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Frog Tadpoles (frog + tadpole)
Selected AbstractsEffects of the synthetic estrogen ethinylestradiol on early life stages of mink frogs and green frogs in the wild and in situENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 8 2005Bradley J. Park Abstract Estrogenic contaminants are known to disrupt growth and development in amphibians. Field-based research is needed to elucidate their potential impacts on wild populations. Hatch success, larval growth and development rates, and gonad development were examined in native amphibians exposed to low ng/L concentrations of 17,-efhinylestradiol (EE2) in a whole-lake addition experiment at the Experimental Lakes Area, northwestern Ontario, Canada. Egg masses were reared in situ in the EE2-amended lake and in two reference lakes in 2001 and 2002. Hatching success was reduced significantly in green frogs (Rana clamitans) but not in mink frogs (Rana septentrionalis) exposed to EE2. Ethinylestradiol had no consistent effect on mass or development stage of hatchlings in the early larval stages of the caging study. Ethinylestradiol had no effect on sex ratios of either species in situ, and no intersex gonads were observed in exposed or reference green frog tadpoles or in reference mink frog tadpoles. However, 5.6% (total n = 18) and 12.5% (total n = 56) of EE2-exposed mink frog tadpoles were intersex in the 2001 and 2002 caging studies, respectively. Wild mink frog tadpoles also were examined, and EE2 had no effect on sex ratios. No intersex gonads were observed in reference lake tadpoles or in tadpoles from the experimental lake prior to EE2 additions; however, 2.4, 0, and 28.6% of wild EE2-exposed first-year tadpoles had intersex gonads (2001, 2002, and 2003, respectively). These results indicate that exposure to EE2 in the wild and in situ at concentrations comparable to those detected in effluents and, occasionally, in surface waters can impact gonad development and hatch success in native amphibians. [source] Interpreting the smells of predation: how alarm cues and kairomones induce different prey defencesFUNCTIONAL ECOLOGY, Issue 6 2009Nancy M. Schoeppner Summary 1.,For phenotypically plastic organisms to produce phenotypes that are well matched to their environment, they must acquire information about their environment. For inducible defences, cues from damaged prey and cues from predators both have the potential to provide important information, yet we know little about the relative importance of these separate sources of information for behavioural and morphological defences. We also do not know the point during a predation event at which kairomones are produced, i.e. whether they are produced constitutively, during prey attack or during prey digestion. 2.,We exposed leopard frog tadpoles (Rana pipiens) to nine predator cue treatments involving several combinations of cues from damaged conspecifics or heterospecifics, starved predators, predators only chewing prey, predators only digesting prey or predators chewing and digesting prey. 3.,We quantified two behavioural defences. Tadpole hiding behaviour was induced only by cues from crushed tadpoles. Reduced tadpole activity was induced only by cues from predators digesting tadpoles or predators chewing + digesting tadpoles. 4.,We also quantified tadpole mass and two size-adjusted morphological traits that are known to be phenotypically plastic. Mass was unaffected by the cue treatments. Relative body length was affected (i.e. there were differences among some treatments), but none of the treatments significantly differed from the no-predator control. Relative tail depth was affected by the treatments and deeper tails were induced only when tadpoles were exposed to cues from predators digesting tadpoles or cues from predators chewing + digesting tadpoles. 5.,These results demonstrate that some prey species can discriminate among a diverse set of potential cues from heterospecific prey, conspecific prey and predators. Moreover, the results illustrate that the cues responsible for the full suite of behavioural and morphological defences are not induced by tadpole crushing nor can they be induced by generalized digestive chemicals produced when predators digest their prey. Instead, both prey damage and predator digestion of conspecific tissues appear to be important for communicating predatory risk to phenotypically plastic anuran prey. Importantly, the production of chemical cues by predators may be unavoidable and prey have evolved the ability to eavesdrop on these signals. [source] Environmental stress and the costs of whole-organism phenotypic plasticity in tadpolesJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 1 2008U. K. STEINER Abstract Costs of phenotypic plasticity are important for the evolution of plasticity because they prevent organisms from shaping themselves at will to match heterogeneous environments. These costs occur when plastic genotypes have relatively low fitness regardless of the trait value expressed. We report two experiments in which we measured selection on predator-induced plasticity in the behaviour and external morphology of frog tadpoles (Rana temporaria). We assessed costs under stressful and benign conditions, measured fitness as larval growth rate or competitive ability and focused analysis on aggregate measures of whole-organism plasticity. There was little convincing evidence for a cost of phenotypic plasticity in our experiments, and costs of canalization were nearly as frequent as costs of plasticity. Neither the magnitude of the cost nor the variation around the estimate (detectability) was sensitive to environmental stress. [source] Exceptionally preserved tadpoles from the Miocene of Libros, Spain: ecomorphological reconstruction and the impact of ontogeny upon taphonomyLETHAIA, Issue 3 2010MARIA E. MCNAMARA McNamara, M.E., Orr, P.J., Kearns, S.L., Alcalá, L., Anadón, P. & Peñalver-Mollá, E. 2010: Exceptionally preserved tadpoles from the Miocene of Libros, Spain: ecomorphological reconstruction and the impact of ontogeny upon taphonomy. Lethaia, Vol. 43, pp. 290,306. The Libros exceptional biota from the Upper Miocene of NE Spain includes abundant frog tadpoles (Rana pueyoi) preserved in finely laminated lacustrine mudstones. The tadpoles exhibit a depressed body, short tail, low tail fins, dorso-laterally directed eyes and jaw sheaths; these features identify the Libros tadpoles as members of the benthic lentic ecomorphological guild. This, the first ecomorphological reconstruction of a fossil tadpole, supports phylogenetic evidence that this ecology is a conserved ranid feature. The soft-tissue features of the Libros tadpoles are characterized by several modes of preservation. The space occupied previously by the brain is defined by calcium carbonate, the nerve cord is defined by calcium phosphate, and jaw sheaths and bone marrow are preserved as organic remains. Gut contents (and coprolites adjacent to specimens) comprise ingested fine-grained sedimentary detritus and epiphyton. The body outline and the eyespots, nares, abdominal cavity, notochord, caudal myotomes and fins are defined by a carbonaceous bacterial biofilm. A similar biofilm in adult specimens of R. pueyoi from Libros defines only the body outline, not any internal anatomical features. In the adult frogs, but not in the tadpoles, calcium phosphate and calcium sulphate precipitated in association with integumentary tissues. These differences in the mode of preservation between the adult frogs and tadpoles reflect ontogenetic factors. ,Anuran, ecology, soft-tissue, tadpoles, taphonomy. [source] Species-specific communication systems in an introduced toad compared with native frogs in AustraliaAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 6 2009Mattias Hagman Abstract 1.Lineage-specific communication systems may offer innovative ways of targeting control measures at invasive species. 2.Recent work has identified such a scenario in invasive cane toads (Bufo marinus) in Australia: toad tadpoles flee from chemical cues derived from crushed conspecifics, and this ,alarm pheromone' reduces tadpole survival rates and reduces body size at metamorphosis. 3.Before this method can be applied in the field, however, the signal's specificity needs to be tested against a wide range of Australian frog taxa, especially tropical species sympatric with cane toads. A signal that affected native frogs as well as toads clearly would be of little use for toad control. 4.Laboratory studies on cane toads and nine native frog taxa from the wet,dry tropics of the Northern Territory (Cyclorana australis, C. longipes, Limnodynastes convexiusculus, Litoria caerulea, L. dahlii, L. nasuta, L. rothii, L. rubella, Opisthodon ornatus) show that toad tadpoles rarely react to chemical cues from crushed frog tadpoles, and that frog tadpoles rarely react to chemical cues from crushed toad tadpoles. Crushed toad tadpoles occasionally elicited low-level attraction (to a potential food source) by frog tadpoles. 5.Overall, frog tadpoles were less responsive to chemical cues (either from crushed conspecifics or crushed toads) than were toad tadpoles. The low level of cross-lineage reactivity is encouraging for the feasibility of using cane toad alarm pheromones to control this invasive species in Australia; the risk of collateral damage to sympatric native frogs appears to be minimal. Copyright © 2009 John Wiley & Sons, Ltd. [source] | ||||||||||