Color polymorphism in Leptodactylus fuscus (Anura, Leptodactylidae): A defensive strategy against predators?

Color patterns are strongly related to defensive strategies in anurans. Some anurans present more than one morphotype. Leptodactylus fuscus, for example, present two morphotypes (with and without vertebral white line). The proportion of each pattern in nature is different, whereby there are always more individuals without stripes. Therefore, we speculated if this difference in the observed color pattern is due to unequal predation pressures (i.e. stronger over the striped morphotype), and/or if there is a genetic component related to autossomic heritage. To test the selective predation over the morphotypes, we prepared plasticine models of L. fuscus with both phenotypes and placed them in the field. We did not find evidence of predation selection and as we found significant relationships between the proportions of the phenotypes and Mendelian proportions, we suggest that the phenotypes observed in this species are genetically determined (involving dominant and recessive alleles) and may not have a defensive function.

Colors and some morphological traits as defensive mechanisms in anurans

Anurans may be brightly colored or completely cryptic. Generally, in the former situation, we are dealing with aposematism, and the latter is an example of camouflage. However, these are only simple views of what such colorations really mean and which defensive strategy is implied. For instance, a brightly colored frog may be part of a mimicry ring, which could be either Batesian, Müllerian, or Browerian. These are only examples of the diversity of color-usage systems as defensive strategies. Unfortunately, reports on the use of colors as defensive mechanisms are widespread in the available literature, and the possible functions are rarely mentioned. Therefore, we reviewed the literature and added new data to this subject. Then, we the use of colors (as defensive mechanism) into categories. Mimicry was divided into the subcategories camouflage, homotypy, and nondeceitful homotypy, and these groups were also subcategorized. Dissuasive coloration was divided into behavioral display of colors, polymorphism, and polyphenism. Aposematism was treated apart, but aposematic colorations may be present in other defensive strategies. Finally, we propose functions and forms of evolution for some color systems in post-metamorphic anurans and hope that this review can be the basis for future research, even on other animal groups. © 2009 L. F. Toledo and C. F. B. Haddad.

Use of the elevated T-maze to study anxiety in mice

We have recently suggested that the elevated T-maze (ETM) is not a useful test to study different types of anxiety in mice if a procedure similar to that originally validated for rats is employed. The present study investigated whether procedural (five exposures in the enclosed arm instead of three as originally described for rats) and structural (transparent walls instead of opaque walls) changes to the ETM leads to consistent inhibitory avoidance acquisition (IAA) and low escape latencies in mice. Results showed that five exposures to the ETM provoked consistent IAA, an effect that was independent of the ETM used. However, the ETM with transparent walls (ETMt) seemed to be more suitable for the study of conditioned anxiety (i.e. IAA) and unconditioned fear (escape) in mice, since IAA (low baseline latency with a gradual increase over subsequent exposures) and escape (low latency) profiles rendered it sensitive to the effects of anxiolytic and anxiogenic drugs. In addition to evaluation of drug effects on IAA and escape, the number of line crossings in the apparatus were used to control for locomotor changes. Results showed that whereas diazepam (1.0-2.0 mg/kg) and flumazenil (10-30 mg/kg) impaired IAA, FG 7142 (10-30 mg/kg) did not provoke any behavioral change. Significantly, none of these benzodiazepine (BDZ) receptor ligands modified escape latencies. The 5-HT1A partial receptor agonist buspirone (1.0-2.0 mg/kg) and the 5-HT releaser fenfluramine (0.15-0.30 mg/kg) impaired IAA and facilitated escape, while the full 5-HT1A receptor agonist, 8-OH-DPAT (0.05-0.1 mg/kg) and the 5-HT2B/2C receptor antagonist, SER 082 (0.5-2.0 mg/kg) failed to modify either response. mCPP (0.5-2.0 mg/kg), a 5-HT2B/2C receptor agonist, facilitated IAA but did not alter escape latency. Neither antidepressant utilized in the current study, imipramine (1.0-5.0 mg/kg) and moclobemide (3.0-10 mg/kg) affected IAA or escape performance in mice. The well-known anxiogenic drugs yohimbine (2.0-8.0 mg/kg) and caffeine (10-30 mg/kg) did not selectively affect IAA, although caffeine did impair escape latencies. Present results suggest the ETMt is useful for the study of conditioned anxiety in mice. However, upon proximal threats (e.g. open arm exposure), mice do not exhibit escape behavior as an immediate defensive strategy, suggesting that latency to leave open arm is not a useful parameter to evaluate unconditioned fear in this species. (C) 2003 Elsevier B.V. All rights reserved.

Is it all death feigning? Case in anurans

Anurans are known to feign death as a way to avoid or minimize the risk of predation. However, information on this defensive strategy is scattered and we believe that there is more than one behaviour type referred to as thanatosis. Here we review the literature, add original data, and propose definitions and new names that complement the present knowledge on the subject. We collected information on 334 individuals of 99 species in 16 families and grouped the recorded displays into two categories of tonic immobility: (1) thanatosis, death-feigning, or playing possum, and (2) shrinking or contracting. These two categories are treated as different behaviour types because of the display pattern (position of fore- and hindlimbs, eye opening), presence of skin toxins (shrinking is mostly displayed by toxic species, whereas thanatosis is mostly displayed by non-toxic species), social context (interaction with predators), and their putative or actual functions. © 2010 Taylor & Francis.

Comportamento de lek, frugivora e dispersão de sementes por Manacus Manacus (Linnaeus 1766, Pipridae) em áres de restinga no sudeste do Brasil

Pós-graduação em Ciências Biológicas (Zoologia) - IBRC

Explanations and Representations of Violence by School-age Brazilian Youths

The violence staged by young people has often been subjected to scientific analysis. The way youths speak, in their role as aggressors or as victims, is examined to determine how they experience violence in a number of different spheres. Repeated group interviews are used to analyze how violence is explained and depicted within the family, at school and in the neighbourhood by two groups of young people (14-17 years old) attending the same school on the outskirts of Rio Claro, Sao Paulo, Brazil. One of the groups involved is identified by the school as violent, and the other, as non-violent. Discourse analysis leads to two conclusions. First, the different contexts of violence infuse a mistrust of institutions, the environment and personal relationships into the subjects' experience, forming a fabric that clouds future prospects. Second, the group of youths identified as violent have a more simplistic, pessimistic view of reality: They see the world in black and white, and they lay no stock in the possibility that violence can be avoided. Consequently, they use violence and understand violence as a defensive strategy that gives one identity. On the other hand, the group identified as nonviolent feels it possible to intervene in situations with nonviolent tools like words. For the young subjects, violence is a context that they assume; it cancels their ability to identify rules and institutions, but it does not generate an effective interaction strategy. Violence causes their social microcontext (in which action prevails over meaning or meaning equals action) to assume overblown dimensions. Any intervention strategy must take into account this indissoluble unity between meaning and action.