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Video playback is a widely used technique for presentation of visual stimuli in animal behavior research. In the analysis of behavioral responses to social cues, presentation of video recordings of live conspecifics represents a consistently reproducible stimulus. However, video-recordings do not interact with the experimental subject, and thus this stimulus may be inferior in the social context. Here, we evaluated how angelfish (Pterophyllum scalare) respond to a video playback of conspecifics versus a live shoal of conspecifics. Using binary choice tests, subjects were presented different stimuli. Time spent close to one versus the other stimulus was considered an index of preference. We found angelfish to prefer a live shoal of conspecifics to an empty tank, and also the video playback of a shoal of conspecifics to a blank screen, although the level of preference in the latter was lower than in the former. These results indicate that video-playback of live conspecifics may be appropriate in angelfish, thus allowing manipulation of specific cues that angelfish may use in quantity discrimination. However, when we directly contrasted a live and a video recorded shoal, both having the same number of members, experimental fish preferred the live shoal. When the choice consisted of a live shoal of four conspecifics versus a video playback of a shoal of nine conspecifics no clear preference emerged. These results imply that video-playback has disadvantages in quantity discrimination studies with angelfish. Exploring procedural and/or technological parameters will verify the suitability of video-recording-based stimulus presentation for future use in angelfish.

Zebrafish are used as model species in biomedical research in which behavior is often used as readout for screening purposes or studying neurobiological processes. In general, the outcome of behavioral assays and thereby replicability between and within laboratories is sensitive to test environments, husbandry conditions, and strains (genotype). This chapter focuses on strain as source of variation. Currently, different strains are being used, such as AB, TU, WIK, and TL. These strains differ in genetic makeup due to their differences in origin and breeding history and to specific mutations such as in TL. This may lead to substantial differences in behavior. Here, we highlight differences between AB and TL, the focus of our recent studies. TL carries a mutation leading to spots or “tupfel” (a mutation in the connexin 41.8 (Cx41.8) gene) and a mutation leading to long fins (mutation in the lof gene). Cx41.8 plays a role in gap junctions that allow intercellular communication and is present in the eye, heart, and brain in addition to the skin. Therefore, mutations herein may be expected to have effects in behavioral assays. We have shown that larvae of the TL strain habituate more slowly to a series of acoustic/vibrational stimuli than larvae of the AB strain. Larvae of a leopard strain that carry a similar mutation also show slower habituation. This makes it likely that the mutation in Cx41.8 underlies this difference in habituation. Adults of the TL showed long periods of inactivity compared to adults of AB, which we argue may be related to the long fins due to the mutation in lof. Thus, we show that strain is a source of variation that should be taken into account to enhance replicability of data.

The paradise fish, a small insectivore, coinhabits marshes of Southeast Asia with several predator fish species. Its ability to recognize and avoid harmful fish may depend upon both genetic factors and experience. Here we demonstrate genetic variability between the 20-day-old larvae of two inbred strains of paradise fish (P and S) in predator exploration and avoidance, using predator models. We show that, in comparison to S larvae, P larvae exhibited an elevated frequency of leaping and backing and an increased approach latency when faced with a predator model with eyespots. Analysis of a classical cross system between the two strains revealed significant departure from an additive-dominance genetic model and suggested the involvement of both epistatic effects of several genes and paternal effects. The effect of the paternal influence during the 5-day postspawning period was found to be strain dependent: later predator avoidance behaviors were influenced by the presence of the father in P larvae but not in S larvae. On the basis of these and previous results, we speculate that the 5 postspawning days may represent a developmentally sensitive period during which specific environmental stimulation, e.g., stimuli associated with the father, is critical for later development of appropriate antipredatory responses. We conclude that developmental aspects of antipredatory behavior in paradise fish are influenced by a complex interplay between genetic and environmental factors.