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Temporal patterns of diatom ingestion by larval net‐winged midges (Diptera: Blephariceridae: Blepharicera )
Author(s) -
Alverson Andrew J.,
Courtney Gregory W.
Publication year - 2002
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.1365-2427.2002.00951.x
Subject(s) - diatom , biology , fragilaria , ingestion , instar , larva , nitzschia , botany , food web , zoology , nutrient , ecology , trophic level , phytoplankton , biochemistry
SUMMARY 1. Monthly patterns of diatom ingestion by Blepharicera magna and B. similans (Diptera: Blephariceridae) larvae were examined to determine whether dietary attributes fluctuate within the final‐instar stadium. The two species are isolated temporally: B. magna diets were examined from October to December, and B. similans diets were examined from June to August. Each month, the diatom assemblage of larval diets was assessed and compared with that of the forage base. In addition, total diatom ingestion was estimated. 2. Larval gut samples were ordinated on the basis of relative abundance of common diatom taxa, and month–month comparisons of larval diets were made, which revealed that (i) B. magna dietary assemblages did not vary significantly from October to December; (ii) diatom species composition of B. magna diets generally resembled that of the forage base; and (iii) B. similans dietary assemblages varied significantly from June to August, with few changes attributable to seasonality of ambient diatom flora. 3. Total diatom ingestion by B. magna was relatively stable from October to December. For B. similans , total diatom ingestion was greatest in July, when larvae were midstage of instar IV. The latter result was accompanied by increased ingestion of grazer‐resistant diatom taxa (e.g. Achnanthes deflexa var. alpestris , Achnanthidium minutissimum , and Cocconeis placentula var. lineata ), which can be more digestible than grazer‐susceptible taxa (e.g. chain‐forming Fragilaria and rosette‐forming Synedra species). This result suggests demand for a large quantity of nutritionally rich food at midstage of instar IV, which could represent a period of critical growth for B. similans .