MTN 164:12-15 Malformations in Green Turtle Embryos and Hatchlings in Syria

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Malformations in Green Turtle Embryos and Hatchlings in Syria

ALan F. Rees¹, Mohammad Jony², Adib Saad³ & Andrea D. Phillott⁴
¹ARCHELON, Solomou 57, GR104 32 Athens, Greece (E-mail: alanfrees@gmail.com);
²Latakia, Syria (E-mail: mohammadjony@gmail.com);
³Tishreen University, Latakia, Syria (E-mail: adibsaad52@gmail.com);
⁴FLAME University, Pune, Maharashtra, India (E-mail: andrea.phillott@gmail.com)

In terms of color and carapacial scute patterning, the green turtle hatchling phenotype is rather conservative. The carapace is dark grey with a narrow cream/white border and most commonly there is a central row of five vertebral scutes flanked by four pairs of costal scutes. These are bounded by 11 pairs of marginal scutes, with a single nuchal scute anteriorly and two supracaudal scutes at the posterior. This is the most prevalent arrangement for Mediterranean green turtles (supplemental Table 8 in Casale et al. 2018). However, variation in, or anomalies to this configuration, along with other morphological and chromatic malformations, have been reported for hatchlings of this species from around the globe. For example, carapace scute variation and albinism in hatchlings and embryos of green turtles have been reported globally from Sri Lanka (Hewavisenthi 1990), Japan (Sagunama et al. 1994), Mexico (Bárcena-Ibarra et al. 2015) and the United States (Perrault & Coppenrath 2019), and from both Turkey (Türkozan & Durmus 2001; Ergene et al. 2011) and Cyprus (Özdemir & Türkozan 2006) in the Mediterranean. Anomalous scale counts and other congenital malformations may result from genetic, epigenetic, and environmental factors in isolation or combination (Zimmi et al. 2017; Martín-del-Campo et al. 2021), whereas albinism may result from single recessive genetic traits (Perrault & Coppenrath 2019).

Regionally important green turtle nesting in Syria was first scientifically recorded in 2004 on a 12.5 km beach south of Latakia City (Rees et al. 2008). As part of the two-month survey, undisturbed green turtle nests were excavated, the day following the observation of hatchling tracks, which indicated the incubation period had finished, to assess their hatching and emergence success (Rees et al. 2009) and to examine the contents of unhatched eggs. Data on malformed embryos and hatchlings in the nest were also noted and some turtles were photographed. Robust records were not kept, never-the-less we consider the qualitative and anecdotal information that these records represent a useful addition to the literature. We, therefore, present a summary of the observations on congenital malformations observed in green turtle embryos and hatchlings during the 2004 nest excavations.

We examined a total of 29 green turtle nests. Dead (mean = 1.2, SD = 4.5, range 0 - 24) and live (mean = 2.4, SD = 4.9, range 0 - 25) hatchlings were found in the sand above the egg mass during excavation, with a combined mean of 3.7 hatchlings (SD = 9.1, range 0 - 49) that had failed to emerge from the nest in a total of 20 (69.0%) of the nests. We recorded hatchlings with notable carapace and flipper malformations in 3 (10.3%) of the 29 nests. Unhatched eggs containing embryos were recorded in 22 (75.9%) of the 29 nests (mean = 3.9, SD = 4.4, range 0 - 19) and we noted malformed embryos in 5 of the 22 nests (17.2% of the total nests). One nest produced both a malformed embryo and hatchling, resulting in a total of 7 (24.1%) nests presenting abnormal embryological development (Table 1). This is within the rates of malformations summarized by Bárcenas-Ibarra et al. (2015).

Hatchling malformations comprised anomalous carapace scutes and dysmelia (Table 1; Fig. 1) whereas embryo malformations included those of the head, carapace and leucistic appearance (Table 1; Figs. 1 & 2).

Table 1. Descriptions of some malformed embryos and hatchlings from green turtle nests excavated during 2004 at Latakia beach, Syria. LH = live hatchling, LE = live embryo, DE = dead embryo. Types of malformations from Bárcenas-Ibarra et al. (2015, 2017).

Figure 1. Some malformed hatchlings and embryos photographed from green turtle nests excavated during 2004 at Latakia beach, Syria. a) misshapen vertebral and subnumerary scutes (Nest 1), b) dysmelia in the hind left flipper (Nest 2), c) misshapen vertebral and supernumerary scute pattern anomaly (Nest 3), d) embryo with schistosomus reflexus (Nest 6). Types of malformations from Bárcenas-Ibarra et al. (2015, 2017).

Figure 2. Eggs with dead embryos photographed from excavation of Nest 2 (Table 1) during 2004 at Latakia beach, Syria. a) Stage 20-25 embryo. b) Stage 20-25 embryo. c) Ca. Stage 25 embryo showing cephalic malformation and leucistic appearance. d) Ca. Stage 20-25 embryo. e) Ca. Stage 16-19 embryo. f) Ca. Stage 20-25 embryo. Development stages for embryos are based on Miller et al. (2017).

This paper presents the first data on malformations in green turtle embryos and hatchlings incubated in Syria. Whilst research on whether anomalous scalation counts and patterns represents reduced fitness continues (e.g., Bentley et al. 2020; Maffucci et al. 2020) it can be assumed that hatchlings with malformed flippers, such as shown in Fig. 1b in this present study, will have reduced likelihood of survival. The remaining observations of congenital malformations presented herein were found in embryos that would not hatch and hence would not contribute their genes to the population.

Further research on the overall rate and prevalence of different malformations in green turtles both from the Mediterranean and other locations is needed to definitively determine their relevance to changing environmental conditions (e.g., Zimm et al. 2017; Wyneken & Salmon 2020), and to hatchling fitness and survivorship. This in turn may lead to modifications in conservation practice to minimize incidence of incubation conditions that cause such abnormalities (see Martin-del-Campo et al. 2021), which could consequently contribute to a suite of management options for bolstering population recruitment.

Acknowledgements. The fieldwork was supported by the Marine Conservation Society Turtle Conservation Fund and by the British Chelonia Group.

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