Distributional Relationship and Migration of Leeches (Hirudinea) in the Exposed Littoral of Lake Esrom, Denmark
1979; Wiley; Volume: 33; Issue: 1 Linguagem: Inglês
10.2307/3544519
ISSN1600-0706
Autores Tópico(s)Ecology and biodiversity studies
ResumoThe leech fauna living in the shallow, stony exposed littoral in Lake Esrom, Denmark, was investigated in 1975 and 1976. Total numbers of individuals varied between 2900 and 400 m-2. Five species were found in such numbers that it was possible to estimate production. One species, Glossiphonia complanata L., occurred in two distinct subspecies i.e. G. comply. typica L. and G. comply. concolor Apathy. Erpobdella octoculata L. and Helobdella stagnalis L. constituted 45.4 and 36.0% of the leeches, respectively. Fortnightly sampling showed periodical increases of E. octoculata and H. stagnalis during autumn and spring, and increased numbers of Erpobdella testacea Sav., Glossiphonia heteroclita L., G. comply. typica, and G. comply. concolor in early spring. These variations, which were not caused by reproduction, indicated immigration from deeper water to the shallow zone lacking macrophytic vegetation. The mean individual weight of immigrating leeches was in several cases either higher or lower than the mean weight of the resident leeches. Mortality rates did not indicate any periods of emigration. The total immigration was estimated to be at least 2500 individuals m-2 in autumn and 1000 m72 during spring.
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