Suboptimal Diet Research Articles

A framework for the study of macronutrient intake in fish

A good understanding of the capabilities of commercially reared fish species to regulate intake of specific macronutrients has potential economic, welfare and environmental benefits. We present a conceptual and experimental framework for studying macronutrient intake in fish. This ‘geometric’ approach addresses the multidimensional and interactive nature of nutrition. It was developed from work on insect herbivores and has successfully been applied to mammals and birds. The various components of the framework are introduced in simple outlines, and key experimental designs are described for assessing whether or not fish specifically regulate their intake of macronutrients, how they balance over-ingesting some nutrients against undereating others when provided with suboptimal diets, and how they regulate growth post-ingestively.

Relationships of Physical Activity with Dietary Behaviors among Adults

Background. Physical activity and diet are important influences on health, but few data are available about the relationship between these two factors. The purpose of this study was to examine relationships between physical activity and dietary quality and to identify determinants of the combination of sedentary behavior and suboptimal diet.Methods. The design of this study was cross-sectional. The setting was a large managed-care organization and the participants were 1,322 racially diverse men and women ages 25–91 years. We categorized subjects' physical activity into vigorous, moderate, and sedentary based on answers to two validated interviewer-administered questions about intensity and duration of specified activities. Dietary assessment was by means of a validated short food frequency questionnaire. We defined suboptimal diet as consuming unhealthful quantities of at least two of the following five food groups: fruits, vegetables, whole grain foods, whole-fat dairy foods, and red and processed meats.Results. Seven hundred fifty-four (57%) subjects were sedentary and 617 (47%) consumed a suboptimal diet. Using multiple linear regression, we found that sedentary individuals consumed smaller amounts of foods and nutrients considered to be healthful, such as fruits and vegetables, fiber, calcium, folate, and vitamins A, C, and E, than more active participants. For nutrients considered to be harmful, such as saturated fat, trans fat, and dietary cholesterol, the association with physical activity was inverse. In multiple logistic regression analyses, the strongest sociodemographic correlates of the joint presence of inactivity and poor diet were less education [odds ratio for 1-year decrease 1.14 (95% confidence interval 1.06, 1.22)], nonwhite race [1.48 (1.05, 2.07)], and nonmarried status [1.49 (1.06, 2.10)].Conclusions. Physical activity and diet quality are correlated behaviors. Suboptimal diet and sedentary behavior tend to cluster in individuals who are less educated, not married, and of nonwhite race. Programs that target diet and activity together, informed by their joint determinants, may attain enhanced outcomes.

Patterns, Factors, and Pathways Contributing to Nutritional Risk Among Rural African American Elders

In the United States, the increasing life expectancy and burgeoning older population have raised concerns about the adequate provision of health care for chronic medical conditions. One fundamental factor in the prevention and management of medical conditions is optimal dietary intake, which is notably lacking among older adults. Most researchers investigating factors associated with suboptimal diets limit their studies to developing nutritional risk profiles, and many conclude by advocating patient education. Using telephone surveys and in-depth interviews, this article identifies particularly vulnerable elders and explores the contextual and experiential pathways that place individuals at nutritional risk. Surveys of African American and white elders indicate that rural African American elders are disproportionately at risk of inadequate nutrition. In-depth interviews revealed four pathways to nutritional risk, including transitions in the social and physical significance of food, inaccessibility of res...

The influence of nutritional status on the feeding behaviour of the field slug, Deroceras reticulatum (Müller)

The field slug, Deroceras reticulatum, a common pest of agricultural and horticultural crops, is a generalist herbivore with distinct preferences for particular food items. However, these preferences are not fixed, but are influenced by the recent dietary history of the slugs. In particular, slugs tend to select novel food items (‘neophilia’). We investigated the basis of such influences, using artificial diets in which protein and carbohydrate composition could be controlled and non-nutritional (‘secondary’) chemicals added as flavours. The slugs showed no general inclination for neophilia based on taste alone. There was a possible learned association between protein content and taste, but this was weakly expressed. However, the slugs selected food items, when given a choice, containing nutrients that were deficient in earlier diets, even though all the food items contained the same familiar secondary taste chemicals. Injections of missing nutrients into the haemocoel of slugs inhibited such changes in food preference, indicating that slugs' feeding preferences are influenced directly by their internal nutritional status. We suggest that neophilia inD.reticulatum is a physiological response to a nutritional imbalance arising from a suboptimal diet.

Growth performance and biochemical composition of Ruditapes decussatus (L.) spat fed on microalgal and wheatgerm flour diets

Trials were carried out for different growth diets, consisting wholly or partially of wheatgerm flour, for the spat culture of the little-neck clam, Ruditapes decussatus (L.). The following diets were tested: diet A, consisting of 100% of the daily food ration of the microalga Isochrysis galbana, clone T-ISO; diet B, consisting of 50% microalgae and 50% wheatgerm; diet C, consisting of 25% microalgae and 75% wheatgerm; and diet D, consisting of 100% wheatgerm. Diet A was taken as the reference diet and two control diets were added: suboptimal algal diet B, consisting of 50% of the daily ration of microalgae, and suboptimal algal diet C, consisting of 25% microalgae. Spat growth was determined by live weight, dry weight, organic content and length. Biochemical analyses of the diets and the spat were carried out at the beginning and the end of the 35-day experimental period. The growth achieved when 50% of the daily ration of microalgae was replaced by wheatgerm was similar to that obtained with control diet A, consisting of 100% microalgae. As regards organic matter, the growth of the spat fed on this diet, diet B, was double that shown by the spat fed on suboptimal algal diet B. When 75% of the microalgae were replaced by wheatgerm the growth rates decreased, being only equivalent to 60% of those for reference diet A. Nevertheless, the percentage of organic matter of this spat, indicative of the index of condition, was comparable to that of the spat fed on the reference diet. The total replacement of microalgae by wheatgerm produced a considerable decrease in spat growth, 20% of that obtained with reference diet A. The percentage of organic matter in the spat fed on the extreme diets, diet D and suboptimal diets B and C, was observed to be significantly less than that found in the spat fed on the other diets. Another characteristic of the diets tested was a decrease in protein and lipid content, together with an increase in that of carbohydrates, which corresponded to the extent to which microalgae were replaced by wheatgerm. The biochemical composition of the spat reflects a limitation in the lipid content of diets C and D, reflected in a lower lipid growth rate in the spat compared to that of other body matter.

Protists and detrital particles as prey for the first larval stage of the brachyuran crab, Hemigrapsus oregonensis

Newly-hatched larvae of the brachyuran crab, Hemigrapsus oregonensis, were raised in the laboratory on an autotrophic dinoflagellate ( Prorocentrum micans), a heterotrophic dinoflagellate ( Noctiluca milaris), a green alga ( Dunaliella tertiolecta), an unfed control, and a fed control of Artemia sp. nauplii. Larvae also were fed preparations of seagrass detritus that had been cultured both to promote microbial colonization and to discourage it. Detrital diets were used both alone and in combination with sub-optimal applications of Artemia sp. nauplii. Larvae raised on P. micans showed survival to zoeal stage II equal to those raised on the Artemia sp. nauplii control, although development was delayed. Larvae raised on N. milaris showed substantial (34.7%) survival to zoeal stage II; however survival was lower and development slower than for Artemia sp. nauplii-fed larvae. Survival on D. tertiolecta was less than 3%. Larvae fed microbially-enriched detritus showed a delay in mortality as compared to unfed controls. No larvae fed solely on detritus survived to zoeal stage II. When larvae were fed a sub-optimal diet of Artemia nauplii, supplemented by detrital particles, survival to zoeal stage II increased, although not to the level shown by Artemia-fed larvae in optimal application. Development was not accelerated over the sub-optimal diet in either treatment. The potential for larval crabs to utilize a wide variety of potential prey immediately upon hatching is significant given their susceptibility to early starvation. Such omnivory also suggests a trophic link between carbon sources of the microbial loop and crab larvae.

Effects of limiting access to prey on development of first zoeal stage of the brachyuran crabs Cancer magister and Hemigrapsus oregonensis

We tested the influence of limiting access to prey on larval development of the crabs Cancer magister and Hemigrapsus oregonensis by raising their Stage 1 larvae in the laboratory on different prey densities and with various periods of access to prey. Experiments were conducted in 1995 and 1996 at the Shannon Point Marine Center in Anacortes, Washington, USA. Our results show that crab larvae do not require continuous access to prey for optimal development nor do they appear to require light for prey capture. Survival and duration of Stage 1 C. magister fed continuously on only one-fourth the amount of the control density of prey and those fed at the control density for only 6 h per day were the same as for larvae fed continuously at the control density (20 ml−1). Larvae with cyclic access to prey at the control density for 24 h and then starved for 72 h showed significantly lower survival and longer instar duration to Stage 2. Experiments on Stage 1 H. oregonensis which investigated a combination of prey density, period of access to prey and light/dark conditions during feeding revealed that survival decreased with decreasing prey density or with decreasing feeding period, but no differences were observed during periods of limited prey availability as a function of light or dark conditions. Stage duration was not affected by reduced prey density nor by the light/dark condition at the time of feeding, but it was prolonged when the period of access to prey was limited. The period of access to prey did not affect the weight of Day 1 Stage 2 larvae. Larvae fed high densities of prey for 4 h followed by 20 h of reduced-density diet exhibited the same survival and stage duration as controls that were continuously fed high-density prey. Our results define sub-optimal diets that can be used experimentally to determine the nutritional contributions made by naturally-occurring prey organisms during larval development in the two species. In nature, larvae may satisfy nutritional requirements through periodic encounters with dense prey patches during vertical migrations by day or night.

Dietary Management of the “Old–Old”: An Individualized Approach

The population of the United States continues to shift toward the “oldest–old,” often defined as 85 years old or more. Multiple personal and environmental factors may contribute to suboptimal diets among this group. However, practitioners are urged to assess each older patient on an individual basis because many health‐related problems that occur with advancing age do not affect all older people at the same rate or in the same manner. ▪ Key Words: aged, aging, elderly, nutrition assessment, geriatrics, nutritional requirements

Free radicals, exercise and antioxidant supplementation

Although conflicting data exist, the preponderance of available information suggests that physical exercise promotes an increase in free-radical generation. However, few studies have actually measured exercise-induced free radicals directly, primarily because of a lack of sophisticated methodologies to measure this phenomenon. Instead, researchers have relied heavily on the measurement of lipid peroxidation as the principal indicator of exercise-induced free radicals. It should be noted that free radicals can also alter and inactivate enzyme complexes, damage DNA and RNA, and promote mutations and cancer, among other activities. However, there have been few reported studies dealing with exercise and oxidant stress which have measured these outcomes. It should also be noted that free-radical species are continuously produced in the human body, and that some have beneficial effects (Arouma, 1994), notably as a part of the body's natural immune system. It is not presently known if long-term ingestion of antioxidant compounds will affect these positive aspects of free-radical generation. The preponderance of available evidence suggests that antioxidant supplementation, particularly with the vitamins C and E, has favourable effects on markers of lipid peroxidation following exercise. Although the physiological implications of these effects remain to be elucidated, the prudent use of an antioxidant supplement can provide insurance against a suboptimal diet and/or the elevated demands of physical activity. Future research may uncover additional nutritional antioxidants that can benefit the physically-active individual. Numerous additional questions regarding the antioxidant needs for physical activity remain to be answered. Little is known about the needs of physically-active women, particularly those who habitually consume an energy-restricted diet, or the effects of monthly menstrual blood loss (coupled with exercise) on antioxidant requirements. The needs of the 'weekend warrior' (an individual who participates in strenuous activity sporadically) v. those of the habitual exerciser have not been addressed adequately. The needs of the ageing athlete are largely unknown; a study by Meydani et al. (1993) suggested that elderly, physically-active people can benefit from antioxidant supplementation more than their younger counterparts, but follow-up studies have not been reported to-date. Dietary issues also need to be addressed. How much supplementation is too much, and can chronically-elevated antioxidant intakes have an adverse impact on the positive effects of free radicals in living systems? Does a high-carbohydrate diet raise antioxidant needs, particularly of the fat-soluble vitamin E? Does a high polyunsaturated fat intake, or increased Fe intake affect needs? Obviously, there are a number of issues regarding the antioxidant needs of the physically-active individual that need to be elucidated. Future research utilizing newer, more sophisticated methodologies should provide answers to many of these questions.

Science and medicine of rowing: A review

The biology and medicine of rowing are briefly reviewed. Effort in a 2000 -m race is about 70% aerobic. Because the boat (and in some instances a cox) must be propelled, successful competitors are very tall, with a large lean mass and aerobic power. Large hearts may lead to erroneous diagnoses of a cardiomyopathy. Large respiratory minute volumes must be developed by chest muscles that are also involved in rowing. The vital capacity is typically large, and breathing becomes entrained. Expiration cannot be slowed relative to inspiration (as normally occurs at high rates of ventilation) and the limiting flow velocity may be reached, with the potential for airway collapse. Performance is strongly related to the power output at the ‘anaerobic threshold’, and lactate measures provide a guide to an appropriate intensity of endurance training. Peak blood lactate levels are higher in males (commonly 11–19 mmol·l -1 and occasionally as high as 25 mmol·l -1) than in females (9–11 mmol·l -1), probably because males have a greater muscle mass in relation to blood volume. The skeletal muscles are predominantly slow twitch in type, developing an unusual force and power at low contraction velocities. Many rowers have a suboptimal diet, eating excessive amounts of fat. Lightweight rowers also have problems of weight cycling. Aerobic power and muscle endurance often change by 10% over the season, but such fluctuations can be largely avoided by a well-designed winter training programme. Injuries include back and knee problems, tenosynovitis of the wrist and, since the introduction of large blades, fractures of the costae.

Nutritional role of protists in the diet of first stage larvae of the Dungeness crab Cancer magister

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 169:237-242 (1998) - doi:10.3354/meps169237 Nutritional role of protists in the diet of first stage larvae of the Dungeness crab Cancer magister Stephen Sulkin*, Jason Lehto, Suzanne Strom, Debbie Hutchinson Shannon Point Marine Center, 1900 Shannon Point Road, Anacortes, Washington 98221, USA *E-mail: sulkin@cc.wwu.edu ABSTRACT: Two naturally occurring dinoflagellates, the autotrophic Prorocentrum micans and the heterotrophic Noctiluca scintillans (non-bioluminescent), and the green alga Dunaliella tertiolecta were tested as prey for the first zoeal stage of the brachyuran crab Cancer magister under controlled laboratory conditions. Each dinoflagellate was tested alone and in combination with a suboptimal application of the nauplius of the brine shrimp Artemia sp., a diet of known value. When offered alone, both dinoflagellates delayed mortality as compared to an unfed control, but neither supported development to the second zoeal stage. When larvae were fed a cycle of 1 d of Artemia sp. nauplii, followed by 2 d of either dinoflagellate, survival to zoeal stage II was significantly higher than for larvae fed 1 d of nauplii followed by 2 d unfed. Indeed, survival was equal to a control that had been fed nauplii continuously, although there was a significant delay in time to molt. Larvae fed D. tertiolecta in combination with nauplii showed a reduction in survival as compared to the suboptimal nauplius diet alone and no difference in time to molt. All 3 protists were consumed and the 2 dinoflagellates contributed nutritionally. Given the susceptibility of newly hatched brachyuran larvae to starvation, their ability to prey upon protists may be significant, especially for C. magister, a species that hatches in the Puget Sound (WA, USA) region in winter, a time of very low primary productivity. Crab larvae that can consume protistan prey may serve as a link between the rich carbon sources of the microbial food web and metazoans. KEY WORDS: Crab larvae · Nutrition · Protists · Dinoflagellates Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 169. Publication date: August 06, 1998 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1998 Inter-Research.

Metabolic response to dietary phosphorus intake in rainbow trout ( Oncorhynchus mykiss)

The objectives of this study were to determine which indicators were most responsive to suboptimal phosphorus intake in fingerling rainbow trout, and to observe the magnitude of these changes over time. Fish with an initial mean weight of 1.8 g were hand-fed one of five semipurified wheat-gluten based diets containing between 0.23%–1.16% dietary phosphorus, or a fish meal control diet (1.8% P) for 8 weeks. Phosphorus, calcium and magnesium concentrations in whole body, skin (with scales), and plasma were measured bi-weekly. Alkaline phosphatase activity was determined in plasma and in a crude intestinal homogenate. There was no correlation between dietary phosphorus concentration and body weight of rainbow trout. Of all tissues and metabolites examined, skin was the most responsive to differences in dietary phosphorus concentration. Dietary treatment had a significant effect on the concentrations of ash, phosphorus, calcium and magnesium in rainbow trout skin at weeks 4 and 8. Whole body ash, phosphorus, calcium, and magnesium concentrations were also highly responsive to graded levels of dietary phosphorus at week 8. Rainbow trout fed suboptimal phosphorus diets had significantly lower plasma phosphorus concentrations and alkaline phosphatase activity, and significantly higher whole body lipid than those fed adequate phosphorus diets. Alkaline phosphatase activity of the intestinal homogenate was not significantly correlated with dietary phosphorus intake.

Chronic Exercise Affects Vitamin B-6 Metabolism but Not Requirement of Growing Rats , ,

The effect of chronic exercise (forced swimming) on vitamin B-6 status and metabolism was studied in growing male rats fed deficient (0 mg pyridoxine-HCl/kg), suboptimal (2 mg pyridoxine-HCl/kg) or control (7 mg pyridoxine-HCl/kg) diets for 9 wk. Sedentary rats were fed the same diets. Body weight gain was lower in deficient rats than in both other dietary groups. Sedentary rats were heavier than trained rats of all diet groups. Erythrocyte aspartate aminotransferase, urinary 4-pyridoxic acid excretion, blood (plasma and erythrocytes) and tissue B-6 vitamers were measured. Urinary 4-pyridoxic acid, plasma pyridoxal 5′-phosphate and erythrocyte aspartate aminotransferase values of exercised and sedentary rats responded to changes in dietary pyridoxine but were not different from one another. After 9 wk of vitamin B-6 depletion, tissue concentrations of pyridoxal 5′-phosphate and pyridoxamine 5; 5'-phosphate were 41–66% and 26–49% lower, respectively, in the deficient groups than in the control groups. Larger percentage differences occurred in plasma than in tissues (95 vs. 22–66%). In liver, pyridoxal 5′-phosphate concentrations were lower, whereas pyridoxal concentrations were higher in trained than in sedentary rats. In gastrocnemius muscle, pyridoxal 5′-phosphate, pyridoxamine 5′-phosphate and total vitamin B-6 concentrations were higher in trained than in sedentary rats. Concentrations of vitamin B-6 compounds in heart, kidneys, brain and adrenals were not affected by training. On the basis of the vitamin B-6–dependent variables measured in this study, we conclude that prolonged exercise affects the metabolism of vitamin B-6, but does not increase the vitamin B-6 requirement in growing rats.

Influence of dietary protein level on ovarian recrudescence in Nile tilapia, Oreochromis niloticus (L.)

Ovarian recrudescence was investigated in Nile tilapia, reared on isocaloric, semi-purified diets of 10, 20 and 35% protein content, for 2 and 4 month periods. Females immediately after spawning were used with a view to ensuring that all individuals investigated would have ova in a regressed state initially, so that subsequent changes could be correlated to dietary protein affects. In females reared for 2 months, the dietary effects on ovarian recrudescence became most evident only by Day 14, when a significantly higher percentage of Stage 4 oocytes (diameter > 2.4 mm, pear-shaped, bright yellow, post vitellogenic oocytes) were present in the 35% protein fed females as compared to those fed the 10% protein diet. In females reared on the diets for 4 months, comparable differences were evident on Day 7 after spawning. Here ovarian recrudescence of 10% protein fed females was slower than in females maintained on 20 and 35% dietary protein levels. In females reared for 2 and 4 months on the experimental diets, GSI, however, did not vary significantly amongst fish fed 10, 20 and 35% diets, in the regressed and recrudescing ovaries at Day 7 and Day 14. There was evidence to indicate that even when the females are reared on a sub-optimal diet (e.g. 10% protein) they make an attempt to go through the recrudescence process, perhaps by utilizing existing body reserves.

Diet and Health: What Should We Eat?

Many recent studies have implicated dietary factors in the cause and prevention of important diseases, including cancer, coronary heart disease, birth defects, and cataracts. There is strong evidence that vegetables and fruits protect against these diseases; however, the active constituents are incompletely identified. Whether fat per se is a major cause of disease is a question still under debate, although saturated and partially hydrogenated fats probably increase the risk of coronary heart disease. One clear conclusion from existing epidemiologic evidence is that many individuals in the United States have suboptimal diets and that the potential for disease prevention by improved nutrition is substantial.

Twin children in The Gambia: evidence for genetic regulation of physical characteristics in the presence of sub-optimal nutrition.

It has been demonstrated that physical growth characteristics are subject to genetic regulation. However, in developing countries, environmental factors such as food availability and frequent infections are associated with growth faltering which is particularly marked in infancy. We have conducted anthropometric measurements of a cohort of twin children aged less than 14 years living in a rural area of The Gambia to ascertain the extent to which genetic factors influence physical growth in the presence of a sub-optimal diet. Almost 25% of the children were more than 2SD below the median of the reference population in terms of their height-for-age Z score, indicating a marked level of undernutrition. Nevertheless, the within-pair variances were significantly less for monozygous than for dizygous twin pairs for the following variables: height, head circumference and body mass index (p < 0.01); weight (p < 0.02) and mid upper arm circumference (p < 0.1), indicating that there is a strong genetic influence on growth regulation despite the sub-optimal nutrition.

Dietary amino acid analogs alter activities of some amino acid-metabolizing enzymes in rat liver

Dietary amino acid analogs often strongly and selectively modify rat tissue amino acid profiles. These effects are accompanied by altered activities of several enzymes of amino acid catabolism. In a preliminary study, activities of hepatic serine dehydratase (SDH), glutamate-pyruvate (GPT), GABA and tyrosine (TAT) aminotransferases, and ornithine carbamoyltransferase (OCT) were high in rats fed diets containing a mixture (3%) of analogs (norleucine, norvaline, α-aminophenylacetate, and α-aminooctanoate); pyruvate kinase (PK) was low. Raising the protein content of the diet often lessened the effect. Analog effects on SDH, GPT, and PK occurred within 2 days, but not within 4 hr. After adaptation to a 50% protein diet that raised SDH and GPT and lowered PK, rats were fed a 6% protein diet with or without the analogs; the normal decline in initially high SDH and GPT was slowed within 4 days in rats fed the analogs, whereas the normal increase in PK induced by a low protein diet was strongly blocked by day 1. In rats fed a 6% amino acid diet, dietary norleucine stimulated branched-chain ketoacid dehydrogenase (BCKAD) activity about 290%, had lesser effects on SDH, GPT, and OCT, and did not alter PK, TAT, or branched-chain aminotransferase; norvaline stimulated only BCKAD (85%). In rats fed an 8% amino acid mixture limiting in leucine. SDH activity was stimulated (up to 800%), depending on norleucine level in the diet, and was lessened by added dietary leucine; similar, but less striking patterns occurred for GPT. If all indispensable amino acids were fed in adequate amounts, SDH and GPT were not stimulated by norleucine. Overall, analog effects were usually more prominent in rats fed suboptimal diets.

The nature of erythrocyte stroma lipid components required for normal reproduction in Stomoxys calcitrans (Diptera: Muscidae)

Adult Stomoxys calcitrans require erythrocyte membrane components in their diets for normal reproduction. Nutritionally sub-optimal diets consisting of stroma-free, lipid-free haemoglobin and serum albumin were greatly improved by supplementation with either erythrocyte ghost preparations or lipid mixtures containing cholesterol, sphingomyelin and phosphatidyl ethanolamine. The apparent nutritional requirement of dietary erythrocyte membrane components by adult Stomoxys calcitrans is discussed in terms of the nutritional value of the erythrocyte membrane lipid components.

The effects of gregarine parasites on longevity, weight loss, fecundity and developmental time in the field crickets Gryllus veletis and G.pennsylvanicus

ABSTRACT. 1. Gregarines, debilitating gut parasites, significantly reduced longevity and increased weight loss in the field cricket Gryllus pennsylvanicus Burmeiser when adults were kept on suboptimal diets, but in G.pennsylvanicus and G.veletis (Alexander and Bigelow) fed ad libitum, weight change, longevity, and fecundity were not significantly different in infected and control individuals.2. Adults harbouring gregarines at eclosion took significantly longer to develop from the second and third instars than did uninfected adults.3. Longevity of nymphs kept in the laboratory without food was decreased in infected individuals compared with uninfected ones, but not significantly so.4. The evolutionary and ecological implications of nonlethal parasites are discussed.

Studies on the biochemical basis of the nutritional quality of tsetse fly diets

1.1. Batches of freeze-dried pig and cow blood, whose nutritional value to G. p. palpalis ranged from low to near optimum, were analysed for amino acid, triglyceride and cholesterol content.2.2. The results of the chemical analyses were compared with the nutritional quality parameters observed when each batch of blood was fed to G. p. palpalis in an attempt to establish a chemical basis for the nutritional quality of diets for Glossina.3.3. In general, those pig or cow blood diets that had a higher nutritional quality also had a significantly higher amino acid content than the suboptimal diets.4.4. There were significant differences between the triglyceride and cholesterol content of pig and cow blood, with pig blood having more triglyceride, but less cholesterol than bovine blood.5.5. There was no apparent correlation between the triglyceride and cholesterol content and the nutritional quality of blood.