Carapacial scute variation in Loggerhead Turtles,<i>Caretta caretta</i>

Türkozan, Oğuz; Ilgaz, Çetίn; Sak, Serdar

doi:10.1080/09397140.2001.10637893

Cited by 19 publications

(20 citation statements)

References 3 publications

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“…These variations have been observed in individuals of all species of marine turtles except Dermochelys coriacea (Hill, 1971;Limpus, 1971;Limpus et al, 1983;Mast & Carr, 1989;Türkozan et al, 2001;Ergene et al, 2011; and hatchling turtles from the same population have found a higher incidence of non-modal scute patterns in hatchling turtles compared to adult turtles (Limpus, 1971;Limpus et al, 1983;Türkozan et al, 2001;Ergene et al, 2011). Mast and Carr (1989) Few sea turtle hatchlings survive to breeding age (Frazer, 1986;Heppell et al, 1996), and it has been hypothesised that the lower frequency of non-modal scute patterns observed in adult turtles is due to higher initial mortality of hatchlings with non-modal scute patterns, resulting in fewer surviving to breeding age (Türkozan & Yilmaz, 2007).…”

Section: Introductionmentioning

confidence: 97%

“…Studies have also shown similar size and locomotor performance of male and female hatchlings produced at the same temperatures, suggesting that factors other than sex affect hatchling mortality (Booth et al, 2004). Because of this discrepancy between hatchlings and adults, it is often assumed that non-modal scute patterns indicate lower quality hatchlings that experience higher initial mortality, thus explaining their lower frequency in the adult population (Türkozan et al, 2001). However, this hypothesis has never been tested.…”

Section: Study Speciesmentioning

confidence: 99%

“…There is evidence to suggest that non-modal scute patterns indicate lower quality hatchlings, meaning fewer survive to reach maturity (Türkozan et al, 2001). A previous study showed that N. depressus hatchlings with the modal scute pattern out-performed hatchlings with major non-modal scute patterns during the first twenty minutes of swimming (Sim et al, 2014).…”

Section: Scute Pattern Variationmentioning

confidence: 99%

“…Non-modal scute patterns have been reported for all marine turtle species (Hill, 1971;Limpus, 1971;Mast & Carr, 1989), and usually include supernumerary scutes (Zangerl & Johnson, 1957). Non-modal scute patterns are generally more common in hatchling turtles than in adult turtles (Limpus, 1971;Mast & Carr, 1989;Türkozan et al, 2001). The decrease in the proportion of individuals with non-modal scute patterns in breeding adults suggests that fewer turtles with non-modal scute patterns survive to breeding age (Türkozan et al, 2001).…”

Section: Introductionmentioning

confidence: 99%

“…Non-modal scute patterns are generally more common in hatchling turtles than in adult turtles (Limpus, 1971;Mast & Carr, 1989;Türkozan et al, 2001). The decrease in the proportion of individuals with non-modal scute patterns in breeding adults suggests that fewer turtles with non-modal scute patterns survive to breeding age (Türkozan et al, 2001). It is likely that non-modal scute patterns do not influence survival directly, but are indications of greater internal abnormalities (Mast & Carr, 1989).…”

Section: Introductionmentioning

confidence: 99%

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Nest environment and hatchling fitness correlates in the sea turtles Caretta caretta and Natator depressus

Sim¹

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Marine turtles have a complex lifecycle and face threats in both marine and terrestrial environments.Nesting females lay a large number of eggs, very few of which produce hatchlings that survive to reach breeding age. As hatchlings cross the beach, they are exposed to predation, disorientation, dehydration and debris on the beach. When hatchlings enter the water they are exposed to aquatic predators. Hatchlings do not actively avoid predators, or defend themselves, so simply being able to move quickly through this environment would increase their chance of survival. A number of variables can affect hatchling locomotor performance, and this thesis examines three of these: incubation temperature, scute pattern and rookery location in two species of sea turtle, loggerhead (Caretta caretta) and flatback turtles (Natator depressus).The first part of this thesis focuses on scute pattern. Scutes cover the carapace of turtles and tortoises, and each species has a modal pattern. Deviations from this modal pattern are more common in hatchlings than in adult turtles, suggesting that hatchlings with non-modal scute patterns have higher mortality rates, but this hypothesis has not been tested previously. Hatchlings with modal scute patterns were larger and heavier than hatchlings with non-modal scute patterns in both species examined, however this size difference did not translate into a difference in terrestrial locomotor performance. However, N. depressus hatchlings with the modal scute pattern produced more thrust than hatchlings with non-modal scute patterns in the first 40 minutes of swimming, which may give them an advantage over hatchlings with non-modal scute patterns.The second part of this thesis focuses on incubation temperature. Marine turtle eggs successfully incubate within a narrow range of temperatures. Even within the viable developmental temperature range, it has been proposed that hatchlings from eggs incubated close to the thermal tolerance limits may have reduced fitness compared to hatchlings from eggs incubated at intermediate temperatures.In this study, C. caretta hatchlings from hot nests were less likely to emerge from the nest, were smaller, and also performed poorly during crawling and swimming trials compared with hatchlings incubated in moderate temperature nests.The third part of this thesis focuses on differences in hatchling morphology and locomotor performance between two N. depressus rookeries representing two separate 'evolutionarily significant units' (ESUs). Hatchlings at the two sites differed in size, but this size difference did not translate into a difference in either crawling speed or self-righting ability.ii This thesis contributes to our understanding of factors that influence marine turtle hatchling fitness, both environmental and morphological. This information can be used in the monitoring of endangered marine turtle populations.iii DECLARATION BY AUTHOR This thesis is composed of my original work, and contains

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Section: Introductionmentioning

confidence: 97%

Section: Study Speciesmentioning

confidence: 99%

Section: Scute Pattern Variationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Nest environment and hatchling fitness correlates in the sea turtles Caretta caretta and Natator depressus

Sim¹

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Investigating the effects of nest shading on the green turtle (Chelonia mydas) hatchling phenotype in the Ogasawara islands using a field‐based split clutch experiment

Kobayashi

Endo

Kitayama³

et al. 2020

J Exp Zool Pt A

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No evidence of selection against anomalous scute arrangements between juvenile and adult sea turtles in Florida

Bentley

McGlashan

Bresette

et al. 2020

Journal of Morphology

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Variations in the number and arrangement of scutes often are used for species identification in hard‐shelled sea turtles. Despite the conserved nature of scute arrangements, anomalous arrangements have been noted in the literature for over a century, with anomalies linked to sub‐optimal environmental conditions in the nest during development. Long‐held assumptions suggest that anomalous scute arrangements are indicative of underlying physiological or morphological anomalies, with presumed long‐term survival costs to the individual. Here, we examined a 25‐year photo database of two species of sea turtle (Caretta caretta and Chelonia mydas) captured incidentally and non‐selectively on the eastern coast of Florida. Our results suggest that C. mydas is substantially more variable with respect to the arrangement of carapacial scutes, while C. caretta had a relatively higher proportion of individuals with anomalous plastron scute arrangements. We also show evidence that (a) the forms and patterns of anomalous scutes are stable throughout growth; (b) there is limited evidence for selection against non‐modal arrangements in the size classes that were examined; and (c) that their frequency has remained stable in juvenile cohorts from 1994 until present. These findings indicate that there may not be a survival cost associated with anomalous scute arrangements once the turtles reach juvenile size classes, and that variation in scute arrangements within populations is relatively common.

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Carapacial scute variation in Loggerhead Turtles,Caretta caretta

Cited by 19 publications

References 3 publications

Nest environment and hatchling fitness correlates in the sea turtles Caretta caretta and Natator depressus

Nest environment and hatchling fitness correlates in the sea turtles Caretta caretta and Natator depressus

Investigating the effects of nest shading on the green turtle (Chelonia mydas) hatchling phenotype in the Ogasawara islands using a field‐based split clutch experiment

No evidence of selection against anomalous scute arrangements between juvenile and adult sea turtles in Florida

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