Population Dynamics of two Species of Tardigrada, Macrobiotus hufelandii (Schultze) and Echiniscus (Echiniscus) testu do (Doyere), in Roof Moss from Swansea

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Abstract
The Tardigrada were extracted from the mosses Bryum argenteum L. and Ceratodon purpureus on the campus of University College of Swansea [Wales]. The dietary requirements of Macrobiotus hufelandii Schultze, Milnesium tardigradum Doyere, Hypsibius (Hypsibius) oberhaeuseri (Doyere) and Echiniscus (Echiniscus) testudo (Doyere) are discussed together with notes on their susceptibility to fungal and protozoan attack. Population densities of up to 823 individuals/g of moss were recorded. Temporal variation in numbers of M. hufelandii and E. (E.) testudo was cyclical. The annual cycle of population fluctuation was positively correlated with daylight hours and temperature. A secondary, long-term cycle is suggested. Increases in humidity and rainfall, 10-20 days prior to sampling, produced a decrease in tardigrade numbers but a corresponding increase in the average size of individuals. Increased rainfall also reduced the number of M. hufelandii with pigmentation. Size frequency analysis of monthly population samples indicated a lifespan between 3-7 mo. for M. hufelandii and up to 3 mo. for E. (E.) testudo. Rapid development of juveniles led to early recruitment into the middle size classes which were slower growing and persisted longer. Egg production in E. (E.) testudo continued throughout the year but proceeded at an increased rate during spring/early summer.

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