Pigmentation plasticity enhances crypsis in larval newts: Associated metabolic cost and background choice behaviour

In heterogeneous environments, the capacity for colour change can be a valuable adaptation enhancing crypsis against predators. Alternatively, organisms might achieve concealment by evolving preferences for backgrounds that match their visual traits, thus avoiding the costs of plasticity. Here we examined the degree of plasticity in pigmentation of newt larvae (Lissotriton boscai) in relation to predation risk. Furthermore, we tested for associated metabolic costs and pigmentation-dependent background choice behaviour. Newt larvae expressed substantial changes in pigmentation so that light, high-reflecting environment induced depigmentation whereas dark, low-reflecting environment induced pigmentation in just three days of exposure. Induced pigmentation was completely reversible upon switching microhabitats. Predator cues, however, did not enhance cryptic phenotypes, suggesting that environmental albedo induces changes in pigmentation improving concealment regardless of the perceived predation risk. Metabolic rate was higher in heavily pigmented individuals from dark environments, indicating a high energetic requirement of pigmentation that could impose a constraint to larval camouflage in dim habitats. Finally, we found partial evidence for larvae selecting backgrounds matching their induced phenotypes. However, in the presence of predator cues, larvae increased the time spent in light environments, which may reflect a escape response towards shallow waters rather than an attempt at increasing crypsisFinancial support was provided by the Spanish Ministry of Science and Innovation (MICINN), Grant CGL2012-40044 to IGM, and by the Universidad Autónoma de Madrid, Short Stay Grant to NPC. Additional financial support was provided by the MICINN, Grant CGL2015-68670-R to NP

Bovine Leukemia Virus: An Exogenous RNA Oncogenic Virus?

Short term cultures of bovine leukemic lymphocytes release virus particles with biochemical properties of RNA oncogenic viruses. These particles, tentatively called bovine leukemia virus (BLV), have a high molecular weight RNA reverse transcriptase complex and a density of 1.155 g/ml in sucrose solutions. Molecular hybridizations between BLV [3H] cDNA and several viral RNAs show that BLV is not related to Mason Pfizer monkey virus, simian sarcoma associated virus, feline leukemia virus, or avian myeloblastosis virus. These results were confirmed by hybridization between BLV 70S RNA and [3H] cDNA synthesized in the various viruses tested. The high preference of BLV reverse transcriptase for Mg++ as the divalent cation suggests that BLV might be an atypical mammalian leukemogenic 'type C' virus. DNA DNA hybridization studies using BLV [3H] cDNA as a probe strongly suggest that the DNA of bovine leukemic cells contains viral sequences that cannot be detected in normal bovine DNA.SCOPUS: ar.jinfo:eu-repo/semantics/publishe