Regional and annual variation in plasma steroids and metabolic indicators in female green turtles, Chelonia mydas
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Variation in environmental conditions at a foraging area or at a nesting rookery has the potential to impact reproductive output of green sea turtles (Chelonia mydas) by affecting food resources or the nesting substrate. In this paper we test whether turtles‘ physiological characteristics reflect variation in relevant environmental conditions. We did this by profiling metabolic and hormonal markers among (1) non-vitellogenic females from three different foraging areas and (2) nesting females from different rookeries and breeding seasons. Among the non-vitellogenic females, the highest plasma triglyceride concentrations (4.29 mmol/l) and the lowest plasma cholesterol concentrations (1.27 mmol/l) were found in non-vitellogenic females residing in Moreton Bay during the El Niño year of 1997. Furthermore, during 1997, these Moreton Bay females had higher plasma triglyceride and lower cholesterol concentrations than those recorded in non-vitellogenic females foraging at Heron Reef (triglyceride 1.22 mmol/l and cholesterol 4.53 mmol/l) and Shoalwater Bay (triglyceride 1.69 mmol/l and cholesterol 3.50 mmol/l) in the same year. Among nesting turtles, those nesting at Raine Island had low mean plasma triglyceride concentrations during the high density 1996 nesting season. For those nesting at Heron Island, the mean triglyceride concentrations were the lowest during the 1997 nesting season. This is the first time that hormone and metabolic markers have been used in concert to compare the physiological condition of nesting and foraging sea turtles and its relationship with the environment. Collectively, our data indicate that variation in the environmental conditions at both foraging and nesting areas are reflected at a physiological level. Moreover, our study indicates that turtles feeding during El Niño years are able to attain higher levels of body condition, and that physiological data combined with morphometric data is a useful proxy for assessing the condition of turtles in foraging areas.
KeywordsBody Condition Great Barrier Reef Green Turtle Plasma Metabolite Nest Season
This study was undertaken as part of the QPWS Turtle Conservation Project, funded by an ARC grant to JMW and CJL, and a small ARC (95/96) grant to JMW. Partial support for the passage to the northern Great Barrier Reef islands and for the collection of samples in Moreton Bay was provided by the Raine Island Corporation and Sea World Research and Rescue Foundation, respectively. P&O Resorts Australia provided transport of research staff and volunteers to and from Heron Island. The assistance of the Marine Parks staff of Gladstone, Roslyn Bay, Heron Island and Moreton Bay was invaluable. Additionally, this project also owes a considerable amount to many staff and volunteers of the QPWS Turtle Conservation Project, in particular I. Bell, D. Broderick, S. Clark, M. Forrest, D. Limpus and M. Read. This manuscript was improved following comments from C. Schäuble. The University of Queensland (ANAT/121/99/ARC/PHD) and QPWS animal ethics permits covered this project.
- Bjorndal K.A. (1997) Foraging ecology and nutrition of sea turtles. In: Lutz PL, Musick JA (eds), The biology of sea turtles. CRC Press, Boca Raton, pp 199–232Google Scholar
- Bustard HR (1972) Sea turtles: natural history and conservation. Collins, LondonGoogle Scholar
- Chaloupka M (2000) Modelling sea turtle growth, survivorship and population dynamics. PhD Thesis, Department of Zoology and Entomology, The University of QueenslandGoogle Scholar
- Hamann M (2002). Reproductive cycles, interrenal gland function and lipid mobilisation in the green sea turtle (Chelonia mydas). PhD Thesis, Department of Anatomical Sciences, The University of QueenslandGoogle Scholar
- Limpus CJ, Reed P (1985) The green turtle, Chelonia mydas, in Queensland: a preliminary description of the population structure in a coral reef feeding ground. In: Grigg G, Shin R, Ehmann H (eds) Biology of Australasian frogs and reptiles, Royal Zoological Society of New South Wales, pp 47–52Google Scholar
- Limpus CJ, Eggler P, Miller JD (1994) Long interval remigration in eastern Australian chelonia. In: Schroeder BA, Witherington BE (eds) Proceedings of the 13th annual symposium on sea turtle biology and conservation. NOAA Technical Memorandum NMFS-SEFSC-341, MiamiGoogle Scholar
- Limpus CJ, Carter D, Hamann M (2001) The green turtle, Chelonia mydas, in Queensland, Australia: the Bramble Cay rookery in the 1979–1980 breeding season. Chelon Conserv Biol 4(1):34–46Google Scholar
- Limpus CJ, Miller JD, Parmenter CJ, Limpus DJ (2003) The green turtle, Chelonia mydas population of Raine Island and the northern Great Barrier Reef: 1843–2001. Mem Queensl Mus 49(1):349–440Google Scholar
- Miller JD (1997) Reproduction in sea turtles. In: Lutz PL, Musick JA (eds) The biology of sea turtles. CRC Press, Boca Raton, pp 51–82Google Scholar
- Owens DW, Ruiz GJ (1980) New methods of obtaining blood and cerebospinal fluid from marine turtles. Herpetologica 36:17–20Google Scholar
- StatSoft Inc (2001) STATISTICA. StatSoft Inc., TulsaGoogle Scholar