An Assessment of Egg Size in The Green Turtle (Chelonia mydas) on Samandağ Beach, Turkey

Natural and Engineering Sciences 33 Volume 1, No. 3, 33-41, 2016 -RESEARCH ARTICLEAn Assessment of Egg Size in The Green Turtle (Chelonia mydas) on Samandağ Beach, Turkey Bektaş Sönmez * Koyulhisar Vocational Training School, Cumhuriyet University, Koyulhisar/Sivas, Turkey Abstract Many environmental factors such as temperature and moisture are known to influence the eggs of sea turtles. Egg diameter, egg circumference and egg weight were compared in the three stages on Samandağ beach, Turkey. Also, distance from sea, total nest depth, total eggs (clutch size), number of unhatched eggs were measured. In total, 284 eggs from 44 nests were measured. There were significant differences among the stages in term of egg diameter and egg weight. However; there are no significant differences among the stages in term of egg circumference. The egg diameter and egg weight were positively correlated with distance from the sea. Total nest depth was positively correlated with egg circumference and egg weight. The nests further from the sea and deeper from the surface have large egg size. If larger females produce large eggs, large females are attempting to nesting further from the sea and deeper from the surface. The morphometric characters of female turtles not measure in this study. Similar research can be done including female measurements in the future. These results would be useful for conservation workers or nest site managers. Keywords: Egg size, Reproduction, Green turtle, Chelonia mydas, Samandağ Article history: Received 01 September 2016, Accepted 15 September 2016, Available online 19 September 2016 Introduction The green turtle (Chelonia mydas L. 1758) regularly occurs in the Mediterranean, nesting along the coasts of Greece, Northern Cyprus and Turkey (Kasparek et al. 2001). * Corresponding Author: Bektaş Sönmez, e-mail: Natural and Engineering Sciences 34 Previous studies indicate that Samandağ Beach is an important nesting site for green turtles (Yalçın Özdilek, 2007). The green turtle is globally categorized as Endangered using criteria A2bd (ver 3.1), but the Mediterranean subpopulation is listed as critically endangered (HiltonTaylor, 2000) based on criteria A1a, B1+2ce, E. Moreover, the green turtle is listed on Appendix 1 of CITES and, are protected by the Bern Convention. Sea turtle eggs are deposited in a large clutch in a nest excavated by the female on sandy beaches. The incubation period of the eggs is about two month process to become a complete organism of the embryo. As well as genetic factor, physical properties such as moisture, temperature, gas flow are important to complete the embryonic development, too. (Glen et al., 2003; Wallace et al., 2006). All sea turtles have flexible-shelled eggs which exchange water with the surrounding substrate (Packard & Packard, 1988), and successful development of them dependent on uptake of moisture from the environment. (Packard & Packard, 1988; Ackerman, 1996). To the development of the embryo, O2, CO2, H2O and heat exchange plays an important role. Gas exchange should be sufficient for the development of the embryo. If gas exchange is insufficient, the embryo either develops slowly or dies (Ackerman, 1996). Cheng et al. (2009) stated that the eggs, which has a larger surface area make more water and gas exchange rate than smaller. Successful development of the embryo in sea turtles is influenced by climatic factors, salinity, pH, environmental factors such as temperature and moisture, bacterial and fungal diseases (Miller, 1985; Garcia et al., 2003). Especially, the climate is geting higher in this region (Turan et al., 2016). Therefore, the information on the size of sea turtle eggs and the location of the nest are important. It's also known that female turtles have effects on their hatchlings and eggs (Özdemir et al., 2007; Cheng et al., 2009). Most hypotheses addressing the significance of intra specific variation in size of reptilian eggs have focused on the potential benefits accruing to the large hatchlings that usually emerge from large eggs (Gutzke & Packard, 1985; Van Burskirk & Crowder, 1994) and large female that usually produce large eggs (Bjorndal & Carr, 1989). At this point, egg size is important for survival of their own hatchlings, because larger size may allow hatchlings to escape gapelimited predators, to swim faster, and to handle successfully larger prey items, i.e. the "bigger is better hypothesis" (Booth et al., 2004). Janzen et al. (2000) found that larger hatchlings of Cheldra serpentina (Linnaeus, l758) exhibited significantly greater survivorship than smaller individuals. Given the importance of morphological data on egg size for survival of hatchlings, research on egg size would be useful for conservation workers or nest site managers. This research addresses the following questions; (1), are there any significant differences in the egg diameter, egg circumference and egg weight among the different stages on the beach? (2) Are there any correlation between eggs size and distance from sea, total nest depth, total number of eggs, total number of unhatched eggs? Which parameters are important in term of affecting on egg size among stages? Material and Methods Data were collected on Samandag Beach (36"07'N, 35"55'E) located in the eastern Mediterranean in Turkey during the 2010 nesting season. Samandağ Beach is about 14 km in length and it extends from the Çevlik Harbour on the North to Sabca Promontory on the south. The study area corresponded to a 9-km stretch of beach between Çevlik Harbor to the north and the mouth of the Asi River to the south (Figure 1), because this section has the highest nesting activity (Yalçın-Özdilek & Sönmez, 2011). According to the distance from the sea, the nests were divided into three stages, where is the first stage (0 - 20 meter) and second stage (21 - 40 meter) and third stage (41 meter and Natural and Engineering Sciences 35 more). Distance from sea (DFS) of each nest was measured with a flexible tape measure to the nearest distance when the nest was first found as a straight beach surface distance from the egg chamber to the sea (Sönmez et al., 2011). The nests were excavated and the remains examined about one week after the first hatchlings emerged from the nest (Whitmore & Dutton, 1985). Total eggs (TE, Clutch size) of each nest was determined by counting the number of unhatched eggs (UHE) and empty egg shells. Concurrently, total nest depth (TND) of each nest was measured with a flexible tape measure to the nearest depth as a straight vertical distance from the sand surface to the deepest point of the nest (Sönmez et al., 2011). During the nest excavation, unhatched eggs were collected for measurement, and transferred to laboratory in the research center. In total, 361 eggs from 49 nests were measured, and then all unhatched eggs were checked for the embryos. Unhatched eggs were divided into 3 groups, they are (1) early embryonic st (...truncated)