Exploratory and fear behaviour in the Macropodus opercularis subspecies, M. o. opercularis and M. o. concolor.

The exploratory and fear behaviours of the black paradise fish M. o. concolor, a subspecies of Macropodus opercularis, were studied and compared with those of an outbred and two inbred populations of M. o. opercularis. Adult females of both subspecies were used in the behaviour tests (open-field, novel-object approach, restricted space), and their behaviour in novel and startling situations was described by recording the sequence of ethologically defined units. It was found that M. o. concolor more often responded passively to novelty and fear-evoking stimuli. In 11 out of 14 test measures they were less active (p less than 0.01 and 0.001) than the outbred M. o. opercularis, but were very similar to our extremely timid strain P. Subtle differences of behaviour units were found between the subspecies, e.g. the absence of interrupted movements and unoriented panic behaviour in M. o. concolor. It is supposed that alternative passive and active strategies represent genetic polymorphism of defensive behaviour.