Aversive sexual learning in the kissing bug Rhodnius prolixus: Modulation of different sexual responses in males and females

Although sexual learning can be a key process in the reproductive success of animals, research focused on the experience-dependent modulation of courtship in insects is scarce. In kissing bugs, the behavioural steps implicated in mating have been exhaustively studied, but not the involvement of learning in them. Our objective was to determine whether the sexual behaviour of Rhodnius prolixus could be modulated by experience. During training, couples were submitted to eight assays, in which they received a vibration (negative reinforcement) when the male attempted to copulate the female. Immediately after, they were separated, not allowing the occurrence of copulation. We found that along training, males' latency to perform a copulatory attempt increased, male's copulatory attempts were less frequent, and females' locomotor activity did not change. These results suggest that males, and not females, learned to avoid the vibration by reducing their intention to copulate. In post-training tests, conditioned males presented with new naïve females reverted to low copulatory attempt latencies, suggesting that the modulation was partner-specific. Besides, conditioned females increased their rejection frequencies to males' copulatory attempts, suggesting that a second type of learning occurred in females. These results constitute the first evidence of sexual learning in hematophagous insects. Males and females seem to change their selectivity according to their previous sexual experience. We discuss the relevance that this plasticity might have in the fitness of this epidemiologically relevant insect.

Probabilistic inference and Bayesian-like estimation in animals: Empirical evidence

Animals often make decisions without perfect knowledge of environmental parameters like the quality of an encountered food patch or a potential mate. Theoreticians often assume animals make such decisions using a Bayesian updating process that combines prior information about the frequency distribution of resources in the environment with sample information from an encountered resource; such a process leads to decisions that maximize fitness, given the available information. I examine three aspects of empirical work that shed light on the idea that animals can make such decisions in a Bayesian-like manner. First, many animals are sensitive to variance differences in behavioral options, one metric used to characterize frequency distributions. Second, several species use information about the relative frequency of preferred versus nonpreferred items in different populations to make probabilistic inferences about samples taken from populations in a manner that results in maximizing the likelihood of obtaining a preferred reward. Third, the predictions of Bayesian models often match the behavior of individuals in two main approaches. One approach compares behavior to models that make different assumptions about how individuals estimate the quality of an environmental parameter. The patch exploitation behavior of nine species of birds and mammals has matched the predictions of Bayesian models. The other approach compares the behavior of individuals who learn, through experience, different frequency distributions of resources in their environment. The behavior of three bird species and bumblebees exploiting food patches and fruit flies selecting mates is influenced by their experience learning different frequency distributions of food and mates, respectively, in ways consistent with Bayesian models. These studies lend support to the idea that animals may combine prior and sample information in a Bayesian-like manner to make decisions under uncertainty, but additional work on a greater diversity of species is required to better understand the generality of this ability.

The causes and evolutionary consequences of variation in female mate choice in insects: the effects of individual state, genotypes and environments

Sexual selection generally involves males evolving secondary sexual characters that satisfy the mating preferences of females. Behavioral ecologists have spent considerable research effort on identifying how variation in sexually-selected traits in insects is maintained among males at the expense of investigating the proximate and ultimate causes of variation in female mating preferences for those male traits. The past decade has witnessed improved effort in redressing this bias in insects with researchers identifying a host of factors intrinsic and extrinsic to the female as mediating flexibility in female mating behavior. Evidence is mounting that a female's social environment, whether experienced during development or as an adult, is key to shaping her mating preferences. Others have extended these observations to show that the genetic identity of the conspecific individuals comprising the social environment can have profound effects on female mating preferences via indirect genetic effects (IGEs), or through interspecific indirect genetic effects (IIGEs) if the genotype of heterospecifics influences plasticity in mating preferences. Considerably more work is needed to not only expand our list of mediating intrinsic and extrinsic factors but also to identify how their interaction influences individual variation in male and female mating preferences.