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The drag coefficient of cased caddis larvae from running waters: experimental determination and ecological applications
Author(s) -
WARINGER J.A.
Publication year - 1993
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 - 10.1111/j.1365-2427.1993.tb00776.x
Subject(s) - instar , reynolds number , drag , drag coefficient , larva , position (finance) , zoology , mechanics , physics , biology , ecology , finance , turbulence , economics
SUMMARY1 Drag coefficients of cylindrical‐case caddis larvae from running waters were investigated in the laboratory using an artificial stream channel. 2 Dead larvae of the limnephilids Allogamus auricollis (first to fifth instars), fifth instars of Potamophylax cingulatus, Chaetapteryx fusca, Drusus monticola, Metanoea rhaetica and fourth instars of the brachycentrid Micrasema minimum , were exposed to different current speeds. When the heads of the larvae were directed towards the water flow (frontal position), the current necessary to dislodge the larvae ranged from 3.00cms‐ 1 ( A. auricollis , first instar) to 70.50cms‐ 1 ( P. cingulatus ). With flow normal to the long axis of the case (lateral position), these speeds ranged from 2.20cms‐ 1 ( M. minimum ) to 20.80cms‐ 1 ( P. cingulatus ). 3 In frontal position, individual Reynolds numbers at the moment of dislodgement ranged from 74 ( A. auricollis , first instars) to 14100 ( P. cingulatus ), and from 14 ( M. minimum ) to 1143 ( P. cingulatus ) in lateral position. Regression equations correlating case length, mean case width or fresh weight with Reynolds numbers at the moment of dislodgement (frontal and lateral position) were very highly significant with r 2 0.91. 4 For the range of Reynolds numbers given above, the drag coefficient varied between 5.05 ( A. auricollis , first instars) and 0.26 ( P. cingulatus ) in frontal case position and from 2.97 ( M. minimum ) to 0.69 ( C. fusca ) in lateral case position. Furthermore, the relationship between Reynolds number and drag coefficient was found to be linear on a In/In scale for both frontal and lateral case position.