Life History Consequences of Food Quality in the Freshwater Copepod Boeckella triarticulata

Abstract

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. Ecological Society of America is collaborating with JSTOR to digitize, preserve and extend access to Ecology.Abstract. Food quality often has profound effects on life history traits and individual fitness, altering rates of growth and development, changing the timing of reproduction, and shifting the trade-off between egg size and egg number. Few data are available on the effects of food quality on copepod life history traits. We measured several life history traits on a large number of individuals to document the effects of food quality on individual traits, on life history correlates, and on a composite measure of individual fitness in the freshwater copepod Boeckella triarticulata Thomson. Nauplii were raised individually on two diets: one consisted of the high quality alga Cryptomonas sp. (abbreviated as CR), and the second diet consisted of a combination of Cryptomonas sp. and the low quality cyanobacterium Anabaena flos-aquae (CA). The mixed CA diet slowed growth and development so that individuals raised on this diet were older and smaller at metamorphosis and maturity. Despite these effects, there were no differences between diets in survival to maturity, and male copepods raised on the mixed diet lived significantly longer than females or than either sex raised on Cryptomonas alone. Females raised on the mixed diet produced more and larger clutches than those raised on CR, so that total egg production increased on this diet, although large intradiet variation obscured statistical differences between diets in these parameters. Intradiet variation was due to a large range in the number of clutches produced by individual females: some individuals produced 10-15 clutches, contradicting previous descriptions of this species as semelparous. Although diet affected age at first reproduction, it had no significant effect on individual fitness, estimated as X. Boeckella triarticulata achieved high fitness either by minimizing age at first reproduction (CR diet) or by increasing reproductive output (CA diet). Data collected from cast-off exuviae allow nondestructive measures of individual life history traits along with a composite measure of individual fitness. Combining these two analyses is an important step in unraveling life history correlates and in identifying the selective forces driving life history evolution in these crustaceans.

Reduced Fitness of Daphnia magna Fed a Bt-Transgenic Maize Variety

“…For example, higher juvenile mortality is generally linked to an early onset of reproduction (Stearns and Koella 1986). In organisms with plastic life-history traits, like D. magna (Enserink 1995), a response to low-level toxicity might thus lead to an allocation of resources to increase the fecundity early in the life cycle (Hansen et al 1999;Mauri et al 2003;Twombly et al 1998). At high levels of toxicity, the general development of the organisms is severely impaired and all reproductive characters are negatively affected (i.e., maturity is delayed and fecundity is reduced) (Enserink et al 1995;Hansen et al 1999;Mauri et al 2003).…”

Morphology-based classification of functional groups for potamoplankton

“…Some species of copepods and Cladocera can maximize adaptation via selective feeding or detoxification mechanisms (Ger et al, 2014). However, zooplankton taxa with detoxification mechanisms are challenged by the limited ability to handle individual food particles (e.g., Daphnia) (Ger et al, 2014) or the metabolic cost of maturing at a slower rate (e.g., Boeckella) (Twombly et al, 1998). Apparently, neither existing predators nor their future evolved forms would actually use phytoplankton of this group for food (Ger et al, 2014).…”

Disrupted seasonal clockwork in the population dynamics of a freshwater copepod by climate warming

“…Growth and development of these key planktonic taxa are subject to periodic (seasonal) and stochastic environmental variation, and their populations undergo extensive cyclic fluctuations both within and among years (Burns 1992;Twombly et al 1998). Copepods have distinct reproductive pulses and recurring population oscillations produced through endogenous and exogenous drivers.…”

“…Both temperature and food availability regulate life cycle duration of pelagic copepods, ranging from 1 to several months (Twombly et al 1998), and, depending on temperature and seasonal time constraints, their life histories can alternate between univoltine or multivoltine strategies among lakes (Allan and Goulden 1980). Environmental conditions also alter life cycle strategies in copepods, which differ from year-round active stages to strong seasonality with resting stages of varying length (Hairston et al 1996).…”