Post-embryonic durations of Tropodiaptomus spectabilis (Kiefer) and Metadiaptomus colonialis (van Douwe) were determined at 20-degrees-C in laboratory factorial experiments involving four algal food enrichment levels (0, 100, 500 and 2500-mu-g l-1 C of Selenastrum added to 20-mu-m filtered water from respective source-lakes) and three suspended sediment levels (filtered, natural, and 2- to 3-fold sediment-enriched lake water). Food effects (30, 75, 225 and 600-mu-g l-1 C of Scenedesmus) were tested alone at 20-degrees-C for Metadiaptomus meridianus (van Douwe). Total naupliar (D(n)) and total copepodid (D(c)) development times [summed to give total post-embryonic duration (D(t))] and metasome lengths at maturity were measured. In all taxa, food supply maximally affected D(c) values 2- to 3-fold, whereas its maximal influence on D(n) values was relatively slight (generally approximately 25%). The measured effect of food supply on D(t) was as strong as the predicted influence of temperature over an appropriate annual range. Food supply influenced size at maturity, and probably thereby fecundity, thus exerting additional demographic influences. Sediment effects were inconsistent, and quantitatively weaker than food effects. Total development of T. spectabilis was approximately 20% faster, and that of M. colonialis approximately 15% slower in sediment-enriched than in natural sediment level treatments; contrasting baseline sediment levels (2-3 times higher for the latter species) and different enrichment procedures confound interpretation. Unexpectedly, and inexplicably, development almost invariably failed in sediment-free water, implying an apparent dependency on inorganic particles in these taxa. This contrasts with the generally adverse influences of high sediment concentrations upon zooplankton. Minimal male and female D(t) values at 20-degrees-C were comparable and significantly longer in M. colonialis (15.5 and 17.7 days) and M. meridianus (16.5 and 21.5 days) than in T. spectabilis (11.7 and 12.2 days). These differences in duration are ecologically incongruous in relation to expected r - K life history strategies of genera characteristic of temporary or semi-permanent waters and permanent waters respectively.
