EVOLUTIONARY AESTHETICS AND SEXUAL SELECTION IN THE EVOLUTION OF ROCK ART AESTHETICS

This theoretical proposal applies evolutionary aesthetic, animal signalling and sexual selection to understand our artistic cognition, especially rock art aesthetics. Iconographic motifs, universally found in rock art, indicate which set of pre-artistic aesthetic psychological bias has been co-opted to catch the viewer`s attention. The co-evolutionary process of sexual selection could have shaped the design features of both rock art images and their aesthetic cognition by conferring mutual benefits on both producers, via manipulation, and receivers, via information extraction. We show some strategic techniques identified in rock art and art that indicate the occurrence of this co-evolution between producers and receivers.

Loss of male secondary sexual structures in allopatry in the Neotropical butterfly genus Arcas (Lycaenidae: Iheclinae: Eumaeini)

Male secondary sexual characters in Lepidoptera may be present or absent in species that otherwise appear to be closely related, an observation that has led to differences of opinion over the taxonomic usefulness of these structures above the species level. An evolutionary issue raised by this debate is whether male secondary sexual characters (1) can be regained after being lost evolutionarily, (2) are not lost after being evolved, or (3) are 'switched on and off' by genes that regulate development. A second evolutionary issue is the conditions under which male secondary sexual characters might be lost or gained evolutionarily. Because these structures are thought to promote species recognition, theory predicts evolutionary losses to be most likely in allopatry; evolutionary gains to be most likely during the process of secondarily establishing sympatry or during sympatric speciation. We updated the species-level taxonomy of the brilliant emerald winged Neotropical lycaenid butterfly genus Arcas and performed an analysis of phylogenetic relations among species to assess these evolutionary issues. We morphologically detail a scent pouch on the ventral hindwing of Areas and report that six species possess the pouch with androconia, one possesses the pouch without androconia, and the remaining two species have neither pouch nor androconia. In addition, eight Areas species have a morphologically species-specific male forewing scent pad, and one lacks a scent pad. This variation appears to be the result of three evolutionary losses and no gains of male secondary sexual organs. The four Areas species lacking a scent pouch or a scent pad are allopatric with their closest phylogenetic relatives while four of five with both of these structures are sympatric. Although Arcas is a small genus, these results are significantly more extreme than predicted by chance. For taxonomy, this study provides a rationale for the evolutionary loss of male secondary sexual structures and suggests that their absence, but itself, does not indicate a lack of relationship above the species level.

Mating behaviour, nympho-imaginal development and description of a new Mesabolivar species (Araneae: Pholcidae) from the Brazilian dry forest

A new species of Mesabolivar is described from Brazilian forests: Mesabolivar delclaroi. The mating behaviour, postembryonic development, number of egg sacs and eggs, birth rate, number of instars, developmental time until adulthood, sex ratio and size of cephalothorax (per instar) were recorded. The sexual behaviour was described and categorized into four steps: courtship, pre-copulation, copulation and post-copulation. After hatching, individuals presented five instars until maturity. The mean number of eggs (42 +/- 16.6) and live births (31.5 +/- 3.4) of the first egg sac were significantly greater than that of a second one (23.8 +/- 3.8, and 19.25 +/- 3.9, respectively). The developmental time from birth to adulthood (130.8 +/- 9.6 days) did not differ significantly between egg sacs produced (128.61 +/- 11.1). The size of the cephalothorax did not differ among adults or between sexes. The sex ratio revealed a shift in favour of females (4: 3).

Reproductive interference between two sibling species of gift-giving spiders

We investigated the possibility of reproductive interference between two sibling spider species, Paratrechalea azul and Paratrechalea ornata, which occur syntopically and reproduce synchronously. Males of both species offer a nuptial gift composed of prey wrapped in silk to females. Through laboratory experiments, we evaluated possible asymmetries in the outcome of heterospecific encounters between males and females, and investigated whether chemical signalling could function as a premating barrier between the two species. Males of P. azul were unable to discriminate conspecific from heterospecific female draglines, which resulted in wasted time and energy in nuptial gift construction. Males of P. ornata incurred a higher cost for discrimination mistakes because most of them were attacked by heterospecific females; 95% lost the nuptial gift upon the attack and 33% were preyed upon. This pattern is probably a consequence of differences in body size between males and females of each species. Both species showed erroneous female choice, but only P. ornata females courted heterospecific males, which are considerably larger than conspecific males and may resemble high-quality mating partners. Males of P. ornata also made discrimination mistakes, but at a much lower frequency compared to P. azul males. The selective pressure for precise recognition of conspecific female signs is probably stronger on P. ornata males because misdirected courtship may increase their chances of encountering predatory heterospecific females. This study provides the first detailed evidence of reproductive interference between two reproductively isolated spider species, showing that the costs paid by individuals of different sexes and different species are highly asymmetric. (C) 2012 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.

The neuroimmune changes induced by cohabitation with an Ehrlich tumor-bearing cage mate rely on olfactory information

Cohabitation for 14 days with Ehrlich tumor-bearing mice was shown to increase locomotor activity, to decrease hypothalamic noradrenaline (NA) levels, to increase NA turnover and to decrease innate immune responses and decrease the animals' resistance to tumor growth. Cage mates of a B16F10 melanoma-bearer mice were also reported to show neuroimmune changes. Chemosignals released by Ehrlich tumor-bearing mice have been reported to be relevant for the neutrophil activity changes induced by cohabitation. The present experiment was designed to further analyze the effects of odor cues on neuroimmune changes induced by cohabitation with a sick cage mate. Specifically, the relevance of chemosignals released by an Ehrlich tumor-bearing mouse was assessed on the following: behavior (open-field and plus maze); hypothalamic NA levels and turnover; adrenaline (A) and NA plasmatic levels; and host resistance induced by tumor growth. To comply with such objectives, devices specifically constructed to analyze the influence of chemosignals released from tumor-bearing mice were employed. The results show that deprivation of odor cues released by Ehrlich tumor-bearing mice reversed the behavioral, neurochemical and immune changes induced by cohabitation. Mice use scents for intraspecies communication in many social contexts. Tumors produce volatile organic compounds released into the atmosphere through breath, sweat, and urine. Our results strongly suggest that volatile compounds released by Ehrlich tumor-injected mice are perceived by their conspecifics, inducing the neuroimmune changes reported for cohabitation with a sick companion. (C) 2011 Elsevier Inc. All rights reserved.

Paternal Care Decreases Foraging Activity and Body Condition, but Does Not Impose Survival Costs to Caring Males in a Neotropical Arachnid

Exclusive paternal care is the rarest form of parental investment in nature and theory predicts that the maintenance of this behavior depends on the balance between costs and benefits to males. Our goal was to assess costs of paternal care in the harvestman Iporangaia pustulosa, for which the benefits of this behavior in terms of egg survival have already been demonstrated. We evaluated energetic costs and mortality risks associated to paternal egg-guarding in the field. We quantified foraging activity of males and estimated how their body condition is influenced by the duration of the caring period. Additionally, we conducted a one-year capture-mark-recapture study and estimated apparent survival probabilities of caring and non-caring males to assess potential survival costs of paternal care. Our results indicate that caring males forage less frequently than non-caring individuals (males and females) and that their body condition deteriorates over the course of the caring period. Thus, males willing to guard eggs may provide to females a fitness-enhancing gift of cost-free care of their offspring. Caring males, however, did not show lower survival probabilities when compared to both non-caring males and females. Reduction in mortality risks as a result of remaining stationary, combined with the benefits of improving egg survival, may have played an important and previously unsuspected role favoring the evolution of paternal care. Moreover, males exhibiting paternal care could also provide an honest signal of their quality as offspring defenders, and thus female preference for caring males could be responsible for maintaining the trait.

Male dimorphism of a neotropical arachnid: harem size, sneaker opportunities, and gonadal investment

Serracutisoma proximum is a harvestman with alternative male morphs. Large males use sexually dimorphic second legs in fights for the possession of territories on the vegetation, where females oviposit. Small males have short second legs and do not fight but rather sneak into the territories and copulate with egg-guarding females. We investigated the presence of male dimorphism across 10 populations of S. proximum, compared gonadal investment between male morphs, and assessed if the distribution of the sneakers is influenced by harem size. In all populations, there was male dimorphism, indicated by the bimodal distribution of the leg II length/body length. Gonadal investment did not differ between morphs and was not affected by male size, second leg length, and morph relative frequency in the populations. We found 361 territories, 90.0% containing 1 male, 9.7% containing 2 males (dyads), and 0.3% containing 3 males. The probability of encountering dyads increased with the number of females present in the territories. Moreover, the proportion of sneakers in territories containing dyads was higher than would be expected by chance. One possible reason for the ubiquity of alternative morphs in S. proximum could be the high mating opportunities experienced by sneakers in spatially structured populations with a resource defense polygyny system. Additionally, the high frequency of successful invasions by sneakers and hence the high sperm competition risk for both morphs may explain the similarity in gonadal investment between male morphs.

It is a matter of taste: chemical signals mediate nuptial gift acceptance in a neotropical spider

Nuptial gift offering is a courtship trait found among several insect orders and some spider families. Recent studies indicate that this gift-giving behavior in spiders represents the male mating effort acting on female receptivity through a mechanism of foraging motivation. However, little attention has been given to the sensory channels that are influencing female acceptance. To understand the role of these sensory channels in female perception of a nuptial gift, we focused on the nuptial gift of the neotropical spider Paratrechalea ornata (Araneae, Trechaleidae). The nuptial gift of this species is composed of a prey item wrapped in silk, and previous works suggest that visual and/or chemical cues may be involved in inducing female grasping behavior. We isolated sensory channels using mimetic nuptial gifts (artificial items) or by manipulating real nuptial gifts. Isolated visual signals were not responsible for female acceptance, whereas chemical signals found within the nuptial gift silk layer induced female acceptance. Our findings clearly indicate that a chemical signal located in the silk of the nuptial gift is the main attractant channel, and we formulated 2 hypotheses to explain the mechanisms of action in the female sensory system. We also discuss the consequences of such signaling over female acceptance.

Territoriality and male-biased sexual size dimorphism in Argia reclusa (Odonata: Zygoptera)

In Odonata, many species present sexual size dimorphism (SSD), which can be associated with male territoriality in Zygoptera. We hypothesized that in the territorial damselfly Argia reclusa, male-male competition can favor large males, and consequently, drive selection pressures to generate male-biased SSD. The study was performed at a small stream in southeastern Brazil. Males were marked, and we measured body size and assessed the quality of territories. We tested if larger territorial males (a) defended the best territories (those with more male intrusions and visiting females), (b) won more fights, and (c) mated more. Couples were collected and measured to show the occurrence of sexual size dimorphism. Results indicated that males are larger than females, and that territorial males were larger than non-territorial males. Larger territorial males won more fights and defended the best territories. There was no difference between the mating success of large territorial and small non-territorial males. Although our findings suggest that male territoriality may play a significant role on the evolution of sexual size dimorphism in A. reclusa, we suggest that other factors should also be considered to explain the evolution of SSD in damselflies, since non-territorial males are also capable of acquiring mates.