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Carmen Díaz-Paniagua

Abstract

Common chameleon eggs spend the first months of incubation at low temperatures. I incubated eggs of different clutches at 25°C in four treatments with respectively 0, 84, 119 and 149 days of initial cold period (at 14°C). Treatments with longer cold periods had longer total incubation but shorter periods of incubation at 25°C. Eggs which did not experience initial cold period showed low synchronization at hatching. Hatchling body mass and length were influenced by the length of the cold period. Hatchlings were largest and heaviest for cold periods of intermediate length which had similar duration than the cold period experienced by eggs in nature. These results suggest that the cold torpor period of Common chameleon embryos contributes to optimization of development and growth, and synchronizes hatching.

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Carmen Diaz-Paniagua

Abstract

The diets of the larvae of five anuran species are described (Discoglossus pictus, Bufo calamita, Hyla meridionalis, Pelobates cultripes and Rana perezi). They all are basically composed of three abundant categories of food: algae, detritus and phanerogams. Other rarely encountered food categories are pollen, fungi, animals, bacteria and protozoa. A classification can be deduced by relating the use of the space in the ponds, diets and several morphological characters of larvae of each species: a) bottom-dwellers —tadpoles with a depressed body form which feed mainly on detritus — b) water column users — tadpoles with larger dorsal tail crests and tail surfaces which feed mainly on algae and phanerogams.

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Carmen Diaz-Paniagua

Abstract

Diets of both species studied were basically composed of algae and detritus. For Pelodytes punctatus, other food types exhibited minor contributions to the diet. For Bufo bufo, phanerogams reached considerable proportions too and the frequency of animals may be considered noteworthy if related to other species in the area. Morphologically they seem to be both conditioned to bottom dwelling rather than to the use of water column.

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Carmen Diaz-Paniagua

Abstract

The amphibian community of the Biological Reserve of Doñana (SW Spain) is composed of 10 species, their period of larval occurrence commonly taking place from autumn to early summer, although it may vary from year to year in relation to the flooding conditions of ponds. A segregation is observed according to temporal use of temporary ponds by larvae of different species. Pelobates cultripes and Discoglossus galganoi tadpoles occur in ponds during their whole persistence, from flooding to drying up. Hyla meridionalis, Triturus marmoratus and Triturus boscai larvae commonly exploit a shorter temporal range, appearing about two months later until early summer. Bufo bufo, Bufo calamita and normally also Rana perezi have the shortest larval periods, of about two months. Rana perezi is also characterized by its delay in temporal use of the ponds in comparison with the other species. The flexibility of the larval period season is considered an adaptation to the unpredictability of temporary ponds. Thus, under certain climatic conditions, the two first groups of species may occur in the same temporal range.

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Elisa Cabrera-Guzmán, Carmen Díaz-Paniagua and Ivan Gomez-Mestre

Abstract

Invasive species are one of the main causes of amphibian declines worldwide, often through direct predation. Even species or life stages that may not be prone to predation by invasive animals can be affected through alterations of their reproductive behaviour and/or performance. This aspect is less commonly investigated, and may be important for understanding the full impact of invasive species on local amphibian populations. We used laboratory experiments to measure effects of the invasive Eastern mosquitofish (Gambusia holbrooki) on gravid pygmy newts (Triturus pygmaeus) from southern Spain. Gravid newts altered their position in the water column by moving from the bottom of the aquaria to the surface when in the presence of free-swimming mosquitofish, presumably to reduce physical contact with them. Newts also detected and consumed less prey in presence of free mosquitofish. Newts exposed to caged or free-swimming mosquitofish laid fewer eggs than newts not exposed to the invasive species, suggesting that chemical or visual cues alone were sufficient to alter the behaviour of gravid newts. Our results suggest that mosquitofish can reduce the reproductive success of native pygmy newts in the wild, highlighting the need for management efforts to mitigate this impact.

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Carmen Díaz-Paniagua, Natividad Pérez-Santigosa, Judith Hidalgo-Vila and Margarita Florencio

Abstract

Nowadays, established populations of exotic turtles, Trachemys scripta elegans, coexist with native turtles in the wild in southern Spain. We analysed the diet of this exotic species and compared it with the diet of the two native species (Mauremys leprosa and Emys orbicularis) in two ponds. The exotic turtle is an opportunistic omnivore. In one of our study ponds where exotic invasive crayfish were very abundant, adult and juvenile exotic turtles fed mainly on this prey. In the other study pond, juveniles fed mainly on animal matter and adults ate similar proportions of plants and animals. Native turtles also ingested mainly crayfish in the first study pond, but M. leprosa were mainly herbivorous in the second pond. We did not detect strong differences among the diets of the three species. While native species significantly differ in their diets, the exotic turtles did not differ from some groups of native ones. Exotic turtles had the widest range of food, overlapping the food spectra of different age groups of the two native species in both localities. Comparing with previous reports on native turtles diet of the same area, our results did not reveal changes in the diet which could be associated to interactions with exotic turtles, but the observed shift to a higher proportion of animals in the diet in one of the ponds were mainly due to the high abundance of exotic crayfish.