Histological characterization of the special venom secretory cells in the stinger of rays in the northern waters of Persian Gulf and Oman Sea Hadi Dehghani a, * , Mir Masoud Sajjadi a , Paria Parto b , Hamid Rajaian b , Amin Mokhlesi a a Department of Marine Biology, School of Basic Sciences, University of Hormozgan, P.O. Box 3995, Bandar Abbas, Iran b Department of Basic Sciences, School of Veterinary Medicine, Shiraz University, P.O. Box 71345, Shiraz, Iran article info Article history: Received 1 November 2009 Received in revised form 5 January 2010 Accepted 9 January 2010 Available online 18 January 2010 Keywords: Stingray Stinger Histology Venom secretory cells Persian Gulf and Oman Sea abstract 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. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction Rays are common elasmobranches found in the northern coasts of Persian Gulf and Oman Sea (Behzadi, 2007). These fishes are also widespread in tropical, subtropical and temperate waters worldwide (Fenner, 1998; Scharf, 2002; Perkins and Morgan, 2004; Forrester, 2005). No comprehensive research has yet been done concern- ing different species of rays in that region. Many spiny species from different genera of Dasyatidae, Myliobatidae and Gymnuridae families are found in this area and Dasyatidae species (stingrays) are the most common (Behzadi, 2007). Dasyatidae family has demersal species seen at the bottom of shore water to offshore regions. Myliobatidae specimens swim on the water column and are often observed in offshore waters. Gymnuridae family has only one species that is a demersal fish distributed in shores. Spiny species of rays have one or more spines on their whip shape tail, such as some shark and ratfishes; the location, size and number of stings varies with the species, habitat and age of fish (Russell et al., 1958; Quay, 1972), however, these stings are dermal palps (adnexa) (Quay, 1972). These serrated spines are covered by an epithelial layer that has venom secretory cells (especially stingrays). The cells are located in the epithelium or in close contact with it (Russell, 1969; Weiss and Wolfenden, 2001; Scharf, 2002; Campbell et al., 2003; Pedroso et al., 2007). Dispersal * Corresponding author. Tel.: þ98 917 3054586; fax: þ98 761 7660012. E-mail address: haddehghani@gmail.com (H. Dehghani). Contents lists available at ScienceDirect Toxicon journal homepage: www.elsevier.com/locate/toxicon 0041-0101/$ – see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.toxicon.2010.01.010 Toxicon 55 (2010) 1188–1194