The El strain, which is an epileptic mutant originated from ddN mice and is characterized by the developmental increase of seizure sensitivity, has been taken to have emotional abnormalities, but with few detailed investigations on its behavioral and emotional responses. The recent study indicated that the genetic and maternal factors were the most important for the behavioral development in mice. In this study, therefore, we investigated the developmental characteristics of behaviors (especially the emotional responses) of the El strain, the genetic dominance of the behaviors, the effects of the maternal environment on them, and the relationship between the behavioral development and the occurrence of epileptiform seizure of the strain.
The El pups, the ddN pups, and their reciprocal hybrids were subjected to the observation and test of walking, three reflexes, and three emotional responses from birth till 34 days. They were also subjected to the seizure-provoking test at 10 to 16 weeks of age.
In result, many differences of emotional responses between the El and ddN pups were found : these responses of the El pups developed faster than those of the ddN pups (Table 1, Fig. 1). Three types of dominance (complete dominance, partial dominance, and overdominance) were evaluated by comparing the emotional responses of the parental strains with those of their hybrids. These indicate that the behavioral differences between the El and ddN pups are regulated by their genetic differences, and that different emotional response is produced on the different genetic basis. Many reciprocal maternal effects were found in the emotional responses (Table 1). The maternal environment plays an important role in the development of emotional responses. The occurrence of seizure in the hybrids was similar to that in the ddN pups (Fig. 2). This finding is inconsistent with the report which took the seizure of the El strain as a genetically dominant anomaly. The direct relationship between the development of emotional responses and the occurrence of seizure was not found. It suggests that they are the different characters of the El strain.

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This investigation sought to describe the mother-infant relationship during infant development in captive chimpanzees.
Two mother-infant pairs of chimpanzees at the Tama Zoological Park were the subjects of this study. The infants, respectively two (Nana) and three (Apple) years old, were observed at a week interval over a year.
On the basis of naturalistic observations,
1) the physical and cognitive development of infants were assessed,
2) the effect of other chimpanzees “especially siblings” on the mother-infant relationship was ascertained
Results indicated that these infants, from 2 to 3 years old, were more independent from their mothers than 0 or 1 year olds. But, contrary to expectations, Apple, 3 years old, appeared to be more dependent on its mother than 2 years old Nana. It is thought that Nana's siblings and the mother's ranking may have been responsible for this. Thus, after 2 years old, the mother-infant relationship becomes apparently affected by the social organization.
These results are discussed with other studies about chimpanzees and early human mother-infant interactions.

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[in Japanese]

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