Blood and fluid balance of the common tarantula, Dugesiella hentzi

Abstract

1. Blood of Dugesiella hentzi, the common tarantula of the United States, was analyzed. Protein concentration of serum averaged 74 mg/ml with hemocyanin the major constituent since the Cu/protein ratio of 0.00175 is close to that of purified hemocyanin from other arthropods. Concentrations of non-protein nitrogen, glucose, and total anthrone reactive material were 0.32, 0.04, and 0.13 mg/ml respectively. Freezing point depression of the serum was 0.75° C and pH ranged from 7.25 to 7.35. 2. Blood volumes of males and females expressed as percent of body weight averaged 19.65 and 18.10% respectively. Water content of females was about 73.2% of body weight. Fat content averaged 10.3% of body weight. Exoskeleton represented 5.8% of body weight with a water content of 40%. A value of 74.7% was calculated for intracellular water. 3. Evaporation rates were determined. During the first hour of exposure to moving dry air, 0.168 mg/cm2/hr was lost at 20° C increasing to 0.915 mg/cm2/hr at 40° C. By the fifth hour of exposure these losses had decreased to 0.088 mg/cm2/hr at 20° C and 0.674 mg/cm2/hr at 40° C (Fig. 1). 4. Drinking habits in the laboratory were observed. Fed regularly, 2 crickets per week, the spiders usually drank once weekly, soon after eating. Volumes taken varied from a few mg to more than 1 g. Fasted spiders drank somewhat more, tending to maintain constant weight; the contribution of metabolic water was only 5% of the total. 5. Desiccation for periods to 1 week resulted in approximately 20% decreases in both blood volume and body weight. This represents a loss of 27% of the total body water and a decrease of only 9.4% in intracellular water. 6. After removal of 15–50% of the total blood volume, entry of fluid diluted the remaining blood and the normal volume was restored by about 3 weeks after bleeding. Synthesis of blood protein was slow. Not until after two months was the protein level back to the initial level. Protein synthesis averaged 0.0064 mg/g/day when 20–36% of the initial blood volume had been removed. 7. Results suggest that when a loss of body contents occurs from bleeding, egg laying or withholding of food, these animals replace the lost volume with water.