SKELETONS, SHELTERS AND SPECIAL DEFENCES 



667 



pressure on the glands causes venom to be forced into the wound. The 

 poison of the stonefish is excruciatingly painful and sometimes fatal. More 

 complex is the poison apparatus of the toadfish Thalassophryne. In this 

 animal the two spines of the first dorsal fin are hollow, and the base of each 

 spine bears a special poison gland leading into the duct. In other toad- 

 fishes poison spines and glands also occur on the operculum (34, 118, 133). 

 The poisonous spines just described in teleosts are employed in defence. 

 The actual release of poison does not appear to be under control of the 

 animal. In experiments with venoms of sting-rays, chimaeroids and weever- 

 fish, it has been established that extracts of the poison glands cause sick- 



Fig. 15.18. Stonefish Synanceichthys verrucosus Dissected to show 

 the Poison Glands on the Dorsal Spines. (From Whitley (133).) 



ness and death of test animals (fish, amphibians, reptiles and mammals). 

 An antivenomous serum has actually been prepared against weever-fish 

 venom. Several principles are involved in these fish poisons, including 

 haemolytic and neurotoxic factors. Sting-ray toxin (Urobatis), in sufficient 

 concentration, causes vasoconstriction and cardiac arrest in small mam- 

 mals. There appears to be a direct effect on the pacemaker of the heart. 

 The poison of the weever-fish also has a deleterious effect upon leucocytes, 

 thus opening the way to secondary infections (34, 48, 51, 113). 



REFERENCES 



1 . Abbott, B. C. and Ballantine, D., "The toxin from Gymnodinium venereum 

 Ballantine," /. Mar. Biol. Ass. U.K., 36, 169 (1957). ' 



\a. Andrews, E. A., "Shell repair by the snail, Neritina" J. Exp. Zool., 70, 70 

 (1935). 



2. Berrill, N. J., "The polymorphic transformations of Obelia," Quart. J. 

 Micr. ScL, 90, 235 (1949). 



3. Berrill, N. J., The Timicata: with an account of the British species (London, 

 Ray Soc, 1950). 



4. Bevelander, G., "Calcification in molluscs. 3. Intake and deposition of 

 Ca 45 and P 32 in relation to shell formation," Biol. Bull., 102, 9 (1952). 



