Class Chondrichthyes

Abstract

The Chondrichthyes (comprising the sharks, rays and chimaeras) are characterised by a skeleton that is entirely cartilaginous, but more or less hardened by calcification. In this group fertilisation is internal and accomplished by means of the paired intromittent organs at the inner edge of the pelvic fins of males. These organs, misnamed “claspers”, are actually used to transfer sperm into the oviducts of the female during copulation. Although a few elasmobranchs have adapted to life in fresh water, the chondrichthyans are primarily marine fishes. They have developed an unusual solution to the osmotic problems of life in the sea. By keeping a high concentration of urea in their blood and other tissues, the chondrichthyans are able to maintain the ionic balance of their tissues relative to seawater. After death, the urea is soon broken down to ammonia, which may give the shark flesh an unpleasant smell or taste. Soaking the flesh in a 50% solution of water and vinegar for an hour before cooking will remove all traces of urea and ammonia. Most chondrichthyans are good eating, but the flesh is usually somewhat dry (like the white meat of tuna fishes) and should be cooked accordingly. Any chondrichthyan destined for the table should be thoroughly bled immediately after death and kept on ice or frozen until it is to be cooked.