A Study of Distribution, Habitat, Behaviour, Venom Apparatus, and Venom of the Stone-Fish

Abstract

Two species of stone-fish occur in Queensland waters. Synanceja verrucosa Bloch & Schneider is found on the Great Barrier Reef, whilst S. trachynis Richardson occurs in mainland waters. S. trachynis is found commonly in sheltered bays and estuaries. It usually occurs partially embedded in mud or sand amidst weed-encrusted rubble, and it may be exposed to the atmosphere at low tide. The mean standard length of 62 specimens examined was 20.3 cm. Twin venom glands are attached to each of the 13 stout dorsal spines which are normally covered by sheaths of tubercular skin. Venom production results from a holocrine type of secretion. Proteinaceous granules, 1.6-3.5� in diameter, are the end products of glandular activity. The venom ducts, which extend from the venom glands to the tips of the spines, are essentially attenuated portions of the glands. However, the ducts are enclosed within grooves in the spines and these grooves are spanned by dense collagenous fibres. The distal extremities of the grooves are plugged with connective tissue. Only the tip of each spine can normally be protruded through the small aperture in its sheath. When a spine penetrates an object, such as a rubber sheet', the sheath is pushed down the tapering spine away from the tip of the spine and towards the twin venom glands. The sheath constricts the venom glands and, when sufficient pressure is transmitted to the intraglandular contents, the connective tissue plug at the distal end of the duct belonging to each gland tears. The intraglandular contents are thereby injected into the wound made by the spine. Each spine must penetrate to a certain depth before expulsion of venom occurs. This depth depends on the distance of the attached glands from the tip of the spine. Small fish of standard length about 8 cm have a well-developed venom apparatus. Regeneration of the intraglandular contents occurred after firing of venom glands in the one specimen where this regeneration was studied. The contents of each gland are expelled in a single burst and the venom contains gland cells and venom granules. Dilute acid disrupts the venom granules.