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Estimation of earthworm cocoon development time and its use in studies of in situ reproduction rates

1997; Elsevier BV; Volume: 7; Issue: 1 Linguagem: Inglês

10.1016/s0929-1393(97)00016-4

1873-0272

Klaus S. Jensen, Martin Holmstrup,

Aquatic Invertebrate Ecology and Behavior

Data from the literature on development rates of earthworm cocoons were used to predict the time of hatching of cocoons incubated in the field. The numerical integration of a deterministic equation with the incorporation of individual variation in development rate made it possible to predict the hatching time distribution of a sample of cocoons produced over one week with good precision. This was shown for three species of earthworms, Aporrectodea caliginosa, Allolobophora chlorotica, and Dendrobaena octaedra. By reversing the direction of time, the same algorithm finds the probability distribution for the expected production time of a cocoon, whose time of hatching is known. It is suggested that the method can be applied to cocoons sampled from soil cores and incubated in the laboratory. Thus, the most probable production time for each cocoon can be determined with its confidence interval; subsequently, the number of cocoons produced per square meter during a given time interval can be calculated. If the density of adult earthworms is known for the same time interval, the reproductive rate (based on surviving cocoons) can be estimated.