Digit ratio is a morphological feature regarded as a biomarker of the balance of sex hormones during early development. The exposure of embryos to a set of sex hormones and the mutual relations between those hormones cause the emergence of individual morphological and/or behavioural characteristics as well as differences between sexes. We have thus hypothesised that differences in one of these morphological traits-digit ratio-may be a proxy representing a tendency towards tail autotomy. The aim of this study is to investigate the digit ratio (2D:3D, 2D:4D, 3D:4D) of the sand lizard, Lacerta agilis, Lacertidae, a species characterised by well-developed sexual dimorphism, whereby females are larger than males. We also tested associations between patterns in digit ratio and caudal autotomy, a common defensive mechanism among lizards. To our knowledge, the relationship between a tendency towards autotomy and digit ratio pattern has never been researched. To date, studies on autotomy have mainly focused on the consequences, costs or evolutionary background of tail loss. Hence, researchers examined mostly the frequency of autotomy in the context of predatory pressure or habitat conditions, omitting an individual's behavioural tendency to shed its tail. However, behavioural traits can affect an individual's exposure to predator attack and consequently the need to use an anti-predator strategy. Thus, following this logic, dropping the tail may be the result of the lizard's intraspecific personality characteristics, resulting from the effect of hormones on behaviour or innate traits. Therefore, we suggest that the inclusion of autotomy as a factor explaining observed digit ratio patterns and their variability between taxa has great potential. We used computerised measurements of photographed limbs to determine the length of digits. We found that the digit ratios for all four limbs were significantly lower in females than in males, excluding the 3D:4D ratio for the right hindlimbs. Therefore, the results confirmed the pattern already observed for most lizards. The novel element in our study is the detection of the relationship between a tendency towards caudal autotomy and digit ratio. Individuals with a tendency towards autotomy have a higher 2D:4D ratio in the right forelimbs and a lower 2D:3D ratio in the right hindlimbs. Obtained results suggest that these morphological characteristics are most likely related to intraspecific differences (between bold and shy individuals) which consequently may determine an individual's reaction or susceptibility to be a prey and escape behaviour. Thus, our results are probably the first attempt to link digit ratio to the susceptibility of lizards to tail autotomy.
- MeSH
- biologická evoluce MeSH
- druhová specificita MeSH
- ještěři anatomie a histologie fyziologie MeSH
- ocas fyziologie MeSH
- pohlavní dimorfismus MeSH
- přední končetina anatomie a histologie MeSH
- zvířata MeSH
- Check Tag
- mužské pohlaví MeSH
- ženské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Tail autotomy is a crucial antipredatory lizard response, which greatly increases individual survival, but at the same time also compromises locomotor performance, sacrifices energy stores and induces a higher burden due to the ensuing response of regenerating the lost body part. The potential costs of tail autotomy include shifts in energy allocation and metabolic rates, especially in juveniles, which invest their energy primarily in somatic growth. We compared the metabolic rates and followed the growth of juvenile males with and without regenerating tails in the Madagascar ground gecko (Paroedura picta), a nocturnal ground-dwelling lizard. Geckos with intact tails and those that were regrowing them grew in snout-vent-length at similar rates for 22weeks after autotomy. Tail regeneration had a negligible influence on body mass-corrected metabolic rate measured at regular intervals throughout the regenerative process. We conclude that fast-growing juveniles under the conditions of unrestricted food can largely compensate for costs of tail loss and regeneration in their somatic growth without a significant impact on the total individual body mass-corrected metabolic rate.
- MeSH
- bazální metabolismus MeSH
- časové faktory MeSH
- energetický metabolismus * MeSH
- hmotnostní přírůstek MeSH
- ještěři růst a vývoj fyziologie MeSH
- náhodné rozdělení MeSH
- ocas růst a vývoj fyziologie MeSH
- regenerace * MeSH
- reprodukovatelnost výsledků MeSH
- spotřeba kyslíku MeSH
- velikost těla MeSH
- zvířata MeSH
- Check Tag
- mužské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
BACKGROUND: Many animals rely on their escape performance during predator encounters. Because of its dependence on body size and temperature, escape velocity is fully characterized by three measures, absolute value, size-corrected value, and its response to temperature (thermal sensitivity). The primary target of the selection imposed by predators is poorly understood. We examined predator (dragonfly larva)-imposed selection on prey (newt larvae) body size and characteristics of escape velocity using replicated and controlled predation experiments under seminatural conditions. Specifically, because these species experience a wide range of temperatures throughout their larval phases, we predict that larvae achieving high swimming velocities across temperatures will have a selective advantage over more thermally sensitive individuals. RESULTS: Nonzero selection differentials indicated that predators selected for prey body size and both absolute and size-corrected maximum swimming velocity. Comparison of selection differentials with control confirmed selection only on body size, i.e., dragonfly larvae preferably preyed on small newt larvae. Maximum swimming velocity and its thermal sensitivity showed low group repeatability, which contributed to non-detectable selection on both characteristics of escape performance. CONCLUSIONS: In the newt-dragonfly larvae interaction, body size plays a more important role than maximum values and thermal sensitivity of swimming velocity during predator escape. This corroborates the general importance of body size in predator-prey interactions. The absence of an appropriate control in predation experiments may lead to potentially misleading conclusions about the primary target of predator-imposed selection. Insights from predation experiments contribute to our understanding of the link between performance and fitness, and further improve mechanistic models of predator-prey interactions and food web dynamics.
- MeSH
- larva anatomie a histologie fyziologie MeSH
- ocas anatomie a histologie fyziologie MeSH
- plavání MeSH
- potravní řetězec * MeSH
- Salamandridae anatomie a histologie růst a vývoj fyziologie MeSH
- teplota MeSH
- vážky růst a vývoj fyziologie MeSH
- velikost těla MeSH
- zvířata MeSH
- Check Tag
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
We investigated the role of prostaglandin E2 in reptilian regeneration. Prostaglandin E2 is known to play a vital role during wound healing and cell proliferation. A significant delay in the rate of growth of regenerate after autotomy was observed when the production of prostaglandin E2 was blocked by usage of specific cyclooxygenase inhibitors as compared to control animals and this delay continued to all the defined stages of regeneration. Therefore, prostaglandin E2 could be one of the essential requirements for a successful process of regeneration.
- MeSH
- cyklooxygenasa 2 biosyntéza MeSH
- dinoproston antagonisté a inhibitory fyziologie MeSH
- inhibitory cyklooxygenasy farmakologie MeSH
- ještěři fyziologie MeSH
- ocas fyziologie účinky léků MeSH
- pyrazoly farmakologie MeSH
- pyridiny farmakologie MeSH
- regenerace fyziologie účinky léků MeSH
- sulfonamidy farmakologie MeSH
- sulfony farmakologie MeSH
- zvířata MeSH
- Check Tag
- mužské pohlaví MeSH
- ženské pohlaví MeSH
- zvířata MeSH
OBJECTIVE: To describe histological and ultrastructural changes of cardiomyocytes in experimental rats following subplantar administration of carrageenin. MATERIAL AND METHODS: In adult rats, an acute inflammatory reaction was induced by subplantar injection of 0.1 ml of 1% sterile carrageenin solution. In a total of 10 rats, which developed gangrene of tails in 5- to 12-cm-long segments, were killed and their internal organs fixed in 10% formaldehyde solution and subsequently processed for paraffin embedding. Later, blocks of the ventricular heart tissue were refixed and reprocessed for Araldite embedding and ultrastructure observation. Similarly, the cardiac muscle of control, carrageenin-injected rats which did not develop vascular thrombosis was processed. RESULTS: The cardiomyocytes of rats injected with carrageenin showed focal dystrophic alterations, enlarged mitochondria with densely packed concentrically oriented cristae, and many dense and irregularly shaped deposits with microgranular helicoid organization. Normal cardiomyocytes were observed in control rats. Complicating thrombosis of tail blood vessels leading to extensive tail necroses were also histologically confirmed. CONCLUSION: These findings demonstrate specific pathogenic effect in the cardiovascular system of the carrageenin-treated rats. 2007 S. Karger AG, Basel
- MeSH
- karagenan aplikace a dávkování škodlivé účinky MeSH
- kardiomyocyty účinky léků ultrastruktura MeSH
- krysa rodu rattus MeSH
- modely nemocí na zvířatech MeSH
- nekróza MeSH
- ocas fyziologie patologie MeSH
- potkani Wistar MeSH
- trombóza chemicky indukované patologie MeSH
- zvířata MeSH
- Check Tag
- krysa rodu rattus MeSH
- ženské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- srovnávací studie MeSH
