1990 Volume 37 Issue 1 Pages 17-28
The larval development of Tribolodon hakonensis is described, and its sequence is characterized by six intervals of morphological, functional and behavioral development. The larval development of this species is a roughly double-folded process consisting of feeding and swimming functions, developments of which begin independently. A comparison with other related species of different reproductive and larval life styles reveals that the development of only one function, such as feeding-related development, may be shifted in adapting and regulating their sequence of intervals to the natural environments. Then the path through the development, i.e. the sequence of intervals, can vary according to different reproductive and larval life styles. For example, Abramis, a phyto-lithophils open substratum spawner, and Carassius, a phytophils open substratum spawner, develop feeding-related functions, absorb yolk and start to feed before notochord flexion. In the case of an ostracophils brood hider, Rhodeus reserves rich yolk and does not feed until it metamorphoses to a juvenile, although it develops feeding-related characters just after notochord flexion as in the case of T. hakonensis. On the other hand, T. hakonensis is a lithophils open substratum spawner and the larval adaptation of this species is characterized by its rich supply of yolk persisting beyond the start of notochord flexion. It starts to feed after notochord flexion with a short mixed endo-and exogeneous feeding period. This is probably closely related not only to the reproductive style but also to the scarcity of food for the larvae of this species.