1Miyako Station, Japan Sea-Farming Association, Miyako, Iwate 027-0097, 2Graduate School of Agriculture, Kyoto University, Kyoto, Kyoto 606-8502, Japan
The morphological development and growth of slime flounder, Microstomus achne, from newly hatched larva to early juvenile were described for laboratory-reared specimens. The duration of the pelagic larval period was about 85 days after hatching, and that of the metamorphic phase was 40 days under mean water temperature 13.9 (9.2-21.1) °C. The maximum size of metamorphic larvae was about 25mm TL, having deep-body form, protruded eyes and otic spines. These diagnostic characteristics appeared early at the metamorphic phase and disappeared at settlement and/or completion of metamorphosis, indicating that these morphological characters are adaptive to pelagiclife. The larvae hatched at a much larger size, and in a more advanced developmental stage, than those of other coastal flatfish species. They had a long metamorphic phase, and the eye migration was not synchronized with the habitat shift from planktonic to benthic. These observations revealed that slime flounder has a unique early ontogeny characterized by specialized morpho-ecological features for the long duration of its pelagic life stages.