Species Toxicity Tests Research Articles

Use of Gammarus pulex (L.) in safety evaluation tests: Culture and selection of a sensitive life stage

A simple and effective method for the laboratory culture of Gammarus pulex is described. Over 70% of juveniles survived, reaching sexual maturity within 130 days at 13°C, and animals of different ages were available for toxicity tests throughout the year. The acute toxicity of cadmium to cultured animals of several known ages and to field-collected animals of unknown age was determined. Juveniles (1 day old, 48 hr LC 50 0.019 mg Cd liter −1) were found to be almost 250 times more sensitive than the oldest age group tested (220 days old, 48 hr LC 50 4.7 mg Cd liter −1). In view of its ease of culture and sensitivity to pollutants, it is proposed that G. pulex should be more widely employed as a standard toxicity test species in the hazard evaluation process.

Problems associated with selecting the most sensitive species for toxicity testing

When the field of aquatic toxicity testing began its first major expansion about 40 years ago, it was uncommon to use more than one test species (usually a fish). Later, it became customary to use individual microorganisms (usually algae) and macroinvertebrates as well. Most attention was then given to the response of the most sensitive species in that test series when calculating the ‘biologically safe’ concentration acceptable for use in natural systems. However, in recent years, there has been an attempt to equate the most sensitive species in a laboratory test series to the most sensitive species in natural systems. Since laboratory test species represent only a tiny part of natural systems and since response variability is well established, that can be a dangerous assumption. The purpose of this discussion is to re-examine the scientific support for this practice.

Assessment of primary vs. secondary toxicity of Aroclor 1254 to mink.

Dietary tests were conducted, using mink as a surrogate mammalian wildlife carnivore, to develop and evaluate procedures for the assessment of primary vs secondary toxicity of potentially hazardous chemicals to mammalian carnivores. Test methods included comparison of mortality, body weight change, feed consumption and calculated LC50 values in mink fed diets that contained polychlorinated biphenyls (PCBs),i.e., Aroclor® 1254 (primary toxicity) with mink fed diets that contained the same concentrations of the metabolized xenobiotic (secondary toxicity). Mean feed consumption and body weight gains were lower for the mink fed the metabolized Aroclor 1254 (secondary toxicity) than for mink that received the same concentrations of Aroclor 1254. The tests yielded 28- and 35-day LC50 values of 79.0 and 48.5 ppm (mg/kg) for the primary toxicity test and 47.0 and 31.5 ppm (mg/kg) for the secondary toxicity test, respectively. The results indicated that mink were a suitable carnivorous species for secondary toxicity testing and showed the necessity of using a withdrawal period of appropriate duration.

Responses of blue-green and green algae to streptomycin in unialgal and paired culture

Streptomycin sulfate prevented growth of six blue-green algae at concentrations (0.09 to 0.86 mg/l) substantially lower than needed to prevent growth of 7 of 8 green algae tested. Chlorella vulgaris, Scenedesmus obliquus and Ulothrix sp. grew in active streptomycin concentrations less than 21 mg/l, while Chlamydomonas reinhardtii growth was prevented at concentrations of 0.66 mg/l. Algal growth in sublethal concentrations of streptomycin was slowed or delayed, and the maximum density attained by several species was decreased. These data suggest that attempts to select ‘representative’ species for toxicity testing may have mixed success: any blue-green alga would be a suitable representative of Cyanophyta with respect to streptomycin, but no single green alga would adequately represent the wide range of response to streptomycin seen among the Chlorophyta species tested. To test for interactions between competition and chemical inhibition, paired cultures of S. obliquus with Anabaena cylindrica, Ankistrodesmus sp., C. vulgaris and Selenastrum capricornutum were observed with and without 6.6 mg/l streptomycin. The outcome of competition was consistent with predictions based on single-species assays, where major differences in chemical sensitivity were present, although significant interactions were observed. S. obliquus populations when treated with streptomycin were competitively superior to A. cylindrica and S. capricornutum. Significant interactions between competition and streptomycin treatement were also observed for paired cultures of C. vulgaris and S. obliquus; neither population fit the model of additive effects of chemical inhibition and competition.

Differences in the toxicities of an oil dispersant and a surface active agent to some marine animals, and their implications in the choice of species in toxicity testing

The toxicities of an oil dispersant (BP 1100X) and a surface active agent (Shell Herder) upon 18 marine species from different taxa, were investigated. The results showed that the toxicity of a product depends very much on the species tested. Some species exhibited high mortality when treated with BP 1100X, and low mortality when treated with Shell Herder, whereas the reverse was true for certain other species. The results therefore indicated a large bias potentially incurred in present procedures, by the use of one or two species in toxicity testing and screening of oil dispersants/surface active agents. It is here suggested that toxicity tests should be carried out on species which are ecologically important (e.g. ‘key species’ of a community or population with a high energy flow value) in identified receiving environments, rather than on those which are easy to obtain and maintain in the laboratory.

Variation in the response of plasma enzyme activities in avian species dosed with carbophenothion

The response of various species of Anser and Branta geese and other avian species to the ingestion of carbophenothion ( S-[/(4-chlorophenyl)thio/methyl] O,O-diethyl phosphorodithioate) has been investigated. Optimum assay conditions for measurement of glutamate oxaloacetate transaminase, glutamate dehydrogenase, sorbitol dehydrogenase, and cholinesterase in avian plasma were developed for the study. The administration of acutely toxic doses of carbophenothion to Japanese quail, pigeons, and chickens, and to Greylag, Pink-footed, Greenland White-fronted, and Canada geese led to species-dependent responses for both plasma glutamate oxaloacetate transaminase and cholinesterase levels. Carbophenothion administered to Japanese quail at several dose levels produced changes in plasma enzyme levels which were dependent on dose and time. The level of plasma glutamate oxaloacetate transaminase after dosing in the Anser family of geese rose more rapidly than in the Branta species but no change was found in this enzyme in either chickens or pigeons. In contrast to geese and pigeons, chickens exhibited no plasma cholinesterase inhibition for 3 hr after dosing. These enzyme changes demonstrate a species variation in the toxicological response of birds to a pesticide and indicate the desirability of using more than one avian species for pesticide toxicity testing.

Breeding the convict cichlid (Cichlasoma nigrofasciatum) for use in laboratory fish toxicity tests

A procedure is described for breeding Convict Cichlid (Cichlasoma nigrofasciatum) tropical fish under laboratory conditions. Three generations of Convict Cichlids were bred successfully using this procedure and there was no significant incidence of deformities from in–breeding to the F3, which contrasts with a high incidence of skeletal deformities observed when Zebra Danio tropical fish were inbred to the F3 generation. The Convict Cichlid is a suitable species for laboratory toxicity testing, particularly studies to assess effects on breeding performance.

Toxicity tests with Daphnids: Its application in the management of water quality

The possible role of Daphnia species in toxicity tests is discussed. In screening tests, effluent monitoring tests and legal tests daphnids are recommended as useful test organisms. They also may help to establish concentration limits for chemical water pollution (water quality criteria). As biological indicator organisms their use is limited.