INTRODUCTION
The insect egg chorion plays a crucial role in protecting the developing embryo and facilitating gas exchange during embryonic development (Lou et al., 2018). It acts as a barrier against external agents while allowing for the exchange of gases required for respiration (Pampolini et al., 2020). The chorion contains structures that aid in fertilization and can serve as a diagnostic feature for species identification (Gaino et al., 1987). Additionally, the ultrastructure of different chorionic modifications has demonstrated morphological, physiological, and ootaxonomic importance in various insect orders (Hinton, 1981).
Dragonflies exhibit a variety of oviposition behaviors when it comes to laying their eggs. These behaviors can be classified into three main categories: exophytic, endophytic, and epiphytic (Rodrigues et al., 2018). Exophytic species lay their eggs directly on the water surface, while endophytic species lay their eggs inside plant tissue, either aerial or underwater (Rodrigues et al., 2018; Corbet, 1983). Dragonflies that exhibit exophytic oviposition, including Gomphidae, are capable of laying eggs in water sources that lack plant or other materials (Ware et al., 2012). This adaptation allows them to complete their egg-laying process in a wider range of environments compared to species that lay eggs endophytically or endosubstratically. The ability to lay eggs in diverse aquatic habitats contributes to the ecological success and distribution of Gomphidae (Ware et al., 2012).
Gomphidae eggs have received more attention than eggs from other species that lay their eggs externally. However, research on gomphid eggs is scarce. Currently, two types of eggs have been observed in Gomphidae. Both types are generally elliptical in shape, and the eggs are enclosed in a soft, jelly-like shell that is believed to come from accessory glands (spumalin) in the female (Hinton, 1981). The first type is surrounding with a thick jelly in the micropylar projection (Sahlen, 1995). The second type, found in a small number of species, lacks this layer in the micropylar projection and instead carries a filament coil the posterior pole (Gambles, 1956; Gambles & Gardner, 1960; Trueman, 1990; Andrew & Tembhare, 1992; Corbet, 1983). For example, studies have been conducted using TEM on the species Onychogomphus forcipatus unguiculatus , which is surrounded by a thick jelly in the micropylar projection (Sahlen, 1995). Additionally, SEM and light microscopy studies have been conducted on species Lestinogomphus africanus ,Ictinogomphus australis and I. rapax , which have a filament coil the posterior pole (Trueman, 1990; Andrew & Tembhare, 1992; Gambles & Gardner, 1960).
L. tetraphylla is geographically distributed in Western and Central Asia, as well as in Europe, including the Balkans and the countries surrounding the Mediterranean. It is most commonly found in northern Oman, along the Persian Gulf, and along the Euphrates and Tigris rivers in Syria and southern Turkey (Schorr et al., 1998, Steinmann, 1997; Boudot et al., 2021). There are records from Aydın, Muğla, Hatay, Adana, Şanlıurfa, Adıyaman, Gökçeada in Turkey (Kalkman, 2006; Kalkman et al., 2004; Salur & Kıyak, 2007; Boudot et al. 2021; Schorr et al., 1998). L.tetraphylla larvae breed in large stagnant waters, slow-flowing rivers, and temporary ponds in both fresh and brackish waters (Schorr et al. 1998).
Lindenia tetraphylla eggs are finding uncommon among dragonflies due to the presence of a posterior filament coil. In this study, the ultrastructure of Lindenia tetraphylla eggs was examined for the first time using scanning electron microscopy (SEM).