Morphology and Histology of Venom Gland of Scorpio Maurus Kruglovi (Birula, 1910) (Scorpionidae:Scorpiones) Pp
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Zanco Journal of Pure and Applied Sciences Vol.27, No.5, 2015 Morphology And Histology Of Venom Gland Of Scorpio Maurus Kruglovi (Birula, 1910) (Scorpionidae:Scorpiones) pp. (59-62) Sherwan Taeeb Ahmed Department of Biology,College of Science,University of Salahaddin/Erbil -Iraq [email protected] Received: 18/05/2015 Accepted: 12/07/2015 Abstract The venom apparatus of Scorpio maurus kruglovi (Birula,1910) collected from Latifawa (Erbil city, Kurdistan/Iraq) were examined morphologically and histologically. The results showed that they are composed of a bulbous vesicle and a curved stinger, both situated in the last segment of the metasoma. The vesicle bears numerous sensory hairs or setae but the stinger bears no hairs. Cross sections of the vesicles showed two similar venom glands separated by bundles of striated muscles, covered with a thick cuticle and lined with extensively simply folded secretory epithelium. There are two layers of cuboidal cells between cuticle and glandular epithelium surrounding the wide lumen. The venom-producing cells are apocrine type, filled with coarse granules. Keyword: Scorpionidae, Scorpio, venom gland, histology Introduction corpions are venomous arthropods,there are more than 16 different families, and about 1500 species (Yigit and Benli,2008). Their venom apparatus or telson which is situated S at the end of the metasoma, is usually composed of a bulbous vesicle that contain the venom glands and a sharp, curved stinger or aculeus to deliver venom used for both prey capture and defense (Polis,1990). Hundreds of venom peptides and proteins have been characterized from various scorpion species majority of them are the neurotoxic polypeptides. These neurotoxins fulfill their functions by targeting a variety of ion-channels present in excitable cells of their prey (Shirmardi et al.,2010).Venoms or whole tails of scorpions have been used as a traditional Chinese medicine to treat some neurological diseases such as stroke, rheumatism and tetanus for more than 2,000 years. Therefore, it is very interesting to identify the pharmacologically effective components, and gain further insight into their functions and action mechanisms(Yigit and Benli, 2009). Recently, many antibacterial peptides were identified and functionally characterized from the different scorpion species(Zeng et al.,2004; Baradaran et al.,2012).Scorpion venom represents an interesting natural source for a set of diseases therapy like diabetes , cancer and others. BMK venom has shown significant cytotoxicity towards tumor brain (Wang and Ji, 2005).Venom and peptides from Tytius discrepans exhibited anticancer effect against the breast cancer(D’Suze et al., 2010).Additionally, venom from Odontobuthus doriae induces a cytotoxic effect against human neuroblastoma cells (Zargan et al., 2011). There are about 25 species whose venom is capable of causing human death in some cases within few hours, but almost 1500 other species, including the investigated species are no more than efficient predators of insects and other small animals, the sting of these scorpions is usually far less painful than that of a honeybee (Possani et al., 1999). There are many studies on scorpion venoms of various species. However the histology of their venom glands has been investigated by several researchers (Halse et al., 1980; Zeng et al., 2004), nevertheless, these studies were limited to a few scorpion species whose stings are recognized for being fatal to humans (Polis, 1990).In present study, we describe the morphology and histology of Scorpio maurus kruglovi (Birula, 1910) venom apparatus which is not sufficiently potent to harm humans, and widely distributed in Kurdistan region but not studied previously in Iraq. Materials and Methods Scorpions: During August 2012, 25 adult male and female scorpions were collected from underground in Latifawa (Erbil city,Kurdistan/Iraq)(44.30ʹ E, 36.45ʹ N).The scorpions were identified according to valid keys of Pringle (1960) and Kovarik (2009) and then reared in Vol.27, No.5, 2015 95 Zanco Journal of Pure and Applied Sciences Vol.27, No.5, 2015 special cages where they were fed insects at Biology Department of Salahaddin University. Telsons of 10 scorpions were removed, and the venom apparatus were dissected out under dissection microscope (Olympus). Histological preparation: The telsons were fixed in Bouin’s fluid for five days then processed for paraffin wax embedding by dehydrating through ascending concentration of ethanol (50%, 70%, 90% and 100%), cleared in xylol, infiltrated in paraffin wax and finally embedded in paraffin wax. Sections were cut at 5-10µm with a rotary microtome. The sections were stained by haematoxylin and eosin (H&E) method(Drury and Wallington 1980) and examined under light microscope (Olympus), and photo documentation was done by using a Sony digital camera. Results Adult Scorpio maurus kruglovi collected in this study has yellowish brown appearance but carapas and mesosoma have dark brown colour. Its length ranges between 6-8cm with two largepincers (Figure 1A). Their venom apparatus are composed of a bulbus vesicle and a stinger. The vesicle has numerous sensory hairs or setae but the stinger has no setae (Figure 1B). The stinger is in the shape of a sickle, two minute openings at the outer sub terminal part of the stinger in each side are seen which represent the opening of the two venom ducts (Figure 1C). In the cross sections of the vesicle two similar venom glands separated by bundles of striated muscle and covered by a thick cuticle are observed. This homogeneous layer of cuticle is composed of an exocuticle and an endocuticle. There are some hemolymph vessels and numerous cuticle canals in the endocuticle (Figure 2A). The muscle layer terminates at the cuticle, where the glandular epithelium is attached by two layers of cuboidal cells i.e. a muscle layer is not present on the side of the glandular epithelium facing the cuticle. There are two layers of cuboidal cells between cuticle and glandular epithelium surrounding the wide lumen. These cells form a continuous layer under the cuticle and are attached to the basal lamina of secretory epithelium (Figure 2B). The glandular epithelium is simply folded at the inner side of the gland side and consists of a mass of secretory epithelium. The glandular epithelium consists of venom-producing cells and non-secretory supporting cells. The venom-producing cells are apocrine type, high columnar in shape and filled with course granules. Supporting cells are subcuboidal in shape, located between venom-producing cells and the underlying basement membrane, a third type of goblet cells also observed found among secretory epithelium cells (Figure 2, C&D). Simple folding are observed on one side of the cellular layer of the gland. The extruded venom, within the gland lumen, and within the apical cytoplasm of the venom-producing cells, contains fine and coarse granules, with discrete morphologies, that show variable colouration patterns when exposed to the same histological stain. Figure 1: Scorpio maurus kruglovi; A, Dorsal view, telson (arrow). B,venom apparatus, Vesicle (v) with setae (se), stinger(s).C, venom pore (arrow). Vol.27, No.5, 2015 06 Zanco Journal of Pure and Applied Sciences Vol.27, No.5, 2015 L g o p Figure 2: Cross section of the venom gland; A, the two glands (arrows), cuticle (c), lumen (L), striated muscles (s) (4X). B, cuticle layer, exocuticle (ex), endocuticle (e) and Canals (cl). C, epithelial cells (p), goblet cells (o).D, gland cells (gl), granules (g)(B,C&D,40X). Discussion: The telson of S. maurus kruglovi investigated in the present study was found to consist of a bulbous vesicle bearing numerous hairs or setae like the rest of the metasomal segments, many circular pits were also observed on the telson. SEM study of the telson of Euscorpius migrelicus scorpion (their venom is not sufficiently potent to harm humans like Scorpio maurus) showed those pits with setae of variable sizes, which exhibited microanatomical features characteristics for chemoreceptors(Yigit et al., 2007). The present study revealed that the venom apparatus of the investigated species comprises of two glands with a common duct. Similarly, the venom apparatus of Leiurus quinquestriatus is composed of two completely separated but similar glands, each with its own canal, which fuse into a single common canal(Taib and Jarrar, 1993). The differentiation of the venom gland into lobes was observed by Kanwar et al.(1981)in the venom gland of Buthus tamulus where the glands divided longitudinally into parts by septum. According to Quiroga et al.(1998) the venom gland of Tityus caripitensis made of two ovoid lobes that fill the vesicle except a small cavity (lumen) where the venom accumulates; the cavity continuants distally with excretory duct, these characters are similar to Scorpio maurus and the others. The secretory epithelium of Scorpio maurus kruglovi investigated in this study is a simple glandular epithelial type which has simple folding in one side of the cellular layer of the gland. Similar folding were mentioned by Halse et al.(1980), but Polis (1990) classified the venom gland of Scorpio maurus as complexly folded gland, also classified the venom gland of Compsobuthus arabicus, Leiurus quinquestriatus, Androctonus crassicauda, Androctonus bicolor, Buthacus leptochelys, which are all dangerous scorpions, as complex folded glands,while Scorpio maurus kruglovi as simply folding similar to our findings.Samano- Bishop and Ferriz (1964) studied the Mexican scorpions from three genera: Vejovis, Diplocentrus, and Centrurus, and concluded that the morphology of the venom gland presents highly constant generic characteristic which could be used to classify the scorpion to family. The results showed that Scorpio maurus kruglovi venom gland is composed of different cell types. One type is the venom-producing cells that have several granules of different sizes, shapes and densities. Another type, the supporting cells, is found between glandular epithelium and cuticle or between glandular epithelium and muscle bundles.