Age relationships with telomere length, body weight and body length in wild dugong (Dugong dugon)

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.

Genetic diversity in a unique population of dugong (Dugong dugon) along the sea coasts of Thailand

“…Skin samples were extracted using DNA extraction kits according to manufacturer’s instructions (DNeasy Blood & Tissue Kit, Qiagen, Germany) at the Faculty of Veterinary Medicine, Chiang Mai University, and the DNA measured qualitatively and quantitatively by agarose gel electrophoresis and spectrophotometry, respectively 16 .…”

Dugongs (Dugong dugon) along hyper-urbanized coastlines

“…In northeast Brazil, the anthropogenic-mediated loss of birthing grounds (Parente et al, 2004) was linked to the increased chances of mother-calf separation, and calf stranding rates of Antillean manatees (Balensiefer et al, 2017). This phenomenon is also reflected in our dataset; calf carcasses (≤ 2m in length; see Marsh, 1980;Cherdsukjai et al, 2020) accounted for more than 45% of the records with biometric information (Table S1). The autopsy of a 1.4m male recovered within our study site in 2021 concluded that pre-mature mother-calf separation was the likely cause of death as the suckling calf presented with no signs of physical trauma or disease, and its stomach was full of milk and seagrass (S. Z. H. Ng and Z. Jaafar, pers.…”

Microsatellite Polymorphism and the Population Structure of Dugongs (Dugong dugon) in Thailand

“…The samples were processed using DNA extraction kits according to manufacturer's instructions (DNeasy Blood & Tissue Kit, Qiagen, Germany) at the Faculty of Veterinary Medicine, Chiang Mai University [32], and the DNA measured qualitatively and quantitatively by agarose gel electrophoresis and spectrophotometry, respectively [4].…”

“…The dugong (Dugong dugon), order Sirenia, family Dugongidae, is the only herbivorous marine mammal in the world, with a diet consisting of seagrass [1]. Dugongs have a life span of around 60-70 years [2], sexual maturity at ~10-12 years of age [3], and reach adulthood at 20 years of age [4]. Seagrass is the main food source of dugongs [5][6][7][8], so degradation and disappearance of these meadows are major reasons for declining dugong populations.…”