Effects of dextrin and cellulose on feeding and reproduction in female brown-banded cockroaches, Supella longipalpa

Abstract Food consumption and reproduction were compared through two gonotrophic cycles in female brown-banded cockroaches, Supella longipalpa (F.), fed a standard rat food diet which had been serially diluted with methyl cellulose, alpha cellulose or dextrin. Females did not increase daily intake to compensate for dilution, and reproductive rate was highly dependent upon the degree of dilution of the diet. With increasing dextrin concentrations, digestibility increased, but reproductive rate, size and mass of oothecae, and efficiency of food utilization progressively decreased.
On diets containing 75% rat food and 25% methyl cellulose, females consumed minimal amounts of food and 80% of the females did not mate or produce oothecae within 30 days. On identical diets containing 25% alpha cellulose, food digestibility decreased and females ate significantly more than females fed 25% methyl cellulose, but less than females fed rat food. Many (65%) females fed 25% alpha cellulose produced oothecae which were smaller and took longer to form than in control females fed on rat food. At concentrations higher than 50% of either methyl or alpha cellulose daily intake was further reduced and females died rapidly.     

Interactive effects of temperature and concentration of the flavonol rutin on growth, molt and food utilization of Manduca sexta caterpillars

A factorial experiment tested the effects of varying concentrations of the flavonol rutin and daytime temperatures of 20 and 30°C on growth, molting and food utilization efficiencies of third instar tobacco hornworms (Manduca sexta (L.)). Cool temperature prolonged both the growth (=feeding) and non-feeding periods and consequently the relative consumption rates (RCR) and relative growth rates (RGR). Temperature had no impact on the amount of food consumed and the utilization indices of efficiency of conversion of ingested food and efficiency of conversion of digested food to larval biomass. But rutin was more concentrated in the frass of the larvae at the warm temperature. With increasing levels of rutin in the diet, the efficiency of conversion of ingested food tended to decline. Rutin reduced RCR and RGR. At the cool temperature, rutin increased the time spent in the first portion of the non-feeding period disproportionately. Analysis of growth rate intervals within the growth period indicated that at the cool temperature rutin had no discernible impact over the first half of the growth period, during which developmental competence to molt is likely achieved. Overall, these results indicate an overlap in the growth and molting phases and suggest that rutin interferes with physiological processes at the time of molt initiation, with these effects magnified at a cool temperature.     

Food intake, conversion efficiency, and feeding behaviour of tobacco hornworm caterpillars given artificial diet of varying nutrient and water content

ABSTRACT Fifth stadium tobacco hornworm caterpillars, Manduca sexta (L.), given artificial diet diluted to varying extents with either cellulose or water compensated for the food's reduced nutrient content by eating more of it. This compensation was, however, in most cases not sufficient to maintain normal growth rates. When the water content of the diet was reduced, the insects ate less than the usual fresh weight of food but maintained their intake of nutrients. Nevertheless, growth rate was impaired. The insects were better able to compensate for dilution of their food with water than with cellulose. The efficiency of conversion of ingested food (ECI) was decreased when the diet was adulterated with cellulose. At moderate dilution (50% nutrient) this was due mostly to decreased approximate digestibility (AD), but at greater dilution (25% and 10% nutrient content) the efficiency of conversion of digested food (ECD) was decreased. ECI was maintained when the water content of the diet was increased to give 50% nutrient concentration, but was decreased when water content was changed more radically (200%, 25% and 10% nutrient diets). This was due mostly to increased metabolic costs (decreased ECD) in all cases. The retention time of food in the gut was progressively decreased (i.e. speed of passage was increased) as nutrients were replaced by cellulose. By contrast, dilution of the diet with water resulted in only slight changes in retention time, except at extreme dilution (10% nutrient content) when retention time was reduced. Compensation of food intake was achieved by spending more (or less) time eating. Video analysis of feeding behaviour showed that there were significant changes in the length of feeding bouts and of interfeed gaps when caterpillars fed on diets of altered composition. For diets diluted with cellulose, changes in bout length and bout frequency contributed substantially to the increased time spent feeding on the adulterated food. For diets diluted with water, however, almost all of the compensatory change in behaviour was due to increased bout length, with bout frequency affected only slightly. This suggests that volumetric feedback contributes principally to the termination of feeding bouts in caterpillars, while nutrient flow may affect both the initiation and termination of feeding.     

Compensatory responses of the fall armyworm (Spodoptera frugiperda) when fed water- and cellulose-diluted diets

Abstract Caterpillars of the noctuid moth, Spodoptera frugiperda (J. E. Smith), reared on artificial diets diluted with cellulose and water, increased fresh weight (fw) consumption 2.2–2.5-fold over those on the undiluted diet. At moderate levels of water- or cellulose-dilution, the increased consumption, combined with increased digestion and absorption of nutrients (ADNU), sufficiently compensated for the reduced nutrient intake to achieve pupal biomass equivalent to that of pupae from the undiluted diet. At higher levels of water- and cellulose-dilution, fw consumption and ADNU increased further but pupal dry weight declined on the water-diluted diets. At each level of dilution fw consumption and ADNU increased similarly on the water- and cellulose-diluted diets, but biomass gain was reduced on the water- compared with the cellulose-diluted diets. This was due in part to lowered food conversion efficiency on the water-diluted diets, possibly caused by increased costs of metabolizing the wetter diets. Our data support the hypothesis that consumption rates are regulated by a nutrient feedback mechanism. Our data also suggest that digestive enzyme activity is correlated with consumption. Furthermore, the cost of increased consumption rates on diets of reduced energetic value may constitute a substantially greater energy expenditure than previously believed. However, this cost was insufficient to reduce relative growth rates but was apparently manifested in lowered lipid accumulation.     

Food consumption and utilization by 6th-instar larvae of spruce budworm, Choristoneura fumiferana: a comparison on three Picea (spruce) species

The effects of tree species, shoot age, and sex of larvae on food consumption and utilization were investigated in a factorial experiment. Diets prepared from lyophilized and powdered current-year shoots, from two age classes (sample dates) of Picea glauca (Moench) Voss, Picea rubra, Sarg., and Picea mariana (Mill.) B.S.P., were evaluated for eight performance criteria. All factors had significant effects on all criteria except for tree species on assimilation efficiency, shoot age on development time, and sex on net growth efficiency. Eight of the possible 24 two-factor interactions and one of the possible eight three-factor interactions were significant. Food utilization efficiencies and relative growth rate were in the low and moderate characterization limits for immature arthropods; relative consumption rates were high. The higher performance values on Picea glauca were related to this species greater vulnerability to spruce budworm. Performance criteria of similar larvae on an artificial diet were compared with those on the foliage-diets.

---

Résumé L'auteur a déterminé la quantité d'aliments utilisées, à 22±0,5 °C, par des larves de Tordeuse des bourgeons de l'épinette parvenues à leur sixième stade de développement qui s'étaient nourries d'un régime artificiel et d'aiguilles de l'année en cours lyophilisées et réduites en poudre, prélevées à deux dates différentes, à 10 jours d'intervalle, et provenant d'épinettes blanchés (Picea glauca [Moench] Voss), d'épinettes rouges (Picea rubra Sarg.) et d'épinettes noires (Picea mariana [Mill.] B.S.P.). Les femelles ont invariablement ingéré une quantité significativement plus importante de tous les régimes que les mâles, consommant 24% de plus d'aiguilles d'épinette noire et 73% de plus d'aiguilles d'épinette blanche.Les femelles prenaient en général plus de temps pour parvenir au stade de chrysalide et avaient un taux d'utilisation des aliments significativement plus élevé. L'efficacité nette de la croissance chez les deux sexes ne présentait toutefois aucune différence significative. La performance des larves ayant ingéré des aiguilles provenant de deux classes d'âge différait de façon significative mais non pas uniforme d'un régime à l'autre: les aiguilles d'épinette blanche plus récentes donnaient une performance généralement plus élevée contrairement aux aiguilles plus jeunes d'épinette rouge et d'épinette noire. Les larves ingéraient une quantité significativement plus élevée, avaient un taux de consommation et de croissance supérieur et augmentaient davantage leur biomasse avec des aiguilles d'épinette blanche. L'efficacité d'utilisation des aliments et le taux de croissance relatif étaient de faibles à modérément faibles pour un lépidoptère arboricole phyllophage; la vitesse d'ingestion relative était élevée. La qualité des aiguilles des trois essences d'épinettes était faible. Les aiguilles d'épinette blanche permettaient aux larves d'avoir une performance significativement plus élevée, performance mesurée à partir de plusieurs critères, alors que les aiguilles d'épinette rouge et d'épinette noire donnaient une performance égale. La supériorité des performances obtenues avec l'épinette blanche explique la plus grande vulnérabilité de cette essence à la Tordeuse des bourgeons de l'épinette.