ISSN:
1365-2427
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Biology
Notes:
SUMMARY. 1. The chief objective was to determine the major environmental factors affecting the swimming activity of Hirudo medicinalis L. because the latter will affect the feeding and growth periods. 841 leeches were caught in samples taken every 2 weeks in 1982, 1983 and 1984.2. There were four major size groups, probably corresponding to year-classes. Only nine leeches were in their fourth year (Group IV), most leeches found on stones were in their first year (Group I) and most swimming leeches were in their second or third year (Groups II, and III). Size groups I-III overlapped considerably and could not be treated separately in subsequent analyses.3. Water temperature appeared to be the dominant factor affecting swimming activity, the threshold for activity being 7°C (range 5–9°C). A curvilinear regression provided the best description of the relationship between temperature and catches of swimming leeches; 62% (range 50–75%) of the catch variation could be explained by temperature.4. Atmospheric pressure at the time of sampling and its rate of change over 24 h preceding sampling had no significant effect on catches of swimming leeches, not even on the residuals of catches after the dominant effect of temperature had been removed. Similar analyses showed that there were no significant seasonal effects on swimming activity.5. From a discussion of the implications of this study, it is concluded that the absence of the medicinal leech from many water bodies may be due partially to the relatively high temperatures required for swimming activity in a large proportion of the population (11.9°C, 19.0°C, 22.7°C for 10%, 50%, 90% active respectively).
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1365-2427.1986.tb00981.x
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