184 Adaptations of Fishes 



In certain groups (wrasse-fishes, parrot-fishes, etc.) in the 

 tropics, individual fishes are sometimes rendered poisonous by 

 feeding on poisonous mussels, holothurians, or possibly polyps, 

 species which at certain times, and especially in their spawning 

 season, develops alkaloids which themselves may cause cigua- 

 tera. In this case it is usually the very old or large fishes which 

 are liable to be infected. In some markets numerous species 

 are excluded as suspicious for this reason. Such a list is in 

 use in the fish-market of Havana, where the sale of certain 

 species, elsewhere healthful, or at the most suspected, was rigidly 



FIG. 138. The Trigger-fish, Balistes carolinensis Gmelin. New York. 



prohibited under the Spanish regime. A list of these suspicious 

 fishes has been given by Prof. Poey. 



In many of the eels the serum of the blood is poisonous, but 

 its venom is destroyed by the gastric juice, so that the flesh 

 may be eaten with impunity, unless decay has set in. To eat 

 too much of the tropical morays is to invite gastric troubles, 

 but no true ciguatera. The true ciguatera is produced by a 

 specific poisonous alkaloid. This is most developed in the 

 globe fishes or puffers (Tetraodon, Spher aides, Tropidichthys, etc.). 

 It is present in the filefishes (Monacanthus, Alutera, etc.), prob- 

 ably in some toadfishes (Batrachoides, etc.), and similar com- 

 pounds are found in the flesh of sharks and especially in sharks' 

 livers. 



