Meeting Abstract
P3.29 Monday, Jan. 6 15:30 Linking Metabolic Hormones to Nutritional Status in Weddell Seals (Leptonychotes weddellii) KROTZ, R T*; SHERO, M R; COSTA, D P; BURNS, J M; RICHMOND, J P; University of North Florida, Jacksonville; University of Alaska Anchorage; University of California Santa Cruz; University of Alaska Anchorage; University of North Florida, Jacksonville rileytkrotz@gmail.com
The metabolic hormone insulin-like growth factor (IGF)-I facilitates anabolism, increasing growth rate and the synthesis of lean and adipose tissue. Growth hormone (GH) acts directly on adipose, inhibiting nutrient deposition during periods of adequate intake and mobilizing energy during reduced intake. In many species, IGF-I and GH accurately reflect nutritional or metabolic status. In the Antarctic, Weddell seals exhibit seasonal life history patterns in intake which affects nutritional status. Seals actively forage at sea for 8-months (March-October), followed by 3-months of reduced intake due to land based life-history events including breeding, pupping and molting (November-February). As a result, nutritional status is expected to be reduced in January compared with October. To evaluate the relationship between nutritional status and metabolic hormones in Weddell seals, morphometrics, body fat percentage, and serum were gathered from 97 adults over 3 years. As expected, mass (p<0.01) and percentage body fat (p<0.01) were greater in October (347.1±73.1kg; 36.0±4.0%) compared with January (293.8±75.0kg; 30.9±3.6%). Unexpectedly, IGF-I (p=0.20) concentrations were not different between January (71.08±33.72ng/mL) and October (59.2±35.2ng/mL). However, GH (p=0.03) was greater in January (26.46±13.12ng/mL) compared with October (15.90±15.42ng/mL). Even though animals were larger and fatter in October, the reduced IGF-I in conjunction with increased GH suggests a low nutritional status at both time points. Alternatively, low IGF-I concentrations may suggest protein conservation mechanisms required for energetically expensive life-history events during the austral summer.
