Chromosome malsegregation induced by the rodent carcinogens acetamide,pyridine and diethanolamine in Drosophila melanogaster females

The effect of the rodent carcinogens acetamide (AC), pyridine (PY) and diethanolamine (DEA) on meiotic chromosome segregation was assessed in 4-day-old Drosophila melanogaster females. After oral treatment with 0.05, 0.1, 0.2 and 0.3% PY; 0.5, 1, 1.5, 2 and 4% AC; or 5, 10, 20, 40 and 80% DEA, the females were mated to 7-day-old males and three 24h broods were obtained to sample cells exposed mainly as mature oocytes (brood I), and nearly mature oocytes (brood II) with an increasing proportion of early oocytes (brood III). Viability was not affected at the two (PY) or three (AC, DEA) lowest concentrations, decreasing thereafter. PY increased the frequency of nondisjunction exclusively in brood II suggesting its interaction with specific targets. AC and DEA (the most active of the three) induced similar frequencies of nondisjunction in all broods suggesting unspecific cell division perturbations probably due to toxicity. No clear dose effect relationships were observed.     

Genotoxic damage induced by isopropanol in germinal and somatic cells of Drosophila melanogaster

Isopropanol (isopropyl alcohol, 2-propanol, IPA) is a volatile solvent widely used in domestic or industrial environments and reported as innocuous in various test systems. The aim of this work was to search for in vivo genotoxic effects of IPA in Drosophila melanogaster, studying its ability to induce nondisjunction (ND) in females, sex linked recessive lethals (SLRL) in males, and somatic mutation and/or recombination (SMART) in larvae. Treatments were acute (60min) and were administered via inhalation. IPA had low toxicity in adult flies (75% IPA mortality index, MI=12.7% (females) and 2.6% (males)) and larvae (MI=14.3%, 75% IPA). Female fertility was severely affected during the first 24h (brood I, BI) after treatment, but, afterwards, control values were recovered. IPA induced a 50-fold increase of ND (%) in 24h old females, and a six-fold rise in 4-5 d old BI offspring. Nondisjunction frequencies (%) in the offspring of broods II to V (24h in each case) were similar to control values. IPA doses of 25% and 50% (v/v), tested in 24h old females, showed a significant dose-dependent increase of ND(%)in BI only, with control values in subsequent broods. Flies gave normal offspring when kept in regular media for 24h before mating. The eye spot test (SMART) showed a significant increase at 50% IPA (p<0.05, m=2), but the response was not dose-dependent. IPA failed to induce SLRL in any of the spermatogenesis stages tested. These findings suggest that the main effect of IPA is to induce chromosomal malsegregation; IPA must be present at the resumption of M-phase I after fertilization, to exert these effects. The alcohol does not affect DNA directly, but perturbations of the nuclear membrane may be responsible for induction of ND.     

Effect of hydroquinone on meiotic segregation in Drosophila melanogaster females

The induction of sex chromosomes meiotic nondisjunction (ND) by hydroquinone (HQ) given orally was investigated in Drosophila melanogaster 2-7, 8-22, 24, 48, 72 and 96 h-old females. ND was assessed by a system where exceptional females (XXY) and only 1/4 of the expected regular progeny are viable. Oocytes were treated at different stages of development. 4% HQ tested only in 72 h-old females induced ND in oocytes sampled in brood I (mostly mature oocytes at metaphase I). 6% HQ increased ND in brood I of 8-22 h-old females, while other broods, (including cells treated at early prophase) were also affected in older flies, the highest significance being attained in the 48 h-old series. Newly hatched females (2-7 h-old) were refractory to the treatment, though oocytes sampled in the first three subcultures are comparable to cells showing enhancement of ND in series run with older females. Toxicity of 2, 4 and 6% HQ increased with concentration and females' age: (a) 2% was not toxic; (b) 4% was toxic only to 72 h-old females; (c) 6% was increasingly toxic to females 24, 48 and 72 h-old. The results indicate that age plays a significant role on both chromosomal segregation and toxicity and suggest that in Drosophila HQ is metabolized to its reactive species. The lack of toxic and aneugenic effect in very young females could reflect a more efficient detoxification due to the known high specific activity of glutathione-S-transferase (GST) after eclosion. The decline in GST activity around day 2 of adult life coincides with the high effect of HQ in 48 h-old females.     

A rapid selection technique for detecting meiotic X-chromosomal nondisjunction in Drosophila melanogaster

A chemical selection technique is described for the rapid and easy detection of X-chromosomal nondisjunction in females of Drosophila melanogaster. The method employs the maroon-like (ma-1) gene and depends on the known hypersensitivity of ma-1 flies lacking xanthine dehydrogenase (XDH) activity to killing by treatments with aqueous purine solutions. Parental females, heterozygous for two ma-1 alleles which produce 25% of wild-type XDH activity, are mated to males bearing a non-complementing ma-1 allele. After treatment of developing cultures with a 6-mM purine solution, only those individuals possessing 25% or greater XDH activity survive to eclosion. The present report demonstrates that this system can be used to measure accurately the spontaneous frequency of X-chromosomal nondisjunction as well as increased maternal nondisjunction produced by cold treatment, X-irradiation or meiotic mutants. The rapidity and ease of this system suggest that it can be used for the routine monitoring of environmental agents for those which produce this class of meiotic segregational anomalies.     

Effects of sucrose concentrations and fly age on feeding responses and survival of female and male western cherry fruit flies, Rhagoletis indifferens

Abstract. The effects of single meals of different sucrose concentrations on feeding responses and survival of 8–24-h-old, 1–2-, 10–12- and 31–36-day-old female and male western cherry fruit flies, Rhagoletis indifferens Curran, were determined. Feeding time and food consumption response patterns in both sexes within age groups were curvilinear. Feeding times increased as sucrose concentrations increased, and were longest when the sucrose concentration was 100% (dry). Consumption of dilute wet sucrose was low, whereas consumption of concentrated wet sucrose was high. However, consumption of dry, 100% sucrose was also low. One to 2-day-old flies of both sexes that had not previously fed consumed more sucrose foods than unfed 8–24-h-old flies and 10–12- and 31–36-day-old flies that had been starved for 16–24 h. Females consumed more than males, but they consumed the same amount as males per mg bodyweight. When fed single 20% and 60% sucrose meals, 1–2-day-old flies survived longer compared to flies in all other age groups, with 31–36-day-old flies surviving shortest. Despite age-related differences in survival, in general, no sex differences in survival were seen in flies fed sucrose within any age groups, or in flies fed sucrose-yeast, cherry juice and honeydew foods. The results suggest that sugar-feeding behaviours and the energy invested in sugar 'seeking' by both sexes of R. indifferens should be the same throughout life.     

Polyploidy and aneuploidy induced by colcemid in Drosophila melanogaster

Colcemid was fed to Drosophila melanogaster larvae throughout most of the larval period. Surviving individuals were then mated with untreated flies, and their progeny were examined for polyploid flies or flies resulting from X-chromosome nondisjunction. A total of 251 polyploid offspring was recovered from the experimental matings, none from the control. All of the polyploids were evidently triploids, and all but one were obtained from colcemid-fed females: males produced significantly lower frequencies of triploid offspring than females. The highest average frequency of triploid offspring obtained from any treatment group was 18%. Nonrandom distributions of triploid offspring were observed among females raised identically, indicating tht polyploidization occurs mitotically, rather than meiotically, giving rise to clones of tetraploid oogonia. 9 colcemid-fed females produced exclusively triploid offspring. Colcemid also caused a significant increase in X-chromosome nondisjunction in females, though the frequencies of such offspring were at least several-fold lower than the frequencies of triploid offspring. Somatic polyploidy was apparently also indiced since patches of large cells were found on the wings of some flies raised on colcemid-containing food. Various teratological abnormalities were observed among the treated flies, including deformed or missing eyes and partially duplicated thoraxes.     

Do reproductive tactics vary with habitat heterogeneity in the intertidal sea anemone Actinia tenebrosa?

Cnidarians display a diverse range of reproductive tactics including sexual and asexual modes of reproduction. Although few studies have looked for intraspecific variation in reproductive tactics, flexible expression of such life-history traits may be favoured in species that occupy a range of habitats. We tested this in the sea anemone Actinia tenebrosa by comparing cycles of reproductive activity and the mode of production of brooded larvae in local populations occupying boulder fields and stable rock platforms. We determined the mode of production of broods from eight rock platforms (separated by up to 1600 km) and two boulder shores on the south east coast of Australia using a combination of allozyme data and four newly characterised microsatellite markers.

We determined seasonal patterns of brooding and gonad development by monthly dissection of 15–30 adults from each of two boulder fields and two stable platforms. Previous genetic studies have shown that populations of A. tenebrosa on rock platforms can be highly clonal, whereas anemones on more heterogeneous boulder habitats display levels of genotypic diversity similar to that expected for sexual reproduction. We genotyped a total of 221 juveniles from 37 brooding adults including 11 broods and 80 juveniles from boulder shores. We did not detect any evidence of sexual production of broods. All brooded juveniles displayed identical multi-locus genotypes to their brood parent irrespective of habitat of origin or location, including 28 broods (200 juveniles) that were heterozygous at one or more locus. Similarly, we found that temporal patterns of gonad formation and brooding were consistent across habitats and locations. We detected 346 mature males, 234 non-reproductive or immature individuals, and no mature females within a total of 580 dissected individuals. These data suggest that the reproductive tactics of A. tenebrosa are essentially fixed and that variation in the genotypic diversity of populations may reflect variation in factors such as the input of sexually derived planktonically dispersed recruits or post-settlement processes. However, the apparent lack of females paradoxically implies that sexual reproduction, and hence recruitment, must be rare or no longer possible within some populations, and highlights the need for long-term studies of these populations.     

Productivity and mortality of mohua (Mohoua ochrocephala)

Abstract

Mohua (Mohoua oehrocephala) breeding and mortality were studied in the Eglinton Valley, Fiordland National Park, New Zealand. Mohua on the valley floor (380 m a.s.l.) bred from early October until March, though birds at higher altitude in the Eglinton and elsewhere started later. In low altitude areas, most pairs raised two broods a year, but elsewhere they seemed to raise only one. Eggs were laid daily, and incubation began with the laying of the last egg and lasted about 20 days. The nestling period was about 23 days. Clutches contained 1–5 eggs, most often three. During three breeding seasons there was no significant nest predation by introduced mammals, but in 1990/91, when stoat (Muslela erminea) numbers were high, 67% of nests and 50% of nesting females were destroyed by stoats. When stoat numbers were low, the productivity and mortality of double‐brooded mohua were well within the ranges recorded for other forest‐dwelling bird species, and the productivity of single‐brooded mohua was lower than that of most other forest‐dwelling passerines. During years when stoat numbers were high, the productivity and mortality of even the double‐brooded mohua were lower than for most other forest‐dwelling passerines. There is some evidence that there were density dependent mechanisms influencing the productivity and survival of chicks.     

Timing of breeding in Black Grouse Tetrao tetrix and Capercaillie Tetrao urogallus and distribution of insect food for the chicks

In Perthshire (Scotland), Black Grouse Tetrao tetrix broods less than 3 weeks old preferred herb-rich grassy flushes with Bog Myrtle Myrica gale , whereas in the northern Pennines (England), all broods were found on grass-dominated moorland or enclosed rough grazing habitats chiefly of grass and rushes. In both areas, broods used habitats with taller vegetation that had more invertebrates, particularly moth caterpillars and sawfly larvae (Sym-phyta, Hymenoptera). Within preferred habitats, broods were found in vegetation containing more flies (Diptera), plant bugs (Hemiptera) and ichneumon flies (Hymenoptera) than at randomly chosen sites. The main hatch of Black Grouse chicks in Perthshire coincided with the peak availability of moth caterpillars preferred by chicks. Broods in the Pennines hatched 1 week later than those in Scotland, and this later breeding in the south may be an adaptation to utilize the later peak biomass of sawfly larvae, the chief insect prey there. Data collected for Capercaillie Tetrao urogallus suggest a similar degree of synchronization between their peak hatch and the availability of moth caterpillars on Bilberry Vaccinium myrtillus.     

Mating systems in the Lapwing Vanellus vanellus

The Lapwing Vanellus vanellus has traditionally been regarded as a monogamous, single brooded species, defending a single territory. Recent studies involving individually recognizable Lapwings have begun to challenge the ubiquity of these statements, with high frequencies of polygyny and the production of second broods being reported. Breeding Lapwings were studied in Upper Teesdale, County Durham, U.K., between 1993 and 1995, where both adults and chicks had been individually colour-ringed since 1990. A total of 90 territorial males and 64 females were intensively studied during the 3 years. Overall, 30% of territorial males had more than one mate in any year, with 19% more adult males than yearling males mating polygynously. On two occasions, polygynous males simultaneously defended two territories. Five females attempted to produce second broods, and one was polyandrous.     

Effects of alpha-mangostin from mangosteen pericarp extract and imidacloprid on Nilaparvata lugens (Stal.) and non-target organisms: toxicity and detoxification mechanism

The brown planthopper, Nilaparvato lugens Stat. (BPH) is the most devastating insect pest in rice fields. Outbreaks of BPH, which are resistant to many synthetic insecticides, can cause total rice crop loss. This research was done to evaluate the efficiency of extracts of mangosteen pericarp (Garcina mangostana L.) as an alternative control of BPH Thailand strain. Topical spraying was applied to various stages of nymphal and adult BPH to determine toxicity. An ethanol extract of mangosteen pericarp extract gave the best control of BPH, with LC50 of 4.5% w/v (r2 = 0.95) with 3rd instar BPH nymphs when compared with the other solvents, hexane, acetone and dichloromethane. The active compound, alpha-mangostin showed an LC50 of 5.44%w/v (r2 = 0.88). The toxicity of this extract was less than that of Imidacloprid which showed an LC50 of 0.0042% w/v (r2 = 0.99). The toxicity to non-target organisms was determined. This extract showed toxicity to guppies ((LC50 = 2.53 and 4.27 ppm for females and males, respectively; r2 = 0.97 and 0.97, respectively), bees (LC50 = 4.38% w/v, r2 = 0.95) and mice (no oral acute toxicity and no dermal inflammation but showed eye irritation in 1 day which became normal within 3 days). In vitro detoxification enzyme activities of carboxylesterase, acetylcholinesterase and glutathione-s-transferase from BPH after 24 hours exposure were also observed. Carboxylesterase showed stronger activity than other enzymes. Toxicity in terms of LC50 values of both the extract and imidacloprid treatments increased in each generation. The LC50 values for each generation were 4.22-6.67 after sequential spraying. After the ethanol extract was kept at 4 degrees C, room temperature and 55 degrees C for 3 months, the quantity of alpha-mangostin and the BPH control efficiency was lower at 55 degrees C than those for other temperatures. The results from this research indicate that mangosteen pericarp extract can be an alternative insecticide for the control of BPH, which may possess high efficiency, cause with fewer environmental problems and result in less resistance in the BPH.     

Brood provisioning rates and fledgling behavior of Cordilleran Flycatchers in southwestern Colorado

The behavior of young songbirds after fledging is one of the least understood phases of the breeding cycle, although parental provisioning rates and movement of fledglings are key to understanding life history evolution. We studied Cordilleran Flycatchers (Empidonax occidentalis) at two sites in southwestern Colorado, USA, from 2012 to 2017. We banded and sexed breeding adults to determine the relative contributions of males and females to nestling and fledgling care, and attached radio‐transmitters to nestlings to facilitate observations of brood behavior after fledging. Females made 60% and 78% of total observed feedings of nestlings and fledglings, respectively. Parental provisioning rates increased with nestling age, and per‐nestling provisioning rates increased with brood size. Parental provisioning rates declined just before fledging, then increased just after fledging. Fledging times of individuals in broods were asynchronous and concentrated during the late afternoon and early evening. Males stopped caring for fledglings before females even though this species is single‐brooded, with some late‐season broods being abandoned by males. Broods spent the first three weeks after fledging within 400 m of nests, after which they began to disperse. Most aspects of the breeding biology of Cordilleran Flycatchers in our study, including the duration of nestling and fledging periods, female‐dominated provisioning, and movement patterns of fledglings, were similar to those of other Empidonax species. However, the times when young fledged were not concentrated in the morning as reported in most other songbirds, and this result warrants additional study of the timing of fledging in ecologically and taxonomically similar species. The increased per‐nestling provisioning rate with increasing brood size was unexpected, and additional study is needed to determine if this increase results from a trade‐off between adult annual survival and productivity favoring increased provisioning of young in larger broods, or from the existence of high‐quality individuals where larger clutches and higher provisioning rates are linked.     

A temperature effect on nondisjunction of the X chromosomes among eggs from agedDrosophila females

The effects of temperature and aging on the frequency of nondisjunction inDrosophila melanogaster eggs were investigated. At 25°C offspring arising from 3–5 day old control females had a nondisjunction frequency (0.943/1000 offspring) very similar to that for females who were 24–26 or 27 days old when eggs were collected (1.044/1000 offspring). When females were aged for the same length of time at 10°C the frequency of nondisjunctional exceptions increased to 3.368 per 1000 offspring. These results indicate that aging the females at 25°C does not increase the nondisjunction rate over that obtained from non-aged females raised at 25°. The increase in nondisjunction frequencies when the females were aged at 10°C reflects an influence of temperature on the meiotic process inDrosophila melanogaster. At the low temperature eggs were also aged since few or no eggs were laid during the aging process. Thus in addition to a temperature effect on nondisjunction rates at 10°C there may also be an age effect.     

Toxicity of ethanol during proliferation and adventitious root formation in apple microcuttings in vitro

We have examined the toxicity of ethanol in tissue culture of the apple rootstock ‘Jork 9’. During proliferation through axillary branching, 0.2% (v/v) ethanol slightly stimulated proliferation whereas significant inhibition occurred at concentrations of 0.4 % or higher. In adventitious root formation, significant inhibition occurred at concentrations of 0.1 % or higher. The effect of ethanol was stage-dependent: during the induction period (i.e. from 24 to 72 h after the start of the rooting treatment), there was little or no inhibition. During autoclaving, ethanol evaporated to ca. 50 %. This revised version was published online in July 2006 with corrections to the Cover Date.     

ACUTE ETHANOL EXPOSURE DECREASES THE ANALGESIC POTENCY OF MORPHINE IN MICE

Chronic (7 days), forced ethanol drinking can decrease the analgesic potency of opioid agonists in mice. In the present study, the effect of short-term ethanol treatment was examined using forced ethanol access and ethanol injection protocols. Mice were given forced access to 1, 3 or 7% (v/v) ethanol for 24 hr and then tested for s.c. morphine analgesia using the tailflick assay. Controls had access to water. Another group of mice was injected i.p. with 2.5 g/kg ethanol or water 4 times over a 21 hr period and tested 3 hr after the final injection for morphine analgesia. Other mice were injected once i.p. with 1, 2 or 3 g/kg ethanol or water and tested 24 hr later using the tailflick. In the forced access study, ethanol dose-dependently decreased morphine's analgesic potency with the highest dose (7%) producing a 1.6-fold shift in the ED₅₀. This decrease in morphine potency was similar to that found in a related study using 7% ethanol for 7 days (1.8-fold shift). Repeated ethanol injections significantly reduced the analgesic potency of morphine (1.9-fold shift), whereas, a single injection of 1, 2 or 3 g/kg ethanol did not alter the potency of morphine. Control studies indicated that neither 24 hr water nor food deprivation affected morphine potency. Overall, these data show that sustained exposure to ethanol over a 24 hr period will dose-dependently decrease morphine's analgesic potency. © 1998 Elsevier Science Inc.     

Parental care in Semipalmated Sandpipers Calidris pusilla: brood desertion by females

Although Semipalmated Sandpipers Calidris pusilla are monogamous, with biparental incubation, most females (86–97%) deserted their broods to the care of their mates, 0–11 days (average 6) after their eggs hatched. Males left the brood an average of 8 days later, shortly before or after the chicks fledged. In several instances, females that deserted in one year remained with the chicks the next year, and vice versa. Females deserted chicks at nests that hatched later in the season at an earlier age than those had hatched earlier ( r ²> o.6). Since females appeared to have an energy deficit in at least some years, and suffered higher mortality rates than males during breeding, it is possible that females deserted broods in order to take advantage of better feeding conditions at migratory stopovers in northeastern North America early in the season. There was little evidence of higher nesting success or earlier hatching date in reuniting pairs, although if both members of a pair returned to the breeding area, 80% reunited. Increased survival of their mate may be most advantageous to males in ensuring that they obtain a female the following year.     

Paradoxes in exogenous androgen treatments of bluegill

Three experiments were conducted to investigate the effect of oral administration of trenbolone acetate and 17a-methyltestosterone on sex determination in 28-day-old bluegill, Lepomis macrochirus Rafinesque, fry. Multiple androgen doses and various treatment durations were tested. All treatments produced fewer males and females than did the control group (P < 0.01). All concentrations of both androgens produced a high proportion of intersex fish (38–81%). The number of males and females declined with the increase in androgen dose or treatment duration. Sterile fish were found in treatments with a higher dose rate or a longer treatment period. The predominance of intersex fish and reductions of both males and females in the androgen treatments suggest that gonadal development of both genotypic male and female fish were being altered by the hormone treatment.     

Effects of selected insecticides on Diadegma insulare (Hymenoptera: Ichneumonidae), a parasitoid of Plutella xylostella (Lepidoptera: Plutellidae)

Effects of eight insecticides on Diadegma insulare (Cresson), a parasitoid of the diamondback moth, Plutella xylostella L., were evaluated under the laboratory conditions. The insecticides were three azadirachtin-based products (Ecozin, Agroneem and Neemix), two Bacillus thuringiensis (Bt) products (Xentari and Crymax), indoxacarb, spinosad, and λ-cyhalothrin. When D. insulare pupae were treated, none of the insecticide treatments except λ-cyhalothrin significantly reduced adult emergence, with 76-90% adults emerged from the treated pupae. In the λ-cyhalothrin treatment, only 10% D. insulare pupae produced adult wasps. Indoxacarb, spinosad, and λ-cyhalothrin caused 100% D. insulare adult mortality in 24 h in Petri dishes sprayed with insecticides in the contact bioassays, and 95.8, 100 and 95.8% adult mortality in 24 h in the ingestion bioassays, respectively. In contrast, all three azadirachtin-based insecticides and the two Bt-insecticides caused only 0-10.4% mortality of D. insulare adults after ingestion. The surviving D. insulare from ingestion treatments with Bt- and azadirachtin-insecticides parasitized 50.8-67.6% of P. xylostella larvae, respectively, compare to 72.1% for the water control. After ingesting indoxacarb, spinosad and λ-cyhalothrin mixed in honey-water, both the females and the males lived significantly shorter than those ingesting Bt- and azadirachtin-insecticides and the non-insecticide honey-water. Effects of leaf residues of indoxacarb, spinosad and λ-cyhalothrin varied significantly. The leaf residues of spinosad had the least effects on D. insulare adults, and 7- and 10-day-old residue only caused 5.6 and 7.4% mortality in 24 h, whereas 10-day-old leaf residues of indoxacarb and λ-cyhalothrin caused 40.7 and 57.4% mortality in 24 h, respectively.     

Effect of maternal diabetes and ethanol interactions on embryo development in the mouse

The aim of this study was to determine the possible fetal effects of interaction between maternal diabetes and acute doses of alcohol. Pregnant TO mice were made diabetic by a single injection of streptozotocin (STZ) on gestation day (GD) 2. Single dose of 0.003 or 0.03 ml/g body weight of fresh ethanol (25% v/v of absolute alcohol in normal saline) was injected into groups of diabetic and nondiabetic animals on GD 7 or 8. One group of diabetic animals had a daily dose of 6-8 IU of insulin subcutaneously. Fetuses were collected on GD 18. There was a significant increase in the incidence of implantation failure in the diabetes plus ethanol groups and insulin control group. Ethanol injection on GD 7 accentuated diabetes-related embryonic resorption and intrauterine growth retardation (IUGR). This effect was less marked in the diabetic group treated with ethanol on GD 8. Diabetes alone produced a greater incidence of IUGR than ethanol alone. Midfacial hypoplasia and minor anomalies were found more frequently in the combination treatment groups. Holoprosencephaly and thymus hypoplasia observed in diabetic groups were found to be reduced in frequency in the diabetes plus ethanol groups, suggesting an antagonistic type of ethanol-diabetes interaction, stage-dependently. Since severely malformed embryos are known to be resorbed/killed in utero in mice, this reduction might reflect the magnitude of early death of severely malformed embryos. These data suggest that the interaction effects are possibly related to alterations in fundamental developmental processes of early embryos.     

Stimulation of mutations suppressing the loss of replication control by small alcohols

Transient exposure of lysogenic Escherichia coli cells to small alcohols stimulated the frequency of mutations suppressing the lethal loss of replication control from a prophage fragment of bacteriophage lambda. The stimulation in mutation frequency paralleled the effect of mutagenic agents, and in this sense the alcohols behaved as mutagens. 10-min treatments above distinct threshold concentrations at 23%, 18%, 10% and 4% (v/v) were required in order for methanol, ethanol, isopropanol and propanol to evoke mutagenic effects. The selected mutant cells were, in general, equally or more sensitive to ethanol than the starting cells. The mutagenicity of methanol and ethanol was detected only with E. coli strains with lambda fragments that included the site-specific and general recombination genes found within the phage int-kil gene interval; whereas, stimulation of the frequency of phenotypically identical mutations by nitrosoguanidine or ionizing radiation did not require that the lambda fragment encode these genes. Treatments of lysogenic cells with mutagenic concentrations of ethanol did not trigger prophage induction and were concluded not to induce a cellular SOS response nor to denature the prophage repressor, or to disrupt repressor-operator binding. The toxicity of ethanol was pH-dependent. Cellular sensitivity to ethanol toxicity was unaffected by the integrated lambda fragment(s) or by an intact lambda prophage; but, it was increased by deletions of the E. coli chromosome extending rightward from bio into uvrB, and rightward from chlA.