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Loose aggregations of fishes, or shoals, are a basal social organization of vertebrates and offer a valuable opportunity to determine how individual perceptions influence group formation. We used zebrafish, Danio rerio, to comprehensively investigate the preference space for shoaling related to adult pigment pattern variation, presented in the form of 17 zebrafish pigment pattern mutants or closely related species. We examined all combinations of these phenotypes in 2,920 initial and replicated preference tests, and used as subjects both domesticated laboratory stocks and wild-caught fish. By using multidimensional scaling and other approaches, we show that laboratory and wild zebrafish exhibit similar preferences, yet, unexpectedly, these preferences differ markedly between sexes, and also from how human observers perceive the same pigment patterns. Whereas zebrafish males respond to two traits (species and stripe patterning) in deciding whether to join a shoal, zebrafish female preferences do not correlate with a priori identifiable traits, and neither perceptual world is correlated with that of human observers. The observed zebrafish sex differences run counter to the most commonly accepted explanations for the individual selective advantages gained by shoaling. More generally, these data describe very different perceptual worlds between sexes and reveal the importance of sex differences in social group formation, as well as the critical importance of defining species specificity in visual signaling. perception | pigment pattern | shoaling | social behavior | zebrafish

Zebrafish are studied for shoaling behavior in warm and cold water temperatures. The fish preferred the larger shoal in general, but the preference was reduced in colder water. Zebrafish were seen to prefer a more active shoal despite a smaller size of shoal.

The mechanisms and the problems faced while determining magnetoreception in animals, the way they orient themselves using the Earth's magnetic field, is discussed. It is suggested that instead of migratory animals, zebrafish and fruit flies should be used to gain better understanding of the phenomenon.

An analysis of the research on knowledge of the ecology and behavior including shoaling, foraging, reproduction, sensory perception and learning of the zebrafish Danio rerio is presented. The researches are analyzed with regards to the aptness of the zebrafish as a framework organism in studies on cognition and learning, development, behavioural and evolutionary ecology, and behavioural genetics.

Understanding the neuronal basis of behavior typically requires monitoring activity of the relevant neurons during behavior, working out the wiring diagrams of the circuits for the behavior of interest, and then perturbing the system to test the contribution of the neurons to behavior. Conventional approaches to studies of neuronal function depend upon recording from individual neurons with microeletrodes. These approaches provide essential information about activity patterns and connectivity, but are limited in their ability to easily monitor and perturb the activity of many neurons throughout the nervous system. We have been developing optical and genetic tools to study neuronal function that compliment electrophysiological methods. Our work focuses on the motor system of larval zebrafish and takes advantage of both the transparency of the fish as well as genetic tools available for zebrafish. By filling neurons with fluorescent calcium indicators, we can look into the intact fish and literally watch the active neurons light up when the fish performs a particular motor behavior. We have used this approach to explore which hindbrain and spinal neurons contribute to swimming and escape behaviors. By imaging several neurons at once, we have examined how activity in groups of spinal motoneurons and identified spinal interneurons varies with behavioral performance. In addition to monitoring activity, we can perturb activity by killing cells with a laser beam to assess more directly the behavioral contributions of neurons. Finally, genetics also allows for perturbation 'experiments' through studies of mutant lines with extra neurons or mis-wired circuits. The combination of optical and genetic approaches with more conventional physiology allows for a powerful attack on the neuronal basis of behavior.

Eyeless zebrafish larvae may still find their way out of darkness by the activation of light-sensitive neurons deep inside the brain. Harold Burgess at the National Institute of Child Health [...]