Mydas Eggs Research Articles

Incubating green turtle (Chelonia mydas) eggs at constant temperatures: Hatching success, hatchling morphology and post-hatch growth

Past studies applying constant-temperature incubation of eggs have involved all species of sea turtles, but rarely can we find a single one incubating eggs at three or more temperatures. Here, we incubated green turtle (Chelonia mydas) eggs from Ganquan Island, South China Sea, at five constant temperatures (26, 28, 30, 32 and 34°C) to determine hatching success, incubation length and hatchling phenotype at each test temperature and temperatures optimal for embryonic development. Temperature affected hatching success, incubation length and all seven examined hatchlings traits, and clutch origin affected three (head length, fore-flipper length and hind-flipper length) of the seven. Hatching success was lowest at 34°C and none of hatchlings hatched at this temperature was normal and survived over one week. The rate of embryonic development and the rate of post-hatch growth both were lowest at 26°C. Given that low survival and growth rates can translate into reduced individual fitness, we conclude that both 26°C and 34°C are unsuitable for incubation of C. mydas eggs. Post-hatch growth was fastest in hatchlings incubated at 30°C, and eggs of C. mydas incubated at temperatures around 30°C are more likely to produce mixed sexes. Accordingly, we conclude that temperatures within the range from 28°C to 32°C are generally optimal for embryonic development of C. mydas.

Trialling seawater irrigation to combat the high nest temperature feminisation of green turtle Chelonia mydas hatchlings

Global increases in beach sand temperatures are predicted to skew hatchling sex ratios of marine turtle populations towards female bias. Currently, shade structures and freshwater irrigation are management strategies used to cool nest temperatures, but require resources that are limited at remote rookeries. Here, we report on a novel investigation that used seawater irrigation as a sand-cooling method. Various volumes of seawater were applied to sand to determine the optimal application required to lower sand temperatures at nest depth to produce male-biased sex ratios. We performed these experiments during the 2019-2020 nesting season at Heron Island on the southern Great Barrier Reef, Australia, and at Panasesa Island, Papua New Guinea. We found the amount of cooling at nest depth was site dependent and varied with the seawater irrigation regime used. At Heron Island, we used a one-off application of the equivalent of 120 mm of rainfall either as freshwater or seawater to the sand above incubating clutches 18 d after oviposition to determine whether this affected the hatching success of green turtle Chelonia mydas eggs. Both treatments had higher hatching success (83.8 ± 3.5% and 71.2 ± 6.3%, respectively, means ± SE) compared to control clutches (63.5 ± 6.0%). Our results indicate that a one-off application of seawater may be an effective management option for reducing nest temperatures during the sex-determining period of marine turtle clutches incubating in situ. Seawater irrigation could be used in areas where populations are at highest risk of feminisation caused by a hot drying climate where freshwater is not available for irrigation.

The influence of temperature on embryonic developmental arrest in marine and freshwater turtles

Temporary arrest of embryonic development can occur both pre- and post-oviposition in turtles. Pre-ovipositional arrest is an obligate part of the life cycle and occurs universally in turtle embryos, commencing while eggs are in the oviduct and persisting until after oviposition. Pre-ovipositional arrest allows turtle mothers the flexibility to choose an optimum time to nest and provides embryos some capacity to respond to varying environmental conditions immediately after eggs are laid. Following oviposition, turtle embryos are known to be significantly affected by incubation conditions and specifically, temperature has a profound influence on developmental rate and success of embryos. We conducted a comparative investigation of how temperature influences (1) the duration of pre-ovipositional arrest after eggs are laid, (2) the number of embryos that fail to recommence development and (3) hatching success, using eggs of the green sea turtle (Chelonia mydas), and three species of freshwater turtle; the western oblong turtle (Chelodina oblonga), the eastern longneck turtle (Chelodina longicollis), and the Murray River turtle (Emydura macquarii). We incubated arrested eggs of each species at three different temperatures (low, medium, high) and monitored embryonic development immediately after oviposition and throughout incubation. Interspecific variation was evident in the effects that temperature had on pre-ovipositional arrest, subsequent embryonic development and hatching success. A major finding of this study was that, with the exception of E. macquarii, there was no significant difference in the time to white spot development (the first external visible sign of embryological development following arrest) between temperature treatments, suggesting that the resumption of development and the breaking of pre-ovipositional arrest after eggs are laid are independent of temperature. Furthermore, although the number of C. mydas eggs to successfully recommence development after oviposition was consistently high (~97–100%) across the three temperature treatments, a significant proportion of C. oblonga and E. macquarii eggs failed to resume development. In both the low and high temperature treatments the rate of C. oblonga embryo mortality was 95% and 60%, respectively, and for E. macquarii it was 53% and 24% respectively. These findings bring us a step closer to understanding why failure to recommence development after oviposition causes high rates of early stage embryo mortality and decreased hatching success in turtles.

Persistent organic pollutants in the green sea turtle Chelonia mydas: nesting population variation, maternal transfer, and effects on development

Persistent organic pollutants (POPs), such as polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs) and polybrominated diphenyl ethers (PBDEs), have a wide range of toxic effects on humans and wildlife, and have been reported in a number of endangered sea tur- tle populations. The present study screened for POPs in a green sea turtle Chelonia mydas popula- tion in Peninsular Malaysia and investigated the maternal transfer and effects of POPs on embryonic development. At the Ma'Daerah Turtle Sanctuary, blood, eggs and hatchling blood were collected from 11 nesting female C. mydas. Samples were analysed for 83 PCBs, 23 OCPs and 19 PBDEs using gas chromatography with tandem mass spectrometry. The chemical profiles of eggs from individual turtles were significantly different, indicating variable contaminant uptake during foraging. There was evidence of maternal transfer of POPs to eggs and hatchlings, with significant correlations in sum of PCBs (ΣPCB), sum of PBDEs (ΣPBDE), γ-hexachlorocyclohexane (γ-HCH), trans-chlordane and mirex concentrations between maternal blood and eggs (p < 0.05, R 2 < 0.71), between eggs and hatchling blood (p < 0.05, R 2 < 0.83), and between maternal and hatchling blood (p < 0.05, R 2 < 0.61). In addition, there was congener-specific transfer of PCBs with less lipophilic congeners (e.g. PCB 99) more readily transferred to hatchlings than the more lipophilic congeners (e.g. PCBs 180 + 193). There was also a significant correlation between increasing egg POP concentration and decreasing hatchling mass:length ratio. POPs may therefore have subtle effects on the development of C. mydas eggs, which may compromise offshore dispersal and predator avoidance.

Dangerous Delicacy: Contaminated Sea Turtle Eggs Pose a Potential Health Threat

Vol. 117, No. 9 NewsOpen AccessDangerous Delicacy: Contaminated Sea Turtle Eggs Pose a Potential Health Threat John Tibbetts John Tibbetts Search for more papers by this author Published:1 September 2009https://doi.org/10.1289/ehp.117-a407bAboutSectionsPDF ToolsDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InReddit The eggs of the green turtle (Chelonia mydas) and other sea turtle species are a popular food in areas such as Peninsular Malaysia—so popular, in fact, that nesting populations in the region have declined by more than 80% since the 1950s, largely because of their eggs being collected for human consumption. Persistent organic pollutants (POPs) and heavy metals have been reported in the eggs of a number of C. mydas populations. Now a team of Australian and Malaysian scientists reports that the concentrations of POPs found in C. mydas eggs from markets in Peninsular Malaysia could pose a considerable threat to human health [EHP117:1397–1401; van de Merwe et al.].In August 2006, the investigators surveyed 33 markets along 730 miles of coastal Peninsular Malaysia. C. mydas eggs were available in 9 of these 33 markets. A random sample of 3–13 eggs was purchased from each market where they were sold. In total, 55 eggs were collected and frozen until they could be analyzed.The eggs were analyzed for numerous POPs, among them 83 polychlorinated biphenyls (PCBs), 23 organochlorine pesticides, and 19 polybrominated diphenyl ethers. Eggs were also analyzed for zinc, copper, cobalt, selenium, arsenic, cadmium, lead, and mercury. For each metal and category of POP, the authors calculated the percentage of the acceptable daily intake (ADI) found in the eggs, providing an estimate of potential human health risks involved in consuming the eggs. ADIs are set by the World Health Organization.The concentrations of POPs and metals measured were generally lower than those reported elsewhere for loggerhead sea turtle (C. caretta) eggs. Nevertheless, all the eggs analyzed had at least 3 times the ADI of coplanar PCBs, which are among the most toxic members of their chemical family. One egg had 300 times the ADI for this contaminant.The authors note that the rate of C. mydas egg consumption in Peninsular Malaysia was not investigated in the present study, nor has it been well quantified. However, there is a cultural perception in this area that sea turtle eggs have medicinal qualities. The authors write that a public education campaign could highlight the health consequences of consuming contaminated eggs. This in turn could reduce egg collection pressure and hence potentially contribute to the recovery of the C. mydas populations in this region.C. mydas eggs for sale in Kuala Terengganu, Penisular MalaysiaFiguresReferencesRelatedDetails Vol. 117, No. 9 September 2009Metrics About Article Metrics Publication History Originally published1 September 2009Published in print1 September 2009 Financial disclosuresPDF download License information EHP is an open-access journal published with support from the National Institute of Environmental Health Sciences, National Institutes of Health. All content is public domain unless otherwise noted. Note to readers with disabilities EHP strives to ensure that all journal content is accessible to all readers. However, some figures and Supplemental Material published in EHP articles may not conform to 508 standards due to the complexity of the information being presented. If you need assistance accessing journal content, please contact [email protected]. Our staff will work with you to assess and meet your accessibility needs within 3 working days.

Chemical Contamination of Green Turtle ( Chelonia mydas ) Eggs in Peninsular Malaysia: Implications for Conservation and Public Health

BackgroundPersistent organic pollutants (POPs)—such as organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs)—and heavy metals have been reported in sea turtles at various stages of their life cycle. These chemicals can disrupt development and function of wildlife. Furthermore, in areas such as Peninsular Malaysia, where the human consumption of sea turtle eggs is prevalent, egg contamination may also have public health implications.ObjectiveIn the present study we investigated conservation and human health risks associated with the chemical contamination of green turtle (Chelonia mydas) eggs in Peninsular Malaysia.MethodsFifty-five C. mydas eggs were collected from markets in Peninsular Malaysia and analyzed for POPs and heavy metals. We conducted screening risk assessments (SRAs) and calculated the percent of acceptable daily intake (ADI) for POPs and metals to assess conservation and human health risks associated with egg contamination.ResultsC. mydas eggs were available in 9 of the 33 markets visited. These eggs came from seven nesting areas from as far away as Borneo Malaysia. SRAs indicated a significant risk to embryonic development associated with the observed arsenic concentrations. Furthermore, the concentrations of coplanar PCBs represented 3 300 times the ADI values set by the World Health Organization.ConclusionsThe concentrations of POPs and heavy metals reported in C. mydas eggs from markets in Peninsular Malaysia pose considerable risks to sea turtle conservation and human health.

Incubation of the Eggs of the Green Sea Turtle, Chelonia Mydas, in Torres Strait, Australia: the Effect of Movement on Hatchability.

Of the eggs of green sea turtle (Chelonia mydas) in Torres Strait, Australia, 92% hatched when they were incubated artificially soon after being laid but only 68% when they were transported to other experimental turtle farms. Other eggs were experimentally rolled, i.e., rotated about their horizontal axis, at different times after being laid. Those rolled after 1, 3 or 6 h had 92% hatching rate; after 12 h, 88%; after 24 h, 48%; after 2 or 3 days, none; after 5 days, 4% increasing with the delay to 72% after 20 days delay between laying and rolling. If C. mydas eggs for a hatchery can not be moved to their final destination within 3 h, then they ought not to be moved until at least 20 days after being laid.