Sublethal effects of linear alkylbenzene sulphonate on larvae of the seabream (Sparus aurata): histological approach

Neonate (< 24 h) larvae of the seabream, Sparus aurata, were exposed to sublethal concentrations (0.1-1.0 mg x L(-1)) of the anionic surfactant Linear Alkyl-benzene Sulphonate (LAS) for 72 h under laboratory conditions. The first histopathological changes, such as peri-yolk sac edema, were observed at concentrations of 0.2 mg x L(-1). Higher exposure concentrations provoked disorganisation of the nervous system, trunk musculature and trophoblastic sincitium as well as in the digestive epithelium. Immunohystochemical CYP1A analysis, however, was not shown to be an adequate indicator of sublethal effects produced by exposure to this type of anionic surfactant     

石油污灌渠底泥生态毒性诊断研究

底泥样品采自沈阳东部石油污水灌渠的上、中、下游.进行了重金属Cu、Zn、Pb、Cd、矿物油含量分析和生态毒性试验.结果表明,所有底泥均有污染物积累.矿物油含量为408～118 300 mg·kg^-1,Cu为17.83～78.53 mg·kg^-1,Zn为35.76～155.16 mg·kg^-1,Pb为8.50～31.03 mg·kg^-1,Cd为0.1 mg·kg^-1～1.0mg·kg^-1.底泥对高等植物有不同程度的生长抑制或刺激效应,对蚯蚓有急性致死及慢性亚致死效应.种子发芽根伸长抑制率为-29.81%～93.8%,蚯蚓14d死亡率最大值为100%.蚯蚓14d和28d体重增长抑制率分别为-36.6%～6.08%和-40.4%～6.1%.研究表明,长期石油污水灌溉导致河道底泥中污染物的积累和较强生态毒性.     

Effects of copper and other metals on fertilization,embryo development,larval survival and settlement of the polychaete Nereis (Neanthes) virens

Summary

Nectochaete larvae of the ecologically and economically important ragworm, Nereis virens, were exposed to cadmium, chromium, copper, lead and zinc dissolved in seawater to nominal concentrations ranging from 0 to 5000 μg l^?1. Copper was the most toxic (mean LC50 of 76.5 μg l^?1 ± 95% CI 73.8–79.2 after 96 h exposure) and so was used for subsequent experiments. Exposure of gametes to greater than 500 μg l^?1 copper for 2 or 4 h at 10°C prior to fertilization, or a 10 min exposure during fertilization, significantly reduced embryo developmental success. The effect of copper on larval settlement was also assessed using sediment spiked to a range of concentrations (0, 50, 250, 500, 1000 mg kg!1 dry weight). Significantly fewer larvae were found in sediment of $250 mg kg!1 in comparison to the control or the 50 mg kg!1 treatment. Assessment of living larvae also confirmed a significant reduction in settlement, but in all treatments compared to the control, although the number of dead larvae also increased as the concentrations increased. These effects may have important implications for reproductive success and recruitment of N. virens to polluted sediments.     

Kalisomes in corals: a novel KCl concentrating organelle?

Large membrane-bound inclusions were clearly visible within the gastrodermis and lipid-containing cells of planulae and settled larvae of the zooxanthellate coral, Pocillopora damicornis after fixation or freeze-substitution. We suggest that these inclusions may be a novel potassium (kalium) chloride concentrating organelle, for which we propose the name kalisome. The inclusions were more abundant in settled larvae than in planulae and were not present in mature polyps. In planulae of the azooxanthellate coral, Dendrophyllia sp. these inclusions were extremely rare. Quantitative X-ray microanalysis of freeze-substituted preparations showed that the inclusions in P. damicornis settled larvae contained very high, positively correlated, concentrations of K (2.5 mol x kg(-1)) and Cl (2.5 mol x kg(-1)). Lower concentrations of both K (1.2 mol x kg(-1)) and Cl (1.3 mol x kg(-1)) were detected in P. damicornis planulae, yet higher concentrations were measured in Dendrophyllia planulae (K=6.0 mol x kg(-1); Cl=5.1 mol x kg(-1)). No significant (P>0.05) differences in concentration were observed between inclusions in freeze-substituted and freeze-dried sections of planulae. Symbiotic algae (zooxanthellae) in P. damicornis planulae and settled larvae also contained deposits with high levels of K and Cl, but these were not positively correlated and no structures associated with them were retained by fixation. Significant (P<0.05) concentration differences were also observed between deposits in freeze-substituted and freeze-dried sections. However, similar to 'kalisomes,' zooxanthellae deposits were more abundant in settled larvae than planulae and absent in mature polyps. Higher concentrations of K and Cl were also detected in settled larvae (K=0.7 mol x kg(-1); Cl=1.1 mol x kg(-1)) in comparison to planulae (K=0.4 mol x kg(-1); Cl=0.5 mol x kg(-1)).     

Effect of exposure method to Beauveria bassiana and conidia concentration on mortality, mycosis, and sporulation in cadavers of Chilo partellus (Lepidoptera: Pyralidae)

The effects of exposure methods, conidial concentrations, and temperature on mortality, mycosis and sporulation in second instar Chilo partellus cadavers infected by Beauveria bassiana was investigated in laboratory studies. Larvae directly sprayed with conidia, exposed to conidia-treated leaves, and dipped into conidial suspension resulted in high mortality (98-100%). The longest LT50 (3.5 days) and days to mortality (2.6 days) were observed in the treated-leaves exposure method. The shortest LT50 (1 day) and days to mortality (1 day) were recorded for the dipping method. With increasing conidial concentrations, there were decreasing LT50 and days to mortality. Larvae exposed to treated leaves and larvae directly sprayed with conidial suspensions produced high mycoses in cadavers. Exposure of larvae to treated-leaves resulted in high sporulation. At lower concentrations of conidia, both mycosis and sporulation in cadavers were high. The optimum temperature for mycosis was 20 and 15 degrees C for sporulation.     

Susceptibility of last instar red flour beetles and confused flour beetles (Coleoptera: Tenebrionidae) to hydroprene.

Last instar larvae of the red flour beetle, Tribolium castaneum (Herbst), and the confused flour beetle, Tribolium confusum Jacquelin du Val, were either exposed for 8-144 h on concrete treated with 1.9 x 10(-3) mg(AI)/per cm2 hydroprene, or continually exposed on concrete treated with 9.8 x 10(-4) to 1.9 x 10(-3) mg[AI]/per cm2 hydroprene. In both tests, larvae were exposed and held at 27 or 32 degrees C and 40, 57, or 75% RH. When larvae were exposed with no food to hydroprene for different time intervals, then transferred to untreated concrete containing flour, consistent effects were produced only at 144 h. At this exposure interval, the percentage of beetles arrested in the larval stage after 3-4 wk was generally greater at 75% RH compared with 40 and 57% RH, but there were no differences between species or temperature. The percentages of dead adult red flour beetles and live adults with morphological deformities were also greatest at 75% RH, and defects were more prevalent in red flour beetles than in confused flour beetles. When larvae were continually exposed to different concentrations of hydroprene on concrete that contained flour, the percentage of arrested larvae, dead adults, and live adults of both species generally increased with concentration. There were more deleterious effects at 75% RH compared with either 40 or 57% RH, and effects were more pronounced in the red flour beetle compared with the confused flour beetle. In both experiments, temperature effects were variable and inconclusive. Results indicate that continual exposure of last instar red flour beetle and confused flour beetle to hydroprene can limit population development, but exposure intervals of >6 d may be required for maximum effectiveness.     

Inhalation of methyl bromide gas induces mitotic recombination in somatic cells of Drosophila melanogaster

The fumigant methyl bromide was evaluated for genotoxicity in the somatic wing-spot assay of Drosophila melanogaster. Third instar larvae trans-dihybrid for mwh and flr3 were exposed to varying concentrations (0-16 mg/l) of the gas for 1 h. Following this exposure via inhalation, the larvae were placed into vials containing Instant Medium. 7 days after the exposure, the adult flies in the vials were collected, and their wings were scored under 400X magnification for the presence of clones of cells possessing malformed wing-hairs. Such clones appeared as mwh-flr3 twin spots and single spots of either mwh or flr3 phenotype. Exposure to methyl bromide was found to result in the positive induction of both twin spots and large (greater than 2 cells) single spots. For each endpoint, a significant exponential association was obtained between concentration and frequency of spots per wing. Methyl bromide was found to be a negative inducer of small (1-2 cells) single spots at all concentrations except 16 mg/l where a positive effect was observed. Because twin spots arise exclusively from mitotic recombination, methyl bromide was identified as having recombinogenic activity in the somatic tissue of Drosophila larvae.     

Influence of linear alkylbenzene sulfonate and ethanol on the degradation kinetics of domestic sewage in co-digestion with commercial laundry wastewater

The influence of ethanol on the degradation kinetics of linear alkyl benzene sulfonate (LAS) and organic matter was investigated using batch experiments with different initial LAS concentrations (8.3 mg L⁻¹ to 66.9 mg L⁻¹) and biomass immobilized on sand. Data were fitted with a substrate inhibition model. Concentrations of 2.4 mg LAS L⁻¹ and 18.9 mg LAS L⁻¹ (without and with ethanol) provided the maximum LAS utilization rate by the biomass (S_bm). For LAS degradation, ethanol addition favored a lower decrease in the specific substrate utilization rate (r_obs), even at the LAS concentration usually reported as inhibitory (> 14.4 mg L⁻¹). For organic matter degradation, r_obs was higher with ethanol. Higher biomass differentiation was observed at higher LAS concentrations. With ethanol, microbial selection occurred at LAS concentrations near S_bm. At higher LAS concentrations, the dominance and diversity values did not change significantly with ethanol, whereas without ethanol, their behaviors were irregular.

     

The effect of selenium and organic material in lake sediments on the bioaccumulation of methylmercury by Lumbriculus variegatus (oligochaeta)

The accumulation of methylmercury (MeHg) to an oligochaete worm Lumbriculus variegatus (Müller) was measured in two different lake sediments in the laboratory. ¹⁴C-labelled MeHg was added to sediments at the nominal concentration of 95 ng/g dw sediment. Groups of six oligochaete worms were exposed in glass beakers to 35 g of spiked sediment for 14 days. The two sediments had organic carbon concentrations of 3.4% and 9.9% and natural selenium concentrations of 1.45 and 0.28 mg/kg (dw), respectively. After two weeks exposure, both the accumulation rate of MeHg and the body residue in the worms were much lower in the sediment having a high organic carbon content. The effect of selenium concentration in the sediment on bioaccumulation of MeHg in Lumbriculus variegatus was measured in one sediment (organic carbon 3.4% and Se 1.45 mg/kg) by adding sodiumselenite (Na₂SeO₃) at different concentrations. The added amounts of selenium were 0, 0.1, 0.5, 2.5, 15.0, and 50.0 mg Se/kg dry sediment. In this exposure the nominal concentration of MeHg was 102 ng/g dw sediment. The two lowest selenium concentrations did not affect the bioaccumulation of MeHg. But, the dose of 2.5 mg Se/kg resulted in a 25% reduction in the body residue after two weeks exposure. When 15 and 50 mg Se/kg were added to the sediment the accumulation of MeHg in the organisms was decreased by 75% and 86%, respectively, as compared to the reference.     

五氯酚在污染沉积物泥浆固液两相中厌氧生物降解

研究了污染沉积物泥浆液、固两相五氯酚(PCP)厌氧生物降解.结果表明,投加10g·kg^-1厌氧颗粒污泥,经31d处理泥浆液、固两相PCP降解率达98.9%,平均降解速率达到80mg·kg^-1·d^-1,对照处理平均降解速率仅为4.4mg·kg^-1·d^-1,颗粒污泥生物强化作用明显.作为泥浆修复过程的调控因子,有机溶剂、共基质和表面活性剂对PCP降解效应不同,投加乙醇,可提高PCP解吸和降解速率,4d内两相PCP降解速率达到54.3mg·kg^-1·d^-1;而投加共基质和非离子表面活性剂乙二醇丁醚后,液、固两相PCP降解均出现迟滞,两者均不同程度地抑制PCP降解.     

三种农药对斑马鱼的急性毒性和生物浓缩系数

采用斑马鱼(Brachydanio rerio)为试验生物,研究了吡虫啉、三唑磷和哒螨灵的急性毒性和生物浓缩系数．通过毒性试验,获得了这3种农药对斑马鱼的24、48、72和96h LC50值．这3种农药的96h LC50值分别为281．37mg·L^-1、8．37mg·L^-1和11．66μg·L^-1．根据急性毒性数据和有关技术指南,确定生物浓缩试验浓度和持续暴露时间为14d．经0．5和5mg·L^-1吡虫啉暴露后的生物浓缩系数(BCFs)分别为1．52和0．97．经0．02和0．2mg·L^-1三唑磷暴露后的BCFs分别为9．00和8．45．经0．1和1μg·L^-1哒螨灵暴露后的BCFs分别为5600和4920．     

Trichlorfon, an organophosphorus insecticide, depresses the immune responses and resistance to Lactococcus garvieae of the giant freshwater prawn Macrobrachium rosenbergii

The total haemocyte count (THC), phenoloxidase activity, respiratory bursts (release of superoxide anions), superoxide dismutase (SOD) activity, and phagocytic activity and clearance efficiency to the pathogen Lactococcus garvieae were measured when freshwater giant prawns Macrobrachium rosenbergii (18.2+/-2.1 g) were individually reared in water containing concentrations of trichlorfon of 0, 0.2, or 0.4 mg L(-1) for a 144-h period. No significant differences in the THC were observed among prawns at the beginning and following 144 h of exposure to 0, 0.2, and 0.4 mg L(-1) trichlorfon. However, phenoloxidase activity significantly decreased when the prawns were exposed to trichlorfon at 0.2 and 0.4 mg L(-1), and no significant differences were observed between the two concentrations at any sampling time. The total production of superoxide anion by M. rosenbergii significantly increased with exposure to 0.2 and 0.4 mg L(-1) trichlorfon, and no significant differences were observed between the two concentrations during the 144-h exposure period. However, M. rosenbergii exposed to 0.2 and 0.4 mg L(-1) trichlorfon showed decreased SOD activity from 48 to 144 h. Phagocytic activity and clearance efficiency to L. garvieae significantly decreased when prawns were exposed to 0.2 and 0.4 mg L(-1) trichlorfon for 48 h. In another experiment, prawns were challenged with 5 x 10(5) colony-forming units (cfu)prawn(-1) of L. garvieae, then reared in water containing different concentrations of trichlorfon. The onset of mortality was earlier in prawns exposed to trichlorfon compared to those exposed to the zero control. The cumulative mortality of prawns directly increased with ambient trichlorfon concentrations in the range of 0-0.4 mg L(-1) after 168 h. It is concluded that exposure of M. rosenbergii to trichlorfon at 0.2 mg L(-1) or more caused cytotoxicity resulting in depression of the immune response, and increased its susceptibility to L. garvieae infection.     

Cadmium removal by living cells of the marine microalga Tetraselmis suecica

Cadmium removal by living cells of the marine microalga Tetraselmis suecica was tested in cultures exposed to different cadmium concentrations (0.6, 3, 6, 15, 30 and 45 mg/l). The EC50 for growth was 7.9 mg Cd/l after six days of exposure. The cadmium removed was proportional to the concentration of this metal in the medium and it was dependent on the time of exposure; cultures with higher cadmium concentration removed a higher amount of this metal. In cultures exposed to 0.6 mg/l, T suecica cells removed 98.1% of added cadmium with 0.392 x 10(-6) microg Cd/cell, whereas in cultures with 45 mg/l only 7.7% was removed with 16.052 x 10(-6) microg Cd/cell. The highest amount of cadmium removed per liter of culture was observed in cultures exposed to 6 mg/l, with 3.577 mg/l of cadmium. After six days of incubation, the higher proportion of cadmium was bioaccumulated intracellularly in all cultures except in 45 mg/l cultures, the percentage of intracellular cadmium being always more than 50%. The highest percentage of bioadsorbed cadmium (60.1%) was found in cells of cultures with the highest cadmium concentration (45 mg/l). Furthermore, a relation between intracellular cadmium and the concentration of sulfhydryl groups was observed.     

Acute and chronic effects of an anionic surfactant on some freshwater tubificid species

We report the results of research on acute and chronic effects of linear alkylbenzensulfonate (LAS) on two tubificid species. 96 h LC₅₀ assay values were estimated at 10° for Limnodrilus hoffmeisteri and Branchiura sowerbyi exposed to different concentrations of LAS dissolved in water, both with and without sediment. The presence of sediments modified LAS toxicity and increased values: NOEC and LOEC resulted in values 2.5 times higher for Branchiura sowerbyi and 4–4.5 times for Limnodrilus hoffmeisteri, when the sediments were present. The chronic effects induced by a long exposure to LAS were evaluated for different stages of the biological cycle of Branchiura sowerbyi. Using concentrations between the NOEC and LOEC (0.5, 2.5, and 5 ppm), with control, we could observe that: 1) at 5 ppm the cocoons were laid precociously compared to controls, 2) in all treated series the number of cocoons was lower than in controls, 3) the mean number of oocytes per cocoon was lower for the worms submitted to LAS, compared to the control, 4) the period of embryonic development was similar for all used concentrations and for control, and 5) the number of degenerated cocoons was unchanged by the LAS treatment.     

The effect of dietary nickel on the immune responses of Spodoptera litura Fabricius larvae

By exposing Spodoptera litura Fabricius larvae to nickel (Ni) in artificial diets for successive three generations, we investigated the impacts of the dietary Ni on growth and immune response of the fifth and sixth instar larvae at 24 h intervals. The time of newly moulted fifth instar larvae was labelled as 0 h. After exposure to 5 mg/kg Ni for two generations, Ni exposure significantly improved larval phenoloxidase activity and encapsulation grade in fifth instar larvae when compared to controls, except for encapsulation grade at 72-120 h in the second generation. However, higher concentrations of Ni (≥10 mg/kg) only significantly reduced encapsulation grade at 72-120 h. In the third generation, insects given higher dietary levels of Ni (≥10 mg/kg) showed lower immune responses and retarded relative growth rate (RGR) compared to controls, but those exposed to lower Ni levels (≤5 mg/kg) had a significantly improved encapsulation grade at 24-72 h. Larvae at lower Ni level (≤5 mg/kg) treatments had significantly higher RGR in comparison with that in controls. There was no significant difference in food relative consumption rate (RCR) and RGR among any treatment of the fifth instar larvae in three successive generations. These results indicated that the type and extent of effects on growth and immune responses of S. litura varied with the Ni concentrations and exposure periods.     

河流汞污染对青鳉鱼早期发育的毒性影响

清镇市化工厂是贵州省东门桥河汞污染的重要来源。为了评估这条河流的汞污染程度,本研究调查了东门桥河环境样品中的汞含量和分布情况。河流水体总汞(THg)和甲基汞(MeHg)的平均含量分别为(135.79±47.40)和(0.64±0.58)ng·L-1;生物膜中THg和MeHg的平均含量分别为(3.38±1.91)mg·kg-1和(10.47±0.40)μg·kg^-1;沉积物中THg和MeHg的平均含量分别为(23.21±20.22)mg·kg-1和(32.74±10.96)μg·kg^-1。为了进一步了解这条河流中汞对水生生物的风险,将青鳉鱼胚胎和仔鱼分别暴露于从河中收集的被汞污染的河水、生物膜和沉积物中。青鳉鱼胚胎经15 d暴露后,孵化时间延长、孵化率显著降低,死亡率显著升高,实验暴露还导致胚胎无法破膜、卵黄囊水肿等畸形效应,以及初孵仔鱼不同程度的畸形。青鳉鱼仔鱼经24、48、96 h和21 d暴露后,各暴露组的死亡率和畸形率随着暴露时间的延长而显著升高,且表现出一系列以脊柱弯曲为主的畸形效应。研究表明,东门桥河的汞污染会严重影响青鳉鱼的早期生长发育。     

Gut mucosal damage during endotoxic shock is due to mechanisms other than gut ischemia.

Whether the gut alterations seen during sepsis are caused by microcirculatory hypoxia or disturbances in cellular metabolic pathways associated with mitochondrial respiration remains controversial. We hypothesized that hypoperfusion or hypoxia and local production of nitric oxide might play an important role in the development of gut mucosal injury during endotoxic shock and investigated their roles by using differing levels of fluid resuscitation and occlusion of the superior mesenteric artery (SMA). Anesthetized New Zealand rabbits were allocated to group I (sham, n = 8); group II [low-dose endotoxin (LPS, Escherichia coli-055:B5, 150 microg/kg)/fluid resuscitation (12 ml x kg(-1) x h(-1)); n = 8]; group III [high-dose LPS (1 mg/kg)/fluid resuscitation (12 ml x kg(-1) x h(-1)); n = 8]; group IV [high-dose LPS (1 mg/kg)/hypovolemia (4 ml x kg-1 x h(-1) fluids); n = 8]; and group V [SMA ligation/fluid resuscitation (12 ml x kg(-1) x h(-1)); n = 4]. Luminal gut lactate concentrations and PCO2 gap increased in groups IV and V (P < 0.05), reflecting alterations in gut perfusion. Interestingly, significant histological alterations were observed in all LPS groups but not in group V. Blood and luminal gut nitrate/nitrite concentrations increased only in group IV. The mechanism of gut injury in endotoxic shock seems unrelated to hypoxia and release of nitric oxide. Gut dysfunction may occur as a result of so-called "cytopathic hypoxia."     

Pharmacokinetics and tissue residues of Telazol in free-ranging polar bears

A pharmacokinetic and tissue residue study was conducted to assess the risks associated with human consumption of polar bears in arctic Canada that have been exposed to the immobilizing drug Telazol, a mixture of tiletamine hydrochloride and zolazepam hydrochloride. Twenty-two bears were remotely injected with about 10 mg/kg of Telazol. Following immobilization, serum samples were collected serially at regular intervals until the bears awakened. Sixteen of the bears were relocated and killed under permit by local hunters at various times from 0.5 to 11 days after dosing. Serum, kidney, muscle and adipose tissue samples were collected immediately after death. All samples were stored at -70 C until analysis by HPLC. The concentration-time data of tiletamine and zolazepam in serum during the immobilization period were fitted to curves by computer and the pharmacokinetic parameters assessed. In addition, the serum and tissue samples collected at the time of death were analyzed for both parent drugs, for one metabolite of tiletamine (CI-398), and for three metabolites of zolazepam (metabolites 1, 2 and 4). A one-compartment model with first-order absorption and elimination best fit the time-series data for the drugs in serum during the immobilization period. This model gave half-lives (mean +/- SE) for tiletamine and zolazepam of 1.8+/-0.2 h and 1.2+/-0.08 h, respectively, clearance values of 2.1+/-0.3 l x h(-1) x kg(-1) and 1.1+/-0.1 l x h(-1) x kg(-1), and volumes of distribution of 5.2+/-0.6 l/kg and 1.8+/-0.2 l/kg. The concentrations of both drugs and their metabolites declined rapidly to trace levels by 24 h post-dosing, although extremely low concentrations of some metabolites were encountered sporadically over the entire sampling period. In particular, zolazepam metabolite 2, remained detectable in fat and muscle tissue at the end of the study, 11 days after dosing. It was concluded that during immobilization, both tiletamine and zolazepam levels decline rapidly in a monoexponential fashion, and their pharmacokinetic parameters in polar bears are similar to those observed in other species. Tissue levels of the drugs and their metabolites declined sufficiently rapidly that individuals eating meat from exposed bears would be unlikely to experience pharmacological effects from the drugs. Nevertheless, slight exposure to the drugs and/or their metabolites might be possible for an indeterminate time after dosing.     

杉木人工林土壤活性有机质变化特征

在中国科学院会同森林生态实验站对第一代、第二代杉木林和地带性阔叶林土壤活性有机质主要组分进行了研究.结果表明,土壤活性有机质各组分含量均为杉木林低于阔叶林,而第二代杉木林又低于第一代杉木.第一代杉木林活性有机质总量、微生物生物量碳、水溶性有机碳和碳水化合物含量分别为18.79 g·kg^-1、421.7 mg·kg^-1、22.2 mg·kg^-1和136.3 mg·kg^-1,上述活性有机质组分在第二代杉木林中的含量分别是第一代杉木林的73.6%、87.9%、66.3%和3.2%,地带性阔叶林则分别为22.31 g·kg^-1、800. mg·kg^-1、361.1 mg·kg^-1和220.1 mg·kg^-1.相关性分析结果表明,土壤活性有机质各组分之间具有不同程度的相关性,其中土壤微生物生物量碳与其它活性有机质组分的相关性相对较高.     

Micronuclei induced in erythrocytes of Cyprinus carpio (teleostei, pisces) by X-rays and colchicine.

In the present work the induction of micronuclei in erythrocytes of Cyprinus carpio treated with X-rays and colchicine is studied for the evaluation of mutagenic effects of both clastogenic and mitoclastic (spindle poisoning) agents in this system.Three different experiments were performed treating groups of laboratory-reproduced animals with (1) single doses of X-rays (0.1, 0.5 and 2Gy); (2) a single i.p. injection of colchicine at the concentrations: 1.6x10(-2), 8x10(-2), 0.4 and 2mg/kg b.w. so as to mimic an acute exposure to the agent and (3) six repeated i.p. injections of the first three concentrations of colchicine, over a period of 18 days, so as to mimic a chronic exposure. Repeated blood samplings were performed by cardiac puncture over a period of about 2 months after the treatment and micronucleus frequencies were determined at multiple times on the same individuals after mutagen exposure. A dose-dependent increase in the micronucleus frequency was observed in irradiated fish and a peak value detected at 21 days. Slight increases of micronucleus frequencies were also observed in both colchicine experiments only for the highest concentrations at the earliest sampling time. Higher concentrations of colchicine clearly showed a lethal effect. According to the present data the micronucleus frequency induced by the highest colchicine dose is comparable to that observed after 0.1Gy of X-ray irradiation.