Taxonomy of Finfish

2.1.5.7 Nostrils

Nostrils are a pair of apertures or slits on the snout which are the openings for the smell organs leading to the nasal canal on the skull. They are mostly small to medium and are sunk in the snout, often covered by mucous especially in catfishes. A. pair of nasal barbels is often seen, which may be long, short Orrudimentary and borne on the posterior one. They are generally well separated (Fig. 18A) but in Sisoridae the nasal barbels are closely placed one behind the other, slit-like but separated (Fig. 18 B). In Heteropneustidae the anterior nostril is placed /' on the tip of the snout and produced as short tube. In Ariidae they are closely placed and separated by a valve like structure (Fig. 18C). In some Nemacheilines a flap separates them. In Oreonectes the anterior nostril is prolonged as a long nasal barbel (Fig. 18 D). Whatever variations are seen the nostrils are a vital part of the fish and useful in classification.

Fig 18. Nostrils. A. Placed wide apart Bagridae. B. Close together Sisoridae. C. Separated by a valve Ariidae. D. With a barbel in-between Oreonectes (Oreonectes) evezardi.