Field work was conducted in the southern half of the Molopo Nature Reserve(MNR) near Vostershoop in the North West Province of South Africa to(1) describe the past and present distribution of Red-billed Spurfowl(Ptern...Field work was conducted in the southern half of the Molopo Nature Reserve(MNR) near Vostershoop in the North West Province of South Africa to(1) describe the past and present distribution of Red-billed Spurfowl(Pternistis adspersus) in South Africa and(2) to describe the dispersion of Red-billed Spurfowl at waterholes in the MNR.The Red-billed Spurfowl did not colonize this area from Bo-tswana in the 1990s as reported in Hockey et al.(2005) and their distribution status and population sizes are not determined by long distance(30-100 km) and/or seasonal movements between the two countries.Red-billed Spurfowl are sparsely distributed and mainly occur in clusters near man-made waterholes.Waterholes provide water and food found in and around antelope droppings.The movement of the Red-billed Spurfowl between waterholes over short distances of 2-5 km was probably encouraged by the sinking of more boreholes since the 1980s(and the creation of 'veeposte'(game/livestock camps) around them).Low rainfall that results in limited insects is probably the single most important factor limiting populations of the Red-billed Spurfowl in South Africa.展开更多
Insect infestation, soil moisture, and yield were examined in populations of≈33 140 plants/ha （low） and ≈ 40 340 plants/ha （high） of an oilseed sunflower, Helianthus annuus L, cv. ＇ Triumph 660CL＇ with two lev...Insect infestation, soil moisture, and yield were examined in populations of≈33 140 plants/ha （low） and ≈ 40 340 plants/ha （high） of an oilseed sunflower, Helianthus annuus L, cv. ＇ Triumph 660CL＇ with two levels of weediness. Less weedy plots resulted from the application of herbicide combination of S-metolachlor and sulfentrazone, whereas more weedy plots resulted from application of sulfentrazone alone. Among the 12 weed species recorded, neither plant numbers nor biomass differed between crop plant densities. Larvae of the stalk-boring insects Cylindrocopturus adspersus （Coleoptera： Curculionidae） and Mordellistena sp. （Coleoptera： Mordellidae） were less abundant in high density sunflowers, ostensibly due to reduced plant size. However, the same effect was not observed for Dectes texanus （Coleoptera： Cerambycidae） or Pelochrista womanana （Lepidoptera： Tortricidae）, two other stalk-boring insects. Soil moisture was highest in low density and lowest in the high density sunflowers that were less weedy. Stalk circumference, head diameter, and seed weight were reduced for sunflower plants with short interplant distances （mean = 20 cm apart） compared to plants with long interplant distances （mean = 46 cm apart）. These three variables were greater in less weedy plots compared with more weedy plot〉 and positively correlated with interplant distance. Yields on a per-hectare basis paralleled those on a per-plant basis but were not different among treatments. The agronomic implications of planting density are discussed in the context of weed and insect management.展开更多
Paralichthys adspersus is a native species from the Pacific coast of South America that is of great economic importance for Peruvian aquaculture.Even though establishing sustainable farming depends on avoiding irrever...Paralichthys adspersus is a native species from the Pacific coast of South America that is of great economic importance for Peruvian aquaculture.Even though establishing sustainable farming depends on avoiding irreversible damage to the population gene pool due to processes such as inbreeding,studies focusing on genetically characterizing farmed stocks are yet to be documented.By using ten microsatellite loci on captive and wild individuals of P.adspersus,we successfully characterized the only commercial broodstock of this species in Peru by means of determining the genetic diversity and inferring relatedness.Although most microsatellite loci showed deviations from Hardy-Weinberg equilibrium,the genetic diversity levels in the commercial broodstock were considered healthy compared to those obtained for a wild population,with an average number of alleles of 17.40,an effective number of alleles of 9.14,and an observed and expected heterozygosity of 0.49 and 0.87.No significant differences between the broodstock and the wild population in terms of genetic diversity were observed.The fixation index and analysis of molecular variance also indicated a low rate of differentiation between both populations.In relatedness estimation,the analysis based on five method-of-moment estimators and a maximum-likelihood estimator showed the category“unrelated”as being the most probable relationship among the individuals within the commercial broodstock.Our findings reveal the conservation of genetic diversity in this population and outline potential breeding strategies that hatchery managers could use to minimize the loss of genetic diversity and long-term inbreeding.This could help establish proper genetic management in captive populations of P.adspersus and should apply to other captive stocks where pedigree information is lacking.展开更多
Objective: To evaluate the suitability of Palaemon adspersus (P. adspersus) as a bio-indicator for 4 and 10 days of cadmium toxicity bioassays. Methods: Four and ten days experiments were designed. CdCl2·2?H2O wa...Objective: To evaluate the suitability of Palaemon adspersus (P. adspersus) as a bio-indicator for 4 and 10 days of cadmium toxicity bioassays. Methods: Four and ten days experiments were designed. CdCl2·2?H2O was dissolved in distilled water and a stock solution was made. At 4-day bioassay, the larvae of Baltic prawns were exposed to nominal concentrations of 0, 0.02, 0.05, 0.1, 0.5, 1.0 and 5.0 mg/L of Cd for 4 days. The 4-day LC50 was calculated by the probit analysis. At 10-day bioassay, the concentrations of 0.05, 0.1, 0.5, 1.0, 5.0, 10.0 and 20.0 mg/L were introduced into each of the jars in triplicate treatments and 0 mg/L as control. Each tank containing 20 larvae was exposed to test solutions. Results: Results from probit analysis showed that the 96-h LC50 value was 0.14 mg/L for Cd. The 10 days bioassays were conducted with nominal concentrations of 0, 0.05, 0.1, 0.5, 1.0, 5.0, 10.0 and 20.0 mg/L Cd. Mortality increased in parallel with the increase in concentrations of Cd on Zoea – I stage of P. adspersus and time of exposure. The toxicity rate of the organism is concentration-dependent. All organisms except the control group died at the end of 10 days. Less than 25% of the animals survived at the 5 days of the exposure to concentrations of 0.5 mg/kg Cd or more. Only 20% of the organisms survived at the 7 days of the exposure to concentrations of 0.1 mg/kg Cd or less in seawater with clean sediment. Conclusions: The results showed that Cd was highly toxic to P. adspersus. When the larvae were exposed to concentrations of Cd, they become slightly excited and swam erratically, probably due to stress. However, behavioural and swimming patterns in control groups were normal, and there was not any mortality during the course of the experiment.展开更多
文摘Field work was conducted in the southern half of the Molopo Nature Reserve(MNR) near Vostershoop in the North West Province of South Africa to(1) describe the past and present distribution of Red-billed Spurfowl(Pternistis adspersus) in South Africa and(2) to describe the dispersion of Red-billed Spurfowl at waterholes in the MNR.The Red-billed Spurfowl did not colonize this area from Bo-tswana in the 1990s as reported in Hockey et al.(2005) and their distribution status and population sizes are not determined by long distance(30-100 km) and/or seasonal movements between the two countries.Red-billed Spurfowl are sparsely distributed and mainly occur in clusters near man-made waterholes.Waterholes provide water and food found in and around antelope droppings.The movement of the Red-billed Spurfowl between waterholes over short distances of 2-5 km was probably encouraged by the sinking of more boreholes since the 1980s(and the creation of 'veeposte'(game/livestock camps) around them).Low rainfall that results in limited insects is probably the single most important factor limiting populations of the Red-billed Spurfowl in South Africa.
文摘Insect infestation, soil moisture, and yield were examined in populations of≈33 140 plants/ha （low） and ≈ 40 340 plants/ha （high） of an oilseed sunflower, Helianthus annuus L, cv. ＇ Triumph 660CL＇ with two levels of weediness. Less weedy plots resulted from the application of herbicide combination of S-metolachlor and sulfentrazone, whereas more weedy plots resulted from application of sulfentrazone alone. Among the 12 weed species recorded, neither plant numbers nor biomass differed between crop plant densities. Larvae of the stalk-boring insects Cylindrocopturus adspersus （Coleoptera： Curculionidae） and Mordellistena sp. （Coleoptera： Mordellidae） were less abundant in high density sunflowers, ostensibly due to reduced plant size. However, the same effect was not observed for Dectes texanus （Coleoptera： Cerambycidae） or Pelochrista womanana （Lepidoptera： Tortricidae）, two other stalk-boring insects. Soil moisture was highest in low density and lowest in the high density sunflowers that were less weedy. Stalk circumference, head diameter, and seed weight were reduced for sunflower plants with short interplant distances （mean = 20 cm apart） compared to plants with long interplant distances （mean = 46 cm apart）. These three variables were greater in less weedy plots compared with more weedy plot〉 and positively correlated with interplant distance. Yields on a per-hectare basis paralleled those on a per-plant basis but were not different among treatments. The agronomic implications of planting density are discussed in the context of weed and insect management.
文摘Paralichthys adspersus is a native species from the Pacific coast of South America that is of great economic importance for Peruvian aquaculture.Even though establishing sustainable farming depends on avoiding irreversible damage to the population gene pool due to processes such as inbreeding,studies focusing on genetically characterizing farmed stocks are yet to be documented.By using ten microsatellite loci on captive and wild individuals of P.adspersus,we successfully characterized the only commercial broodstock of this species in Peru by means of determining the genetic diversity and inferring relatedness.Although most microsatellite loci showed deviations from Hardy-Weinberg equilibrium,the genetic diversity levels in the commercial broodstock were considered healthy compared to those obtained for a wild population,with an average number of alleles of 17.40,an effective number of alleles of 9.14,and an observed and expected heterozygosity of 0.49 and 0.87.No significant differences between the broodstock and the wild population in terms of genetic diversity were observed.The fixation index and analysis of molecular variance also indicated a low rate of differentiation between both populations.In relatedness estimation,the analysis based on five method-of-moment estimators and a maximum-likelihood estimator showed the category“unrelated”as being the most probable relationship among the individuals within the commercial broodstock.Our findings reveal the conservation of genetic diversity in this population and outline potential breeding strategies that hatchery managers could use to minimize the loss of genetic diversity and long-term inbreeding.This could help establish proper genetic management in captive populations of P.adspersus and should apply to other captive stocks where pedigree information is lacking.
基金Supported by the University of Sinop,Fisheries Faculty,Department of Hydrobiology(Grant No.S.049).
文摘Objective: To evaluate the suitability of Palaemon adspersus (P. adspersus) as a bio-indicator for 4 and 10 days of cadmium toxicity bioassays. Methods: Four and ten days experiments were designed. CdCl2·2?H2O was dissolved in distilled water and a stock solution was made. At 4-day bioassay, the larvae of Baltic prawns were exposed to nominal concentrations of 0, 0.02, 0.05, 0.1, 0.5, 1.0 and 5.0 mg/L of Cd for 4 days. The 4-day LC50 was calculated by the probit analysis. At 10-day bioassay, the concentrations of 0.05, 0.1, 0.5, 1.0, 5.0, 10.0 and 20.0 mg/L were introduced into each of the jars in triplicate treatments and 0 mg/L as control. Each tank containing 20 larvae was exposed to test solutions. Results: Results from probit analysis showed that the 96-h LC50 value was 0.14 mg/L for Cd. The 10 days bioassays were conducted with nominal concentrations of 0, 0.05, 0.1, 0.5, 1.0, 5.0, 10.0 and 20.0 mg/L Cd. Mortality increased in parallel with the increase in concentrations of Cd on Zoea – I stage of P. adspersus and time of exposure. The toxicity rate of the organism is concentration-dependent. All organisms except the control group died at the end of 10 days. Less than 25% of the animals survived at the 5 days of the exposure to concentrations of 0.5 mg/kg Cd or more. Only 20% of the organisms survived at the 7 days of the exposure to concentrations of 0.1 mg/kg Cd or less in seawater with clean sediment. Conclusions: The results showed that Cd was highly toxic to P. adspersus. When the larvae were exposed to concentrations of Cd, they become slightly excited and swam erratically, probably due to stress. However, behavioural and swimming patterns in control groups were normal, and there was not any mortality during the course of the experiment.
