Yakup Kaska

Embryological development of sea turtles (Chelonia mydas, Caretta caretta) in the Mediterranean

Abstract Simple embryonic staging of Mediterranean sea turtles was developed after measuring a set of selected morphological characteristics. The frequency of gross abnormalities among the samples was also calculated. The most common abnormalities were supernumerary and subnumerary scutes, albinos, head and jaw abnormalities and twinning.

SEA TURTLE NEST CONSERVATION TECHNIQUES ON SOUTHWESTERN BEACHES IN TURKEY

Loggerhead turtle nests at risk from tidal inundation and predation were either relocated, screened against predation, or fenced in areas of heavy human activity on Fethiye, Dalyan, and Dalaman beaches during the nesting seasons of 2000-2002. Relocation, screening, and fencing clearly increased the hatching success rate and provided effective protection of sea turtle nests against inundation and predation. The emergence pattern and sex ratios of hatchlings, incubation periods, and distances of nests from the water line were analyzed. Incubation temperatures leading to a high female-biased sex ratio were found on Dalyan Beach. Sand and nest temperatures of the relocated nests at the hatchery site influenced the sex ratios, as seen from histological sexing of dead hatchlings from both in situ and relocated nests.

Population decline of loggerhead turtles: two potential scenarios for Fethiye beach, Turkey

Based on nesting data over a 12-year period (1993–2004), this study points to a negative population trend of the loggerhead turtle population at Fethiye beach, Turkey. The number of nests fluctuated from a maximum of 186 in 1995 to a minimum of 58 in 2004. Successively smaller peaks at 3-year intervals were followed by successively smaller troughs. Two analyses—one representing a dampened oscillation, the other retaining the period and the amplitudes of the nesting cycles—predict that nest number will drop to about 40–50 by 2015, i.e. to about 22–27% of its highest value. This drop at Fethiye does not correspond with a visible increase at neighboring beaches, leading to the interpretation that the number of nesting turtles here is declining. Moreover, the carapace size of emerging adult females is apparently decreasing, as are clutch sizes. Such a potential negative trend at a key Turkish nesting beach is cause for concern, an incentive for continued study, and a call for more coordinated and effective conservation programs in this region of the Mediterranean.

Heavy metals in marine turtle eggs and hatchlings in the Mediterranean

Abstract The concentrations of cadmium, lead, iron, copper and zinc were analysed in Loggerhead Turtle (Caretta caretta) hatchling samples (eggshells, remaining yolk, and liver) from beaches of southwest Turkey. Cd, Pb, Fe, and Cu concentrations were higher in embryo liver than in yolk. Zn concentration was higher in yolk. Hg concentrations in all yolk samples were below the detection limit, but levels could be measured in some embryo livers.

Natural and anthropogenic factors affecting the nest-site selection of Loggerhead Turtles, Caretta caretta, on Dalaman-Sarıgerme beach in South-west Turkey.

Abstract The nesting activities of Loggerhead Turtles (Caretta caretta Stejneger, 1902) and anthropogenic factors affecting them were monitored over 7 years (2002–2008) on Dalaman-Sarıgerme beach, one of the main nesting grounds in Turkey. Out of the 2620 nesting emergences recorded during the entire study period, only 645 (24.6%) resulted in successful nesting, giving an annual mean number of nests of 92. The collective number of eggs in these nests numbered 50239, with 40079 (79.8%) of them producing hatchlings. Out of the total number of eggs laid, 8128 (16.2%) resulted in dead embryos and 2032 (4.0%) in unfertilized eggs. The mean incubation period averaged 49 days (range 40–67 days) and the mean clutch size was 79.0 (range 18–150 eggs). Turtle nests were more concentrated on the undeveloped parts of the beach than on developed parts. In the other sections, few emergences occurred and either no or few nests were recorded. In Section I, which contained hotels and water sports facilities, only a few non-nesting emergences were observed. Of the number of nests that were observed, 32% were laid in Section II, which contained recently built hotels, 60% were in Section III and 8% were in Section IV, the undeveloped portion containing beach rocks. There is very clear evidence that the Loggerhead Turtles are shifting their nesting sites to the undisturbed sites along the beach. The negative factors that seem to be affecting them include water sports, hotel lights and beach rocks. In order to protect sea turtles, there needs to be a better understanding of how effective beach protection can be established.

An Assessment of Initial Body Size in Loggerhead Sea Turtle (Caretta caretta) Hatchlings in Turkey

Abstract Eggs, hatchlings, and adult loggerhead turtles, and incubation durations of clutches, were measured on three Turkish beaches (Dalyan, Fethiye and Göksu Delta), and some physical features of nests were compared. These features were not statistically different among the beaches, except for nest depth and distance to the high water mark. There was a positive relationship between hatchling mass and egg size. The carapace length of hatchlings was correlated with both egg diameter and incubation duration. The duration of asynchronous emergence of hatchlings on Fethiye beach was slightly longer than on the other two beaches, and the size of hatchlings decreased as asynchronous emergence proceeded. Of the hatchlings that emerged first, those that died were significantly smaller in SCL and mass than those that lived. These results suggest that smaller hatchlings may not be vigorous enough to emerge earlier from nests, and that they may be less fit.

Loggerhead sea turtle hatchling sex ratio differences between two nesting beaches in Turkey

Hatchling sex ratios of loggerhead sea turtles (Caretta caretta) were estimated on two main nesting beaches (Dalyan Beach and Goksu Delta) in Turkey using three methods: nest temperature, incubation period and gonad histology. The electronic temperature recorders were placed in 35 selected nests. The mean nest temperature in the middle third of the incubation period was calculated as 29.5 °C on Dalyan Beach and as 31 °C on Goksu Delta. Incubation periods on Dalyan Beach and Goksu Delta were found as 52.9 days and 50.4 days, respectively. Gonad histology method was used only on Dalyan Beach and it was determined that 235 (55.6%) hatchlings were female out of 423 histologically examined hatchlings. Using nest temperatures and incubation periods, sex ratios on Dalyan Beach were estimated as 61% and 69.3%, and on Goksu Delta as 81% and 73.1%, respectively. In light of our sex ratio results, Dalyan Beach has a relatively high proportion of male hatchlings possibly due to its relatively western location. Our fi...

Marine turtle nesting at Patara, Turkey, in 2000

Abstract The reproduction of the sea turtle population at Patara in southern Turkey was investigated in 2000. Two Green Turtle (Chelonia mydas) nests were identified, which is the first record for the area, and the westernmost nesting site in the Mediterranean. 85 Loggerhead Turtle (Caretta caretta) nests were found, but hatchlings emerged from only 19 of them. Beach erosion and the covering of nests by shifting sand dunes was responsible for the loss of 54% of all nests. Although 72% of all emergences occurred on the eastern half of the beach and 74% of all clutches were laid there, there was no significant difference found in nesting success between both beach sections, which differ markedly in structure and human impact.

Shallow genetic divergence indicates a Congo-Nile riverine connection for the softshell turtle Trionyx triunguis

We sequenced 20 new, field-collected individuals for up to seven genes to explore the phylogeography and conservation genetics of the threatened Nile softshell turtle Trionyx triunguis, including the first known-locality specimen from sub-Saharan Africa. Samples from Cameroon (West Africa), the Mediterranean and Nile River differed by at most a single nucleotide per gene, indicating the potential for a recent connection between these currently disjunct populations via the Nile–Congo River systems. Recently reported mitochondrial diversity between Mediterranean and “sub-Saharan” samples of the Nile softshell indicate that significant divergence exists across the species’ range, but that variation cannot be fully incorporated into our analysis since those samples lack specific locality data.

Invertebrate infestation on eggs and hatchlings of the loggerhead turtle, Caretta caretta , in Dalaman, Turkey

The damage caused by some invertebrates to the eggs and hatchlings of loggerhead turtles, Caretta caretta, was investigated during the summer of 2002 on Dalaman beach, Turkey. The specimens, identified to family or genus levels, from nine families representing seven orders were recorded as infesting nests of loggerhead turtles. The heaviest impacts on loggerhead turtle nests was made by Pimelia sp. (Tenebrionidae, Coleoptera). Twenty-four (36.3%) out of 66 intact loggerhead hatched nests were affected by these larvae. Larval damage by Pimelia sp. was recorded in 188 (10.6%) out of 1773 eggs, but only in two (0.28%) hatchlings. The results show that fewer insects were in the nest the further from vegetation and therefore the relocation of nests from the waters edge to further inland close to vegetation may increase the infestation rate of the eggs.