Sex ratio of juvenile loggerhead turtles in the Mediterranean Sea: is it really 1:1?

Maffucci, Fulvio; D'Angelo, Ilaria; Hochscheid, Sandra; Ciampa, Mariapia; Martino, Giovanni; Travaglini, Andrea; Treglia, Gianluca; Bentivegna, Flegra

doi:10.1007/s00227-012-2160-x

Cited by 14 publications

(15 citation statements)

References 40 publications

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“…In the Mediterranean, juvenile and adult sex ratios of C. caretta do not differ significantly from 1:1, although estimates of hatchling sex ratios are highly female-biased (Maffucci et al 2013;Casale et al 2014). In addition, juvenile sex ratios in the Mediterranean are largely unaffected by immigration of Atlantic individuals into the Mediterranean, as previously suggested (Maffucci et al 2013). However, it is difficult to understand the possible causes of unbalanced sex ra- tio of species with a complex life cycle, such as sea turtles, by just collecting data on sex (Casale et al 2006).…”

Section: Discussionmentioning

confidence: 89%

“…In general, species that exhibit environmental sex determination show skewed sex ratios more frequently than species that exhibit genotypic sex determination (Bull 1980). In the Mediterranean, juvenile and adult sex ratios of C. caretta do not differ significantly from 1:1, although estimates of hatchling sex ratios are highly female-biased (Maffucci et al 2013;Casale et al 2014). In addition, juvenile sex ratios in the Mediterranean are largely unaffected by immigration of Atlantic individuals into the Mediterranean, as previously suggested (Maffucci et al 2013).…”

Section: Discussionmentioning

confidence: 95%

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Skeletochronology, age at maturity and cause of mortality of loggerhead sea turtles Caretta caretta stranded along the beaches of Campania (south-western Italy, western Mediterranean Sea)

Guarino¹,

Nocera²,

Pollaro³

et al. 2020

Herpetozoa

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Information on demographic and life-history traits of endangered vertebrate species, such as sea turtles, is crucial for planning management and conservation actions. We applied skeletochronology of phalanges to estimate the age of loggerhead turtles, Caretta caretta, found dead stranded along the beaches of Campania (western Mediterranean) from 2013 to 2017. To obtain maturity data, we examined gonads from a subsample of 7 males and 11 females. Overall, curved carapace length (CCL) ranged from 5.6 to 90.8 cm, but for most turtles (89%) it was 50-79.9 cm. Predominance of stranded females (62%) was recorded. Ten out of the eighteen histologically examined gonads allowed estimating maturity. Based on the lines of arrested growth counting, the estimated age of the examined specimens ranged from 0 (hatchling) to 26 years. The modal age was 14 years for males and 17 years for females. The smallest male with spermatogenetic activity had a CCL of 65 cm and was estimated to be 16 years old. The smallest female with follicular development stage, characterising the transition towards adulthood, had a CCL of 69.5 cm and was estimated to be 20 years old. Anthropogenic factors were responsible for 36% of the mortality of individuals, followed by parasitic/infective pathologies (20%).

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Section: Discussionmentioning

confidence: 89%

Section: Discussionmentioning

confidence: 95%

Skeletochronology, age at maturity and cause of mortality of loggerhead sea turtles Caretta caretta stranded along the beaches of Campania (south-western Italy, western Mediterranean Sea)

Guarino¹,

Nocera²,

Pollaro³

et al. 2020

Herpetozoa

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“…On the basis of genetic markers, Carreras et al (2006) proposed that loggerheads originating from the eastern Mediterranean and entering the western basin follow the main surface currents and disperse in the Tyrrhenian Sea along the Italian coast, and then along the coasts of France and Spain. Recent genetic data from the Tyrrhenian Sea support this hypothesis (Maffucci et al 2013). Four different types of empirical data indicate a relatively low turtle occurrence in the Tyrrhenian Sea.…”

Section: Comparison With Empirical Data On the Distribution Of Older mentioning

confidence: 96%

The first ‘lost year’ of Mediterranean sea turtles: dispersal patterns indicate subregional management units for conservation

Casale¹,

Mariani²

2014

Mar. Ecol. Prog. Ser.

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Identifying highly frequented areas is a priority for sea turtle conservation, and the distribution of young individuals in open waters represents a major knowledge gap due to methodological biases. The drift of hatchlings from 38 loggerhead Caretta caretta and 10 green Chelonia mydas turtle nesting sites in the Mediterranean was simulated for the first 6 mo of life, with simulations repeated for 5 different years (2001 through 2005). Results indicate that hatchlings from the Levantine and south-central Mediterranean sites are mainly retained in the same areas of origin, while those from the Ionian area mainly disperse to the Ionian, Adriatic and southcentral Mediterranean areas. Combining hatchling dispersal with existing empirical information on juveniles and adults, a general distribution model among nesting sites, and oceanic and neritic foraging grounds for Mediterranean sea turtles is proposed. The Levantine zone may be particularly key for the conservation of the Mediterranean populations of both species, since it may host the highest concentration of individuals. Subregional management units identified by dispersal patterns may facilitate turtle conservation through a relatively small-scale international approach. In-water studies in specific zones are identified as a research priority for improving current knowledge and informing conservation plans. KEY WORDS: Caretta caretta · Chelonia mydas · Loggerhead turtle · Green turtle · Dispersal · Conservation · Mediterranean Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 498: [263][264][265][266][267][268][269][270][271][272][273][274] 2014 turtle species could potentially inform conservation plans for their respective Mediterranean populations (e.g. Schofield et al. 2013).The loggerhead turtle is the most abundant sea turtle species in the Mediterranean, and reproduces mainly in Greece, Turkey, Cyprus and Libya (Casale & Margaritoulis 2010). Loggerhead turtles frequent the entire marine area of the Mediterranean, with high occurrences reported in the oceanic zones of (1) the westernmost part of the basin (from the Alboran Sea to the Balearic Islands), where most individuals are of Atlantic origin (Carreras et al. 2006), (2) the Strait of Sicily, and (3) the Ionian Sea. Loggerheads are also found in high abundance in the neritic zones in the north Adriatic, off Tunisia-Libya, off Egypt, and off the southeast coast of Turkey (Casale & Margaritoulis 2010). Green turtles primarily reproduce on nesting beaches in Turkey, Cyprus and Syria (Casale & Margaritoulis 2010). They primarily occupy neritic areas in the easternmost part of the basin, in addition to foraging areas in Greece and Libya (Casale & Margaritoulis 2010).Current knowledge on the distribution of sea turtles in the Mediterranean waters is based on data from strandings (Tomás et al. 2008, Türkozan et al. 2013, incidental catch in fishing gear (reviewed by Casale 2011), tag returns (Margaritoulis et al. 2003, Casale et al. 2007b, Revelles et...

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“…Studies of juvenile loggerheads captured offshore south of Madeira Island (2000–2006) [42] or in the Mediterranean (2000–2011) [43] likewise did not find a significant difference among annual population sex ratios. However, a decreasing proportion of females in Madeira waters for turtles larger than the 45.0 cm SCL size class was noted [42].…”

Section: Discussionmentioning

confidence: 99%

“…Although still biased towards females, sex ratios of foraging juvenile loggerhead populations are not as highly skewed, displaying a 2F:1M ratio in Florida and Virginia [38], 3F:1M in North Carolina [34], 2F:1M in the northeast Atlantic [42], and 1.56F:1M in the Mediterranean [43]. However, operational sex ratios (estimated from adults actively breeding in a season) potentially appear to be more balanced [53] because male sea turtles breed more frequently than females and mate with multiple females, thus, providing a more balanced operational sex ratio despite a population’s highly skewed primary sex ratio.…”

Section: Discussionmentioning

confidence: 99%

Female-Bias in a Long-Term Study of a Species with Temperature-Dependent Sex Determination: Monitoring Sex Ratios for Climate Change Research

et al. 2016

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Alterations have occurred and continue to manifest in the Earth’s biota as a result of climate change. Animals exhibiting temperature dependent sex determination (TSD), including sea turtles, are perhaps most vulnerable to a warming of the Earth as highly skewed sex ratios can result, potentially leading to population extinction resulting from decreased male recruitment. Recent studies have begun to quantify climate change impacts to sea turtle populations, especially in terms of predicting effects on hatchling sex ratios. However, given the inherent difficulty in studying sex ratios at this life stage, a more accurate assessment of changes in population sex ratios might be derived by evaluating the juvenile portion of foraging aggregations. We investigated the long-term trend in sex ratio of a juvenile loggerhead (Caretta caretta) sea turtle population inhabiting Pamlico and Core Sounds, North Carolina, USA. We used plasma testosterone reference ranges measured using radioimmunoassay (RIA) to assign sex for 959 turtles and confirmed sex assignment of a subset (N = 58) of the sampled turtles through laparoscopic examination of their gonads. Our results demonstrate that for this particular population of loggerheads, sex ratios (3Females:1Male) had not significantly changed over a 10 year period (1998–2007), nor showed any significant difference among 5-cm straight carapace length (SCL) size classes. Ultimately, these findings provide a basis for comparison with future sex ratios, and highlight the importance of establishing similar long-term studies monitoring secondary, rather than primary, sex ratios, so that needed mitigation measures to climate change impacts can be implemented.

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Sex ratio of juvenile loggerhead turtles in the Mediterranean Sea: is it really 1:1?

Cited by 14 publications

References 40 publications

Skeletochronology, age at maturity and cause of mortality of loggerhead sea turtles Caretta caretta stranded along the beaches of Campania (south-western Italy, western Mediterranean Sea)

Skeletochronology, age at maturity and cause of mortality of loggerhead sea turtles Caretta caretta stranded along the beaches of Campania (south-western Italy, western Mediterranean Sea)

The first ‘lost year’ of Mediterranean sea turtles: dispersal patterns indicate subregional management units for conservation

Female-Bias in a Long-Term Study of a Species with Temperature-Dependent Sex Determination: Monitoring Sex Ratios for Climate Change Research

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