Larval development of
Odontobutis obscura obscura, reared with
Artemia sp.and Limnodrilus sp.for about two months, was observed in a room maintained at 20±0.5°C. The development was classified into nine nominal stages, and was compared with that of
O. o. interrupta and of
O. platycephala. The size and shape of the eggs and the development of this species are similar to those of
O. o. interrupta and
O. platycephala. From the juvenile stage,
O. obscura is distinguishable from
O. platycephala by the appearance of dark bands on the body located in the same position as in adults.
O. o. interrupta is also distinguished from
O. o. obscura in the juvenile stage by the presence of melanophores on the dorsal and ventral sides of the caudal peduncle. The anal fin fold of
O. obscura is higher than the dorsal fin fold, but the two folds are equal in height in
O. platycephala. O. obscura has a well-developed air bladder and swims high in the water at the feeding stage.
O. platycephala has a poorly developed air bladder and swims on the bottom. Xanthophores are observed at an earlier stage and more strongly developed in
O. obscura than in
O. platycephala. Growth rate is faster in
O. obscura than in
O. platycephala. O. obscura spawns at a smaller body size than
O. platycephala. In
O. o. obscura, the arrangement of cephalic pit organs is completed at 14mm SL. In
O. o. interrupta, this arrangement is completed at the same time or a little later than in
O. o. obscura. The infraorbital and verticalantorbital pit lines of
O. platycephala, which are separated in the adults, are connected until the juveniles measure about 30mm SL. These pit lines are connected even in the adults of
O. o. obscura and
interrupta. In
O. platycephala, the sensory canals are first formed behind the eyes, then dorso-anterior to the eyes, then at the posterior edge of the preopercles and finally anterior to the eyes. Postocular canals begin to form in individuals more than 20mm SL. All individuals of
O. o. interrupta more than 70mm SL have postocular canals.
O. o. obscura has no sensory canals throughout life. The differences in growth rate, body size at spawning, and the time of completion of the cephalic lateral line system suggest paedomorphosis in the three taxa studied here.
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