Effect of food and temperature on the growth and development of Moina irrasa (Cladocera : Moinidae)

Body length, instar duration, fecundity, and survival rate of Moina irrasa from a subtropical Chinese lake were studied at three food concentrations (4, 8, and 40 mg/L, wet weight) and six temperatures (10, 15, 20, 25, 30, and 35degreesC) in the laboratory. Body length tended to decrease with increase of temperature, while the trend was reversed as food concentration rose. M. irrasa had three juvenile instars, except there were four at 10degreesC, and the number of adult instars showed great variation (3-15). Water temperature and food concentration both affected the duration time of adult instars. The largest broods were from the third to sixth adult instars, depending on food and temperature, and the mean highest number of offspring per brood was 56 at 25degreesC. A significant relationship between body length and brood size appeared at high (40 mg/L) and medium (8 mg/L) food concentrations, while there was no significant relationship at low food concentration except at 25 degreesC. The intrinsic rate of population increase ranged between 0.104 and 1.825 ind./day.

Studies on the biology of Chaoborus flavicans (Meigen) (Diptera : Chaoboridae) in a fish-free eutrophic pond, Japan

Population dynamics of Chaoborus flavicans larvae of various instars was studied from November 1986 to December 1987 in a eutrophic, fish-free pond, Japan. First and 2nd instar larvae were observed from late April to late October, indicating a reproductive period of about half a year. C. flavicans overwintered in the 4th instar larvae. In water column samples, total density of all instars was 680-23 680 m(-2), and pupal density 0-2 600 m(-2); larvae of the Ist, 2nd, and 3rd instars showed 5-6 density peaks in 1987, suggesting that 5-6 generations occur during a year (peaks of the 4th instar larvae were not clear, probably due to their longer development than those of younger instars). In sediment samples, no Ist and 2nd instar larvae were found, 3rd instar larvae were found occasionally but density of the 4th instar larvae was 280-18 600 m(-2), and pupal density varied between 0-502 m(-2). Fouth instar larvae accumulated in sediment in the cold season and in the water column in the warm season; high temperature and low oxygen concentration were the most important factors limiting the distribution of larvae in the sediment in summer in the NIES pond. The dry weight of total C. flavicans larvae was 0.08-4.2 g m(-2) in sediment samples and 24-599 mu g l(-1) (0.10-2.40 g m(-2)) in water column samples. Comparisons of maximum densities in the NIES pond in different years and in waters of different trophic status show that density is generally higher in eutrophic than in oligotrophic habitats.

Effects of azadirachtin on hemolymph protein expression in Ostrinia furnacalis (Lepidoptera : Crambidae)

The botanical insecticide azadirachtin affects a variety of biological processes. Our early work indicated that protein level and type are significantly influenced by azadirachtin in pupae of Osttiniafumacalis (Guenee) (Lepidoptera: Crambidae) because a correlation exists between protein content and azadiraebtin concentration. By use of proteomic techniques, we analyzed changes in hemolymph protein expression of 48-h-old pupae in O. furnacalis induced by azadirachtin treatment. After feeding by third instars on an artificial diet containing 10 ppm azadirachtin until pupation, 48-b-old pupae were collected, and hemolymph protein samples were prepared. They were separated by two-dimensional polyacrylamide gel electrophoresis, and six proteins were significantly affected by azadiracbtin treatment compared with an untreated control. Two of these proteins were identified by database searching with peptide mass fingerprinting by using matrix-assisted laser desorption/ time-of-flight mass spectrometry after in-gel trypsin digestion. They belong to the insect apolipophorin-III and phospboribosyltransferase family, respectively. These two proteins may function on lipid metabolism in insect hemolymph. Furthermore, fat body is the center of synthesis and secretion of hemolymph proteins. We suggest that the azadirachtin exerts its insecticidal effects on the fat body of O. furnacalis by interfering with protein expression related to hemolymph lipid metabolism.