scholarly journals Influence of short-term temperature drops on sex-determination in sea turtles

2021 ◽  
Author(s):  
Ellen Porter ◽  
David T Booth ◽  
Col J Limpus
Keyword(s):  
Sex Determination ◽  
Heavy Rainfall ◽  
Incubation Temperature ◽  
Sea Turtles ◽  
Sex Ratios ◽  
Temperature Drop ◽  
Sea Turtle ◽  
Short Term ◽  
Sand Temperature

All sea turtles exhibit temperature-dependent sex-determination, where warmer temperatures produce mostly females and cooler temperatures produce mostly males. As global temperatures continue to rise, sea turtle sex-ratios have become increasingly female-biased, threatening the long-term viability of many populations. Nest temperatures are dependent on sand temperature, and heavy rainfall events reduce sand temperatures for a brief period. However, it is unknown whether these short-term temperature drops are large and long enough to produce male hatchlings. To discover if short-term temperature drops within the sex-determining period can lead to male hatchling production, we exposed green and loggerhead turtle eggs to short-term temperature drops conducted in constant temperature rooms. We dropped incubation temperature at four different times during the sex-determining period for a duration of either 3 or 7 days to mimic short-term drops in temperature caused by heavy rainfall in nature. Some male hatchlings were produced when exposed to temperature drops for as little as 3 days, but the majority of male production occurred when eggs were exposed to 7 days of lowered temperature. More male hatchlings were produced when the temperature drop occurred during the middle of the sex-determining period in green turtles, and the beginning and end of the sex-determining period in loggerhead turtles. Inter-clutch variation was evident in the proportion of male hatchlings produced, indicating that maternal and or genetic factors influence male hatchling production. Our findings have management implications for the long-term preservation of sea turtles on beaches that exhibit strongly female-biased hatchling sex-ratios.

scholarly journals Population viability at extreme sex-ratio skews produced by temperature-dependent sex determination

2017 ◽  
Vol 284 (1848) ◽  
pp. 20162576 ◽  
Author(s):  
Graeme C. Hays ◽  
Antonios D. Mazaris ◽  
Gail Schofield ◽  
Jacques-Olivier Laloë
Keyword(s):  
Sex Determination ◽  
High Mortality ◽  
Egg Production ◽  
Incubation Temperature ◽  
Sea Turtles ◽  
Sex Ratios ◽  
Population Viability ◽  
Temperature Dependent ◽  
Population Extinction ◽  
The World

For species with temperature-dependent sex determination (TSD) there is the fear that rising temperatures may lead to single-sex populations and population extinction. We show that for sea turtles, a major group exhibiting TSD, these concerns are currently unfounded but may become important under extreme climate warming scenarios. We show how highly female-biased sex ratios in developing eggs translate into much more balanced operational sex ratios so that adult male numbers in populations around the world are unlikely to be limiting. Rather than reducing population viability, female-biased offspring sex ratios may, to some extent, help population growth by increasing the number of breeding females and hence egg production. For rookeries across the world ( n = 75 sites for seven species), we show that extreme female-biased hatchling sex ratios do not compromise population size and are the norm, with a tendency for populations to maximize the number of female hatchlings. Only at extremely high incubation temperature does high mortality within developing clutches threaten sea turtles. Our work shows how TSD itself is a robust strategy up to a point, but eventually high mortality and female-only hatchling production will cause extinction if incubation conditions warm considerably in the future.

Estimating past and present sex ratios of sea turtles in Suriname

1996 ◽  
Vol 74 (2) ◽  
pp. 267-277 ◽  
Author(s):  
Matthew H. Godfrey ◽  
N. Mrosovsky ◽  
R. Barreto
Keyword(s):  
Sea Turtles ◽  
Sex Ratios ◽  
Negative Relationship ◽  
Chelonia Mydas ◽  
Sea Turtle ◽  
Dermochelys Coriacea ◽  
Green Turtles ◽  
Sand Temperature ◽  
Turtle Conservation ◽  
Sea Turtle Conservation

Leatherback (Dermochelys coriacea) and green (Chelonia mydas) sea turtles in Suriname lay eggs over several months of the year. During this nesting season, changes in rainfall produce changes in sand temperature, which in turn influence the sexual differentiation of incubating sea turtle embryos. The overall sex ratio of leatherback and green sea turtle hatchlings produced at Matapica beach in Suriname was investigated. Estimates of the sex ratios of these turtles in 1993 (green turtles 63.8% female, leatherbacks 69.4% female) were roughly 10% more female-biased than those from an earlier study in 1982. For both species, a significant negative relationship was found between monthly rainfall and monthly sex ratios. Using this relationship and data on rainfall in the past, it was possible to estimate overall sex ratios for an additional 12 years. These estimates varied considerably among different years, ranging from 20 to 90% female in the case of green turtles. Nevertheless, males tended to be produced primarily in April and May, while some females were produced in all months. Such seasonal patterns of production of turtles of different sexes have implications for sea turtle conservation programs that involve manipulating or harvesting eggs.

scholarly journals Vulnerability of sea turtles and fishes in response to two catastrophic Caribbean hurricanes, Irma and Maria

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
J. K. Matley ◽  
S. Eanes ◽  
R. S. Nemeth ◽  
P. D. Jobsis
Keyword(s):  
Prey Availability ◽  
Sea Turtles ◽  
Space Use ◽  
Sea Turtle ◽  
Virgin Islands ◽  
Extreme Weather Events ◽  
Short Term ◽  
Eretmochelys Imbricata ◽  
Us Virgin Islands

Abstract Extreme weather events (e.g., cyclones, floods, droughts) are capable of changing ecosystems and altering how animals obtain resources. Understanding the behavioural responses of animals being impacted by these natural events can help initiate and ameliorate conservation or management programs. This study investigated short- and long-term space-use of the critically endangered hawksbill sea turtle (Eretmochelys imbricata), as well as five species of fishes and stingrays, in response to two of the most destructive Caribbean hurricanes in known history – Irma and Maria, which were at their peak intensity when they passed the US Virgin Islands in September of 2017. Using passive acoustic telemetry in St. Thomas, US Virgin Islands, we show a variety of short-term behavioural patterns initiated across species to reduce exposure to the strong environmental conditions, such as moving to deeper habitats within the study area. Although short-term expansion of activity space was evident for several sea turtles, long-term impacts on space-use and body condition were limited. In contrast, southern stingrays (Hypanus americanus) left the study area shortly after the hurricanes, suggesting vulnerability stemming from altered habitat, prey availability, or temperature/oxygen profiles. This study shows the strong spatial resilience of several nearshore species despite exposure to two consecutive category 5 hurricanes.

scholarly journals The Impact of Temperature-Dependent Sex Determination on the Population Dynamics of Green Sea Turtles (Chelonia mydas)

Bionatura ◽  
2020 ◽  
Vol 5 (1) ◽  
pp. 1029-1038
Author(s):  
Candy Herrera ◽  
Evelyn Guerra ◽  
Andrea Rosas ◽  
Yingying Wei ◽  
Jack Pringle ◽  
...  
Keyword(s):  
Incubation Temperature ◽  
Sea Turtles ◽  
Sex Ratios ◽  
Chelonia Mydas ◽  
Continuous Model ◽  
Sea Turtle ◽  
Green Sea Turtle ◽  
Green Sea Turtles ◽  
Turtle Population ◽  
The Impact

The sex of the turtles is determined by the incubation temperature of the eggs during the mid-trimester of development. In green sea turtles (Chelonia mydas), recent studies show that sex ratios are changing, producing a female-biased sex ratio within the population. We developed a novel continuous model to analyze the dynamics of the green sea turtle population long-term. We determine the safe operating space for the proportion of eggs that become male at which the population of green sea turtle can exist without going to extinction. When the proportion of male eggs leaves this range the overall turtles’ population collapses. Additionally, we examined how temperature changes affect the sex ratios of the green sea turtle population.

scholarly journals Analysis of the fecal microbiome in Kemp’s ridley sea turtles Lepidochelys kempii undergoing rehabilitation

2020 ◽  
Vol 43 ◽  
pp. 121-131
Author(s):  
MM Samuelson ◽  
EE Pulis ◽  
C Ray ◽  
CR Arias ◽  
DR Samuelson ◽  
...  
Keyword(s):  
Sea Turtles ◽  
Short Term ◽  
Lepidochelys Kempii ◽  
Fecal Samples ◽  
Fecal Microbiome ◽  
Β Diversity ◽  
Kemp's Ridley Sea Turtles ◽  
The Impact ◽  
Kemp's Ridley

The impact of the intestinal and fecal microbiome on animal health has received considerable attention in recent years and has direct implications for the veterinary and wildlife rehabilitation fields. To examine the effects of rehabilitation on the microbiome in Kemp’s ridley sea turtles Lepidochelys kempii, fecal samples from 30 incidentally captured juveniles were collected during rehabilitation. Samples were analyzed to determine alpha- (α) and beta- (β) diversity as well as the taxonomic abundance of the fecal microbiota during rehabilitation and in response to treatment with antibiotics. The fecal microbial communities of animals housed in rehabilitation for a ‘short-term’ stay (samples collected 0-9 d post-capture) were compared with ‘long-term’ (samples collected 10+ d post-capture) and ‘treated’ groups (samples collected from turtles that had received antibiotic medication). Results of this study indicate that the most dominant phylum in fecal samples was Bacteroidetes (relative abundance, 45.44 ± 5.92% [SD]), followed by Firmicutes (26.62 ± 1.58%), Fusobacteria (19.49 ± 9.07%), and Proteobacteria (7.39 ± 1.84%). Similarly, at the family level, Fusobacteriaceae (28.36 ± 17.75%), Tannerellaceae (15.41 ± 10.50%), Bacteroidaceae (14.58 ± 8.48%), and Ruminococcaceae (11.49 ± 3.47%) were the most abundant. Our results indicated that both antibiotic-treated and long-term rehabilitated turtles demonstrated a significant decrease in β-diversity when compared to short-term rehabilitated turtles. Our results likewise showed that the length of time turtles spent in rehabilitation was negatively correlated with α- and β-diversity. This study demonstrates the importance of a judicious use of antibiotics during the rehabilitation process and emphasizes the importance of limiting the length of hospital stays for sick and injured sea turtles as much as possible.

scholarly journals Behavioural inference from signal processing using animal-borne multi-sensor loggers: a novel solution to extend the knowledge of sea turtle ecology

2020 ◽  
Vol 7 (5) ◽  
pp. 200139 ◽  
Author(s):  
Lorène Jeantet ◽  
Víctor Planas-Bielsa ◽  
Simon Benhamou ◽  
Sebastien Geiger ◽  
Jordan Martin ◽  
...  
Keyword(s):  
Sea Turtles ◽  
Time Budget ◽  
Natural Habitat ◽  
Sea Turtle ◽  
Automatic Identification ◽  
Detailed Knowledge ◽  
Supervised Learning Algorithms ◽  
Conservation Of Endangered Species ◽  
Free Ranging

The identification of sea turtle behaviours is a prerequisite to predicting the activities and time-budget of these animals in their natural habitat over the long term. However, this is hampered by a lack of reliable methods that enable the detection and monitoring of certain key behaviours such as feeding. This study proposes a combined approach that automatically identifies the different behaviours of free-ranging sea turtles through the use of animal-borne multi-sensor recorders (accelerometer, gyroscope and time-depth recorder), validated by animal-borne video-recorder data. We show here that the combination of supervised learning algorithms and multi-signal analysis tools can provide accurate inferences of the behaviours expressed, including feeding and scratching behaviours that are of crucial ecological interest for sea turtles. Our procedure uses multi-sensor miniaturized loggers that can be deployed on free-ranging animals with minimal disturbance. It provides an easily adaptable and replicable approach for the long-term automatic identification of the different activities and determination of time-budgets in sea turtles. This approach should also be applicable to a broad range of other species and could significantly contribute to the conservation of endangered species by providing detailed knowledge of key animal activities such as feeding, travelling and resting.

scholarly journals Demographic and genetic consequences of disturbed sex determination

2017 ◽  
Vol 372 (1729) ◽  
pp. 20160326 ◽  
Author(s):  
Claus Wedekind
Keyword(s):  
Population Growth ◽  
Sex Determination ◽  
Sex Ratios ◽  
Natural Populations ◽  
Gonad Development ◽  
Empirical Work ◽  
Sex Reversal ◽  
Negative Effects ◽  
Population Extinction

During sex determination, genetic and/or environmental factors determine the cascade of processes of gonad development. Many organisms, therefore, have a developmental window in which their sex determination can be sensitive to, for example, unusual temperatures or chemical pollutants. Disturbed environments can distort population sex ratios and may even cause sex reversal in species with genetic sex determination. The resulting genotype–phenotype mismatches can have long-lasting effects on population demography and genetics. I review the theoretical and empirical work in this context and explore in a simple population model the role of the fitness v yy of chromosomally aberrant YY genotypes that are a consequence of environmentally induced feminization. Low v yy is mostly beneficial for population growth. During feminization, low v yy reduces the proportion of genetic males and hence accelerates population growth, especially at low rates of feminization and at high fitness costs of the feminization itself (i.e. when feminization would otherwise not affect population dynamics much). When sex reversal ceases, low v yy mitigates the negative effects of feminization and can even prevent population extinction. Little is known about v yy in natural populations. The available models now need to be parametrized in order to better predict the long-term consequences of disturbed sex determination. This article is part of the themed issue ‘Adult sex ratios and reproductive decisions: a critical re-examination of sex differences in human and animal societies’.

How do habitat and climate variation affect phenology of the Amazonian palm, Mauritia flexuosa?

2013 ◽  
Vol 29 (3) ◽  
pp. 255-259 ◽  
Author(s):  
Roxaneh Khorsand Rosa ◽  
Reinaldo Imbrozio Barbosa ◽  
Suzanne Koptur
Keyword(s):  
Sex Ratios ◽  
Climatic Variation ◽  
Fruit Maturation ◽  
Wet Season ◽  
Short Term ◽  
Mauritia Flexuosa ◽  
Males And Females ◽  
Long Term Studies

Abstract:Although the dioecious palm, Mauritia flexuosa plays a pivotal role in Amazonian ecology and economy, little is known about its flowering and fruiting patterns. We investigated the role of habitat and inter-annual precipitation in the phenology of M. flexuosa. We calculated sex ratios and recorded phenology for 20 mo in four populations (N = 246) of savanna–forest ecotone (two sites) and forest (two sites) habitat in Roraima, Brazilian Amazonia. Sex ratios were significantly female-biased, and >98% of females set fruit. No significant relationship was found between habitat and sex. Flowering occurred at the wet/dry season interface (August–November), and fruit maturation occurred during the wet season (May–August). Males and females flowered synchronously, and neither the onset nor termination of flowering differed significantly between habitats. Flowering was negatively associated with present precipitation and positively correlated with prior precipitation (3 mo). Fruiting was positively associated with present precipitation and unrelated to prior precipitation (3 mo). We conclude that habitat has an insignificant effect, although short-term climatic variation may influence phenology of this species in northern Amazonia. These results highlight the need for long-term studies relating flowering and fruiting events, and inter-annual climatic variation.

scholarly journals Suhu inkubasi, pasir pantai peneluran dan sukses penetasan telur penyu pada sarang semi alami di Pantai Warebar - Yenbekaki Distrik Waigeo Timur, Kabupaten Raja Ampat

Cassowary ◽  
2020 ◽  
Vol 3 (1) ◽  
pp. 21-31
Author(s):  
Aditya P. Tarigan ◽  
Ricardo F. Tapilatu ◽  
Marthin Matulessy
Keyword(s):  
Incubation Temperature ◽  
Field Research ◽  
Sea Turtle ◽  
Hatching Rate ◽  
Nest Temperature ◽  
Olive Ridley ◽  
Eretmochelys Imbricata ◽  
Turtle Species ◽  
Lepidochelys Olivacea ◽  
Sand Temperature

The research took place between May and October 2019, and divided into two stages. The first stage was field research to collect data by identifying turtles, calculating hatching successes, measuring the temperature of the nesting beach and nest temperature of each species of turtle in semi-natural nests at Warebar Beach, Yenbekaki village, East Waigeo Sub District, Raja Ampat. The second stage after the field was conducting an analysis of hatching rate in hatchery, sand temperature and nest temperature for each species of turtle. The species of turtles nesting at Warebar Beach are olive-ridley  (Lepidochelys olivacea) and hawksbill (Eretmochelys imbricata) turtles. Based on the measurement results at semi-natural nests, it was obtained that the hatching rate of olive ridley sea turtle was 71.6%±28.3 (X±SD) and hawksbill sea turtle was 59.8%±41.3, the overall mean temperature of nesting beach was 28oC, the mean incubation temperature for both sea turtle species was 31oC.

scholarly journals Maternally derived sex steroid hormones impact sex ratios of loggerhead sea turtles

2020 ◽  
Author(s):  
Emma C. Lockley ◽  
Thomas Reischig ◽  
Christophe Eizaguirre
Keyword(s):  
Sex Determination ◽  
Steroid Hormones ◽  
Sex Ratios ◽  
Physiological Mechanism ◽  
Sea Turtle ◽  
Sex Steroid Hormones ◽  
Sex Steroid ◽  
Loggerhead Sea Turtles ◽  
Loggerhead Sea Turtle ◽  
Egg Yolks

AbstractGlobal warming could drive species with temperature-dependent sex determination to extinction by persistently skewing offspring sex ratios. Evolved mechanisms that buffer these biases are therefore paramount for their persistence. Here, we tested whether maternally-derived sex steroid hormones affect the sex-determination cascade and provide a physiological mechanism to buffer sex ratio bias in the endangered loggerhead sea turtle (Caretta caretta). We quantified estradiol and testosterone in nesting females and their egg yolks at oviposition, before incubating nests in situ at standardised temperatures. Upon hatchling emergence, we developed a new, non-lethal method to establish the sex of individuals. Despite standardised incubation temperatures, sex ratios varied widely among nests, correlating non-linearly with the estradiol:testosterone ratio in egg yolks. Males were produced at an equal ratio, with females produced either side of this optimum. This result provides evidence that maternal hormone transfer forms a physiological mechanism that impacts sex determination in this endangered species.

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