title: Acute and chronic effects of pulse exposure of Daphnia magna to dimethoate and pirimicarb.
abstract: Short-term (<48 h) and long-term (21 d) effects of dimethoate and pirimicarb were studied in Daphnia magna exposed to pulses of 0.5 to 8 h in duration. During a 21-d postexposure observation period, the following parameters were monitored: Mortality, mobility, day for first offspring, animal size, weight of offspring and adults, and number of offspring produced. In general, animals exposed to a single pulse of dimethoate or pirimicarb regained mobility after 24 to 48 h in clean media. Animals exposed to repeated pulses of dimethoate did not recover mobility during a 48-h postexposure observation period, and mortality was significantly increased. Animals exposed to two pulses of pirimicarb showed less recovery of mobility compared with those exposed to one pulse. Exposure of D. magna to 30 mg/L of dimethoate or 100 microg/L of pirimicarb for 2 to 6 h resulted in a significant reduction in the number of offspring and in the average weight of offspring. The average body length was reduced after pulse exposure to 30 mg/L of dimethoate for 3 h or 70 microg/L of pirimicarb for 4 h, and these exposure concentrations caused a delay in the day for first offspring at exposure durations of 2 to 6 h. The most important new findings in the present study are that short-term (<4 h) pulse exposure of neonates to acetylcholinesterase-inhibiting pesticides caused reproductive damage in D. magna and that repeated-pulse exposure significantly increased mortality in animals that apparently had recovered after a single-pulse exposure.
authors.affiliation: Institute of Environment and Resources, Building 115, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark.
authors.forename: Tobias Henrik
authors.initials: TH
authors.lastname: Andersen
authors.forename: Rikke
authors.initials: R
authors.lastname: Tjørnhøj
authors.forename: Leah
authors.initials: L
authors.lastname: Wollenberger
authors.forename: Tina
authors.initials: T
authors.lastname: Slothuus
authors.forename: Anders
authors.initials: A
authors.lastname: Baun
mesh_terms: D000375:Aging / Q000502:physiology; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D049628:Body Size / Q000187:drug effects; D001835:Body Weight / Q000187:drug effects; D002219:Carbamates / Q000633:toxicity*; D003621:Daphnia / Q000033:anatomy & histology / Q000187:drug effects* / Q000254:growth & development; D004117:Dimethoate / Q000633:toxicity*; D011743:Pyrimidines / Q000633:toxicity*; D012098:Reproduction / Q000187:drug effects / Q000502:physiology; D015996:Survival Rate; D013997:Time Factors
chemical_list: D002219:Carbamates; D011743:Pyrimidines; C011994:pirimicarb; D004117:Dimethoate