Histological characterization of the special venom secretory cells in the stinger of rays in the northern waters of Persian Gulf and Oman Sea.

Rays are common elasmobranches in the northern waters of Persian Gulf and Oman Sea that may have one or more mineralized serrated stingers on the whip-like tail. The stingers are covered by epidermal cells among which some can produce venom. When these animals are dorsally touched, the stinger can be introduced into the aggressor by a whip reflex mechanism of the tail when the pectoral fins are touched, causing severe mechanical injuries and inoculating the venom. The exact localization of the venom secretory cells in the stinger of different species is controversial, but it is known that the cells are preferentially located in the ventro-lateral grooves in marine stingrays. A comparative morphological characterization of the stinger epidermal tissue of different ray species in the northern part of Persian Gulf and Oman Sea was carried out in this study. EDTA was used for decalcification of stings and conventional histological processes were subsequently employed. The results indicated that structure of dermis and epidermis layers of stings in all species are similar to the structure of corresponding layers in other parts of fish's body. The results of the present study have shown that all examined species of Dasyatidae family, but not Myliobatidae and Gymnuridae families, had venom secretory cells. Distribution of venom secretory cells varies in each species and is often located around or inside the stinger ventro-lateral grooves. These differences among the stingers of various species may explain the envenomation severity in these species.

Study of patient's injuries by stingrays, lethal activity determination and cardiac effects induced by Himantura gerrardi venom.

Stingrays are common inhabitants in the northern waters of the Persian Gulf and Oman Sea. In the present study, the clinical aspects of injuries induced in three patients bitten by stingrays in Hormozgan province waters were first examined. The LD(50) of crude venom extract obtained from the most common stingray in Hormozgan province (Himantura gerrardi) was then estimated by up-and-down dosing and double dose methods in mice. Third and finally, the cardiac symptoms induced by injection of the extract from the venomous spines were evaluated in rats. Intense pain was noticed in all human cases. Redness was observed in two cases, and spasm and seizure were each recorded in only one case. LD(50) of the venom extract in mice was about 100 mg kg(-1). The observed cardiac symptoms in rats included an increase in pulse rate and various changes in electrocardiogram (ECG) parameters such as T and Q values, and PR and RR intervals.