Target of Rapamycin drives unequal responses to essential amino acid depletion in egg laying

Nutrition shapes a broad range of life history traits, ultimately impacting animal fitness. A key fitness-related trait, female fecundity is well known to change as a function of diet. In particular, the availability of dietary protein is one of the main drivers of egg production, and in the absence of essential amino acids egg laying declines. However, it is unclear whether all essential amino acids have the same impact on phenotypes like fecundity. Using a holidic diet, we fed adult female D. melanogaster diets that contain all necessary nutrients except one of the 10 essential amino acids and assessed the effects on egg production. For most essential amino acids, depleting a single amino acid induced as rapid a decline in egg production as when there were no amino acids in the diet. However, when either methionine or histidine were excluded from the diet, egg production declined more slowly. Next, we tested whether GCN2 and TOR were involved in this difference in response across amino acids. While mutations in GCN2 did not eliminate the differences in the rates of decline in egg laying among amino acid drop-out diets, we found that inhibiting TOR signalling caused egg laying to decline rapidly for all drop-out diets. TOR signalling does this by regulating the yolk-forming stages of egg chamber development. Our results suggest that amino acids differ in their ability to induce signalling via the TOR pathway. This is important because if phenotypes differ in sensitivity to individual amino acids, this generates the potential for mismatches between the output of a pathway and the animal's true nutritional status.

Effects on Brood Development in the Carpenter Ant Camponotus vicinus Mayr after Exposure to the Yeast Associate Schwanniomyces polymorphus Kloecker

The yeast Schwanniomyces polymorphus is associated with the infrabuccal pocket in the carpenter ant Camponotus vicinus (Hymenoptera: Formicidae), but its role in ant development is poorly defined. The potential effects of this yeast on brood development were examined on sets of larval groups and workers over a 12 week period. Worker–larval sets were fed variations of a completely artificial, holidic diet and exposed or not exposed to live S. polymorphus. Worker–larval sets in half of the experiment were defaunated using a two-step heat and chemical process. Brood development and number of adult ants produced were significantly affected by the heat/chemical defaunation process. Compared to worker–larval groups fed a basal, complete diet, all treatments resulted in no or deleterious larval development. Brood weights and number of worker ants produced from the original larval sets at initiation were significantly higher in non-defaunated ant groups fed a diet lacking both B vitamins and cholesterol and exposed to live S. polymorphus. We propose that this yeast may help ants to more efficiently assimilate nutrients when fed nutrient-deficient diets, particularly those deficient in sterols.

NUTRITION OF THE ONION MAGGOT, DELIA ANTIQUA (DIPTERA: ANTHOMYIIDAE)

A holidic diet which allowed the onion maggot, Delia antiqua (Meigen), to undergo complete development to the adult reproductive stage was developed. The effects of various concentrations of choline and salts on development were investigated. The amount of choline which gave optimal development was approximately 1/50 that used in most other artificial diets. It was found that the complex salt mixture (Wesson salts) normally used could be replaced by a solution of salts containing specific trace element ions (Fe, Mn, Cu, and Zn) and the two salts CaHPO4·H2O and KH2PO4.

Besoins qualitatifs en acides aminés chez la punaise de l'asclépiade, Oncopeltus fasciatus (Dallas) (Hemiptera, Lygaeidae)

Qualitative amino acid requirements of Oncopeltus fasciatus (Dallas) larvae reared on holidic diets were studied. All experiments began at the third instar. Amino acids are required in the diet for the growth and survival of the large milkweed bug larvae. By omitting each amino acid individually from the basic holidic diet, we showed that the 10 amino acids generally essential for the insects are also all required for growth of O. fasciatus. In contrast with the observations recorded for most insects, none of the amino acids tested was individually required for the survival of the larvae of this hemipteron. Simultaneous omission of aspartic acid, glutamic acid, asparagine, and glutamine from the diet did not result in a reduction of growth of the milkweed bug. D-Alanine in the holidic diet was neither beneficial nor toxic to the insect.

SOME MINERAL REQUIREMENTS OF THE PEA APHID, ACYRTHOSIPHON PISUM (HOMOPTERA: APHIDIDAE)

Performance of the pea aphid, Acyrthosiphon pisum (Harris), on a holidic diet containing different metal ions was studied by individually incorporating into the diet a salt of the metal ion to be tested. The performance of the pea aphid was markedly improved when the diet contained iron; the first-generation adults reproduced, and the second-generation nymphs moulted twice or thrice, but did not reach the adult stage. Molybdenum, boron, and copper, at certain concentrations, induced the production of some live nymphs, but manganese, zinc, calcium, and cobalt did not. However, the presence of zinc, cobalt and calcium, at most of the concentrations used, slightly improved growth and reduced mortality. Furthermore, the presence of calcium appeared essential for development to the adult stage. Tolerance to all these metals was fairly high, but sodium molybdate at a concentration of 50.0 mg, and sodium borate at concentrations of 40–100 mg/100 ml of diet, appeared to reach toxic levels.Iron was found to be essential for reproduction and a range of 53–211 μg of elemental iron per 100 ml of diet appeared to be optimum. It is suggested that a synergistic effect between at least some of these metals is required for continuous reproduction of the pea aphid.