E.J. Taylor

Toxicity of four common pollutants to the freshwater macroinvertebratesChironomus riparius Meigen (Insecta:Diptera) andGammarus pulex (L.) (Crustacea:Amphipoda)

The lethal toxicities of the four pollutants 3,4-dichloroaniline (DCA), atrazine, copper, and lindane were determined for the 2nd larval instar of the insectChironomus riparius Meigen and the juvenile stage (2nd or 3rd moult) of the crustaceanGammarus pulex (L.). Median lethal concentrations (LC50s) were determined over a 240 h test period. The order of toxicity of the test chemicals is different for each species. ForC. riparius, lindane was the most toxic, followed by copper, DCA, and atrazine. During the first 96 h of exposure, the order forG. pulex was copper, lindane, then DCA and atrazine with similar LC50 values. However, at 240 h lindane replaced copper as the most toxic chemical toG. pulex. The relative sensitivity of the two species was dependent on both the toxicant and the exposure period. The lethal concentrations determined for the four chemicals are compared to the results of other toxicity studies and discussed with respect to current standard test methods.

Laboratory and field evaluation of a behavioural bioassay—The Gammarus pulex (L.) precopula separation (GaPPS) test

Abstract A bioassay, based upon the reproductive behaviour of the amphipod Gammarus pulex , was evaluated for its application in detecting freshwater pollutants. In the laboratory the bioassay proved to be useful in rapidly detecting a wide range of pollutants at concentrations significantly below those causing acute lethal toxicity and in the field it responded rapidly to a variety of pollutant inputs. The results indicate that this bioassay is simple, cost-effective and reliable and could be employed effectively for detecting and quantifying pollutants.

Gammarus pulex (L.) feeding bioassay : effects of parasitism

Taylor et al. (1993) described a pollutant bioassay based upon a change in the rate at which Gammarus pulex (L.) consumes a novel food source (eggs of the brine shrimp Anemia salina) when the animals are stressed by exposure to a pollutant. The bioassay is rapid and non-destructive, and produces results with less variation than reported using conventional leaf-feeding bioassays. However, it is important to determine the extent to which results may be influenced by the physiological status (e.g., due to parasitism) of the animals used in the bioassay. The acanthocephalan parasite Pomphorhynchus laevis Muller, 1776 uses the freshwater amphipod G. pulex as its sole intermediate host with the cystacanth, the final developmental stage in G. pulex being infective to fish, particularly the barbel Barbus barbus (L.) and chub Leuciscus cephalus (L.). Cystacanths are known to affect the respiration (Rumpus and Kennedy 1974), behavior (Brown and Thompson 1986), mating decisions (Poulton and Thompson 1987), reproduction (Poulton and Pascoe 1990), behavioral drift (McCahon et al. 1991) and hemolymph concentrations (Bentley and Hurd 1993) of their amphipod host. The aim of this work was to determine whether the feeding activity of the shrimp G. pulex is also modified by the presence of the parasite, and, if so, the consequences for pollution evaluation using the feeding bioassay. MATERIALS AND METHODS Shrimps were collected by kick-sampling from the River Teme, Herefordshire (Brown and Pascoe 1989) where, at the time of collection, water quality conditions were: pH, 7.98; temperature, 12.5oC; dissolved oxygen, 9.5 mg/L; conductivity, 298/~S/cm. Twenty large animals (approx. 7 mm in length) and 20 small (approx. 5 mm in length) were selected from the collection and transferred to individual perspex dishes (base area 18 cm 2) containing 18 ml of river water, together with 10 shell-less eggs of Anemia salina. The feeding bioassay was carried out immediately, as described by Taylor et al. (1993), by recording, at regular time intervals, the number of eggs consumed by each animal. On returning to the laboratory the length and weight of each shrimp were measured and the animals were then dissected to reveal the presence of any infestation with the parasite P. laevis. This allowed a classification of both large Correspondence to: D. Pascoe

A new method for measuring the feding activity of Gammarus pulex (L.)

Abstract A new method is described which quantifies the feeding activity of the freshwater amphipod Gammarus pulex (L.). The bioassay, which utilises a time response analysis of the feeding of G. pulex on eggs of Artemia salina, is rapid and non-destructive allowing the frequent monitoring of test organisms during both toxicological and autecological studies.

Effects of lindane on the life-cycle of a freshwater macroinvertebrateChironomus riparius Meigen (Insecta: Diptera)

The effects of lindane on the hatching, survival and development ofChironomus riparius Meigen were investigated over a complete life-cycle. Pupation and adult emergence were identified as the criteria most sensitive to lindane. The no-observed-effect-concentration (NOEL) and lowest-observed-effect-concentration (LOEC) of lindane to the life-cycle of C. riparius were determined as 1.1 and 9.9 μg/L, respectively. The results are discussed with respect to previous toxicity data and the potential role of life-cycle toxicity tests in hazard evaluation.

Effects of lindane on the predator-prey interaction between Hydra oligactis Pallas and Daphnia magna Strauss

Laboratory tests were developed to allow identification of the effects of toxicants on the predator-prey interaction between Hydra oligactis Pallas and Daphnia magna Strauss. Three test methods, which differed with respect to initial Daphnia population, test period, and management of predation level, were used to determine the influence of the organochlorine insecticide lindane on the interaction. The criteria examined were the population structures of the two species. The lindane treatments did not alter the production of Hydra. However, the final population structure of Daphnia was variously affected by the toxicant in the different test systems. The most sensitive endpoint, with a lowest observed effect concentration of 4 μg/L lindane determined after a 14 day exposure period, was increased recruitment of juvenile Daphnia in a test system which incorporated management of the Hydra. The results are compared to previously reported data derived from single species chronic tests, and the suitability of the test methods for hazard evaluation is discussed.

Effects of lindane on the growth of the freshwater amphipod Gammarus pulex (L.)

Abstract A bioassay for determining the effects of toxicants on the growth of a sensitive life stage of Gammarus pulex (L.) is described. The experimental design minimised variation: a non-destructive weighing technique produced initial treatment groups with a low coefficient of variation for mean wet weight and also facilitated the introduction of a standard artificial diet regime. The chemical investigated was the organochlorine insecticide lindane for which the lowest observed (LOEC) and no observed effect concentrations (NOEC) of 6.1 and 2.7 μgl −1 respectively were determined after the 14 day exposure period. These results are compared to toxicity data from other studies.

Effects of 3,4-dichloroaniline on the growth of two freshwater macroinvertebrates in a stream mesocosm.

The growth of the freshwater macroinvertebrates Gammarus pulex (L.) and Chironomus riparius Meigen exposed to 3,4-dichloroaniline in chambers within stream mesocosms was determined. DCA significantly affected the growth of neonate G. pulex and third instar C. riparius over 25 and 12 days, respectively. The no-observed-effect concentrations (NOECs) obtained in the tests were 0.08 mg DCA liter-1 (G. pulex) and 0.76 mg DCA liter-1 (C. riparius) and these are compared to toxicity data from other investigations. Inclusion of single-species bioassays in mesocosm studies provides complementary information on toxicant effects and indicates the suitability of the results of such tests (which may be routinely performed under laboratory conditions) for protecting particular ecosystems.