Two Daphnia species exhibited similar dynamic patterns in western Lake Erie. Populations peaked in early summer, declined to minimum abundance in mid-July, and then disappeared after August. To determine relative importance of food limitation and young-of-year (YOY) fish predation in regulating Daphnia dynamics, we examined relationships (I) between edible phytoplankton abundances and Daphnia f...

Toxin-producing cyanobacteria have frequently been hypothesized to limit the ability of herbivorous zooplankton (such as Daphnia) to control phytoplankton biomass by inhibiting feeding, and in extreme cases, causing zooplankton mortality. Using limnocorral experiments in hyper-eutrophic ponds located in Alabama and Michigan (U.S.A.), we tested the hypothesis that high levels of cyanobacteria an...

The hypothesis that negative effects of Microcystis on Daphnia growth and reproduction can be explained from the presence of microcystin in the Microcystis cells was tested by comparing the effects on Daphnia life history characteristics of a microcystin-free mutant strain and microcystin-containing strain of the cyanobacterium Microcystis aeruginosa PCC7806. To avoid nutritional deficiency, Mi...

Direct predation upon parasites has the potential to reduce infection in host populations. For example, the fungal parasite of amphibians, Batrachochytrium dendrobatidis (Bd), is commonly transmitted through a free-swimming zoospore stage that may be vulnerable to predation. Potential predators of Bd include freshwater zooplankton that graze on organisms in the water column. We tested the abili...

Ferromagnetic resonance (FMR) with an electron spin resonance (ESR) apparatus was investigated for super-paramagnetic particles within Daphnia resting eggs. High-field (HF) resonance lines near g=2 resulted from single superparamagnetic particles, were detected from ESR spectra of Daphnia resting eggs. The size of isolated superparamagnetic particles within Daphnia resting eggs was calculated t...

Lake restoration practices based on reducing fish predation and promoting the dominance of large-bodied Daphnia grazers (i.e., biomanipulation) have been the focus of much debate due to inconsistent success in suppressing harmful cyanobacterial blooms. While most studies have explored effects of large-bodied Daphnia on cyanobacterial growth at the community level and/or on few dominant species,...

Life is tough for water fleas. In addition to the usual troubles faced by every organism, Daphnia have to worry about being eaten by many types of predators. To make them less vulnerable, some Daphnia species grow large helmets or protective spines on their heads and tails. But at least one predator, the stickleback, only fancies a Daphnia diet at certain times of year, so it would be inefficie...

The functional response of Daphnia, a common pelagic herbivore in lakes, was assessed with a combination of secondary and meta-analyses of published data and new data from an experiment conducted using very low food levels. Secondary analyses of literature data (28 studies, n = 239-393) revealed a significant positive influence of food concentration on Daphnia clearance rate at low food levels,...

1. Haemoglobin production was measured for two populations of Daphnia putex, one from a temporary pond (GR Pond) and one from a permanent pond (Rash Pond). Surface water in Rash Pond remains high in oxygen, while by late summer very Uttle oxygen remains in GR Pond. Haemoglobin synthesis was induced in the laboratory by artificial oxygen deficiency. 2. Reproductive state influenced the level of ...

The hear ts of vertebrates are myogenic whereas those of most ar thropods are neurogenic. However, the hear t of Daphnia is an exception, as indicated by Bekker and Kri jgsman (1) whose studies led to the conclusion that Daphnia hear t is myogenic with apparen t inhibi t ion by extracardiac cholinergic nerves. Since Daphnia have hearts similar to ver tebra te hearts and are transpa ren t and ea...