Laboratory populations for long-term toxicity tests

Laboratory populations for long-term toxicity tests

Laboratory Populations for Long-Term Toxicity Tests International standardization o[ toxicity tests demands 'standard' animals. These are not to be fo...

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Laboratory Populations for Long-Term Toxicity Tests International standardization o[ toxicity tests demands 'standard' animals. These are not to be found in nature, and transferring o/~uaisms from their natural habitat to the laboratory may add to the streu on them and interfere with the tests. Laboratory cultured animals may help reduce this problem. Recently Perkins (1972) summarized some of the problems encountered while undertaking marine toxicity studies. The test organisms must be in the normal physiological state free of stress prior to use in a bioassay. He summarized the procedures and difficulties in the collection, transportation, and laboratory maintenance of field test organisms. Furthermore. cultured specimens are so adapted to life in the laboratory making comparisons to natural populations difficult because of such factors as genetic drift from the wild condition with time. These observations by Perkins are valid and thought provoking. However, one might ask whether the inherent variability of field collected specimens during the selection, transportation, and laboratory maintenance procedure is greater or less than the possible genetic drift from the wild stock of a laboratory bred population. T o this point we might add the convenience and time-saving merits of laboratory reared specimens or the inevitable take-over of marine toxicity tests by technicians unfamiliar with many of the problems of field marine biology. Certainly a considerable amount of variability exists between the laboratory white rat and the wild stock, for example, behavioural differences, but has this diminished the usefulness of the laboratory population in biological research? The purpose of this report is not to discourage the use of field collected specimens as test organisms for toxicity studies, but rather to discuss the advantages of laboratory populations of polychaetes in such investigations. The advantages of a laboratory bred colony may be summarized as: (1) specimens are available when needed, (2) specimens are already adapted to laboratory conditions eliminating a conditioning phase, (3) laboratory specimens will not decimate the field populations of a desired species, a problem especially in populous areas, (4) the diet is known and controlled, which is particularly advantageous if biochemical analyses are involved, (5) many of the species of polychaetes have short life histories making it possible to study the effects of the pollutant on reproduction, and (6) specimens can be transported to other parts of the world making cooperative studies possible. The availability of test organisms when needed would be particularly valuable in the case of marine ecological disasters. One can only contemplate the possible consequences of the Torrey Canyon oil spill if even a short-term bioassay were conducted on the oil spill remover BP 1002 before its use. Specimens would be available immediately without the necessity of collecting (tides permitting) and adapting them to laboratory conditions.

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The diet of a laboratory bred specimen would be known throughout its life history; this is particularly advantageous if a chemical analysis of the test organism for the presence of residual pollutant tested is made at the conclusion of the bioassay. Since the diet is controlled, the test organism would have little or no prior exposure to the pollutant tested. Therefore, in all likelihood the variability of results would be less with the use of a laboratory population. Most toxicity tests are of a short-term duration and therefore are not measuring long-term effects on such biological factors as reproduction. Many species of polychaetes have life histories of less than 4 months duration, making the study of long-term effects feasible. Bellan et al. (1972) demonstrated the long-term effects of a detergent on the various stages of the life history of Capitella capitata. The long-term TL~0 of this detergent on adults was approximately 1.0 rag/1., but some specimens were able to live in concentrations as high as 100 mg/1. The number of females developing eggs, the number of females laying eggs, the total number of eggs laid, the time for embryonic development, the number of trochophores produced and the number of young benthic worms which survived was inversely related to the concentration. A 90 per cent decrease in the number of benthic worms produced occurred between the control and highest concentration of detergent employed. Interestingly, the difference between the control and the lowest concentration studied became greater as the experiment progressed. Transportation of marine animals to other geogeographical localities have become quite routine with the advent of instant sea-water and air freight: laboratory colonies of Neardhes arenaceodentata have been air-mailed to laboratories in Calgary, Texas, and Rhode Island by the author. Akesson (personal communication) has informed me of sending Ophrotrocha labronica to other geographical localities with good results. In summary, with the greater interest in protecting the marine environment and with the appearance of long-term effects of pollutants upon organisms, for example Minamata disease, it is readily apparent that long-term bioassays are necessary. The use of laboratory inbred colonies makes it possible to study long-term effects of pollutants with the minimum amount of time and effort which will result in obtaining the maximum amount of meaningful data. DONALD J. RE1SH Department of Biology, Cali[ornia State University, Long Beach, Long Beach, Calilornia 90840, USA Bellan, G., Reish, D. J., Foret, J. P. 11972). The sublethal effects of a detergent on the reproduction, development and settlement in the polychaetous annelid Capitella capitata. Marine Biol., 14: 183-188. Perkins, E. J. (1972). Some problems of marine toxicity tests. Mar Poll. Bull. 3:13-14