Abstract
The lateral line system of two cobitoid fishes, viz. Cobitis biwae and C. delicata, was compared. C. biwae prefers the sandy bottom of the slow-moving water and has almost similar feeding habit to the common loach, Misgurnus anguillicaudatus. While, C. delicata lives in upper waters, especially in clear cold mountain stream, and swimming actively, eats algae on the stones of the stream.
Generally speaking, C. biwae has more developed pit organ (free neuromast) system than C. delicata, but the canal system in the latter is more prominent than that of the former. However, these differences in the lateral line system of the above-mentioned two fishes seem to have no intimate relations with the difference in the way of living between the two.
The canal system of the two cobitoid fishes shows degenerative tendency, namely the canal system is found only on the anterior portion of the trunk. Furthermore it is found that among the neuromasts of middle line of the trunk of C. delicata, these in the most anterior portion are enclosed in canal, and these in the subsequent anterior are surrounded by a wall of epidermal projection and become more superficial in situation, as proceeding caudally. This fact seems to support DIJKGRAAF's view (1952) that the degeneration of the canal system in trunk stars from the caudal to the cranial.
