Sanguivory in leeches and its effects on growth, survivorship, and reproduction of Theromyzon rude

Abstract

The trophic effects of the timing of the blood meals of Theromyzon rude on its population dynamics and life cycle were determined in the laboratory and compared with field data based only on the population size structure. It was found that a minimum of three full blood meals are necessary before T. rude reaches sexual maturity. The laboratory data show that the majority (> 80%) of the population take all three meals in the first 6 months after hatching. The remainder of the population overwinters after two meals and take their third meal in the spring so that all the population reproduces within approximately 12 months of hatching. Some individuals overwintering after three meals decline in weight to below 150 mg before spring and these individuals require a fourth blood meal before reproduction commences. After each blood meal there is a further increase in body weight as a result of water uptake. It is suggested that this dilution of the blood facilitates the faster digestive rates shown by T. rude compared with other sanguivorous species which rapidly eliminate water from their guts after feeding. Sanguivory in T. rude is compared with sanguivory in other Glossiphoniidae and Hirudinidae.