engleski

Growth-related pectoral Fe accumulation in loggerhead sea turtle Caretta caretta : implications for diving physiology

We analyzed Fe in liver, kidney, pectoral muscle (Pectoralis major) and heart muscle of 40 dead stranded loggerhead turtles with the mean curved carapace length (CCL) ranging from 25.0 – 84.5 cm (mean: 44.9, SD: 12.9) from the eastern Adriatic Sea (Croatia and Slovenia) by a flame atomic absorption spectrometry. As about 99% of Fe in muscles of vertebrates is hem-related by knowing the muscles weight of each individual, we were able to transform pectoral c(Fe) into the total muscles Fe burden (WFe) and subsequent oxygen volume (VO2) in 100% hem saturation. The highest Fe concentration was found in the liver (302.20 μ g/g wet weight) > kidney (180.51) > heart (146.31) > pectoral muscle (22.16). However, only pectoral muscle showed significant correlation of Fe with CCL (r = 0.457, p < 0.01). Significant difference in pectoral Fe was also found between loggerheads in the pelagic (CCL < 50 cm ; c(Fe) = 19.40 μ g/g w.w.) and benthic (CCL > 50 cm ; c(Fe) = 28.15 μ g/g w.w.) ontogenetic stages (Student’ s t test, p < 0.05). Our results suggest that loggerheads accumulate Fe in pectoral muscles during growth. In order to compare these results with theoretical stimulation when c(Fe) is constant and equal to the mean concentration found in pelagic juveniles, we set a model which predicts changes in WFe and VO2 as a function of the somatic growth alone. The model showed that due to the existence of pectoral Fe accumulation, loggerheads with CCL of 70 cm may store about 44% more O2, whilst turtles with CCL of 80 cm may store up to 60% more O2 in their skeletal muscles in comparison with the model predictions. The tendency of Fe accumulation with growth found in this study could indicate the existence of a physiological adaptation of swimming muscles of loggerheads for ontogenetic habitat shift and prolonged dives.

sea turtles; Fe; skeletal muscles; oxygen storage; diving; adaptations; ontogenetic habitat shift

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