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Food Utilization (food + utilization)
Selected AbstractsResource partitioning between lake-dwelling Atlantic salmon (Salmo salar L.) parr, brown trout (Salmo trutta L.) and Arctic charr (Salvelinus alpinus (L.))ECOLOGY OF FRESHWATER FISH, Issue 4 2000L. Jĝrgensen Abstract , Resource partitioning between Atlantic salmon parr, brown trout and Arctic charr was studied throughout the ice-free season in a north Norwegian lake. Juvenile salmon and trout (,160 mm) utilized the littoral zone and juvenile charr the profundal, while adult trout and charr (>160 mm) were found in both. Juvenile salmon and trout had a similar diet, although trichopteran larvae were more important for the trout and chironomid pupae and three-spined sticklebacks for the salmon parr. Small salmon and trout parr (,120 mm) had a higher diet overlap than larger parr (121,160 mm). The feeding habits of adult trout were similar to that of juvenile trout, but the former took larger prey items. At the population level, both salmon and trout were generalistic feeders with a broad diet, but at the individual level, both species had specialized on a single or a few prey categories. Juvenile charr were segregated from salmon and trout in both habitat and food utilization; they had a narrow diet consisting of chironomids and zooplankton, possibly reflecting their confinement to the profundal habitat which have a low diversity of potential prey. Larger charr also took zoobenthos and sticklebacks in the littoral zone., [source] Response of multiple generations of beet armyworm, Spodoptera exigua (Hübner), feeding on transgenic Bt cottonJOURNAL OF APPLIED ENTOMOLOGY, Issue 2 2009G. Wu Abstract Development, reproduction and food utilization of three successive generations of beet armyworm, Spodoptera exigua (Hübner), fed on transgenic and non-transgenic Bt cotton were examined. Significantly longer larval life-span and lower pupal weight were observed in three successive generations of S. exigua fed on transgenic Bt cotton compared with non-transgenic Bt cotton. Significantly higher survival rate and adult fecundity of S. exigua were found in three successive generations of S. exigua fed on transgenic Bt cotton compared with non-transgenic Bt cotton. The survival rate and adult fecundity of S. exigua were occurred significant increase in the third generation compared with the first generation after feeding on transgenic Bt cotton. Significantly lower consumption, frass and relative growth rate (RGR) were observed in three successive generations of S. exigua fed on transgenic Bt cotton compared with non-transgenic Bt cotton. Cotton variety significantly affected all indices of larval consumption and utilization in three successive generations of S. exigua, except for efficiency of conversion of ingested food. However, beet armyworm generation only significantly affected RGR of S. exigua. The results of this study indicated food quality on the diet-utilization efficiency of S. exigua was different along with beet armyworm generation. Measuring multigenerational development and food utilization of S. exigua at individual and population level in response to Bacillus thuringiensis (Bt) can provide a more meaningful evaluation of long-term population dynamics than experiments on a single generation. It is imperative to develop an appropriate multigenerational pest management tactic to monitor the field population dynamics of non-target pests (e.g., beet armyworm) in agricultural Bt cotton ecosystem. [source] Response of multiple generations of cotton bollworm Helicoverpa armigera Hübner, feeding on spring wheat, to elevated CO2JOURNAL OF APPLIED ENTOMOLOGY, Issue 1 2006G. Wu Abstract:, The growth, development and consumption of three successive generations of cotton bollworm, Helicoverpa armigera (Hübner), reared on milky grains of spring wheat grown under elevated CO2 (double-ambient vs. ambient) in open-top chambers (OTCs) were examined. Decreases in protein, total amino acid, water and nitrogen content, and increases in total non-structure carbohydrates (TNCs) and ratio of TNC : nitrogen were found in wheat milky grains grown under elevated CO2 conditions. Changes in quality of wheat grains affected the growth, development and food utilization of H. armigera. Significantly longer larval lifespan for the third generation and lower pupal weight for all generations were observed in cotton bollworm fed on milky grains of spring wheat grown under elevated CO2 conditions. Bollworm fecundity was significantly decreased for the second and third generations under elevated CO2 levels. The consumption, frass per larva and relative consumption rate significantly increased in elevated CO2 compared with ambient CO2 conditions. However, the potential population consumption was significant reduced by elevated CO2 in the second and third generations. The results of this study indicate that elevated CO2 levels adversely affect grain quality, resulting in consistently increased consumption per larva for a longer period to produce less fecund bollworm through generations, suggesting that net damage of cotton bollworm on wheat will be less under elevated atmospheric CO2 levels because increased consumption is offset by slower development and reduced fecundity. [source] EFFECT OF ARTIFICIAL FEEDING ON DIGESTIVE EFFICIENCY, GROWTH AND QUALITIES OF MUSCLE AND OOCYTE OF MATURING ATLANTIC MACKEREL (SCOMBER SCOMBRUS L.)JOURNAL OF FOOD BIOCHEMISTRY, Issue 6 2007KRISNA RUNGRUANGSAK-TORRISSEN ABSTRACT Maturing Atlantic mackerel with and without artificial feeding, kept in sea pens (September to May), showed differences in digestive efficiency (protease activity ratio of trypsin to chymotrypsin), muscle growth (concentrations of RNA, protein, RNA/protein ratio and free amino acids [FAA]) and oocyte quality (trypsin-like specific activity, and concentrations of RNA, RNA/protein ratio and FAA). The artificially fed mackerel had higher body weights (1.7 times) but with less white muscle protein concentration (0.5 time), compared to the control group. Both groups showed higher levels of capacity for protein synthesis in the oocytes than in the white muscle, but it was about two times higher in the artificially fed fish whereas about four times higher in the control group. This indicated that, during maturation, development of oocytes and muscle for growth occurred concurrently in higher growth mackerel, while development of oocytes dominated in slower growth fish. A higher trypsin-like specific activity with higher FAA levels in the oocytes from females fed with an artificial diet, compared to the control group, suggested differences in development and quality between the gametes of the fish with different feedings. PRACTICAL APPLICATIONS The work illustrates differences in digestive efficiency and the quality of growth performance (growth and protein metabolism in muscle and oocytes) in fish with different feedings. The use of various methods for evaluating digestive efficiency and the quality of fish growth performance could provide reasonable information for some important biological differences between fish groups, especially when the number of samples are low. It is more advantageous to apply different methods simultaneously than using growth parameter alone in order to study for precise evaluation of the quality of fish growth performance. The methods are very practical for studying food utilization and growth quality of fish in different environmental conditions and with different behaviors in aquaculture as well as in natural ecosystem where food consumption rate and feeding regime cannot be under control. [source] Determinants of polyphagy by a woolly bear caterpillar: a test of the physiological efficiency hypothesisOIKOS, Issue 2 2001Michael S. Singer The physiological efficiency hypothesis argues that the physiological efficiency of food utilization determines feeding habits of herbivorous insects. Although relatively unsuccessful at explaining dietary specificity, it may explain the food-mixing habit of individually polyphagous herbivores because they may opportunistically increase physiological efficiency by optimizing nutrient balance or diluting toxins in the course of feeding on multiple host-plant species. This study tests two predictions of the physiological efficiency hypothesis with the woolly bear caterpillar, Grammia geneura (Strecker) (Lepidoptera: Arctiidae). Namely, both herbivore performance (survival, developmental rate, pupal mass) and growth efficiency should be better on mixed-plant diets than on single-plant diets. In a series of three laboratory experiments, I found that larval survival and developmental rate on mixed-plant diets were superior to performance on single-plant diets in only one of four cases. In all other cases, mixed-plant diets were either inferior (female pupal mass) to single-plant diets or not detectably different from them. Larval growth efficiency on mixed-plant diets was never superior to that on single-plant diets. In mixed-plant treatments, caterpillars often selected a diet that included plant species of relatively low suitability alone, thereby suffering reduced performance and growth efficiency. These results contradict predictions of the physiological efficiency hypothesis, indicating the limitations of the conventional focus on the physiological constraints on food utilization as an explanation for both individual polyphagy and dietary specificity in herbivorous insects. [source] | ||||||||||