ISSN:
1573-5117
Keywords:
life cycles
;
flight-periods
;
growth
;
production
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract The life cycle and production of Tinodes waeneri (L.) was examined at five shallow littoral localities in Lake Esrom, Denmark, during 1979/80. Five larval instars were demonstrated. The differences in temporal composition of instars indicated three different life cycles. A bivoltine strategy was shown for the most exposed locality which also had the highest average abundance equal to 11 500 ind. m−2. A univoltine population was found in the more sheltered NW part of the lake with an average density of 1 500 ind. m−2. At the three remaining stations the life cycles were partly bivoltine with wintering populations of mixed cohorts and densities between 10 500 and 3 000 ind. m−3. Two distinct flight periods with maxima in June and August were demonstrated for bi- and partly bivoltine populations. Differences in rates of growth and elimination added to the variability in life cycle. Growth rates peaked in August (5.0–7.4% d−1) at an average temperature of 20°C. Estimates of production ranged from 1.9 to 17.5 g AFDW m−2 a−1 with an average of 8.0 g AFDW m−2. The P/B ratios, which were within the expected range for uni- and bivoltine populations of trichopterans, were 5.73 for the bivoltine population and 3.31 for the univoltine population. Estimates of consumption revealed that the populations could be sustained by autochthonous epilithic production in the habitats. Variability in the quality and seasonal availability of food were judged to influence the type of life cycle.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00006912
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