Studies On Spatial Learning And Memory Of Some Freshwater Fishes

The studies on neural sciences elicit the upsurge of cognition researches, leading the development of learning and memory researches in animals. The last 10 years has witness a relative explosion of the number of papers on learning and memory researches in fishes. Those researches change our obsolete conceptions of the psychological and cognitive abilities of fishes. Fishes were no longer dims with"three-second memory". They are steeped in social intelligence and exhibit impressive long-term memories. In present study, the ability of spatial learning and memory of some freshwater fishes were studied through the comparison of differences among different species, sexes and individuals. The adaptation and evolution of spatial cognition in fishes were revealed in this work. The main results are as following:1. The different spatial cognition ability displayed by fishes in 3 setted conditions, with no visual landmark, with a single landmark, and with two different color landmarks, was studied using rose bitterling, zebrafish, gobiocypris minnow, and mandrain fish. The results showed that only rose bitterling and gobiocypris minnow could solve the spatial problem in T-maze with no landmark; all these species could solve the spatial problem with one landmark, while Rose bitterling and zebrafish could solve the similar problem with two different coulor landmarks. The results indicated that capability of spatial cognition in fishes was consistent with their habitats, habits and phylogenetic relationships, and strongly affected by their environments.2. The differences of spatial learning and memory between male and female fishes were investigated using three bitterling species, Rhodeus ocellatus, R. lighti, and R. fangi with T-maze. The results showed that, the capability of spatial cognition in female excelled that in male.3. The differences of cognition capability among individuals were studied using 16 R. ocellatus in T-maze with one landmark. The results revealed that significant difference of learning and memory capacity existed in different individuals of R. ocellatus. Based on their very different trial numbers, the male was found in two types, fast learning type and slow learning type, which was suggested related to their different reproduction strategies: territorier males with inferior spatial cognition ability need more trials times (slow type), and the sneakers with better spatial cognition ability need less trials times (fast type).