Ks. Jensen et M. Holmstrup, ESTIMATION OF EARTHWORM COCOON DEVELOPMENT TIME AND ITS USE IN STUDIES OF IN-SITU REPRODUCTION RATES, Agriculture, ecosystems & environment. Applied soil ecology, 7(1), 1997, pp. 73-82
Data from the literature on development rates of earthworm cocoons wer
e used to predict the time of hatching of cocoons incubated in the fie
ld. The numerical integration of a deterministic equation with the inc
orporation of individual variation in development rate made it possibl
e to predict the hatching lime distribution of a sample of cocoons pro
duced over one week with good precision. This was shown for three spec
ies 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 product
ion 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; subseq
uently, the number of cocoons produced per square meter during a given
time interval can be calculated. If the density of adult earthworms i
s known for the same time interval, the reproductive rate (based on su
rviving cocoons) can be estimated. (C) 1997 Elsevier Science B.V.