Natural diets of anuran larvae vary widely in their relative amounts of nutrients. The proportion of these ingested nutrients has significant influence on larval and post-metamorphic performance.
Here, we use the Common Toad to address the role of diet (exclusively carnivore, exclusively vegetarian and mixed) on growth and development of tadpoles and short-term carry-over effects on post-metamorphic animals. Larvae fed on an exclusively vegetarian diet performed better (faster growth and development) than larvae fed on exclusively carnivore and mixed diets. Larvae fed on the exclusively carnivore diet had the lowest performance. Regarding the carry-over effects of larval diets, although the body condition indices of the toadlets were similar in all treatments, there was a major difference in the survival rate. While toadlets, originating from larvae fed on a vegetarian diet, were more successful and had the lowest mortality, those fed on a carnivore diet had the highest mortality level. Our results suggest that a plant-based diet may contain all the necessary nutrients needed by Bufobufo larvae. Furthermore, a diet based exclusively on food of animal origin might be detrimental for the larval performance and could have significant carry-over effects on the post-metamorphic animal.
Studies on thermoregulation in nocturnal lizards have shown that their thermal regimes are similar to those of diurnal lizards, even though they hide during the daytime and are active mostly at night, when heat sources are very scarce. As a result, nocturnal lizards display an active thermoregulatory behavior consisting of seeking warm shelters to hide during the daytime, using accumulated heat for the nocturnal activity. Based on this information, we hypothesize that when leopard geckos (Eublepharis macularius, Blyth 1954) are presented with the choice of safety in cool shelters or vulnerability in heated open areas, suitable temperature will prevail in importance, i.e. they will trade the advantages provided by the shelter for an exposed, but physiologically necessary heat source. Data on the time juvenile E. macularius spent in shelters, and in open areas along a thermal gradient and under a 12/12 hr photoperiod, from eight individuals confirmed our hypothesis. We found that, not only did they select heat sources over shelters, but, along with the light/dark cycle, temperature may also represent a cue for activity. Additionally we found that substrate moisture plays an important role in shelter preference.
One of the major difficulties of frog farming is providing adequate food in the first few weeks after the metamorphosis. This is a critical time frame, with rapid growth and high mortality. The established feeder insect species used throughout this delicate stage (cricket and mealworm larvae, adult fruit flies) are suitable from a trophic perspective, but present challenges and difficulties that influence the production costs. The aim of this study is to assess the performance of an alternative feeder species - Alphitobius piceus - with a simpler production technology and a lower production cost. Two species of feeder insect were used: the conventionally used Acheta domestica larvae as control species, and Alphitobius piceus larvae as experimental species. As model anuran we used the European common frog, Rana temporaria. The experimental insect species was easily accepted and produced a strong feeding response in the post-metamophic frogs. There were no significant differences between the control and experimental groups in terms of body condition index and mortality, however survival was better in the experimental group. This similarity indicates a high potential of Alphitobius piceus as feeder species for the newly metamorphosed frogs and also a good economic opportunity for frog farms.
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