Heat shock protein induction in the freshwater prawn Macrobrachium malcolmsonii: acclimation-influenced variations in the induction temperatures for Hsp70

The intracellular build-up of thermally damaged proteins following exposure to heat stress results in the synthesis of heat shock proteins (Hsps). In the present study, the upper thermal tolerance and expression of heat shock protein 70 (Hsp70) were examined in juveniles of the freshwater prawn Macrobrachium malcolmsonii that had been acclimated at two different temperatures, i.e. 20 degrees C (group A) and 30 degrees C (group B), in the laboratory for 30 days. Upper thermal tolerance was determined by a standard method. For heat-shock experiments, prawns in groups A and B were exposed to various elevated temperatures for 3 h each, followed by 1 h recovery at the acclimation temperature. Endogenous levels of Hsp70 were determined in the gill, heart, hepatopancreas and skeletal muscle tissues by Western blotting analysis of one dimensional sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). The critical thermal maximum (CT max) for prawns in groups A and B was 37.7+/-0.27 degrees C and 41.41+/-0.16 degrees C, respectively. In general, Western blotting analysis for Hsp70 revealed one band at the 70 kDa region, containing both constitutive (Hsc70) and inducible (Hsp70) isoforms, in the gill and heart tissues; these were not detected in the hepatopancreas and skeletal muscle tissues. The onset temperature for Hsp70 induction in both gill and heart tissues was 30 degrees C for prawns in group A and 34 degrees C for those in group B. The optimum induction temperatures (at which Hsp70 induction was maximum) were found to be 34 degrees C and 32 degrees C, respectively, in the gill and heart tissues of group A prawns, and 38 degrees C and 36 degrees C, respectively, for group B prawns. These results suggest that the temperature at which acclimation occurs influences both upper thermal tolerance and Hsp70 induction in M. malcolmsonii.     

Parasitism capacity of Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae) reared under different temperatures on Bonagota salubricola (Meyrick) (Lepidoptera: Tortricidae) eggs

The parasitism capacity of Trichogramma pretiosum Riley strain bonagota on Bonagota salubricola (Meyrick) eggs was studied under the temperatures of 18, 20, 22, 25, 28, 30 and 32 degrees C. The number of days with parasitism, accumulated parasitism, total number of eggs parasitized per female and parasitoid longevity was evaluated. In the first 24h, parasitism ranged from 1.6 (32 degrees C) to 8.8 (22 degrees C) eggs of B. salubricola. Accumulated egg parasitism of B. salubricola reached 80% in 1st to 4th day at 20 degrees C to 32 degrees C, respectively, and in the 7th day at 18 degrees C. Temperatures from 18 degrees C to 22 degrees C were the best suited for the total eggs parasitized for female, resulting in 35.4 and 24.6 eggs/male respectively. T. pretiosum female longevity ranged from 7.8 to 2.5 days, at 18 degrees C and 32 degrees C, respectively. The results showed that T. pretiosum strain bonagota is better adapted to temperatures from 18 degrees C to 22 degrees C.     

Effects of acclimation temperature on the growth of Perna viridis (Bivalvia: Mytilidae), using the RNA/DNA ratio

Temperature affects growth rate in aquatic organisms. This can be evaluated in short term using biochemical indexes (RNA/DNA and Protein/DNA). The effect of acclimatization temperature on the instantaneous growth and physiological condition of Perna viridis was studied in organisms collected in La Esmeralda, Sucre State (Venezuela) and taken to the laboratory, where groups of 100 organisms (size 3.0 - 3.5 cm, anteroposterior measurement) were acclimatized at 15, 20, 26 or 28 degrees C during four weeks. Later they were kept in a 60 liters aquarium for another six weeks under the same conditions. Each week, ten organisms per group were extracted to measure concentrations of RNA, DNA (by a fluorometric method with ethidium bromide) and proteins (by a colorimetric method), in tissues (digestive gland, adductor muscle and gills). Protein concentration was greater and highly significant at 15 degrees C for all studied tissues. The opposite was obtained with the RNA/DNA and Protein/DNA ratios: the greatest increase was observed at the highest temperature (28 degrees C) for all tissues. At the lowest temperature there was a tendency to reduce both indexes with time. Greater instantaneous growth can be expected at higher temperatures and 28 degrees C was optimal for growth in these specimens.     

Alteration of environmental salinity modulates atrial natriuretic peptide concentrations in the gills of the oyster,Crassostrea virginica

Because gills are frequently important in ion transport and osmoregulation, the present investigation was designed to determine if atrial natriuretic peptides (putative osmoregulatory peptides) are present within the gills of a representative euryhaline osmoconforming invertebrate. Utilizing three radioimmunoassays devised to amino acids 1–30, 31–67, and 99–126 of the 126 amino acid prohormone, the gills of 72 eastern oysters, Crassostrea virginica were examined and each found to contain atrial natriuretic peptides, whose content was approximately one-seventh of that within the heart of the oyster. In high salinity (32 parts per thousand, ppt) the content of atrial natriuretic peptides recognized by each of the three radioimmunoassays was lower at 3 days (P < 0.005) and then became higher (P < 0.001) compared with their content in medium salinity (21 and/or 27 ppt). The content of atrial natriuretic peptides within gills in a low salinity environment (8 ppt) was significantly lower (P < 0.05) at 3, 7, and 14 days compared with their content in either medium or high salinity environments. We conclude that atrial natriuretic peptides are present within the gill tissues of Crassostrea virginica and that their content changes with alterations in environmental salinity. Their lower content at 3 days in high salinity implies a release of stored natriuretic-like peptides that are re-synthesized by 1 week. The decreased content of atrial natriuretic peptides at 3 days, 1 and 2 weeks in low salinity versus medium or high salinity environments suggests that their synthesis is decreased when exposed to a lower salinity in the environment.     

Study of perkinsosis in the carpet shell clam Tapes decussatus in Galicia (NW Spain). I. Identification of the aetiological agent and in vitro modulation of zoosporulation by temperature and salinity

Morphological characters of zoosporulation stages and DNA sequence of the internal transcribed spacer (ITS) region and the small subunit ribosomal RNA (SSU rRNA) gene confirmed that the aetiological agent of perkinsosis in the clam Tapes decussatus from Galicia (NW Spain) was Perkinsus atlanticus Azevedo, 1989. In vitro modulation by temperature and salinity of the zoosporulation of the parasite was studied. The optimum temperature range for zoosporulation was 19 to 28 degrees C. The temperature range allowing zoosporulation in vitro was 15 to 32 degrees C, which is broader than previously reported (24 to 28 degrees C) for P. atlanticus, and strongly suggests that zoospores can be produced in Galician Rias, where temperature ranges from 10 to 22 degrees C. Prezoosporangia held at 10 degrees C for 2 mo (similar to winter conditions in Galician waters) gave rise to viable zoospores after they were transferred to higher temperatures. This suggests that prezoosporangia could overwinter and zoosporulate in the next spring. Zoospores could survive for up to 22 and 14 d at 28 and 10 degrees C, respectively. The optimum salinity range for zooporulation was 25 to 35 per thousand. Zoospore production was abruptly reduced as salinity decreased. The lowest salinity at which zoosporulation was observed was 10 per thousand. The effectiveness of different chlorine concentrations and exposure lengths to kill prezoosporangia and zoospores was tested. No survival of free zoospores, free prezoosporangia and prezoosporangia included in gill tissue was observed after incubation for 1 h with 50, 200 and 3,000 ppm of chlorine, respectively.     

Effects of water temperature and salinity on elimination of Salmonella charity and Escherichia coli from Sydney rock oysters (Crassostrea commercialis)

The elimination of Salmonella charity and Escherichia coli from the Sydney rock oyster, Crassostrea commercialis, was examined during commercial purification of oysters under different water temperatures and salinities. Both organisms were rapidly eliminated at 18 to 22 degrees C. Purification was effective but slower at 24 to 27 degrees C and incomplete and inconsistent at temperatures below 17 degrees C. The oysters suffered stress and were not effectively purified at water salinities of 15 to 20% but were rapidly purified at 32 to 47% salinity. Winter-harvested and summer-harvested oysters were purified similarly in water at 18 to 22 degrees C and 32 to 36% salinity.     

Effects of water temperature and salinity on elimination of Salmonella charity and Escherichia coli from Sydney rock oysters (Crassostrea commercialis).

The elimination of Salmonella charity and Escherichia coli from the Sydney rock oyster, Crassostrea commercialis, was examined during commercial purification of oysters under different water temperatures and salinities. Both organisms were rapidly eliminated at 18 to 22 degrees C. Purification was effective but slower at 24 to 27 degrees C and incomplete and inconsistent at temperatures below 17 degrees C. The oysters suffered stress and were not effectively purified at water salinities of 15 to 20% but were rapidly purified at 32 to 47% salinity. Winter-harvested and summer-harvested oysters were purified similarly in water at 18 to 22 degrees C and 32 to 36% salinity.     

Influence of temperature on the development, reproduction and longevity of Ceratothripoides claratris (Thysanoptera: Thripidae) on tomatoes

Ceratothripoides claratris (Shumsher) is a serious pest attacking tomatoes in Thailand. Temperature-dependent development of C. claratris was studied at seven constant temperatures, i.e. 22, 25, 27, 30, 34, 35 and 40 degrees C. Pre-adult survivorship was greatest (95%) at 25 and 30 degrees C and shortest at 22 degrees C. Egg-to-adult time decreased within the range of 20 to 30 degrees C and at 34 degrees C it started to increase. The lower thermal threshold for egg-to-adult development was estimated at 16 and 18 degrees C by linear regression and the modified Logan model, respectively. The optimum temperature for egg-to-adult development was estimated at 32-33 degrees C by the modified Logan model. The influence of temperature on reproduction and longevity of C. claratris was determined at 25, 30 and 35 and 40 degrees C. Both inseminated and virgin females failed to reproduce at 40 degrees C. Virgin females produced only male offspring, confirming arrhenotoky. The sex ratio of the offspring of fertilized females was strongly female-biased, except at 25 degrees C. Mean total fecundity per female and mean daily total fecundity per female were highest for both virgin and inseminated females at 30 degrees C. Female longevity was longest at 25 degrees C and shortest at 40 degrees C. Male longevity was longest at 30 degrees C and shortest at 40 degrees C. The net reproductive rate (R0) and intrinsic rate of natural increase (rm) was greatest at 30 degrees C while, mean generation time (G) and the doubling time (t) were highest at 25 degrees C. The finite rate of increase (lambda) was fairly constant (1.1-1.5 days) over the three temperatures tested. The pest potential of C. claratris for tropical Asia is discussed.     

Hsp70 expression in thermally stressed Ostrea edulis,a commercially important oyster in Europe

Synthesis of heat shock proteins (Hsps) in response to elevated temperatures and other denaturing agents is a common feature of prokaryotic and eukaryotic cells. The heat-induced expression of Hsp70 family members in the gills and mantle of Ostrea edulis, a highly valued fisheries resource inhabiting primarily estuarine environments, has been studied. O edulis is exposed to a variety of natural and anthropogenic stresses in the environment. Two isoforms of about 72 kDa and 77 kDa were constitutively present in unstressed organisms, reflecting the housekeeping function performed by these proteins under normal circumstances. Their expression in animals undergoing thermal stress was highly variable, and on the average, little change occurred under different experimental conditions. A third isoform of about 69 kDa was induced in both tissues after exposure to > or = 32 degrees C; its synthesis was detected within 4 hours of poststress recovery at 15 degrees C, reaching the maximum expression after 24 hours in the gills and after 48 hours in the mantle and declining thereafter. Hsp69 expression was low at 38 degrees C, a temperature lethal for about 50% of the individuals tested. Densitometric analysis of Western blots revealed that Hsp69 was mostly responsible for the significant heat-induced overexpression of Hsp70s in O edulis. Comparison with heat shock responses in tissues of Crassostrea gigas indicated a similar pattern of Hsp70 expression. In this organism, however, Hsp69 was induced after exposure to > or = 38 degrees C. We conclude that tissue expression of Hsp69 in O edulis, and possibly other bivalves, is an early sign of thermal stress; determining whether these changes also correlate with other major environmental stresses is the goal of ongoing studies.     

Biology, thermal requirements and fertility life table of the broad mite Polyphagotarsonemus latus (Banks) (Acari: Tarsonemidae) in grape (Vitis vinifera L.) cv. Italia

The mite Polyphagotarsonemus latus (Banks) constitutes one of the main pest of grape crop at the Submédio S?o Francisco Valley. The objective of this work was to study the biology of the broad mite Polyphagotarsonemus latus (Banks), to determine its thermal requirements and its fertility life table in grape (Vitis vinifera L.) cv. Italy. Acclimatized chambers (BOD) were used, adjusted to the temperatures of 18, 22, 25, 28 and 32 degrees C, relative humidity of 65 +/- 10% and alternated light of 12h. Egg-adult period was 3.4 and 6.8 days for males and 3.5 and 7.4 days for females, respectively at 32 degrees C and 18 degrees C. At the temperatures of 18, 25 and 32 degrees C, each female deposited, respectively, 16.5, 44.3 and 13.3 eggs. The stages of egg, larva and pupa and egg-adult period presented, respectively, thermal thresholds of 11.23, 9.45, 12.19, and 9.71 degrees C and thermal constant of 28.51, 14.59, 8.33, and 62.73 degrees-day. The mean duration of one generation (T) was 25.6, 10.8 and 8.2 days, respectively, at the temperatures of 18, 25 and 32 degrees C. The net reproductive rate (R0) at the temperature of 25 degrees C was the highest, corresponding to an increase of 30.12 times at each generation. The intrinsic rate of population increase (rm) was 0.10 (18 degrees C), 0.31 (25 degrees C) and 0.12 (32 degrees C) and the finite ratio of population increase (lambda) was 1.10 (18 degrees C), 1.36 (25 degrees C) and 1.13 (32 degrees C). According to the mean temperature values, P. latus can have 95 and 99 generations/year, respectively, for the municipal districts of Petrolina, PE and Juazeiro, BA.     

Effects of temperature and salinity on nitrogenous excretion by Litopenaeus vannamei juveniles

Excretion rates of ammonia-N, nitrite-N, nitrate-N, and dissolved organic nitrogen (DON) for juvenile Litopenaeus vannamei (3.85+/-0.83 g) were quantified in response to nine different combinations of temperature (24, 28, and 32 degrees C) and salinity (10, 25, and 40 ppt) under laboratory conditions. Results indicated that L. vannamei is ammonotelic, with ammonia-N accounting for 61.9-84.3% of total nitrogen (TN) excretion. There were significant effects of temperature and salinity, but no significant interaction between them, on ammonia-N excretion rate (R(AN)). R(AN) increased with increasing temperature, over the interval 24-32 degrees C. R(AN) was lower at 25 ppt than at 10 and 40 ppt, at all temperatures. DON excretion rate (R(DON)) was not significantly influenced by either temperature or salinity; the overall mean R(DON) was about 5.24 μg-N g -1 h -1. However, the percentages of DON in TN (P(DON)) varied from 15.4 to 36.4% under the various temperature-salinity combinations. P(DON) at 28 and 32 degrees C was significantly lower than at 24 degrees C, and P(DON) at 10 ppt was significantly lower than at 25 and 40 ppt. Only very small amounts of nitrogen were excreted by L. vannamei as nitrite-N and nitrate-N.     

Change in lipid composition in eastern oyster (Crassostrea virginica Gmelin) exposed to constant or fluctuating temperature regimes

A temperature decrease usually induces an ordering effect in membrane phospholipids that can lead to membrane dysfunction. Ectotherms typically counteract this temperature effect by remodeling membrane lipids as stipulated in the homeoviscous adaptation theory (HVA). Previous studies mostly focused on the remodeling of membrane lipids during long-term acclimatization or acclimation at constant temperature regimes, whereas in nature, many organisms experience variations in temperature on a daily basis and must react to this changing thermal environment. The objective of this study was to examine the composition of membrane lipids in oysters subjected to long-term acclimation at constant temperatures (12 or 25 degrees C) or to environmentally realistic daily fluctuations in temperature between 12 and 25 degrees C for 7 d. The lipid composition of gill in oysters subjected to long-term acclimation at a constant temperature or to daily temperature fluctuations varied in a way consistent with HVA: oysters adjusted their phospholipid to sterol ratio in response to long-term acclimation to a constant temperature but not to daily temperature fluctuations. In contrast, the unsaturation index of polar lipids in oysters varied in response to both long-term acclimation to a constant temperature and to daily temperature fluctuations, mainly due to changes in 22:6n-3 and 20:5n-3. The 20:4n-6 levels in oyster gills increased as temperature rose, suggesting an increasing availability of this fatty acid for eicosanoid biosynthesis during stress responses.     

Effect of adrenaline, glucagon and insulin on glucose metabolism in carp: influence of temperature]

In carps living since 4 months at 6, 20 or 30 degrees C, epinephrine or glucagon injections produce increase in plasma glucose but affect only slightly liver glycogen: lower is the temperature, slower and longer are the effect. Insulin injection induces more or less delayed hypoglycaemia according to temperature acclimatization; decrease in blood glucose is accompanied by a slight increase of glycogen in all tissues at 6 degrees C and on the contrary by a very strong depletion of this polysaccharide in liver and even heart at 20 and 30 degrees C.     

Biology and thermal requirements of Trichogramma atopovirilia Oatman & Platner (Hymenoptera: Trichogrammatidae) parasitizing eggs of Diaphania hyalinata L. (Lepidoptera: Pyralidae)

The development and parasitism of Diaphania hyalinata L. eggs by Trichogramma atopovirilia Oatman & Platner and its thermal requirements were studied at the temperatures of 18, 21, 24, 27, 30 and 33 degrees C. Thirty eggs of D. hyalinata were exposed to three females of T. atopovirilia for 5h at 25 degrees C and incubated at the different temperatures. The developmental time from egg exposure to adult, parasitism viability, number of adults per parasitized host egg and progeny sex ratio were monitored. The developmental time from egg to adult emergence of the parasitoid exhibited inverse relationship to the temperature, lasting 24.12 days at 18 degrees C and 7.36 days at 33 degrees C. Parasitism viability at 24, 27 and 30 degrees C was higher than 90%. The ratio of T. atapovirilia adult produced per egg and its sex ratio were not affected when using D. hialynata as host. The lowest threshold temperature (Tb) and estimated degree-days over Tb required by T. atopovirilia to develop on eggs of D. hyalinata was 11.99 degrees C and 130.42 masculine C, respectively. Considering the temperature regimes of two areas where cucurbitaces are cultivated in Bahia State (Rio Real and Inhambupe County) it was estimated that T. atopovirilia can achieve more than 32 generation per year. The results suggest that T. atopovirilia has potential to control D. hyalinata eggs with better chance of success under temperature regimes ranging from 24 to 27 degrees C that meets the suitable field conditions for cropping cucurbitaces.     

Thermal acclimatization of hepatic polysubstrate monooxygenase and UDP-glucuronosyltransferase of mature rainbow trout (Salmo gairdneri)

The thermal acclimatization of hepatic cytochrome P-450-dependent polysubstrate monooxygenase (PSMO) and UDP-glucuronosyltransferase of mature rainbow trout (Salmo gairdneri) was studied. The results indicate that the PSMO system, 7-ethoxycoumarin and benzo(a)pyrene as substrates, shows almost ideal acclimatization pattern in autumn during water cooling. The enzyme activities were identical if measurements were carried out at acclimatization (=environmental) temperatures which were 20 degrees C in August and 5 degrees C in November. If a constant incubation temperature (18 degrees C) was used, the PSMO activities were significantly higher in cold (5 degrees C)-acclimatized fish. The acclimatization process could be seen both in specific and total activities. The content of cytochrome P-450 remains at constant level from August to November. In early summer during water warming the PSMO activities increased considerably in both sexes in all incubation conditions. The specific and total UDP-glucuronosyltransferase activities were significantly higher in warm-acclimatized fish both in the autumn and in the spring if the activities were measured at environmental temperature. No differences could be detected if the measurements were carried out at constant experimental temperature (18 degrees C).     

Studies on the toxicity of lindane on Colisa fasciatus (part I: TLm measurements and histopathological changes in certain tissues).

1. In the present investigation static bioassay studies and histopathological changes in some tissues (gills, liver and kidney) induced by Lindane 20% E.C. in the fish Colisa fasciatus have been taken under consideration. 2. With the help of bioassay studies, the TLm were noted. The TLm values were 0.87, 0.78, 0.68 and 0.64 mg/l for the temperature range 17 degrees C to 20 degrees C and 0.60, 0.56, 0.46 and 0.41 mg/l for the temperature range 32 degrees C to 35 degrees C at 12, 24, 48 and 96 h respectively. 3. The statistical analysis of different factors such as concentrations, time and temperature range based on the observed data gave the following results: a) At both temperature ranges, survival rates at different concentrations and time are significant at 1% and 5% level. b) The difference in survival rates at different temperature range are insignificant both at 1% and 5pected survival numbers. The standard errors were also calculated for these two lines which gave the insignificant results and there was no much change in the shape of experimental and expected lines. 4. The histopathological changes in the tissues (gills, liver and kidney) shows the following results: a) In the case of the gills there was a loss of different types of cells i.e. respiratory cells and blood cells. Blood vessels were atrophied and the outer membrane of gill lamellae was ruptured. The erosion of the tips of the gill filaments were also observed. b) In the case of liver the outer membrane was ruptured. Some hepatic cells were vacuolated and some completely degenerated. The central areas were much affected. Due to the toxic effect, large splitting of tissues were found inside the liver. c) In the case of kidney the outer epithelium, the parenchymatous cells of renal tubules, cuboidal cells of uriniferous tubules were much affected. Due to the degeneration of the cells large spaces were formed inside the tissue. Much affection was observed in the central areas.     

Salinity affects growth but not thermal preference of adult mummichogs Fundulus heteroclitus

The effects of an ecologically relevant range of salinities (2, 12, 22, 32) on thermal preferences and growth of adult mummichogs Fundulus heteroclitus were determined for fish from a southern Chesapeake Bay population. Salinity did not affect the mean temperature selected by F. heteroclitus in a thermal gradient, which was identified as 26.6°C based on observations of 240 individuals. Salinity and temperature had significant and interacting effects on growth rates of F. heteroclitus measured over 12 weeks. Growth rates were highest overall and remained high over a broader range of temperatures at moderate salinities (12 and 22), while high growth rates were shifted toward lower temperatures for fish grown at a salinity of 2 and higher temperatures at a salinity of 32. Significant reductions in growth relative to the optimal conditions (28.6°C, salinity of 22) were observed at the coolest (19.6°C) and warmest (33.6°C) temperature tested at all salinities, as well as temperatures ≥ 26.6°C at a salinity of 2, ≥ 28.6°C at a salinity of 12 and ≤ 26.6°C at a salinity of 32. Growth rates provide a long-term, organismal measure of performance and results of this study indicate that performance may be reduced under conditions that the highly euryhaline F. heteroclitus can otherwise easily tolerate. The combination of reduced salinity and increased temperature that is predicted for temperate estuaries as a result of climate change may have negative effects on growth of this ecologically important species.     

Modification of Resistance Expression of Phaseolus vulgaris to Meloidogyne incognita by Elevated Soil Temperatures

The effect of temperature on the reaction of susceptible (Canario Divex) and resistant (A 211) bean pure lines to Meloidogyne incognita was studied with soil temperature tanks housed in a growth chamber at 22 or 24 C. Soil temperature remained constant at 16, 22, 24, 26, 30, or 32 C in several trials. Bean line A 211 was resistant at 16 and 22 C but was susceptible at 24 C and above. Resistance to root-knot nematode reproduction was affected by a lower temperature (24 C) than was resistance to root galling (26 C) in A 211. Incubation of A 211 at 30 C for 3 and 16 days after inoculation with M. incognita resulted in a significant increase in nematode reproduction and root galling, respectively. The resistant reactions of A 211 to nematode reproduction and root galling were retained when inoculated plants were incubated at 21 C for a minimum of 16 and 23 days, respectively, prior to high temperature treatment.     

Effects in mice of high and low environmental temperature on the maternal and fetal toxicity of 2-sec-butyl-4,6-dinitrophenol (dinoseb) and on disposition of [14C]-dinoseb(12).

Swiss-Webster female mice were treated with 2-sec-butyl-4,6-dinitrophenol (dinoseb) and maintained in an increased environmental temperature (32 degrees C) for 24 h or a decreased temperature (0-6 degrees C) for 1.5-4 h. In two experiemtns animals maintained at low temperature were kept wet during the cold exposure, to enhance the reduction in body temperature, by rinsing them with water at approximately 30 min intervals. Results from nonpregnant females indicated that increased temperature lowered the LD50 for single injections of dinoseb from 20.2 to 14.1 mg/kg and that reduced temperature for 4 h had no effect on the LD50. A 24 h exposure to 32 degrees C enhanced the effect of 3 daily dinoseb treatments of pregnant mice; it increased maternal mortality, decreased fetal body weight, and increased frequency of fetal anomalies. Fetal body weight and the frequency of malformations were the same in groups exposed to low temperature and maintained at room temperature. Disposition of [14 C] dinoseb was also determined in nonpregnant mice exposed to temperatures of 0, 24, and 32 degrees C. The periods of environmental temperature studied (3-24 h) had no effect on the rate of disappearance of dinoseb from plasma or other tissues examined.