Responses of nymphs of desert locust,Schistocerca gregaria to volatiles of plants used as rearing diet

Summary Gregarious nymphs of the desert locust,Schistocerca gregaria (Forsk.) (Orthoptera: Acrididae) were more attracted to volatiles from mechanically damaged food plants used for rearing than to either the undamaged or damaged food plants not used as diet in Y-tube olfactometer assays. Comparative analysis of the volatile emissions from plants used for rearing and food plants not used for rearing,e.g. Sorghum bicolor, Pennisetum clandestinum, Schouwia thebaica, wheat (Triticum sp., var. Nyangumi),Zygophyllum simplex, Heliotropium undulatum andTribulus terrestris was carried out by GC, GC-EAD and GC-MS. Significant quantitative and qualitative differences were found in the volatile emissions and olfactory responses of nymphs in GC-EAD assays. Up to 33 compounds were identified in volatiles of the plants of which 9 evoked EAGs. EAG-active components included common green leaf compounds (E)-2-pentenal, (E)-2-hexenal, 4-methyl-3-pentenal, (E)-3-hexenyl acetate, (Z)-3-hexenyl acetate, (Z)-2-hexenyl acetate, (Z)-3-hexen-1-ol and (Z)-2-hexen-1-ol. (Z)-3-Hexenyl butyrate and (Z)-3-hexenyl isovalerate were detected in stimulatory amounts only in the volatiles ofS. thebaica. (E, Z)-2,6-Nonadienal was detected as a component in the volatiles ofT. terrestris and was highly stimulatory. In EAG assays with seven common green leaf volatiles, (Z)-3-hexenyl acetate was most stimulatory while hexanal was the least. No significant differences were recorded between antennal responses of males and females to the tested compounds. These results are discussed with regard to current hypotheses on host plant recognition through detection of their airborne volatiles and the learning behaviour by nymphs ofS. gregaria.     

Survey of Levels of Phthalate Ester Plasticizers in a Sewage Lagoon Effluent and a Receiving Stream

In this study, samples from a sewage treatment lagoon and those from a receiving stream were analyzed for their phthalate esters content. Knowledge of the distribution of ubiquitous phthalate esters in the sewage lagoon and the receiving stream was necessary because of the reports of their subtle toxicity to aquatic biota and humans. Liquid–liquid extraction, Clean-up experiment and High Performance Liquid Chromatography (HPLC) were the methods employed for the quantitative determination of the Phthalates. A study of uncontaminated water was done to establish blank levels. The sewage lagoon and the receiving stream were grossly polluted as several phthalate ester plasticizers: DMP, DEP, DPhP, DBP, DEHP, DOP and DINP were found present at monthly mean levels of between 24.02 mg/L and 139.25 mg/L in the sewage treatment lagoon and 10.41 mg/L and 80.53 mg/L in the receiving stream. The results showed higher levels of phthalate esters in the sewage lagoon compared to the receiving stream. The sewage lagoon was identified as a pollution point source into the receiving stream. Levels of phthalates obtained from the receiving stream are much higher than the water criteria of 3 μg/L phthalates recommended by the United States Environmental Protection Agency (USEPA) for the protection of fish and other aquatic life in water and the Suggested No-Adverse Effect Levels (SNAEL) of 7.5–38.5 μg/L for drinking water. This should give cause for great environmental concern. Peoples’ health downstream is at stake and so is the ‘health’ of the ecosystem.     

Natural radioactivity and trace metals in crude oils: implication for health

Crude oil samples were collected from six different fields in the central Niger Delta in order to determine their natural radioactivity and trace element contents, with the aim of assessing the radiological health implications and environmental health hazard of the metals, and also to provide natural radioactivity baseline data that could be used for more comprehensive future study in this respect. The activity concentrations of the radionuclides were measured using a well, accurately calibrated and shielded vertical cryostat, Canberra coaxial high-purity germanium (HPGe) detector system, and the derived doses were evaluated. The metal concentrations were determined by the graphite furnace atomic absorption spectroscopic (GFAAS) method. The radionuclides identified with reliable regularity belong to the decay series of naturally occurring radionuclides headed by ²³⁸U and ²³²Th along with the non-decay series radionuclide, ⁴⁰K. The averaged activity concentrations obtained were 10.52 ± 0.03 Bq kg⁻¹, 0.80 ± 0.37 Bq kg⁻¹ and 0.17 ± 0.09 Bq kg⁻¹ for ⁴⁰K, ²³⁸U and ²³²Th, respectively. The equivalent doses were very low, ranging from 0.0028 to 0.012 mSv year⁻¹ with a mean value of 0.0070 mSv year⁻¹. The results obtained were low, and hence, the radioactivity content from the crude oils in the Niger delta oil province of Nigeria do not constitute any health hazard to occupationally exposed workers, the public and the end user. The concentrations of the elements (As, Cd, Co, Fe, Mn, Ni, Se and V) determined ranged from 0.73 to 202.90 ppb with an average of 74.35 ppb for the oil samples analysed. The pattern of occurrence of each element agreed with the earlier studies from other parts of the Niger Delta. It was obvious from this study and previous ones that the Niger Delta oils have low metal contents. However, despite the low concentrations, they could still pose an intrinsic health hazard considering their cumulative effects in the environment. Also, various studies on the impact of oil spillage and activities of oil exploration and production on organisms in the immediate environment suggest this.     

Studies on the maturation-accelerating pheromone of the desert locustSchistocerca gregaria (Orthoptera: Acrididae)

Summary The accelerating effect of mature males of the desert locust,Schistocerca gregaria, on the maturation of immature male and female conspecifics was confirmed. The onset of sexual activity was found to correlate with yellowing of the male insects. Using the colour as an indicator of maturation, the maturation-hastening effect of an hexane extract from mature males was also confirmed. Likewise, volatiles from mature males placed in the upper storey of a two-chamber bioassay system (no visual or tactile contact possible) and charcoal-trapped volatiles from the mature males also induced accelerated maturation in recipient males placed in the lower storey. GC and GC-MS analysis of volatiles collected from 4-week-old mature males showed the presence of anisole, benzaldehyde, veratrole, phenylacetonitrile and 4-vinylveratrole, roughly at the ratio 4.8:7.0:3.3:79.8:5.0. In addition, guaiacol, phenol, benzoylnitrile, benzyl alcohol and 2-benzoyloxyphenylacetonitrile were present in smaller amounts. These compounds were either absent or found only in trace amounts in the female volatiles. Earlier, we had shown that essentially the same blend collected from younger males (10–20 d old, not yet demonstrating signs of maturation) induced strong aggregation of both sexes of adult desert locusts, suggesting a parsimonious role for the pheromone system: as an adult aggregation signal and as a maturation accelerant in young adults.     

Heavy metals pollution in a sewage treatment oxidation pond and the receiving stream of the Obafemi Awolowo University, Ile Ife, Nigeria

This work centered on a 1-year evaluation campaign of point source pollution from a sewage treatment oxidation pond and its receiving stream. Water samples were collected from the sewage treatment oxidation pond and the receiving stream during July 2002 and June 2003. Concentrations of heavy metals were determined using Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) after a triple acid digestion of samples using open beaker method. Generally, the results showed high levels of toxic metals such as Cd, Pb, As, Al, Cr, Mn, Co, and Fe in the influent and effluent samples as well as in the receiving stream. The annual mean concentration of metals in the sewage samples ranged from 11.90 to 16.05, 64.96 to 88.27, 38.91 to 76.35, 17.46 to 24.45 mug/L for Cd, As, Pb, Co, and 4.31 to 8.77, 1.71 to 2.45, 0.46 to 0.74 and 13.82 to 20.47 mg/l for Al, Cr, Mn and Fe, respectively; while in the receiving stream, the concentrations were between 6.89 to 10.45, 35.50 to 59.26, 22.85 to 35.94, 11.33 to 18.83 mug/l for Cd, As, Pb, Co, and 1.99 to 3.49, 1.35 to 2.08, 0.21 to 0.48, and 8.93 to 14.15 mg/l for Al, Cr, Mn and Fe, respectively. The discharge of the effluent from the sewage pond into the receiving stream has therefore led to increase in the concentrations of some heavy metals downstream, thus impacting the receiving stream negatively and could pose a serious health hazard to aquatic ecosystems and humans particularly for rural dwellers and peasant farmers downstream that utilize the water from the receiving stream for various domestic and agricultural purposes untreated.     

Determination of endocrine disruptors in Kafue lechwe (Kobus leche kafuensis) samples from the Lochinvar National Park of Zambia

Analysis of serum, whole blood and liver tissue samples from Kafue lechwe in the Lochinvar National Park of Zambia for suspected endocrine disrupting compounds revealed high concentrations for some of the compounds. 45 samples of serum, whole blood and liver tissue were extracted by liquid-liquid extraction followed by an analysis using Gas Chromatography-Electron Capture Detection (GC-ECD). The following endocrine disruptors were analyzed: deltamethrin, aldrin, endosulfan, dieldrin, pp-DDD, heptachlor, d-t-allethrin, pp-DDE, endrin and pp-DDT. For all the samples, dieldrin showed the highest concentration ranging from 1.7 to 44.4 microg/ml in serum and whole blood sample extracts and 0.10-5.1 microg/g wet weight in liver sample extracts. The most frequently detected was deltamethrin in 62% of the samples. Percent recoveries in spiked laboratory blanks ranged between 60% and 100% while calculated detection limits ranged from 0.004 to 0.21 microg/ml for all the endocrine disruptors evaluated. Where endocrine disruptors were detected, the concentrations of most of them far exceeded the maximum residue limits (MRLs) and the extraneous maximum residue limits (EMRLs) set by the Codex Alimentarius of the United Nations (UN), Food and Agricultural Organization (FAO).