Skeletal muscle lipids in Weddell seals (Leptonychotes weddellii): Differences in age class and possible response to resource limitations

In this study, we investigated the intramuscular triglyceride (IMTG) profiles and oxidative metabolism substrates of a deep diving mammal, the Weddell seal. We sampled pups (4–6 wks), juveniles (12–15 mo) and non‐lactating adults (< 15 mo) and tested for age‐class, gender and yearly differences. No gender differences were observed in IMTG or oxidative metabolism substrates. While pup (6g/100g) muscles had consistently three times the IMTG stores than juveniles (2g/100g), no differences were observed between yearly IMTG stores. Also, no yearly differences were found in oxidative metabolism substrates (lipoprotein lipase, citrate synthase, lactate dehydrogenase) among age classes. However, the IMTG stores of 2006 sampled adults (2g/100g) decreased 550% from 2005 to levels (11g/100g). This finding appears to correlate with the receding ice coverage in the McMurdo Sound area and its impact on the population density of adults (increase of 62% in 2006). Assuming breeding aged or lacatating females had similar IMTG values implies these adult animals may be faced with a physiological bottleneck similar to that of juveniles. These data suggest that population density of Weddell seals which may be directly impacted by climate change will have dramatic effects on their reproductive success.