Contrasting effects of sewage sludge and commercial fertilizer on egg to adult development of two herbivorous insect species

The Effect of Different Heavy Metals on the Development of Lucilia sericata (Diptera: Calliphoridae)

This study investigates the impacts of three different heavy metals at different concentrations on some life-history traits of Lucilia sericata (Meigen 1826) (Diptera: Calliphoridae). First-instar larvae of L. sericata were reared on a diet containing four concentrations (0.25, 0.50, 1, and 2 µg/g) of the heavy metals (cadmium, zinc copper). The parameters measured were larval and pupal mortality, larval length, adult, pupal, and larval weight, and development time. Larval and pupal survival decreased as heavy metal concentrations increased. Pupal weight was significantly different among heavy metals andc oncentrations, but the adult weight was not significantly different among heavy metals and concentrations. The larval length was significantly different among concentrations and heavy metals. This study reveals that the presence of heavy metal in carrion or the carrion environment should be inconsidered when estimating the time of colonization in forensic investigations.

Black soldier fly (Hermetia illucens L.) as a high-potential agent for bioconversion of municipal primary sewage sludge

The treatment of municipal wastewater produces clean water and sewage sludge (MSS), the management of which has become a serious problem in Europe. The typical destination of MSS is to spread it on land, but the presence of heavy metals and pollutants raises environmental and health concerns. Bioconversion mediated by larvae of black soldier fly (BSFL) Hermetia illucens (Diptera, Stratiomyidae: Hermetiinae) may be a strategy for managing MSS. The process adds value by generating larvae which contain proteins and lipids that are suitable for feed and/or for industrial or energy applications, and a residue as soil conditioner. MSS from the treatment plant of Ladispoli (Rome province) was mixed with an artificial fly diet at 50% and 75% (fresh weight basis) to feed BSFL. Larval performance, substrate reduction, and the concentrations of 12 metals in the initial and residual substrates and in larval bodies at the end of the experiments were assessed. Larval survival (> 96%) was not affected. Larval weight, larval development, larval protein and lipid content, and waste reduction increased in proportion the increase of the co-substrate (fly diet). The concentration of most of the 12 elements in the residue was reduced and, in the cases of Cu and Zn, the quantities dropped under the Italian national maximum permissible content for fertilizers. The content of metals in mature larvae did not exceed the maximum allowed concentration in raw material for feed for the European Directive. This study contributes to highlight the potential of BSF for MSS recovery and its valorization. The proportion of fly diet in the mixture influenced the process, and the one with the highest co-substrate percentage performed best. Future research using other wastes or by-products as co-substrate of MSS should be explored to determine their suitability.

The vertical variation of nutrients in a sediment core of Delong Lake reveals the anthropogenic effect

Phosphorus content and its species were studied for the core sediments of Delong Lake, using the SMT sequential extraction method, and then were correlated to the contents of total nitrogen and organic matter. According to (210)Pb and (137)Cs dating, the historical profiles of 33 cm core sediments were generated. The objective of this study was to understand how nutrients of lake sediments evolved in order to get insights into the effect of human activities on their sedimentary history. The nutrients contents in the core sediments slowly increased after 1957, showing the human activity influence the natural deposition of the lake sediment. From 1978 to 1985, various nutrients in the lake sediment rapid increased, showing that the human activities strengthened. From 2003 to now, most of nutrients in the sediment rapidly increased and significantly modified the natural deposition of the lake sediment.

Food utilization and growth of cutworm Spodoptera litura Fabricius larvae exposed to nickel, and its effect on reproductive potential

Food utilization and growth of the 5th and 6th instar Spodoptera litura Fabricius larvae, and its effect on reproduction potential was evaluated by feeding larvae diets with different doses of Ni for 3 generations. Dose-dependent relationships between Ni levels and food consumption and growth were variable with different larval developmental period and Ni exposure duration. RCR, AD and RGR of the 6th instar larvae were much more affected by Ni exposure than those of 5th instar larvae, and the effects were strongest in the 3rd generation. It was found that RCR was significantly stimulated after 1 and 20 mg kg(-1) Ni exposure, while AD was significantly inhibited after 1, 5, 10 and 40 mg kg(-1) Ni exposure. However, lower levels of Ni (≤5 mg kg(-1)) significantly increased and higher levels of Ni (≥10 mg kg(-1)) significantly decreased RGR. In 3 successive generations, 10 mg kg(-1) Ni significantly increased the ECI and ECD of the 5th instar larvae, and 5 mg kg(-1) Ni significantly increased the ECD of the 6th instar larvae. However, ECD were all significantly inhibited with 20 mg kg(-1) Ni exposure. Results also revealed that durations of larvae were shortened at low levels of Ni, but extended at high levels of Ni. Fecundity was inhibited by the highest Ni doses in each generation, while improved by low Ni doses in the 3rd generation. Hatching rates in all treatments were significantly decreased in a Ni dose-dependent manner. Study indicated that effects of Ni on these parameters were predominant with the increasing Ni exposure period.

Effects of the heavy metal Cu2+ on growth, development, and population dynamics of Spodoptera litura (Lepidoptera: Noctuidae)

Spodoptera litura (F.) larvae were fed with artificial food containing four different concentrations of copper (25, 50, 100, and 200 mg/kg). Copper affected growth, development, and population dynamics of late instar larvae. Our results indicate that the fourth and fifth instar survival rates were significantly reduced at 50-200 mg/kg copper (Cu2+). Moreover, all the Cu2+ treatments significantly reduced pupation and moth emergence rates in a dose-dependent manner. Larvae fed 25 or 50 mg/kg Cu2+ showed significant reductions in development period compared with non-Cu controls, and the pupation duration of animals fed 200 mg/kg was significantly longer than in non-Cu controls. All Cu2+ concentrations significantly reduced individual pupal weights compared with controls. In addition, Cu2+ at some concentrations significantly affected fertility parameters, such as doubling population time (DT), the net reproduction rate (R(o)), the mean generation time (T), the intrinsic rate of increase (r(m)), and the finite increase rate (A). Our study demonstrates that low concentrations of Cu2+ in the diet (25 and 50 mg/kg) shorten the generation time by 4-5 d, whereas higher Cu2+ concentrations (100 and 200 mg/kg) increase DT for 1-2 d.

Effects of zinc exposure on the reproduction of Spodoptera litura Fabricius (Lepidoptera: Noctuidae)

Reproductive toxicity of Zn to insects was investigated in this study. By exposing phytophagous insect Spodoptera litura Fabricius to Zn in artificial diets of larvae, we investigated the effects of Zn on reproduction at ecological and molecular levels. A significantly shorter period of laying eggs was observed in S. litura exposed to 300-750mg Zn/kg. The oviposition rate, fecundity and hatchability of female adults treated with 750mg Zn/kg were significantly lower than those of the controls (31.43%, 20.95% and 52%, respectively, compared to the control). The Zn accumulation and vitellin (Vn) content in eggs were tested by inductively coupled plasma-atomic emission spectrometry and Bradford combining Western-blot, respectively. The results showed that Zn accumulated in the eggs, which has affected the weight and Vn content of eggs with significant negative correlations. The down-regulated expression levels of vitellogenin (Vg) mRNA were detected by real-time polymerase chain reaction (RT-PCR): the relative quantity of Vg mRNA was less than half of the controls at higher than 450mg Zn/kg wet weight. These results indicated that excess Zn made expression of Vg gene down-regulated and caused poor accumulation of egg yolk, which led to a reduction in egg numbers and failure of eggs to hatch.

Carotenoids in a food chain along a pollution gradient

Carotenoids are synthesized by plants, therefore insects and birds must obtain them from their diet. They function in pigmentation and as antioxidants. We studied the carotenoid profiles in a model food chain (plant-insect-bird) in an air pollution gradient to find out whether heavy metal pollution affects the transfer of carotenoids across the trophic levels. Birch leaves showed higher beta-carotene and, one of the birch species (Betula pendula), higher total carotenoids levels in the polluted area. There was no difference in the lutein concentration of caterpillars' food source, birch leaves, between the study areas. Autumnal moth larvae accumulated lutein more efficiently than beta-carotene while sawfly larvae accumulated beta-carotene over lutein. Because of different antioxidant profiles in different leaf chewing insects their sensitivity to pollution stress may differ. The lutein concentration of plasma and feathers of Great tit nestlings did not differ along the pollution gradient. The lack of difference in lutein concentration of autumnal moth larvae along pollution gradient may partly explain the lutein concentrations of Great tit nestlings, since the abundance of autumnal moth larvae peak during the nestling phase of Great tit. The lutein concentration of autumnal moth larvae was positively associated to circulating plasma lutein level of Great tit indicating the importance of carotenoid rich diet during the nestling phase. In addition, the higher the plasma lutein concentration the more lutein was deposited to feathers, irrespective of the other possible functions of lutein in nestlings. We found that carotenoid levels differed between the polluted and the unpolluted area especially at lower levels of food chain: in birches and in caterpillars.

Acetylcholinesterase, catalase and glutathione S-transferase activity in beet armyworm (Spodoptera exigua) exposed to nickel and/or diazinon

The effect of single and combined action of nickel and pesticide (diazinon) on enzymes activity (glutathione S-transferase, catalase and acetylcholinesterase) in the digestive tract, body wall and fat body as well as basic growth parameters (life span and body mass) of Spodoptera exigua were investigated under laboratory conditions. The experiment was carried out on two nickel treated groups [300 (NiI) and 900 (NiII) mg Ni kg(-1) dry weight of the culture medium] and a control group. The results showed that mortality of caterpillars in NiII group was higher (51.1%) when compare with the controls. The body mass of the caterpillars in the NiI group was higher by 20% than in the control group, and the body mass of the pupae in the NiII group was lower by 22% than in the control group. Exposure to nickel influenced AChE, GST and catalase activity in the body wall (increase up to 66%) and GI tract, while in the fat body the above-mentioned activity remained unchanged. The pesticide application caused a strong, about 70% reduction in AChE activity in GI tract, while in case of GST activity pesticide treatment resulted in multidirectional response depending on the organ. Nickel pre-treatment affects the susceptibility to pesticide, which is manifested in a lower activity of GST and catalase in the fat body (from 26 to 36%), when compare with the other experimental groups.