TOOTH AND GUT MORPHOLOGY IN RELATION TO FEEDING IN 3 GIRELLID SPECIES(PERCIFORMES, GIRELLIDAE) FROM SOUTHERN JAPAN

Jaw dentition, tooth replacement patterns, relative length of the inte stine, intestinal coiling patterns and feeding behaviour in the natura l habitat were studied in three girellid species from Japan, Girella p unctata, G. melanichthys and G. mezina. They share a troughlike struct ure in the premaxilla and the dentary. The trough is larger and deeper in G. punctuta and G. mezina than in G. melanicihthys. Girella puncta ta and G. mezina have 2 or 3-4 rows of slender functional teeth while G. melanichthys has a single row of short and stout teeth. Tooth repla cement waves proceed from mesial to distal side of the jaw on each obl ique tooth row. In G. merina, teeth at the occlusal surface are probab ly replaced almost simultaneously, but this does not apply to G. punct ata and G. melanichthys. Differences in tooth wearing and replacement pattern among the three species suggest differences in their feeding h abits. Girella melanichthys and G. punctata browse epilithic algae, es pecially algal fronds on the rock surface, while G. mezina grazes epil ithic filamentous algae and diatoms in particular. Numerous replacemen t teeth in G. mezina are a possible adaptation for compensating rapid crown wear, differing in this respect from G. melanichthys with fewer replacement teeth and less rapid crown wear. In G. punctata, the repla cement teeth are intermediate between the other two species. Girella m erina has a longer intestine with a more complicated coiling pattern t han G. punctata and G. melanichthys, which have similar intestinal cha racteristics. Morphological characters and feeding observations sugges t that G. mezina is a grazer, G. melanichthys a browser and G. punctat a an intermediate feeder.