| چکیده انگلیسی مقاله |
The aim of the present study was to identify the gastropod fauna of the intertidal areas of Kharg Island using differential identification of the Trochidae, Planaxidae, Turbinidae, and Muricidae families of gastropods by scanning electron microscope (SEM). The sampling of gastropods was done from five stations in intertidal areas of Kharg Island (depths less than 1 meter) in the spring and winter of 2015. The samples were frozen and transferred to the laboratory. After the morphometric study, the organic matter of the oral cavity of gastropods was digested and their radula was isolated and prepared for SEM study. In this research, five species including Trochus firmus, Trochus erithreus (Trochidae), Turbo radiatus (Turbinidae), Planaxis sulcatus (Planaxidae), and Thais savignyi (Muricidae) were identified. The types of radula were ripidoglossan in Trochus firmus, Trochus erithreus and Turbo radiatus and taenioglossan in Planaxis sulcatus and stenoglossan in Thais savignyi. The three types of radula of these gastropods were different in the shape of central, lateral, and marginal teeth. So, the evaluation of radula by Scanning Electron Microscope could be an appropriate method for more exact identification of gastropods.Key words: Gastropods, Radula, Identification, SEM Electron Microscope, Kharg Island, Persian Gulf. IntroductionGastropods are one of the most diverse animal groups. The diversity of the digestive systems of gastropods is known as one of their evolutionary characteristics. The digestive system in gastropods has been well studied, and the radula is one of the most important organs of this system, which is of particular importance in their classification and phylogeny studies. Radula has a tooth shape and is a chitinous ribbon that is usually used to scrape or cut food before it enters the esophagus. Different types of radula have been identified among gastropods, including docoglossan, rhipidoglossan, taenioglossan, stenoglossan, and toxoglossan. Since the shape and tooth structure of radula are often unique to a species or genus, radula can be used as one of the species identification features. In this regard, the purpose of this study is to identify the gastropod fauna and the difference in size and shape of the radula teeth in five species of gastropods of the trochidae, planaxidae, turbinidae, and muricidae families in the intertidal areas of Kharg Island by scanning electron microscopy. Materials and MethodsFirst, five stations were considered in different parts of Kharg Island. Sampling was done at the stations based on the tide table of the region, at the time of full tide, and in the middle of two seasons, winter (2015) and spring (2016). The samples were manually collected, photographed, and then frozen. In the laboratory, after defrosting, the shells of the samples were carefully broken so as not to damage the oral mass, and the radula was separated, placed on an aluminum base, and their surface was coated with gold. The sample was placed inside the scanning electron microscope, and imaging was done under vacuum. Imaging was done with secondary electrons at magnifications of 100, 200, 300, and 1000 times. To identify the type of radula, different teeth in each transverse row of the radula were examined, and the radula was identified by examining the formula of these teeth. Research FindingsIn the present study, five species were collected and identified. The radula of Trochus firmus species (Trochoidae) was rhipidoglossan with the formula ∞M+L5+R1+L5+M∞. A serrated and almost triangular-shaped central tooth, small and serrated side teeth, and marginal teeth were slightly smaller than the side teeth, feather-like, and very numerous. This type of radula is suitable for a vegetarian diet. The radula of Trochus erythreus species (Trochoidae) is the rhipidoglossan type with the formula ∞M+L5+R1+L5+M∞. This radula is suitable for a vegetarian diet. The radula of the Planaxis sulcatus (Planaxidae) species is taenioglossan with the formula of 2+1+R+1+2 that has many marginal teeth bent towards the side teeth. The pair of side teeth were very different from the central tooth. The radula of Thais savignyi (Muricidae) is of stenoglossan type and has rachidian teeth with a wide base and several teeth, which have a central frame-like shape with three maple-like branched teeth on each side. The lateral teeth are sickle-shaped and have a base with a flat end on each side of the rachidian teeth. The formula of this radula is M0+L1+R1+L1+M0. This radula is suitable for a meat-eating diet. The radula of Turbo radiatus species (Turbinidae) was rhipidoglossan with the formula ∞M+D1+L4+R1+L4+D1+M∞. The number of teeth in this species is reduced, and it has a wide and oval rachidian tooth. External marginal teeth are similar in size. The inner marginal tooth is three-toothed, with a larger central tooth and two teeth of similar shape. Marginal teeth are feather-like and multi-layered. Discussion of Results and ConclusionsThe similarities and differences between families and species can be found by studying the shape of the radula. The structure of the radula depends on the size, shape, material, and reaction between the teeth and food. It creates features in the radula that give rise to the radular ribbon. The type of radula, the special order and structure of the teeth, the different functions of the teeth, different diets, and different feeding methods indicate different ecological conditions of the animal. Carnivorous gastropods (toxoglossan) need fewer teeth, and types of herbivores (rhipidoglossan) need more teeth than carnivores. The radula in the gastropods Trochus firmus, Trochus erythreus, and Turbo radiates is the rhipidoglossan type. The present results were in agreement with the results of Hossein et al. (2018) and Eisapour et al. (2015). The radula of Planaxis sulcatus Thais savignyi was taenioglossan and stenoglossan. In agreement with the present research, Gajera et al. (2022) also found the type of radula in Thais sp. as stenoglossans. The results of the present research indicate that examining and identifying the type of radula by electron microscopy is a useful tool for distinguishing and identifying gastropods.AcknowledgementThe results of the present research are related to the Master's thesis in the field of animal biosystematics of the Islamic Azad University, Varamin-Pishva branch. The personnel of the research laboratory of the Faculty of Marine Sciences and Technologies of the Islamic Azad University, North Tehran Branch, are gratefully acknowledged. |