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Nganvongpanit, Korakot; Buddhachat, Kittisak; Kaewmong, Patcharaporn; Cherdsukjai, Phaothep; Kittiwatanawong, Kongkiat
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2017 |
What the skull and scapular morphology of the dugong (Dugong dugon) can tell us: sex, habitat and body length?
Scientific Reports (Nature) 7(1964): 17 pp. 8 tabs. 11 figs. + online supplemental materal. https://www.nature.com/articles/s41598-017-01899-7 May 16, 2017.
–ABSTRACT: The dugong (Dugong dugon, Müller) is an endangered marine mammal species. We examined the relationship between sex, habitat and body length based on the skull and scapular morphology and morphometrics of 81 dugong samples in Thailand. A total of 58 parameters from the skull and scapula (25 from the cranium, 23 from the mandible and 10 from the scapula) as well as tusks were used in this study. Data were analyzed by univariate analysis, followed by discriminant analysis and multivariate linear regression. Here we show, 100% and 98.5% accuracy rates for sexing using large tusks and the skull, respectively. Scapular morphology using the caudal border tubercle and coracoid process showed 91.30% and 96.15% accuracy rates for identifying males and females. Skull morphometrics could categorize dugong habitat, i.e. living in the Andaman Sea or Gulf of Thailand, with 100% accuracy. Moreover, our model could be used to estimate body length with coefficient of determination (R2) of 0.985. The results of our study showed that skull morphology and morphometric measurements could be used as a tool for sex identification, location identification and estimation of body length. But scapular morphology is the best tool for sex identification in dugongs.
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Cherdsukjai, Phaothep; Buddhachat, Kittisak; Brown, Janine; Kaewkool, Manthanee; Poommouang, Anocha; Kaewmong, Patcharaporn; Kittiwattanawong, Kongkiat; Nganvongpanit, Korakot
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2020 |
Age relationships with telomere length, body weight and body length in wild dugong (Dugong dugon).
PeerJ 8: e10319. 4 tabs. 5 figs. + online supplemental information. doi:10.7717/peerj.10319 Nov. 11, 2020.
–ABSTRACT: The ability to estimate age and determine the growth status of free-ranging dugongs (Dugong dugon) is vital to providing insight into the basic biology of this endangered species. Currently, age estimation in dugong carcasses relies on counting dentin growth layer groups (GLGs) in tusks, but a disadvantage is they need to be intact. We explored whether measures of telomere length could be used as an alternative approach to age estimation in dugongs given that in other species, telomere length and age are inversely related. In this study, relative telomere length (rTL) was measured by qPCR in skin samples from 24 dugongs of varying ages determined by counts of GLGs. In addition, relationships between age by GLG counts and body weight and length and were examined. Our findings indicate that age estimated by GLGs was negatively correlated with telomere length using the logistic formula with a rate of telomere attrition of approximately 0.036 rTL/year between the ages of 5–20 years. By comparison, both body weight and length were positively correlated with GLG-based age, with growth rates of ~8.8 kg/year for weight and ~3.58 cm/year for length, respectively. After that, growth rates slowed substantially and then plateaued. The results suggest that physical maturity in dugongs occurs at 20 years of age and that measures of rTL might serve as a tool for age estimation in dugongs, living and deceased.
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Bibliography and Index of the Sirenia and Desmostylia 