Orientation and emigration of larval and juvenile amphibians: selected topics and hypotheses
Most amphibians have a complex life cycle with an aquatic larval and an adult (semi-) terrestrial stage. However, studies concerning spatial behaviour and orientation mainly focus on either the aquatic larvae or the adult animals on land. Consequently, behavioural changes that happen during metamorphosis and the consequences for emigration and population distribution are less understood. This paper aims to summarize the knowledge concerning specific topics of early amphibian life history stages and proposes several testable hypotheses within the following fields of research: larval and juvenile orientation, influences of environmental and genetic factors on juvenile emigration, their habitat choice later in life as well as population biology. I argue that studying larval and juvenile amphibian spatial behaviour is an understudied field of research, however, could considerably improve our understanding of amphibian ecology.
Testing skin swabbing for DNA sampling in dendrobatid frogs
Skin swabbing, a minimally invasive DNA sampling method recently proposed for adult amphibians, was tested on the dendrobatid frog . I compared DNA yield from skin swabs and toe clips by evaluating obtained DNA concentrations and purity of extracts, as well as amplification success using eleven polymorphic microsatellite loci. I also tested whether storing skin swabs for two months at -20°C affected the properties of the extract or microsatellite analysis. Results show that skin swabs of adult suffered from high contamination and yielded significantly lower DNA quality and quantity, resulting in insufficient genotyping success, than DNA obtained from toe clips. The relatively dry skin in dendrobatid frogs may have impeded the collection of sufficient viable cells, and the presence of skin alkaloids and microbiota in the frog mucus may lead to high contamination load of skin swabs.
Induction of Metamorphosis Causes Differences in Sex-Specific Allocation Patterns in Axolotls () that Have Different Growth Histories
We tested the hypothesis that salamanders growing at different rates would have allocation patterns that differ among male and female metamorphic and larval salamanders. We raised individual axolotls, , on four food regimes: constant high growth (throughout the experiment), constant low growth (restricted throughout the experiment), high growth switched to low growth (ad libitum switched after 140 d to restricted), and low growth switched to high growth (restricted switched after 140 d to ad libitum). Because axolotls are obligate paedomorphs, we exposed half of the salamanders to thyroid hormone to induce metamorphosis. We assayed growth and dissected and weighed gonads and fat bodies. Salamanders that were switched from restricted to ad libitum food regime delayed metamorphosis. In all treatment groups, females had larger gonads than males and males had larger fat bodies than females. The association between storage and reproduction differed between larvae and metamorphs and depended on sex.
Characterisation of nine new polymorphic microsatellite loci in the reticulated glass frog (Centrolenidae)
Here we document the development of thirteen novel microsatellite markers for the reticulated glass frog (Centrolenidae). Nine of those markers were polymorphic and contained between 4 and 34 alleles per locus (mean = 20.3) in 138 individuals (91 males, 47 females) from the field site 'La Gamba', Costa Rica. Average observed heterozygosity was 0.76. Two loci () significantly deviated from Hardy-Weinberg equilibrium. We did not find evidence for linkage disequilibrium among any of the loci. These markers will serve to identify the genetic mating system in , investigate gene flow between local populations, and reconstruct parent-offspring relationships for studies on individual mating and reproductive success. Therefore, these markers will serve to answer a wide range of scientific questions in conservation, behavioural ecology, and also evolutionary biology.