5.1 Protection of a species requires prevention of unacceptable effects on the number, health, and uses of individuals of that species. A life-cycle toxicity test is conducted to determine changes in the numbers of individuals and offspring of a test species resulting from effects of the test material on survival, growth, gender ratios, endocrine function, genetic expression, fertility and reproduction ( 1- 3 ) . ³ Information might also be obtained on effects of the material on the health ( 4 ) and uses of the species.

5.2 Published information about the sensitivities of several meiobenthic copepods to several common metals and organic toxicants have been reviewed ( 5 ) . For most compounds tested/published to date, A. tenuiremis is acutely less sensitive than mysid and penaeid shrimp, similarly sensitive as amphipods, and often more sensitive than cladocerans (daphniids, specifically). Reference 96-h aqueous toxicity tests with cadmium at 30 g/kg salinity showed an LC50 for A. tenuiremis adults of 213 to 234 ?g/L (Chandler, unpub.). Reference toxicant tests with sodium dodecyl sulfate showed a 96-h LC50 of 13.3 to 15.5 mg/L (Chandler,unpubl.). A. tenuiremis is a comparatively new toxicity test organism, and an extensive database of species sensitivity to multiple aqueous test compounds is not yet available. Relative to other harpacticoid copepod studies in the literature, A. tenuiremis is more chronically sensitive than all other species published to date where there is comparative data ( 5 ) .

5.3 Results of life-cycle tests with A. tenuiremis can be used to predict long-term effects at the individual and population levels likely to occur on copepods in field situations as a result of exposure under comparable conditions ( 1 , 2 ) .

5.4 Results of life-cycle tests with A. tenuiremis might be used to compare the chronic sensitivities of different species and the chronic toxicities of different materials, and also study the effects of various environmental factors such as temperature, pH, and ultraviolet light on results of such tests.

5.5 Results of life-cycle tests with A. tenuiremis might be an important consideration when assessing the hazards of materials to aquatic organisms (see Guide E1023 ) or when deriving water quality criteria for aquatic organisms ( 6 ) .

5.6 Results of a life-cycle test with A. tenuiremis might be useful for predicting the results of chronic tests on the same test material with the same species in another water or with another species in the same or a different water. Most such predictions take into account results of acute toxicity tests, and so the usefulness of the results from a life-cycle toxicity test with A. tenuiremis is greatly increased by also reporting the results of an acute toxicity test (see Guide E729 ) conducted under the same environmental conditions.

5.7 Results of life-cycle tests with A. tenuiremis might be useful for studying the biological availability of, and structure-activity relationships between, test materials.

5.8 Results of life-cycle tests with A. tenuiremis will depend on temperature, quality of food, composition of seawater, condition of test organisms, and other factors.

5.9 Life-cycle tests with A. tenuiremis are conducted on copepods reared individually in microwells of 96-well microplates. Thus they can be useful for studying endocrine, pre-zygotic and gender-specific toxicities of test materials ( 1- 3 ) .

1.1 This guide describes procedures for obtaining laboratory data concerning the adverse effects of a test material added to seawater, but not to food, on the marine copepod Amphiascus tenuiremis , during continuous exposures of individuals, from immediately after birth, until after the beginning of reproduction using a 200 ?L renewal microplate-culturing technique. The following data are checked and recorded during the test period: stage-specific survival, number of days it takes for development from a first stage nauplius to a reproductively mature copepod, gender ratios, number of days for a female to extrude first and subsequent broods, number of days between first (and subsequent) brood extrusion(s) and hatching of first-generation nauplii, number of hatched and surviving nauplii, number of unhatched or necrotic eggs and aborted unhatching eggsacs, and the total number of females able to produce viable offspring over the entire mating period. This microplate-based full life-cycle toxicity test has a duration of approximately 17 days for toxicants that do not delay development. These procedures probably will be useful for conducting life-cycle toxicity tests with other species of copepods, although modifications might be necessary.

1.2 These procedures are applicable to most chemicals, either individually, or in formulations, commercial products, or known mixtures, that can be measured accurately at the necessary concentration in water. With appropriate modifications these procedures can be used to conduct tests on temperature, dissolved oxygen, and pH and on such materials as aqueous effluents (see also Guide E1192 ), sediment pore waters, and surface waters. Renewal microplate tests might not be applicable to materials that have a high oxygen demand, are highly volatile, are rapidly transformed (biologically or chemically) in aqueous solutions, or are removed from test solutions in substantial quantities by the test chambers or organisms during the test. If the concentration of dissolved oxygen falls below 50?% of saturation, or the concentration of test material in the test solution decreases by more than 20?% between renewals, it might be desirable to renew the solutions more often.

1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory requirements prior to use.