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Food selectivity and diel vertical distribution of Chaoborus edulis (Diptera, Chaoboridae) in Lake Malawi
Author(s) -
IRVINE KENNETH
Publication year - 1997
Publication title -
freshwater biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.297
H-Index - 156
eISSN - 1365-2427
pISSN - 0046-5070
DOI - 10.1046/j.1365-2427.1997.00187.x
Subject(s) - diel vertical migration , instar , predation , zooplankton , biology , larva , ecology
1. Diel diet and vertical distribution patterns of the larval instars of Chaoborus edulis were studied in deep water near the central part of Lake Malawi, Africa. 2. First instar larvae contained very little food in their crops and probably depended on reserves from the egg. Second, third and fourth instars fed on zooplankton and were size‐selective in their feeding. The mean size of prey eaten by the three instars was significantly different from each other, with larger instars feeding on larger prey. Smallest available prey was selected against and the upper size of prey was probably constrained by larval gape. Nauplii were not found in any of several thousand larvae examined. Phytoplankton did not form a significant part of the diet. 3. There was a progressive and related increase in diel periodicity in feeding and vertical migrations of successive instar stages. Fourth instars migrated particularly large distances. Such migrations removed them from their zooplankton food supply but avoided predators. A refuge from predators is probably found in or near the permanent zero oxygen boundary, at depths greater than 200 m.