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Lanyon, Janet M.; Limpus, Colin J.; Marsh, Helene D.
(detail)
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1989 |
Dugongs and turtles: grazers in the seagrass system. In: A. W. D. Larkum, A. J. McComb & S. A. Shepherd (eds.), Biology of seagrasses: a treatise on the biology of seagrasses with special reference to the Australian region.
New York, Elsevier Science Publ. Co., Inc. (885 pp.):
610-634. 1 tab. 5 figs.
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Lanyon, Janet M.; Marsh, Helene D.
(detail)
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1995 |
Digesta passage times in the dugong.
Austral. Jour. Zool.
43(2): 119-127. 3 tabs. 1 fig.
–Captive dugongs kept on a low-fiber, low-intake diet at Jakarta exhibited very slow passage times of 146-166 hours, similar to those of T. manatus. This is attributed to the long digestive tract, and results in almost complete digestion of low-fiber food.
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Lanyon, Janet M.
(detail)
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2003 |
Distribution and abundance of dugongs in Moreton Bay, Queensland, Australia.
Wildlife Research
30(4): 397-409. 4 tabs. 5 figs.
–Results of aerial surveys conducted in 1995.
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Lanyon, Janet M.; Sanson, Gordon D.
(detail)
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2006a |
Degenerate dentition of the dugong (Dugong dugon), or why a grazer does not need teeth: morphology, occlusion and wear of mouthparts.
Jour. Zool.
268(2): 133-152. 4 tabs. 12 figs. Feb. 2006.
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Burgess, Elizabeth A., Lanyon, Janet M.; Keeley, Tamara
(detail)
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2012 |
Testosterone and tusks: Maturation and seasonal reproductive patterns of live, free-ranging male dugongs (Dugong Dugon) in a subtropical population.
Reproduction
143(5):683-697. May 1, 2012
–ABSTRACT: Knowledge of male reproductive status and activity in free-ranging animals is vital to understanding reproductive patterns and population dynamics. Until now, almost all information regarding reproductive behavior of the dugong, a cryptic marine mammal, has relied on post-mortem examination. We examined the relationships between body length, tusk eruption (secondary sexual characteristic), seasonality, and group association on fecal testosterone metabolite concentrations in 322 free-ranging dugongs (159 males, 163 females) in subtropical Moreton Bay, Australia. Fecal testosterone concentrations demonstrated biologically meaningful differences in testicular activity between sexes and across reproductive/age classes, and were correlated with circulating concentrations in serum. Male dugongs have a pre-reproductive period that persists until a body length of 240 cm is achieved. Puberty apparently occurs between 240 and 260 cm body length when fecal testosterone levels increase fourfold (>500 ng/g) over juvenile levels, and is associated with tusk eruption. However, social maturity may be delayed until male dugongs are larger than 260 cm with well-developed tusks. In mature males, the lowest (<500 ng/g) fecal testosterone concentrations occur in the austral autumn months with maximal concentrations in September-October, coincident with the onset of a spring mating season. During spring, solitary mature males had fecal testosterone concentrations double those of mature males sampled within groups, potentially suggesting a mating strategy involving roving of reproductively active males. This study demonstrates that single-point physiological data from individuals across a population have value as indicators of reproductive processes. Our approach provides an efficacious non-lethal method for the census of reproductive status and seasonality in live male dugongs.
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Burgess, Elizabeth A.; Lanyon, Janet M.; Brown, Janine L.; Blyde, David; Keeley, Tamara
(detail)
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2012 |
Diagnosing pregnancy in free-ranging dugongs using fecal progesterone metabolite concentrations and body morphometrics: a population application.
General and Comparative Endocrinology
177(1): 82-92. 2 tabs. 8 figs. DOI: 10.1016/j.ygcen.2012.02.008. May 15, 2012.
–ABSTRACT: Assessing reproductive status and monitoring reproductive rates is important in the effective management of vulnerable marine mammal species such as the dugong (Dugong dugon). Knowledge of the reproductive physiology of this species is limited, and determining reproductive parameters (e.g., sexual maturation, pregnancy, and reproductive senescence) has been restricted by a lack of non-lethal methods for assessing reproductive status in free-ranging individuals. The aim of this study was to develop a method to identify pregnant individuals in a wild dugong population. Using an enzyme immunoassay, we quantified concentrations of fecal progesterone metabolites (fP) in 322 dugongs, including confirmed pregnant females (n=10), presumed non-pregnant adult females (n=25), juvenile females (n=24), subadult females (n=41), adult females of unknown pregnancy state (n=63), and males of all sizes (n=159). External body morphometrics of each dugong were measured, and confirmation of pregnancy in adult female dugongs was determined by ultrasonography or observation of subsequent neonates. Concentrations of fP were different between sexes and reproductive size classes (P<0.001), and similar to 30-fold higher in confirmed pregnant dugongs (2017-7760ng/g) compared to presumed non-pregnant females (30-221ng/g), juvenile females (29-195ng/g), and males (24-261ng/g) (P<0.001). Body measures of maximum and anal girths, and teat length were all greater in confirmed pregnant females than presumed non-pregnant females (all P<0.05). We evaluated a Discriminant Function Analysis (DFA) to provide a model for predicting pregnant and non-pregnant dugongs. Cross-validated results showed that the DFA correctly classified 100% of pregnant and non-pregnant females using fP concentrations, body length, fineness ratio (an index of body shape), and teat length (a female reproductive trait). Using the DFA model, we classified the pregnancy status of all female dugongs and identified a total of 30 females as pregnant and 133 females as non-pregnant from the sampled population over the sample period. Pregnant dugongs in the Moreton Bay population are characterized by fecal progesterone metabolite concentrations>1000ng/g, body length>=260cm, maximum girth>=215cm, anal girth>=126cm, and teat length>=5cm long. In summary, analysis of fP concentrations in combination with body morphometrics may be used to diagnose pregnancy in free-ranging dugongs, and provides a new tool to monitor breeding rates of wild sirenian populations.
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Eigeland, Karen A.; Lanyon, Janet M.; Trott, Darren J.; Ouwerkerk, Diane; Blanshard, Wendy; Milinovich, Gabriel J.; Gulino, Lisa-Maree; Martinez, Emilio; Merson, Samuel; Klieve, Athol V.
(detail)
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2012 |
Bacterial community structure in the hindgut of wild and captive dugongs (Dugong dugon).
Aquatic Mammals
38(4): 402. 3 tabs. 1 fig. DOI:10.1578/AM.38.4.2012.402.
–ABSTRACT: Dugongs (Dugong dugon) are marine mammals that obtain nutrients through hindgut fermentation of seagrass, however, the microbes responsible have not been identified. This study used denaturing gradient gel electrophoresis (DGGE) and 454-pyrosequencing to profile hindgut bacterial communities in wild dugongs. Faecal samples obtained from 32 wild dugongs representing four size/maturity classes, and two captive dugongs fed on cos lettuce were screened using DGGE. Partial 16S rRNA gene profiles of hindgut bacteria from wild dugong calves and juveniles were grouped together and were different to those in subadults and adults. In captive dugongs, the absence of the dominant bacterial DNA bands identified in wild dugongs is probably dependent upon prevailing diet and other captive conditions such as the use of antibiotics. This study represents a first step in the characterisation of a novel microbial ecosystem -- the marine hindgut of Sirenia.
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Lanyon, Janet M.; Sneath, Helen L.; Long, Trevor
(detail)
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2012 |
Evaluation of exertion and capture stress in serum of wild dugongs (Dugong dugon).
Journal of Zoo & Wildlife Medicine
43(1): 20–32. 2 tabs. 2 figs.
–Abstract: Seven hundred fifty-one dugongs (Dugong dugon) were pursued, captured, and handled for up to 20 min for population sampling. Fifty of these dugongs were then removed from the water for up to 55 min for comprehensive medical examination. Fifty whole blood and separated serum samples were analyzed for potassium, sodium, chloride, creatinine kinase (CK), aspartate aminotransferase (AST), alanine aminotransferase (ALT), lactate dehydrogenase (LDH), urea, creatinine, glucose, anion gap, and total blood CO2. Serum biochemical variables of the dugong were compared with those obtained in previous studies of the related West Indian manatee, a mammal that does not appear to experience capture myopathy based on available data. Differences between these species included higher blood sodium and chloride in dugongs, which may reflect differences in salt balance and renal function, and higher blood lactate and CO2. Some biochemical analytes such as CK and AST, which may be indicative of rhabdomyolysis associated with capture stress myopathy (a potentially fatal condition for which dugongs have been thought to be highly susceptible) were high compared with levels previously measured in wild West Indian manatees (Trichechus latirostris). One of the 50 dugongs had marked elevations of CK and AST but showed no other clinical indications of rhabdomyolysis associated with capture myopathy such as hyperthermia. Rather, generally high levels of lactate, CK, and AST most probably reflect metabolic acidosis resulting from the exertion involved in the pursuit prior to capture. Earlier observations suggesting that dugongs were probably susceptible to capture stress myopathy (based on high serum potassium levels) were not supported by this study. Capture and handling methods currently used on dugongs in this research program do not appear to result in acute capture stress.
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Bibliography and Index of the Sirenia and Desmostylia 