Abstract

Annals of Environmental Science
Volume 2, September 2008, Pages 7-10
www.aes.northeastern.edu, ISSN 1939-2621

Gender-Specific Lifespan Modulation in Daphnia Magna by a Dissolved Humic Substances Preparation

Sandra Euent, Ralph Menzel and Christian E.W. Steinberg, Laboratory of Freshwater and Stress Ecology, Institute of Biology, Humboldt University at Berlin, Germany

Received June 4, 2008; in final form August 13, 2008; Accepted August 21, 2008

It is well understood that dissolved humic substances (HSs) are taken up by freshwater organisms and interact on various molecular and biochemical levels, including the development of mild chemical stress combined with lifespan modulation. For instance, with the nematode Caenorhabditis elegans, a lifespan extension could be observed with certain HS qualities. Intrigued by this result, we studied the potential of lifespan extension with further animals, for instance the water flea, Daphnia magna. Upon exposure to the same HS that caused a lifespan extension in C. elegans, the usually parthenogenic females started to produce males. Subsequently, males and females were separately exposed. The lifespans of the females were reduced in a concentration dependent manner, whereby the highest exposure concentration 10.75 mg/L DOC reduced the mean lifespan by more than 25% and the mean numbers of offspring. In contrast, the mean lifespan of males was increased in a hormetic manner: 2.15 mg/L DOC exposure increased it by 20% and 10.75 mg/L DOC by less than 10%. This gender-specific modulation of longevity in D. magna synchronizes the lifespans of females and males and allows an increased period of sexual reproduction.