Status-dependent female mimicry in landlocked red-spotted masu salmon

We observed transient status-dependent female mimicry related to reproductive behaviour in landlocked red-spotted masu salmon (Oncorhynchus masou ishikawae). In females, the lower half of the lateral flank underwent solid blackening as an ovipositional character, and 70% of subordinate males showed a similar lateral pattern (M-type). In contrast, most of the paired males and 30% of subordinate males showed a different lateral pattern in which a melanic stripe ran along the lateral-line organ (N-type). It was possible to bring an M-type pseudo-fish model into closer proximity to a pair than an N-type model. In addition, the rate of successful sperm release in subordinate M-type males was higher than that in subordinate N-type males. Males could transform between N- and M-types according to fluctuations in competitive status among the males. A digital video image related to the article is available at http://www.momo-p.com/showdetail-e.php?movieid=momo050119rm01a.