Predatory ? prey relationships in subtropical zooplankton: water mite against cladocerans in an Argentine lake

Abstract

In a small lake in northern Argentina pelagic water mite Piona sp. had the maximum of population density in January following with a five-day delay after the peak of zooplankton dominant - Daphnia laevis. The mite density was highly predicted by the previous variations of Daphnia density during 4 months of observation (December-March). Daphnia density was a negative delayed function of the predator density but only in December-January when Piona was abundant. During that period Daphnia death rate, d was also correlated with the mite density (r =0.80, P<0.005). In laboratory experiments water mites killed 1-7 Daphnia · predator · hour in a broad range of prey density. Another zooplankton component, Diaphanosoma birgei, was consumed at the same rates. The mite hardly consumed any copepods. In the pelagium during 24 hours the mite was more associated with Daphnia, than with Diaphanosoma, probably, because of the coincidence in photoreactions with Daphnia. Piona contribution to the death rates of its prey estimated by using the data on functional and numerical responses as well as by means of Edmondson-Paloheimo model, could reach 53% for Daphnia and 40% for Diaphanosoma. A computer experiment on the reconstruction of prey dynamics after subtraction of predator influence showed that the mite could have caused a depression in Daphnia numbers observed in the lake, but the declines in Diaphanosoma population were caused by other factors. After the "removal" of mite pressure model Daphnia population increased its average density 10-fold. Experiments on Piona feeding revealed a strong effect of interference among predators. This was eliminated by putting one mite per experimental vessel, which led to a 20-fold increase in predation rate. The effect explains the low feeding rates of Piona obtained by the previous authors who ignored the possibility of interference.

A long-term study on crustacean plankton of a shallow tropical lake: the role of invertebrate predation

“…Half of the mortality of Bosmina could be related to mite densities of 200-300 ind m -3 (Balseiro, 1992). Death rates of Daphnia and densities of mites were correlated, when the mites reached 400 ind m -3 (Matveev et al, 1989). In the key period in Lake Monte Alegre, the mites reached maximum densities of 312 ind m -3 , and in the summer of 1999, aggregates of 1800-2000 ind m -3 were recorded at night (Perticarrari, 2000).…”

Zooplankton of the Paraguay River : a comparison between sections and hydrological phases

“…Large cladocerans, which are abundant in lagoons and channels of the Upper Paraná during low water (Lansac Tôha et al 2004), were conspicuously scarce from our samples taken in the floodplain. Although there is little information concerning planktivorous fish in the Paraguay River, selective predation on cladocerans by both invertebrates and vertebrates may increase mortality in cladocerans (Matveev et al 1989, Hamilton et al 1990, Matveev et al 1992.Abundances of Rotifera have been reported in several studies of tropical, subtropical (Corrales 1979, José de Paggi 1980, Robertson & Hardy 1984, Shiel 1985, Bonetto & Corrales de Jacobo 1985a and b, Vásquez & Rey 1989, Lanzac Tôha et al 2004) and temperate rivers (Pace et al 1992, Gudrun et al 1994, Thorp et al 1994. Rotifera may dominante other taxa because they are opportunists with a short generation time (Rzóska 1976, Pourriot et al 1982, Gulyas 2002, Lanzac Tôha et al 2004, and are better adapted to turbulence and high concentrations of suspended solids (Armengol et al 1983 (Dussart 1979, Dussart & Frutos 1985, 1986.…”

Water mite predation on zooplankton of a tropical lake

“…But interaction with zooplankton has been taken into account when mites were found in relatively large densities in the limnetic zone, reaching values above 100 ind.m -3 (Gliwicz & Biesiadka, 1975;Riessen, 1982a). They can prey on microcrustaceans, such as cladocerans and copepods (Gliwicz & Biesiadka, 1975;Riessen, 1982b;Matveev et al, 1989;Butler & Burns, 1991, having a significant impact on prey populations (Gliwicz & Biesiadka, 1975). They also migrate vertically (Riessen, 1980;Perticarrari, 2000), some species spending part of the day at the bottom, at least when dissolved oxygen is not depleted (Perticarrari, op.…”