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- Studies on the influence of different diets and rearing conditions on the development and growth of the two-spotted cricket Gryllus bimaculatus de Geer (2011)
- •The effect of rearing conditions and different diets on larvae and adults of the two-spotted cricket, Gryllus bimaculatus de Geer (Orthoptera: Gryllidae), was studied. •The percent increase in body and ovary mass of adult females reared under crowded conditions was higher than that of those reared under isolated conditions. •Higher population density increased reproductive investment in adult females, regardless of the presence or absence of adult males. •The presence or absence of adult males appeared to have no significant effect on the pronotum width, increase in body mass, DLM mass and ovary mass of adult females. •Not only the population density plays an important role in morphological, physiological and behavioural changes, but also the absolute number of animals in a population may influence the above-mentioned parameters. •A strong positive correlation was found between increase in body and ovary mass and decrease in flight muscle and fat body mass; the loss of flight muscle and fat body mass is due to a high egg production. •Five different diets were used: standard diet (ca. 20 % protein, 4.5 % lipid, 45.5 % carbohydrate), modified standard diet (ca. 22 % protein, 6 % lipid, 42 % carbohydrate), and three semi-artificial diets, all containing 30 % protein but differing amounts of lipid (A: normal, B: low, C: high). •The amount of diet consumed highly depends on the type of diet given. •Weak relationships were obtained between increase in body mass and different amounts of diets consumed. •The amount of the different storage products in the fat body of 5-day-old adult females can be arranged in the following order: lipid, protein, glycogen and free carbohydrate. •The total lipid concentration in the haemolymph was generally much higher than carbohydrate concentration. •When fed on a high calory diet, the amount of food consumed was reduced. •When crickets were fed on artificial diets from penultimate larval stage, they displayed a lower increase in body mass and some reduction in flight muscle and ovary mass compared with crickets fed on artificial diet from the day of the adult moult only. •With respect to body and ovary mass, when fed to adult females modified standard diet was heartier, followed by diet A, B, C and standard diet. •When fed to penultimate larvae onwards, however, diets B and C resulted in a significantly reduced body and ovary mass. This indicates that when diets too low or too high in lipid content are fed for a longer period, cricket cannot compensate for it. •The development and reproductive investment of Gryllus bimaculatus shows a high degree of dependence on diet availability, diet quality and quantity, and food intake. Therefore, crickets raised on the different diets did not grow at equal rates. •The results unambiguously show that population density dramatically alters cricket behavioural, morphological and physiological characteristics; as a matter of fact there was a strong correlation between crowded conditions and an increase in metabolic rate, which in turn had an influence on the effects of different diets.