reported case of natural paedogenesis in anurans, a phenomenon which has been so far considered impossible mostly for anatomical reasons (e.g., absence of space in the abdominal cavity).
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