Total Daily Energy Requirements Research Articles

Age‐Specific Energetics of the Pea Aphid, Acrythosiphon pisum

A laboratory study of energy flow in different—aged pea aphids was accomplished by the balance sheet method. Growth, reproduction, molted exoskeletons, oxygen consumption, and honeydew production were monitored daily. Absolute amounts of energy expended on reproduction, growth, maintenance, and rejecta all varied with age of the aphid. Efficiencies of production and respiration also varied with the life history stage. Assimilation efficiency did not vary with age. Gross productions efficiency (° = 49%) and assimilation efficiency (°=83%) are higher in this insect than in most other insects reported. The reason for such high efficiency may be the unusually high amino acid content of pea phloem sap. Rates of exudation of amino acids and sugars from pea phloem through severed aphid stylets and greater than twice the total daily energy requirement of continuously feeding aphids. This would be true even for passively feedings aphids. Under the study conditions the daily ingestions of one average adult aphid is approximately 8% of the daily net primary production of a 0.15 a (dry wt) pea seedling.

Adaptational Biology and Energy Relationships of the Collared Peccary (Tayassu Tajacu)

Field and laboratory investigations were conducted to determine the major seasonal adaptations exhibited by the collared peccary (Tayassu tajacu) in the desert. Emphasis was placed on the animal's thermoregulation, water relations, and energy requirements under changing environmental conditions. Body core temperatures were labile and ranged from 37.5 degrees C to approximately 40.9 degrees C during both winter and summer seasons. Skin temperatures were always above ambient and reached a high of 49.2 degrees C during summer. Heat loss across the skin of summer animals averaged 0.041 cal/cm2 min during the day and 0.038 cal/cm2 min at night. Winter animals by basking exhibited a slight heat gain during the day (0.033 cal/cm2 min) but lost heat at a rate of 0.223 cal/cm2 min at night. The pelage of the peccary had a poor insulative value; thermal conductance equaled 0.291 cal/cm2 hr degrees C. Summer animals became lighter in color over certain parts of their body and also decreased density of bristles over most of their body. Total water requirement for summer peccaries was 66.5 ml/kg day and for winter peccaries 38.6 ml/kg day. Respiratory evaporation was the major avenue of water loss and accounted for 6.1% of body wt/day for summer dehydrated pecaries. during dehydration peccaries were able to reduce evaporative water loss by as much as 68% and urinary water loss by 93%, but were unable to produce dry feces. Their maximum osmolar urine/plasm ration was 4.0. Total daily energy requirement for an 18.2 kg peccary was 794.05 Kcal/day in summer and 916.96 Kcal/day in winter. The annual energy requirement was estimated at 17,166 Kcal/kg year. On the basis of these calculations, a herd of 25 individuals occupying a home range of 388 ha at the Three—Bar wildlife Area would require approximately 20% of the annual production of prickly pear cactus (7,985.0 kg/year or 20,130.9 Kcal/ha year).