Agonistic Behavior Is Affected by Memory in the Dusky Damselfish Stegastes fuscus

The ability to discriminate familiar from unfamiliar conspecifics has been demonstrated in several species of fish. Agonistic interactions are among the most frequent behaviors exhibited by territorial species and could offer useful information for the individual recognition process. In agonistic situations, memory may modulate the behavioral response and affect social dynamics, but few studies have explored the memory retention acquired during aggressive encounters. The present study investigated the memory retention of an agonistic encounter in the dusky damselfish Stegastes fuscus. The experimental procedure was divided into three parts: (1) Familiarization; (2) Recognition test; and (3) Memory test. During the familiarization phase, the fish were visually exposed to the same conspecific for 5 days (10 min per day) and the behavior was recorded. On the following day (conspecific recognition test), half of the animals were paired with the same conspecific and the other half with a different conspecific for 10 min, and the behavior was recorded. The fish were retested 5, 10, and 15 days after the test to evaluate memory retention. In the memory test, they were exposed to the same conspecific as before or to a different conspecific. We found that the damselfish reduced their agonistic displays when the stimulus fish was familiar, but when it was unfamiliar, the animals were more aggressive and only reduced their mnemonic response after 10 days. These results suggest that the recognition ability of damselfish can be affected by time and that it modulates agonistic response.

Female choice for large body size in the cave molly, Poecilia mexicana (Poeciliidae, Teleostei): influence of species- and sex-specific cues

Previous studies revealed that females of a cave form of the livebearing fish Poecilia mexicana (cave molly) have maintained the ancestral visual preference for large males, but — as an adaptation to life in darkness — they have evolved the novel capability to assess male size non-visually. Here we examined the mechanisms by which non-visual mate choice for large body size occurs. Are sex- and species-specific chemical cues involved in this preference for large conspecifics? We gave focal females an opportunity to associate with a large and a small stimulus fish in simultaneous choice tests, whereby the females could perceive either multiple cues (visual plus non-visual) from the stimulus fish, solely non-visual cues in darkness, or solely visual cues. Stimulus fish were two conspecific males, conspecific females, or heterospecific females (Xiphophorus hellerii). Cave molly females showed a significant preference for large conspecific males and for large conspecific females in all treatments. When a large and a small swordtail female were presented, cave molly females showed a preference for the larger fish only when exclusively visual cues from the stimulus fish were available. The non-visual preference for large body size appears to be mediated by species- but not by sex-specific cues, suggesting that species-specific chemical cues play an important role during mate choice.

Sex recognition in surface and cave dwelling male Atlantic mollies Poecilia mexicana (Poeciliidae, Teleostei)

Animals colonizing lightless subterranean habitats can no longer rely on visual signals to find mating partners. In the present study, we investigated the ability of males to recognize females in two surface and a cave dwelling population of a livebearing fish, Poecilia mexicana. In surface populations males discriminated between sexes with visual plus non-visual cues available and with visual stimuli only. In the cave form the ability to discriminate with solely visual stimuli is lacking. In all three populations, males did not recognize females in darkness (infrared observations), suggesting that sex recognition via far-field communication is lacking in surface and cave dwelling P.mexicana. Different preferences in large and small males to stay near a female or a male stimulus fish probably reflect differences concerning a trade-off between sexual and aggressive behaviour.

The relationships among nuptial coloration, aggression, and courtship of male three-spined sticklebacks, Gasterosteus aculeatus

A method was devised, using several independent judges, to estimate the degree of nuptial coloration of male three-spined sticklebacks, Gasterosteus aculeatus. Using the color-state scores that resulted from this technique, territorial males were compared with respect to their coloration level and with respect to their responsiveness to live and dummy stimulus fish. These comparisons reveal a positive association between color state and responsiveness: brightly colored males tend to court (zigzag) and attack (bite) stimulus fish more vigorously than duller colored males do. Therefore, the degree to which a male three-spined stickleback's nuptial coloration is developed can be used to some extent to predict its responsiveness, with the particular category of response (courtship or aggression) dependent on the stimulus presented. A close association between zigzag and bite frequencies was also found, responsive males showing higher levels of both courtship and aggression than less responsive ones. These results are consistent with evidence pertaining to the hormonal control of nuptial coloration, courtship, and aggression and to the signal value of nuptial coloration in G. aculeatus.

Retention and Recovery of Habituated Territorial Aggressive Behavior in the Three-Spined Stickleback (Gasterosteus Aculeat Us L.) : the Roles of Time and Nest Reconstruction

Factors involved in the recovery and reinstatement of a territorial resident's aggression directed at an intruder after habituation were studied in the Three-spined Stickleback (Gasterosteus aculeatus). In the first experiment it was demonstrated that following initial habituation to the intruder, there was no recovery of response after 3-5 days, but there was virtually complete recovery after 14 days. It was further shown that if the stickleback's nest is removed and he rebuilds the nest between the first habituation session and the test, there is complete recovery following nest reconstruction. A second series of experiments shows that the recovery following nest removal and reconstruction is prevented if the fish is prevented from reconstructing the nest. It was further found in two additional sub-experiments that allowing post-habituation nest reconstruction appeared to re-set memory for the habituated stimulus such that the intruding stimulus fish appears novel to the territorial resident, thus abolishing the stimulus specific nature of such habituation.