The scent of stress: Pintado catfish differentially respond to chemical cues from stressed conspecifics

We examined whether pintado catfish (Pseudoplatystoma corruscans) can discriminate between scents of non-injured conspecifics stressed by a predator or by confinement and how fish use this information in the trade-off between feeding and predator avoidance. In the confinement stress condition, fish ingested the food, whereas in the predator stress condition, fish did not eat. This finding and comparisons of the latency to food ingestion and the time spent swimming between the confinement and predator-stress conditions indicated that pintado catfish can discriminate between conspecifics stressed by a predator or confinement using chemical cues, and use this information for adjusting the trade-off between food intake and predator avoidance.

Sexual Differences in the Behavior of the Harvestman Leiobunum vittatum (Opiliones, Sclerosomatidae) Towards Conspecific Cues

Preliminary observations of the harvestman Leiobunum vittatum found that individuals rub their bodies against the substrate, presenting the possibility of chemical marking. To determine whether or not L. vittatum individuals can detect substrate-borne chemical cues, we compared responses of L. vittatum males and females to substrate-borne male and female cues. We found that individuals of L. vittatum do respond to conspecific cues and that their responses are sex-specific. In response to substrate-borne conspecific cues, male L. vittatum spent more time, engaged in more scraping with their sensory legs I, and engaged in pedipalpal tapping more often in the presence versus absence of conspecific cues (male and female equally). Furthermore, in the presence of conspecific cues, males engaged in two behaviors never observed in females-(a) "fast approach" and (b) "jerking", the latter of which was never observed in the presence of cricket cues. In contrast to males, females did not spend more time on conspecific cues, but did spend more time tapping their pedipalps in the presence of male vs female cues, suggesting an ability to distinguish between them. A final experiment explored the possibility that females could discriminate among males of varying histories of agonistic interactions based upon their chemical cues. We found no support for this hypothesis. Our results demonstrate that L. vitattum do respond to conspecific cues, and introduce the possibility that intraspecific communication may be mediated in part by chemical cues.

Behavioral characterization of the alarm reaction and anxiolytic-like effect of acute treatment with fluoxetine in piaucu fish

In Ostariophysan fish, the detection of the alarm substance liberated into the water as a consequence of an attack by a predator elicits an alarm reaction or anti-predatory behavior. In this study, experiments were performed to: (i) describe and quantitatively characterize the behavioral and ventilatory responses in piaucu fish (Leporinus macrocephalus), individually and as part of a school, to conspecific alarm substance (CAS) and; (ii) test the effect of acute fluoxetine treatment on alarm reaction. Histological analysis revealed the presence of club cells in the intermediate and superficial layers of the epidermis. The predominant behavioral response to CAS was freezing for fish held individually, characterized by the cessation of the swimming activity as the animal settles to a bottom corner of the aquarium. Fish exposed to CAS showed decrease in the mean ventilatory frequency (approximately 13%) relative to control. In schools, CAS elicited a biphasic response that was characterized by erratic movements followed by increased school cohesion and immobility, reflected as an increased school cohesion (65.5% vs. -5.8% for controls) and in the number of animals near the bottom of the aquarium (42.0% vs. 6.5% for controls). Animals treated with single i.p. injections of fluoxetine (10 mu g/g b.w.) did not exhibit alarm behavior following CAS stimulation. These results show that an alarm pheromone system is present in piaucu fish, evidenced by the presence of epidermal club cells and an alarm reaction induced by CAS and consequently of a chemosensory system to transmit the appropriate information to neural structures responsible for initiating anti-predator behavioral responses. In addition, fluoxetine treatment caused an anxiolytic-like effect following CAS exposure. Thus, the alarm reaction in piaucu can be a useful model for neuroethological and pharmacological studies of anxiety-related states. (C) 2011 Elsevier Inc. All rights reserved.