Energetics of a host-parasite relationship as illustrated by the leech Malmiana Nuda, Richardson and the shorthorn sculpin Myoxocephalus scorpius (L.)

Mace, Thomas Francis (1971) Energetics of a host-parasite relationship as illustrated by the leech Malmiana Nuda, Richardson and the shorthorn sculpin Myoxocephalus scorpius (L.). Masters thesis, Memorial University of Newfoundland.

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Abstract

The weekly energy budget was balanced for two groups of the sculpin, Myoxocephalus scorpius at 10ﾟC. An accurate estimate of weekly energy expenditure could be made by calculating the metabolic energy, measuring the waste production and measuring the energy incorporated into new tissue. The metabolic energy component was measured as the difference between weekly energy input and the sum of calories of growth and calories of waste production. The logarithm of the calculated respiration rate was proportional to the logarithm of body weight, and equal to approximately twice the resting respiration rate as measured in a flowing water-type respirometer. There was no significant difference between the summed components of energy expenditure and weekly energy input. -- There was a significant difference between the expected energy expenditure and the observed energy input of fish parasitized with a known weight of the leech Malmiana nuda. This difference was proportional to the biomass of parasites and equal to 2238 calories/gram of leech. -- The resting energy consumption of the leech was estimated from measurements of resting oxygen consumption. Resting oxygen consumption was proportional to weight, and environmental temperature. It was calculated that the resting leech would consume 63 m./gram/week at 10ﾟC. (equivalent to approximately 285 calories). At this rate of energy expenditure, there would be an additional 75 calories of waste produced. Growth would account for 1240 calories/gram of new tissue. -- The energy input also was estimated by measuring the amount of blood in the gut of recently fed leeches. It was observed that a leech would contain about 2 ml. of blood/gram. One ml. of blood was equal to 575 calories, resulting in an estimated energy input of approximately 1100 calories. This suggests that a leech continuously fed would absorb about 1600 calories of energy per week, or the equivalent of 2 3/4 ml. of blood. -- It was suggested that the ratio of energy loss from the host to energy expenditures of the parasite would be an indication of the degree of adaptation of the system. A well adapted host parasite relationship would exert a metabolic demand which is little more than the energy requirements of the parasite.

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