Extremely early maturity found in Okinawan gobioid fishes

 Extremely small animals including fishes have been reported with discussion of the causes and consequences of their miniaturization. Here we demonstrate, for the first time, very early (i.e., 23–60 days old and 42–67 days old) sexual maturity in two groups of gobioid fishes (Schindleria and Paedogobius, respectively) in warm water, based on the otolith increments. The generation time of Schindleria is the shortest known among vertebrates under natural conditions. We discuss the occurrence and evolutionary significance of the progenesis found in gobioid fishes. Received: September 27, 2001 / Revised: January 26, 2002 / Accepted: February 20, 2002