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THE BIOLOGY OF MARINE ANIMALS 



fifty sting-ray spines embedded in various parts of its body, especially in 

 the mouth and gullet. It is suggested that the sting-ray uses its spine mainly 

 as an offensive weapon (47, 52, 94, 95). 



Other elasmobranchs bearing poisonous spines are the Port Jackson 

 shark Heterodontus, the spiny dogfish Squalus acanthias and the chimae- 

 roids Chimaera monstrosa and Hydrolagus colliei. These animals have a 

 grooved spine in front of the dorsal fin. The arrangement is much the same 

 as in the sting-ray, for the groove contains glandular tissue which secretes 

 a venomous substance. 



Among teleosts in British waters the weever-fishes (Trachinidae) are 

 well-known venomous species. In these fishes spines on the gill-covers and 



Fig. 15.17. Sting Ray (Dasyatis pastinaca) (x J), and Enlarged 

 View of the Poisonous Spine. (After Norman (93).) 



first dorsal fin are equipped with poison-glands. Each opercular spine is 

 grooved and bears a small mass of glandular tissue. Wounds are inflicted 

 when the fish is stepped on or handled. Under these conditions venom is 

 released by rupture of the glandular cells and flows along the groove into 

 the wound. The spines of the weever-fish are reported to cause severe and 

 painful wounds. 



Poisonous spines resembling those of the weever-fish are found on the 

 operculum and in the dorsal fin of other teleosts. Poison glands are located 

 in grooves or occur at the base of the spine. Notable poisonous fishes are 

 scorpion-fishes (Scorpaenidae) and poison-fishes (Synanceiidae). The 

 poison glands discharge their secretions into ducts leading into a deep 

 groove on either side of the spine. The stonefish Synanceia has bag-like 

 glands lying on either side of the dorsal spines (Fig. 15.18). These fishes lie 

 on the bottom and, if trodden upon, the erect spines penetrate the skin, and 



