| Budget Amount *help |
¥3,400,000 (Direct Cost: ¥3,400,000)
Fiscal Year 2004: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 2003: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 2002: ¥2,100,000 (Direct Cost: ¥2,100,000)
|
|---|
| Research Abstract |
"Self-feeding" is an effective tool for studying the sociality of fish group. That is to say, the place of switch of self-feeding system in a tank is recognized as a good baiting field by fish and a competition must occur for occupying this nice place between individuals. Under such a competitive circumstance, the social hierarchy may be established within a fish group and there is a possibility that this complex process can be analyzed using self-feeding method. In this experiment, we analyze the social dominance of bluegill sunfish Lepomis macrochirus and goldfish Carassius auratus using both switch activating frequency and food in take frequency of fish individuals under self-feeding condition.
Self-feeding behavior of two individuals with distinguishable colored markers implanted at the basal part of dorsal fin was recorded with video camera and whether which fish activated the switch and whether which fish took the delivered food was observed. Two sets of competition experiment wer
… More
e established simultaneously, and if the rank is observed at the end of the experiments, then a new experimental group was established using a combination of dominant individuals from the former experimental tanks. At the meantime, a new experimental group using a combination of subordinate individuals was also established. And then, 2 competition experiments were repeated again and their self-feeding behavior was observed.
In the competition experiment, individual concerning the switch activation and the individual that is not concerned were observed in both fish species. This may be due to the difference in the learning ability of each individual. The discrepancy of switch activation frequency between two individuals became larger and larger by the time courses of the experiments, and this may be due to the re-enforcement of learning by the repetition of the switch activation in self-feeding behavior. Concerning the food intake frequency, however, large difference was observed between two fish species. In goldfish, even the subordinate that did not operate the switch was able to take pellet, and the body weight increased. On the contrary, the subordinate in bluegill could not take pellet by the suppression by dominant fish, and the body weight of the subordinate decreased. Therefore, in the bluegill, the difference in the learning ability for the self-feeding and its aggressive temperament complementarily promoted the production of the strong social hierarchy in the fish group. In the goldfish, it is indicated that the social hierarchy may not exist in this species, though the difference of the learning ability for the self-feeding do exists. Less
|
