Nutrition, hormones and life history in burying beetles

Nutrition, hormones and the allocation of physiological resources are intricately related. To investigate these inter-relationships in female burying beetles (Nicrophorus spp.), we examined the effect of diet quality on juvenile hormone (JH) levels and reproduction, and the effect of JH supplementation on reproduction and resistance to starvation. Nicrophorus orbicollis adult females fed a less preferred mealworm larvae diet gained less body mass, had smaller ovaries and had lower titers of JH in their hemolymph than females fed a preferred blowfly diet. When presented a carcass for breeding, females on a less preferred diet oviposited 33% fewer eggs, and eggs were of 18% less mass. Females on the less preferred diet also took longer to begin oviposition as indicated indirectly by the time when their eggs hatched. To investigate the effects of JH, independent of nutrition, JH was topically applied to single and paired females of Nicrophorus tomentosus. When presented a carcass, JH-treated paired females oviposited more eggs (28%-year 1, 44%-year 2) than control females, and also showed a trend toward faster oviposition. JH supplementation had a greater effect on single females. JH treatment increased the proportion of single females attempting reproduction (at least one viable larva), increased the number of eggs (69%-year 1, 123%-year 2), and increased the proportion of females ovipositing early. In separate experiments, treatment with JH or a JH analog negatively affected resistance to starvation in three species. Treatment with JH reduced starvation survival by 10.3% days in N. tomentosus females. Treatment with the JH analog methoprene reduced starvation survival 17.8% in N. orbicollis females and by 18% in Ptomascopus morio females. These results suggest that JH has positive and negative effects on different components of life history.     

Nutrition,population growth and disease: a short history of lactose

Food and nutrition have played a crucial role in biological evolution. Lactation in mammals was one key invention. A central role in milk is played by lactose, otherwise an exotic sugar in nature. Lactose digestion needs the induction of specialized gut enzymes. This enzyme is shut off in a precisely timed developmental step leading to lactose malabsorption promoting weaning in the young and ovulation in the mother. The lactose–lactase system could thus regulate optimal birth spacing in land mammals. The domestication of cattle promoted milk as a food item also for adult nutrition. This was only possible by two further key inventions: the concomitant domestication of lactic acid bacteria which ferment the non‐digestible lactose to the easily absorbed lactic acid and the mutation to lactase persistence (LP) in adults from dairy societies. This mutation represents one of the strongest selected loci of the human genome. Since no crucial nutritional selective advantage is conferred by LP, its dominance might be the result of indirect effects like the spread of cattle pathogens into humans. Lactase is also temporarily lost in rotavirus and Escherichia coli childhood diarrhoea and persistent diarrhoea is consequently best treated with lactose‐free diets.     

Nutrition.

Nutrition appeared somewhat late on the scene in the I.B.P. projects in the U.K., but eventually it occupied an integral part of many of the H.A. (human adaptability) investigations. The nutritional data obtained in the studies of isolated and nearisolated communities in Tristan da Cunha and in New Guinea provided information of wide nutritional significance. There were also detailed and extensive studies in Israel which, similarly to those in New Guinea, attempted to relate nutritional factors to enviroment, working conditions, and physical fitness. Some extraordinarily low energy intakes found in Ethiopians have induced much speculation on the extent which man can adequately adapt to restricted food supplies. Interesting nutritional observations, of general importance, have also arisen from results obtained on such disparate groups as Glasgow adolescents, Tanzanian and Sudanese students, children in Malawi and vegans in the U.K.