Agar Diet Research Articles

Effect of Probiotic Adult Diets on Fitness Components of Sterile Male Mediterranean Fruit Flies (Diptera: Tephritidae) Under Laboratory and Field Cage Conditions

The aim of the current study was to investigate the effect of probiotic adult diets, i.e., adult diets containing viable symbiotic intestinal bacteria, on the pheromone-calling activity, mating success, life expectancy, and survival of mass-reared male Mediterranean fruit flies, Ceratitis capitata (Wiedemann), as an avenue for improving the field performance of sterile males in release programs to eradicate, suppress, or prevent spread of wild populations. The effect of inoculation of two standard adult diets (sugar-yeast granulate [SY] and sugar agar [s]) and two experimental formulations (yeast-reduced granulate [Sy] and yeast-enhanced sugar agar [sy]) with Enterobacter agglomerans and Klebsiella pneumoniae (typically occurring in the gut of wild flies) on the different fitness components was assessed in the laboratory and on field-caged host trees. We found that, in the laboratory, males reared on the probiotic yeast-enhanced agar, sy, had a significant mating advantage over competitors fed the standard s agar (probiotic and control) or noninoculated sy agar; no effect of probiotic enrichment (or lowering the yeast content) was found with the granular diets. Mating test results obtained in the field were inconsistent with laboratory data in that no differences in the numbers of matings were observed between males reared on any of the probiotic and control agar diets (or the SY granulate), whereas males feeding on the probiotic modified granulate, Sy, scored significantly more matings than their control competitors. The pheromone-calling activity of males maintained on the granular diets was not affected by probiotic enrichment on any of the seven observation days. Agar-fed males, however, "called" more frequently on days 6 and 7 (but not on days 1-5) when their diet contained the probiotic load. Laboratory survival of granulate-fed males was found to be significantly prolonged with probiotic inoculation and lowering the yeast content of the standard SY granulate (but not with probiotic inoculation of sy). Similarly, males reared on the probiotic and control modified agars (sy) survived significantly longer than those feeding on the standard s agars (inoculated and control). Again, the results obtained in the field were inconsistent, because no differences between treated and control males were found for any of the diets. The findings are discussed in the light of other published studies on adult nutrition and behavioral ecology in C. capitata.

Effects of supplementation of coated crystalline amino acids on growth performance and body composition of juvenile kuruma shrimp Marsupenaeus japonicus

Supplementation of crystalline amino acids (CAA) in shrimp diets is unsuccessful in most cases. In the present study, various pre-coated CAA were developed to minimize the leaching losses from diets in water and assessed using kuruma shrimp Marsupenaeus japonicus juveniles. Experimental diets were supplemented with coated CAA or non-coated CAA to simulate the dietary amino acid profile to that found in the whole body protein of shrimp. The four diets contained CAA coated with either carboxymethyl cellulose (CMC) (diet 1), zein (diet 2), k-carrageenan (diet 3) or agar (diet 4), respectively. Another four diets contained CMC-coated CAA with the addition of either zein (diet 5), casein-gelatin (diet 6), zein and k-carrageenan (diet 7), or casein-gelatin and k-carrageenan (diet 8), respectively. The 8 weeks feeding trial demonstrated that the diets containing coated CAA gave significantly higher weight gains than diets containing non-coated CAA, with the highest value for the diet 6. The diets containing coated CAA also yielded higher feed conversion efficiency, protein efficiency ratio, and specific growth rate than diets containing non-coated CAA. Leaching trials suggested that shrimp growth performance was improved partly due to the retardation or reduction of CAA leaching by coating them with specific binders.

Adult Reproductive Capacity of <I>Ceratitis</I> c<I>apitata</I> (Diptera: Tephritidae) on a Chemically Defined Diet

Abstract A chemically defined diet (Ceratitis capitata #2 diet) for rearing adult Ceratitis capitata (Wiedemann), the Mediterranean fruit fly, was developed by adding vitamin B12 0.024 mg, ascorbic acid phosphate (vitamin C) 3.68 mg, vitamin D 12 mg, vitamin E 8.16 mg, inositol 243 mg, choline chloride 120 mg, cholesterol 40 mg, nicotinic acid 1.64 mg, sugar 6 g, agar 400 mg, and water 7 ml to each 50 g meridic larval diet (C. capitata #1). The C. capitata #2 diet was prepared in two forms, agar and liquid and both showed comparable performance to the standard diet but the agar diet is considered to be the best diet tested. Adults reared on the agar diet produced more eggs than those on a protein hydrolysate-sugar (1:3) diet. Flies fed on diets lacking nutrient groups, such as the 10 essential amino acids, eight nonessential amino acids or the combination of cholesterol, inositol, and choline, produced fewer eggs. Those fed on the diet without the 14 vitamins, cholesterol, inositol, or choline produced a ...

Baseline susceptibility to imidacloprid and cross resistance patterns in Colorado potato beetle (Coleoptera: Chrysomelidae) populations.

During 1995-1998, we tested 134 geographically discrete populations of Colorado potato beetle, Leptinotarsa decemlineata (Say), from the United States, Canada, Germany, France, and Poland for susceptibility to imidacloprid. Neonates were assayed on potato-based agar diet incorporated with imidacloprid and exposed on filter paper to esfenvalerate, azinphosmethyl, and carbofuran to characterize cross-resistance. In all 4 yr, Long Island populations were the most tolerant to imidacloprid, with LC50s ranging up to 29 times higher than the most susceptible populations. Responses to imidacloprid did not change significantly on farms where populations were assayed over time, except for those from Long Island, which doubled in overall tolerance to imidacloprid since 1995. Much of this tolerance was already present before imidacloprid was used on Long Island. Correlative analysis of the populations tested over the 4 yr indicated positive cross-resistance patterns with esfenvalerate and azinphosmethyl. This response was probably caused by preexisting metabolic and excretion mechanisms selected by previous exposure. There was no significant pattern of cross-resistance with carbofuran or bensultap. Regression slopes were also significantly negatively correlated with LC50 values for imidacloprid, indicating higher heterogeneity, which could lead in further resistance development. We discuss the relative sensitivity of diet-incorporated assays with neonates compared with other bioassay studies. Based on a pooled group of susceptible populations tested in 1995, a baseline LC50 of 0.39 ppm and a discriminating concentration of 8 ppm were suggested to detect early stages of resistance in "suspect" populations. We also suggest application strategies for imidacloprid that reduce selection pressure.

Effects of Terpenes and Phenolic and Flavonoid Glycosides from Douglas Fir on Western Spruce Budworm Larval Growth, Pupal Weight, and Adult Weight

Monoterpenes, sesquiterpenes, and phenolic and flavonoid glycosides typical of the current year's foliage of Douglas fir (Pseudotsuga menziesii) were bioassayed using agar diets to determine the effect of these compounds on natural and colony populations of western spruce budworm (Choristoneura occidentalis). Several terpenes adversely affected budworm larval growth, supporting previous field and laboratory studies. However, larvae collected from a population in southeastern Idaho were significantly more tolerant of the monoterpenes than those from a Montana population. For the Montana population, agar diet studies showed that camphene, myrcene, terpinolene, bornyl acetate, and tricyclene adversely affected larval growth rate and pupal weight. For the Idaho population, agar diet studies showed that only terpinolene and bornyl acetate adversely affected larval growth and pupal weights. For both populations bornyl acetate was the most toxic, and this compound in addition to other monoterpenes represent defensive mechanisms in the current year's growth of Douglas fir. Sesquiterpene and phenolic-flavonoid glycoside fractions extracted from Douglas fir current year's growth also were bioassayed using agar diets. The sesquiterpene fraction showed a significant negative effect on budworm larval growth, but phenolics and flavonoid glycosides had no effect. Sesquiterpenes, in combination with tricyclene, camphene, myrcene, limonene, terpinolene, and the acetate fraction appear to represent an effective mixture of defensive compounds against the budworm.

Sodium polyacrylamide polyacrylate, a gelling agent in diets for cabbage looper, omnivorous looper and western avocado leafroller

AbstractIngredient substitutions for agar or carrageenan in artificial diets for lepidopterous larvae were evaluated. A sodium polyacrylamide polyacrylate gelling agent, Water‐Lock G‐400, was compared with agar for solidifying diets of the cabbage looper, Trichoplusia ni (Hübner), omnivorous looper, Sabulodes aegrotata (Gueneé), and the western avocado leafroller, Amorbia cuneana Walsingham. Water‐Lock G‐400 is considerably less expensive than agar or carrageenan, it does not require heating to gel, and it is made from a dependable supply of agricultural starch.Sabulodes aegrotata pupae from larvae reared on agar were significantly heavier than those reared on Water‐Lock G‐400. However, the remainder of the variables observed (larval survival, developmental times, fecundity, sex ratio and pupal weights for A. cuneana and T. ni) were all independent of diet. Decreasing the total amount of ingredients in a Water‐Lock‐G‐400 diet produced fewer and smaller T. ni pupae than did an agar diet when the larvae were reared using a mass production protocol. However, these lower values were still above acceptable levels for mass production and reduced the cost of diet production by 65%.Further ingredient substitutions impaired larval development (i.e., replacing pinto beans with soy protein or combinations of soy protein and α‐cellulose), while others did not (i.e., excluding pinto beans and reducing water content and replacing pinto beans with α‐ cellulose or corn cob grits). Moisture control by adding corn cob grits to diets increased the yield of pupae, while removing water from diets increased survivorship and the yield of pupae.

Inheritance of Random Amplified Polymorphic DNA Markers in Anastrepha suspensa (Diptera: Tephritidae)

Two full-sibling families of the Caribbean fruit fly, Anastrepha suspensa (Loew), were produced by controlled mating from the USDA–ARS colonies located at Miami, FL. One family was produced from a colony population reared on a corncob diet as larvae. The other family was produced from a colony population reared on an agar diet as larvae. Colonies originated from a common source but each had been maintained as an isolated population for >800 generations. DNA was extracted from both parents and 36 full-sibling progeny from both families. Sixty-three random amplified polymorphic DNA (RAPD) primers were screened using DNA from the 4 parental flies and 97% (61) produced amplification products. Six polymorphic primers were selected for the analysis. These 6 primers amplified 127. bands in both the corncob and the agar flies; of these, 87 and 77 bands were analyzed in the corncob and agar flies, respectively. In the corncob flies, 55.2% of the analyzed loci were polymorphic: 49.4% were polymorphic in the agar flies. Both 1:1 and 3:1 segregation ratios of polymorphic loci were observed with 24 and 28 loci segregating 1:1, and 13 and 9 loci segregating 3:1 in the corncob and agar flies, respectively. Most RAPD primers generated polymorphic bands that segregated as expected. This indicated that polymorphic RAPD bands are useful as genetic markers in Caribbean fruit fly. The markers are potentially useful for host and geographic population studies as they relate to quarantine issues.

Regulation of feeding behavior in adult Drosophila melanogaster varies with feeding regime and nutritional state.

The regulation of feeding behavior in adult Drosophila melanogaster includes such elements as ingestion responsiveness, volume ingested in a single meal, food storage in the crop and rate of defecation. Our results suggest that feeding behavior varies in a manner dependent on feeding regime (food-deprived or ad-libitum-fed) and nutritional state. Fed flies that are subsequently food-deprived become increasingly more responsive to food stimuli over time and, when offered 1% agar diets containing different concentrations of sucrose, ingest greater amounts of diets that have higher sucrose concentrations. When fed ad libitum for 72 h on these same diets, D. melanogaster maintained much smaller crops on average than food-deprived flies fed a single meal. Additionally, ad-libitum-fed flies are grouped into two categories depending on the concentration of sucrose in the diet. Flies fed for 72 h on 1% agar diets having 50 mmoll-1 sucrose or more are not affected by the concentration of sucrose in the diet, while flies fed on diets of 15 or 25 mmoll-1 sucrose increase ingestion responsiveness, crop size and the rate of defecation with decreasing concentrations of sucrose in the diet. Flies fed on even lower sucrose concentrations (5 or 10 mmoll-1 sucrose) for 27-72 h exhibit both a shift over time to larger crop sizes and increased mortality over those of flies fed 15 mmoll-1 sucrose. These data suggest that flies fed ad libitum are capable of modulating their feeding behavior in response to their nutritional state.

Nutrient digestibility and growth of hybrid tilapia, Oreochromis niloticus × O. aureus, as influenced by agar supplementation at two dietary protein levels

An experiment was conducted to study the influence of agar on nutrient digestibility and growth of fingerling tilapia at two dietary protein levels. Average initial body weight of the fish was 1.04±0.04 g. Fish were fed 3% of their body weight/day. Significantly ( P<0.05) lower body weight gain, feed efficiency ratio (FER), protein efficiency ratio (PER) and energy retention were observed in fish fed the agar diet at 35% dietary protein level. Higher body weight gain, FER and energy retention and lower PER were observed in fish fed 35% dietary protein either with or without agar supplementation than those fed a 24% protein diet. Lower carbohydrate and dry matter digestibility values were observed in fish fed the agar diet at both 35% and 24% protein levels. Higher carbohydrate digestibility was observed in fish fed a 24% protein diet with and without agar than those fed a 35% protein diet. These data suggest that the inclusion of 10% agar in the diet reduced growth of tilapia when dietary protein level was 35%. However, growth retardation of the fish was not observed by agar supplementation when the dietary protein level was low (24%).

Role of Douglas fir (Pseudotsuga menziesii) carbohydrates in resistance to budworm (Choristoneura occidentalis)

The current year's growth of Douglas fir contains galactose, unusual in that this carbohydrate makes up 78.7% of the total carbohydrate fraction. An agar diet study was undertaken to determine the effects of galactose, other carbohydrates, and terpenes on western spruce budworm larval mortality, growth rate, and adult biomas production. All concentrations of the carbohydrates and terpenes tested, as well as other mineral elements not tested, were typical of the current year's foliage of Douglas fir. In experiment I, the diet containing 5.61% total carbohydrate did not significantly affect larval mortality when compared to the control diet. However, diets containing 9.45% and 15% total carbohydrate concentrations significantly increased larval mortality 64% and 96.1%, respectively, when compared to the control. Also in experiment I, terpenes alone (78.9% morality) and terpenes in combination with 9.45% and 15% total carbohydrates significantly increased larval mortality (97.2% and 100%, respectively) when compared to mortality on the control diet (44%). To determine which carbohydrate was causing the adverse effect, 6% glucose, 6% fructose, and 6% galactose were placed individually and in combination with terpenes in diets in experiment II. The 6% galactose diet significantly increased larval mortality and reduced growth rate when compared to the control, glucose, and fructose diets. Glucose resulted in 16% less larval mortality, significantly enhanced female larval growth rate and pupal weight, but did not affect male larval growth rate and pupal weight, when compared to the control. Fructose resulted in a significant decrease in larval mortality and a general trend of enhanced female and male larval growth rate and pupal weight. Larval mortality on terpenes alone was not significantly different from the control, but terpenes with 6% galactose increased larval mortality and decreased female and male growth rate and pupal weight significantly when compared to glucose-terpene and fructose-terpene diets. No significant interactions were found between carbohydrates and terpenes in either experiment.

Effect of 37% Formalin Fumigation on Codling Moth Egg Hatch and On the Infectivity of Codling Moth Granulosis Virus, 1992

Abstract When rearing insects for experimental purposes, it is routine practice to treat eggs to assure that microbial pathogens and fungal spores are eliminated. Forty (40) ml of 37% (v/v) formalin (CH20) was placed into each of several one-quart, wide mouth canning jars. CM eggs (12 ± 12-h-old), oviposited on waxed paper, were exposed to CH20 by suspending them inside the jar and then sealing the jar with a ring and lid. Exposure times were 15, 30, 45, 60, 90, or 120 min at 21 ± 1°C. A control group which consisted of eggs suspended over 40 ml of water for 120 min at 21 ± 1°C was included. This test was replicated 3 times with 100 to 200 eggs per replication per time of exposure. To determine the effect on infectivity of CM granulosis virus (CMGV), we also fumigated, in the same manner, small vials (2.5 ml) containing 1 ml of CM agar diet (Bioserv #9370; surface area = 1 cm2) that had been surface-inoculated with 2 × 10s CMGV capsules (dose = 2 × 10" capsules/cm2). A control group of diet cups without CMGV was also fumigated. After fumigation each cup was infested with one CM larva (12 ± 12-h-old) and then held at 27 ± 1°C. Larval mortality was determined after 7 days. The test was replicated 2 times with 25 and 30 larvae, respectively.

Colonic cell growth and mucin degradation in rats fed diets containing various levels of beta-carotene with and without dietary agar

1. 1. To either an agar-containing diet or an agar-free diet, 0, 0.3 and 2.0 mg/100g of beta-carotene were incorporated and fed to groups of five rats for 28 days. 2. 2. Weight gain and food consumption of rats fed different dietary groups did not show a significant difference ( P > 0.05). 3. 3. Colon weight, colonie mucosal DNA and RNA were generally higher in rats fed agar diets than rats fed agar-free diets at either beta-carotene supplementation level. 4. 4. Mucinase activity was higher ( P < 0.05) in rats fed the agar diet than in rats fed an agar-free diet without beta-carotene. However, the difference was not observed ( P > 0.05) when beta-carotene was incorporated. 5. 5. These data suggest that colonie mucin degradation in rats fed an agar diet decreased when the dietary beta-carotene inclusion level increased.

Tolerance of Marine Invertebrate Herbivores to Brown Algal Phlorotannins in Temperate Australasia

Estes and Steinberg hypothesized that the intensity of sublittoral marine plant—herbivore interactions among different temperate regions has differed over the past 5—10 million yr, due to differences in the influence of diving mammals that prey on marine herbivores. They argued that because diving predators have not occurred in temperate Australasia, densities of sublittoral herbivores have been historically higher there than in comparable North American systems. This has resulted in marine algae and herbivores in temperate Australasia having strong selective effects on each other. Estes and Steinberg predicted that one result of these strong interactions would be that invertebrate herbivores in temperate Australasia should have evolved greater tolerance to brown algal phlorotannins (polyphenolic compounds that are the dominant secondary metabolites in temperate brown seaweeds) than similar herbivores in North America. We tested this prediction for five invertebrate herbivores in temperate Australasia. Most work was done on three herbivores from New South Wales, Australia, the sea urchins (echinoids) Tripneustes gratilla and Centrostephanus rodgersii, and the gastropod (snail) Turbo undulata. Additional experiments were done using Evechinus chloroticus (urchin) and Cookia sulcata (gastropod) from New Zealand. Both the short—term effects of phlorotannins on feeding behavior, and the longer term effects of phlorotannins on the growth or mortality of herbivores were assessed by (a) feeding the herbivores an array of algal species that varied in their phenolic content, and (b) extracting mixed fractions of phlorotannins from the algae and using these extracts to experimentally manipulate the phlorotannin content of palatable agar disks. The phenolic content of algae used in feeding experiments in Australia was sampled seasonally for 3 yr, and the algae were divided into two groups. These included a phenolic—rich group of five species with a mean phenolic content = 7.02% dry mass (range of species means 6.6—7.2%), and a phenolic—poor group of four species with a mean of 2.69% (range of means = 2.2—3.1%). In strong contrast to earlier results from North America, no Australian herbivore consistently preferred phenolic—poor species over those rich in phenolics. Algal phenolic levels also were not correlated with feeding preferences of the New Zealand herbivores. The Australian herbivores were generally not deterred by the addition of extracted phlorotannins to agar disks at concentrations of 5 mg/mL (13.5% dry mass) in the disks. However, some extracts deterred some herbivores, indicating that the effects of phlorotannins on the herbivores are variable. The effects of phlorotannins at higher concentrations (8 mg/mL or 18.5% dry mass) were equivocal. Deterrence was increased in some instances, but elevated concentrations of phlorotannins from Carpophyllum maschalocarpum enhanced feeding by Tripneustes gratilla. Algal phenolic levels were not correlated with the growth of juvenile Tripneustes gratilla raised on a variety of algal diets for 7 mo in the field. Conversion efficiencies of algal biomass to urchin biomass by these echinoids also did not covary with algal phenolic content. Growth of T. gratilla on agar diets for 7 mo was not affected by the addition of phlorotannins extracted from Sargassum vestitum to the agar at a concentration of 5 mg/mL. Growth of the gastropod Turbo undulata over 9.5 mo on selected algal diets was fastest for one measure growth for snails fed a diet of the phenolic—poor Sargassum linearifolium, but algal phenolic levels were not correlated with growth of T. undulata for two other measures of growth. Moreover, conversion efficiencies of Turbo undulata did not vary with diet, indicating that any differences in growth among different diets were due to differences in consumption rather than some physiological effect. This last conclusion was supported in an experiment where T. undulata was grown on agar diets. Growth of the snails was not affected by the addition of phlorotannins from Sargassum vestitum or Ecklonia radiata to agar diets, and in this experiment the amount of different agar diets consumed did not differ. These results do not support proposals that algal phlorotannins function as generally effective "digestibility reducers" against marine invertebrate herbivores. The pattern of geographical variation in the production of phenolics by brown algae, and the responses of marine herbivores to these compounds, are also not easily explained by current theoretical models such as those based on plant apparency or resource availability. A number of the algae studied here also contained smaller nonpolar secondary metabolites such as terpenes or lactones. In general, these algae were the least palatable to the herbivores, and the herbivores grew most slowly when fed monospecific diets of algae rich in nonpolar secondary compounds. The one nonpolar compound that was tested experimentally, the terpine geranylacetone extracted from Cystophora moniliformis, significantly deterred feeding by Tripneustes gratilla. We suggest that nonpolar compounds will generally have stronger effects against Australasian herbivores than do phlorotannins.

A simple larval diet for population studies on the blowfly Lucilia sericata (Diptera: Calliphoridae)

1. A simple artificial diet was devised for larvae of Lucilia sericata Meigen. 2. A basic diet of 20 g/l agar with 20% horse blood and added yeast sustained normal growth and development, as compared with a lamb meat control. 3. When yeast was added to the blood agar diet at 50 g/l, both peak and final larval weights were increased by 25-50% at higher larval densities (2-8 larvae/g diet) and the hatchling-adult development period was reduced by about 3 days. 4. No adult insects emerged on an agar-yeast diet without blood. Increasing the concentration of blood from 10% to 20% increased adult weight at emergence by 50%, though developmental period was not significantly affected. 5. Increasing larval density significantly reduced the weights of pupae and emergent adults (by up to 50%), both on the blood-agar-yeast diet and the lamb meat control. Percentage survival fell from 80-90% to below 10% on the blood-agar-yeast diet at the highest densities of 4 or 8 larvae/g diet, though survival on lamb was not significantly affected by density.

Responses of the western spruce budworm to varying levels of nitrogen and terpenes.

An agar diet study using western spruce budworm populations from Idaho and New Mexico was carried out to determine the effects of varying concentrations of nitrogen, beta-pinene, and bornyl acetate on larval growth and survival. Increased availability of nitrogen resulted in increased larval growth rate and survival to the adult stage. Larval growth rates from the Idaho population were higher on the high-nitrogen diet than were growth rates from the New Mexico population. The high level of beta-pinene improved larval growth at the high-nitrogen concentration. Bornyl acetate significantly reduced larval growth at both the low and high levels of nitrogen although the effect was greatest with the high-nitrogen diet. High bornyl acetate concentrations also significantly reduced survival to the adult stage. At high-nitrogen levels, a high concentration of bornyl acetate reduced larval growth rates and adult survival to a level similar to that occurring at the low nitrogen and low bornyl acetate concentrations.

Evaluation of the Effects of Cotinine and Nicotine-&lt;italic&gt;N&lt;/italic&gt;′-oxides on the Development of Tumors in Rats Initiated With &lt;italic&gt;N&lt;/italic&gt;-[4-(5-Nitro-2-furyl)-2-thiazolyl]formamide&lt;xref ref-type="fn" rid="FN2"&gt;2&lt;/xref&gt;&lt;xref ref-type="fn" rid="FN3"&gt;3&lt;/xref&gt;

The effects of cotinine and nicotine-N'-oxides on tumor development in F344 rats initiated with N-[4-(5-nitro-2-furyl)-2-thiazolyl]formamide [(FANFT) CAS: 24554-26-5] were evaluated. When rats were 6 weeks old, FANFT in an agar diet was administered for a 6-week period. Subsequently, cotinine, trans-nicotine-N'-oxide, and a mixture of cis-nicotine-N'-oxide and trans-nicotine-N'-oxide in drinking water were given as promoters in concentrations of 0.1, 0.02, and 0.02%, respectively. These nicotine metabolites were offered ad libitum for 78 weeks. Control groups consisted of rats that received tap water with or without prior administration of FANFT. Cotinine, trans-nicotine-N'-oxide, and the mixture of cis- and trans-nicotine-N'-oxides were neither carcinogens nor promoters of urinary bladder tumors in rats initiated with FANFT. A reduced incidence of urinary bladder tumors was observed in FANFT-pretreated animals that also received a mixture of cis- and trans-nicotine-N'-oxides. FANFT administration increased the incidences of mesothelioma of the peritoneum and thyroid tumors. Tumor formation in the tongue and palate observed in FANFT-treated rats was not affected by administration of these nicotine metabolites. There was, however, a significant increase in the incidence of forestomach tumors in rats that were initiated with FANFT and subsequently received either trans-nicotine-N'-oxide or a mixture of cis- and trans-nicotine-N'-oxides.

Use of chemical variation and predation as plant defenses byEncelia farinosa against a specialist herbivore

Larvae of the monophagous herbivore,Trirhabda geminata, selectively eat particular plants and plant parts of its natural host,Encelia farinosa. Measurements of leaf damage and larval positions on branches through time support this observation. Time-lapse movie photography revealed that larvae are sufficiently mobile to search most of a plant in a 48-hr period and that aggregations were the result of larval activity and not directly the result of oviposition. Experiments withT. geminata larvae on artificial diets containing a range of natural concentrations of chemical extracts fromE. farinosa leaves showed that the larvae grew significantly slower and had a lower overall survivorship at the high concentration. Combining the results of all choice tests, larvae appeared unable to distinguish between high- and low-concentration agar diets. Considered individually, larval preferences for natural production concentrations changed as the season progressed. Early-season larvae preferred low-concentration leaves, while late-season larvae preferred high-concentrations. Measurements of chemical and nitrogen content of leaves selected by larvae in the field confirmed this pattern. Percent parasitism in field-collected larvae increased with season as the larval population decreased. This combination of slowed growth and increasing parasitism and predation is a putative defense strategy ofEncelia farinosa to prevent adaptation by a specialist herbivore to the total range of compounds elaborated.

Sex difference in enhancement of GGTase-positive foci by hexachlorobenzene and lindane in rat liver

The ability of hexachlorobenzene and lindane in diethylnitrosamine (DENA) pretreated rats to enhance the incidence of gamma-glutamyltrans-peptidase (GGTase)-positive foci was determined. In rats that received either DENA followed by a basal agar diet or hexachlorobenzene or lindane without prior administration of DENA, the incidence of GGTase-positive foci was negligible. When hexachlorobenzene or lindane were administered in the diet to rats that previously received DENA, there was an increased incidence of GGTase-positive foci that was greater in females than male rats and rats that received a 2 3 partial hepatectomy prior to the DENA. The results suggest that hepatocarcinogenicity of hexachlorobenzene and lindane results from tumor promotion.

Hypercholesterolemia in rats fed cholesterol in agar gel diets.

AbstractFemale (Exp. I) or male (Exp. II) weanling rats were fed diets containing either 2% Solka‐Floc or 2% agar for 28‐day periods. Some groups received 1% cholesterol, either added in crystalline form or first dispersed in the oil portion of the diet, and some agar groups received their diet in a gelled form. Feces were collected for a 3‐day period after 2 weeks (Exp. II) or during the fourth week (Exp. I) of experimentation. Serum and liver cholesterol, total liver lipids, fecal lipids, and fecal sterols were determined. The results indicated that cholesterol feeding increased serum cholesterol, total liver, and fecal lipids, liver cholesterol, and fecal sterols. Substitution of agar for Solka‐Floc in dry (nongelled) diets further increased total liver lipids (Exp. I), but had no significant effect upon any other measured parameter. Gelling of 1% cholesterol agar diets, in contrast to the 1% cholesterol dry agar diet, resulted in reduced liver cholesterol in both experiments. Gelling significantly increased fecal sterols after 2 weeks feeding (Exp. II), but no significant differences were observed after 4 weeks feeding (Exp. I) when compared to 1% cholesterol‐fed groups. Small, nonsignificant increases of liver cholesterol and total liver lipids with similar reduction of fecal sterols resulted from dispersing the cholesterol in the oil portion of the diet prior to mixing. The results indicate that (a) inclusion of 2% agar in rat diets and (b) dispersing cholesterol in oil had little effect upon serum, liver, or fecal lipids in cholesterol‐fed rats. However, gelling the agar diets reduced liver cholesterol, possibly by initial reduction of dietary cholesterol absorption.

Nutrition of the Tobacco Budworm: an Economical Larval Diet for Rearing123

A new soy flour-grain oil formulation was more efficient and economical than the standard (soybean-wheat germ) larval diet used to rear Heliothis virescens (F.). Weights of larvae and pupae, percent pupation and adult eclosion, number matings per male, and number of eupyrene sperm per single mating were greater in insects reared on the soy flour-grain oil diet. The approximate costs of the standard (high agar) diet for rearing insects in cups or the modified standard (low agar) diet for mass-rearing in tray units are $0.47 and $0.30/liter, respectively. The cost of one liter of the new (low agar) formulation, in which wheat germ is replaced by grain oils, is $0.17 (with wheat germ oil) or $0.14 (with corn oil). The new diet also can be used successfully with both types of rearing container. The use of this diet in our laboratory would produce a savings of ca. $10,000/year.