Energy Allocation in the Allegheny Mountain Salamander, Desmognathus Ochrophaeus

Abstract

The reproductive cycle, energy budget, and relationships between rates and energetics of vitellogenesis, lipid deposition and depletion, and changes in lean carcass tissue were examined in Desmognathus ochrophaeus salamanders from northeastern Ohio. Oviposition begins prior to emergence in mid—April, reaches a peak in mid—May, and continues in greatly reduced frequency into September. Lipids in the carcass and ovarian fat bodies apparently are used for maintenance and vitellogenesis during winter dormancy (mid—October to mid—April) and after emergence in the spring when food reserves are scarce. Carcass lipids, lean carcass tissue, and perhaps fat body lipids are used for maintenance during brooding. A typical female oviposits in mid—May, replaces depleted lipids and lean carcass tissue by late August, and produces intermediate—sized follicles before winter and full—sized follicles during April and early May. Energy ingested, egested, assimilated, and lost through respiration was examined in gravid females, spent females, and males acclimated to four temperature—photoperiod regimes: (1) 5°C, LD 10:14; (2) 5°C, LD 14:10; (3) 15°C, LD 10:14; and (4) 15°C, LD 14:10. Size, sex, reproductive condition, and temperature significantly influence energetics in D. ochrophaeus. Photoperiod does not affect metabolism significantly at either temperature. There is an inverse exponential relationship between body weight and weight—specific rates of ingestion, egestion, assimilation, and respiration. Gravid females, actively depositing yolk in follicles, show higher O₂ consumption rates than recently spent females and males at 15°C, but not at 5°C when yolking rates apparently are reduced. Rates of O₂ consumption are significantly higher at 15°C than 5°C. At 15°C gravid females, spent females, and males lost 43.2, 3.60, and 3.84 cal g^—1 day^—1 metabolic heat; at 5°C they lost 1.92, 1.92, and 1.68 cal g^—1 day^—1, respectively. Salamanders cease to feed at 5°C. At 15°C gravid females, spent females, and males ingested 21.0, 37.8, and 23.8 cal g^—1 day^—1 and egested 2.7, 5.1, and 2.9 cal g^—1 day^—1, with assimilation efficiencies of 87.2%, 86.3%, and 88.2%, respectively. The estimated annual energetics of a typical female are: ingestion = 2,940 cal; egestion = 378; assimilation = 2,562; respiration = 1,104.4; and secondary production = 1,457.6. Reproductive activities (vitellogenesis = 807.5 and brooding maintenance = 430 cal) cost 48.3% of a female's annual energy flow (A = 2,562 cal).