A single drop of the venom is sufficient to kill frogs in about three hours.
Fig. 102.—Cottus scorpius (Sea Scorpion). (After Savtschenko.)
The genus Cottus, which also belongs to the family Triglidæ, includes some forty venomous species found in the seas of the northern hemisphere, in Europe, Asia, and America.
In France the species of Cottus are generally called chabots (bullheads or miller’s thumbs), chaboisseaux (sea-scorpions), or caramassons. They are abundant on the coast of Normandy, and some of them (river bullheads) live in fresh water; they do not exceed 25 cm. in length. They have a liking for holes in rocks, and fishermen are afraid of being stung by them ([fig. 102]).
Their poison-apparatus resembles that of the Weevers, but is less developed. It is situated in the culs-de-sac formed by the opercular spines. The culs-de-sac are lined with cells which produce a toxic secretion only during the spawning season, from November to the end of January. This fact explains how it is that the species of Cottus are declared by certain fishermen to be very venomous, while others say that they are absolutely harmless.
The genera Scorpæna, Pterois and Pelor also belong to the same group.
Fig. 103.—Scorpæna grandicornis (Caribbean Sea). (After Savtschenko.)
In Scorpæna the body is clothed with scales, and the head is large, slightly compressed, armed with spines, and has a bare pit behind; the single dorsal fin is provided with eleven spiny rays, and there are seven branchiostegal rays. Scorpæna grandicornis ([fig. 103]), found in the Caribbean Sea, is from 30 to 50 cm. in length, and has the back red and the eyes and belly yellow; Scorpæna diabolus ([fig. 104]), which occurs in the Indian Ocean and Tropical Pacific, is red and brown, obliquely striped with white and brown; a third species, Scorpæna porcus (Scorpène truie), of smaller size, is met with in the Mediterranean. The venom of the latter has been studied by A. Briot,[143] who sectioned the dorsal and opercular spines, and macerated them either in physiological saline solution, or in glycerine; he then tested the toxicity of these macerations on certain animals—frogs, rabbits, and rats.