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Sublethal Effects (sublethal + effects)
Selected AbstractsAcute Toxicity and Sublethal Effects of Nitrite on Selected Hematological Parameters and Tissues in Dark-banded Rockfish, Sebastes inermisJOURNAL OF THE WORLD AQUACULTURE SOCIETY, Issue 2 2007In-Seok Park Acute toxicity and sublethal effects of nitrite in dark-banded rockfish, Sebastes inermis (83.3 ± 7.2 g), were studied under static conditions for a period of 96 h. The acute toxicity of nitrite evaluated for the 96-h lethal concentration (LC50) was 700 mg/L. The sublethal effects on selected hematological parameters of S. inermis, such as total erythrocyte count (TEC), hemoglobin, plasma glucose, and serum protein content, were measured after 0, 6, 12, 24, 48, 72, and 96 h of exposure to 0, 50, 100, 200, 400, and 700 mg/L of nitrite. Sublethal nitrite caused progressive reduction in the TEC, hemoglobin, and serum protein content in fish depending on the nitrite concentration and exposure period. The 96-h exposure resulted in a 14,42% reduction in TEC and 25,33% reduction in hemoglobin content for 100,700 mg/L of nitrite compared to the control. A dose-related reduction in plasma glucose (25.7,34.2%) was observed for concentrations of 200,700 mg/L of nitrite during 48 h of exposure, followed by an increase through 96 h. A significant reduction in serum protein (7.3,12.6%) was observed for 200,700 mg/L of nitrite after 96 h of exposure. Abnormal histological changes in skin, gill, liver, and kidney tissue were observed in fish exposed to 700 mg/L of nitrite after 96 h of exposure compared to the control. Although no mortality of S. inermis occurred at 500 mg/L of nitrite, all hematological parameters adversely responded to a nitrite dose of 200 mg/L for 96 h. These results showed that although acute toxicity concentration of nitrite in S. inermis is higher than 700 mg/L, sublethal concentrations of nitrite also negatively affect hematological parameters. [source] Sublethal effects of methylmercury on fecal metabolites of testosterone, estradiol, and corticosterone in captive juvenile white ibises (Eudocimus albus),ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 5 2009Evan M. Adams Abstract Methylmercury (MeHg) is a globally distributed neurotoxin, endocrine disruptor, and teratogen, and its effects on birds are poorly understood, especially within an environmentally relevant exposure range. In an effort to understand the potential causal relationship between MeHg exposure and endocrine development, we established four dietary exposure groups (0 [control], 0.05, 0.1, and 0.3 mg/kg wet wt/d of MeHg) of postfledging white ibises (Eudocimus albus) in a divided, free-flight aviary that spanned the estimated range of environmental exposure for this species. Fecal samples were collected from individually identified ibises over six months in 2005 and processed for hormone evaluation. Significant sex-related differences in fecal estradiol concentrations, though unpredicted in direction, suggest that this steroid could be related to juvenile development in this species. Using repeated-measures general linear models, we tested a set of candidate models to explain variation in endocrine expression. We found that MeHg exposure led to significant differences in fecal estradiol concentrations between the control and medium-dose groups, whereas differences in fecal corticosterone concentrations were observed between the control and both the low- and high-dose groups. These results suggest highly nonlinear dose-response patterns for MeHg. Many endocrine-disrupting contaminants are theorized to affect multiple endpoints in a nonlinear manner, making results difficult to interpret using a traditional toxicological approach. The evidence presented here suggests that endocrine effects of MeHg exposure could behave similarly. [source] Lethal and sublethal effects of polychlorinated biphenyls on Rana sylvatica tadpolesENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 1 2002Wesley K. Savage Abstract In static experiments, we exposed tadpoles of the wood frog (Rana sylvatica) to sediment collected from a riverine wetland in the St. Lawrence River basin that is highly contaminated with polychlorinated biphenyls (PCBs). Significant mortality occurred early in the experiment and was not explained by a simple dose-dependent relationship. Direct sediment contact resulted in higher tadpole mortality compared with tadpoles suspended in mesh containers above the sediment. Sublethal effects of exposure were also apparent, characterized by behavioral abnormalities, including reduced activity levels and swimming speed, that differed depending on whether tadpoles were in contact with or suspended above the sediment. We demonstrate in this experiment that PCB-contaminated sediment induced significant mortality and behavioral dysfunction in early development, but the effects on natural populations existing in the contaminated region is not known. [source] Cooler temperatures increase sensitivity to ultraviolet B radiation in embryos and larvae of the frog Limnodynastes peroniiGLOBAL CHANGE BIOLOGY, Issue 6 2007VINCENT O. Van UITREGT Abstract Recent studies suggest that complex interacting processes are driving global amphibian declines. Increased ultraviolet B (UVB) radiation in the solar spectrum associated with ozone depletion has been implicated in declines, and evidence suggests that the effects of UVB radiation on amphibians may be greater at cooler temperatures. We tested the thermal sensitivity of UVB effects on amphibians in a controlled factorial experiment using the striped marsh frog, Limnodynastes peronii as a model species. We compared survival, growth and locomotor performance of embryonic and larval L. peronii reared under low and high UVB exposures at both 20 and 30 °C. Embryonic and larval L. peronii proved extremely sensitive to UVB damage and exhibited greater sensitivity at 20 °C compared with 30 °C. Embryonic survival to Gosner stage 25 was unaffected by UVB exposure at 30 °C, but at 20 °C survival was reduced to 52% under high UVB. Larval survival exhibited a similar trend. At 20 °C, all tadpoles survived under low UVB, whereas under high UVB there was 100% mortality after 15 days of exposure. At 30 °C, 86% survived under low UVB, but only 46% survived under high UVB. Sublethal effects such as, embryonic malformation, retarded larval growth and reduced larval swimming performance were also greater at 20 °C compared with 30 °C. Our results strongly indicate that UVB damage in amphibians is markedly increased at cooler temperatures. Thus, populations of UVB sensitive species occurring at cold climates may be at greater risk of declines due to increased solar UVB radiation. [source] Sublethal effects of selected insecticides on fecundity and wing dimorphism of green peach aphid (Hom., Aphididae)JOURNAL OF APPLIED ENTOMOLOGY, Issue 2 2008X.-Y. Wang Abstract Effects of sublethal concentrations (LC25) of six insecticides (imidacloprid, rotenone, fenvalerate, abamectin, pirimicarb and azadirachtin) on fecundity and wing dimorphism of the green peach aphid, Myzus persicae (Sulzer), were studied both under laboratory and greenhouse conditions. In the laboratory, aphid reproduction reduced by 44.29% and 54.01% when rotenone and abamectin treatments were applied at sublethal dose, respectively, and sublethal fenvalerate application resulted in markedly lower average reproduction per female per day compared with control. Reproductive duration of aphid treated with abamectin significantly decreased by 44.19%. But in the greenhouse, there were no evident differences in the aphid fecundity and reproductive duration between treatments and control. Life-table parameters also demonstrated that the six insecticides at sublethal doses did not stimulate the aphid reproductive potential. In the laboratory, after being exposed to sublethal doses of imidacloprid and fenvalerate, the proportions of alate progeny in aphid progeny were significantly higher than that of the control. In the greenhouse, percentages of alate offspring from the mother aphids treated with imidacloprid, fenvalerate and abamectin increased pronouncedly compared with control. Mortality rates of offspring in the nymphal stages from adults treated with insecticides revealed no significant changes between laboratory and greenhouse. The developmental time in days of the offspring varied in all treatments. Mechanisms of insecticide-induced resurgence are discussed. [source] Sublethal effects of chlorfluazuron on reproductivity and viability of Spodoptera litura (F. ) (Lep., Noctuidae)JOURNAL OF APPLIED ENTOMOLOGY, Issue 5-6 2000F. Perveen To clarify the sublethal effects of chlorfluazuron on reproductivity and viability of common cutworm, Spodoptera litura, some experiments were conducted under laboratory conditions. The LD50 was found to be 12.0 ng/larva when evaluated up to pupation and 9.9 ng/larva up to adult emergence. At lethal dosages the development of different instars, moulting to pupae and emergence into adults were found to be more affected. Reduction in the body weight was also observed in the larvae and pupae when treated with a sublethal dose (LD30 : 3.75 ng/larva) and in the adults when treated with sublethal doses (LD10 : 1.00 ng/larva; LD30 : 3.75 ng/larva) as newly moulted fifth instar larvae of S. litura, although the number of matings per female and life span of adult females and males remained unaffected by the same treatments. When sublethal doses were applied only to females or only to males, or both sexes, the average fecundity reduction was up to 35,44%. When only females were treated with sublethal doses, fertility was reduced by 49,58%; when only males were treated fertility was reduced by 65,81% and when both sexes were treated, fertility was reduced by 68,83%. Hatchability was reduced by 22,26% when only females were treated, by 44,66% when only males were treated and by 45,72% when both sexes were treated with LD10 or LD30 doses as newly moulted fifth instars. The results from these observations suggest that the fecundity was reduced to a similar degree when only females or only males or both sexes were treated with LD10 or LD30 doses as newly moulted fifth instars. However the fertility and hatchability were affected more when only males were treated with LD10 and much more when treated with LD30. Currently, work is in progress to find out the main reasons for the sublethal effects of chlorfluazuron on reproductivity and viability. [source] Acute effects of the antibiotic oxytetracycline on the bacterial community of the grass shrimp, Palaemonetes pugio,ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 12 2009Miguel Uyaguari Abstract The toxicity of oxytetracycline (OTC) was evaluated in adult grass shrimp, Palaemonetes pugio. Initially, static acute (96 h) toxicity tests were conducted with shrimp exposed from 0 to 1,000 mg/L OTC. A calculated lethal concentration 50% value of 683.30 mg/L OTC (95% confidence interval 610.85,764.40 mg/L) was determined from these tests, along with a lowest-observable-effect concentration of 750 mg/L and no-observable-effect concentration of 500 mg/L. Moreover, chronic sublethal effects of OTC exposure on grass shrimp intestinal bacterial population were assessed using doses from 0 to 32 mg/L OTC. The total viable counts in digestive tract content had levels between 5.2 and 1 × 104 colony-forming units per gram of tissue at times 0 and 96 h, respectively. Aeromonas hydrophila were the most resistant isolates (27.78%) to OTC exposure. Vibrio alginolyticus showed significant positive growth following exposure to OTC, whereas other bacterial species abundance declined over time. A total of 268 bacterial isolates were screened using antibiotic resistance analysis from a library containing 459 isolates. Among the tested isolates from the OTC treatments, 15.4% were resistant to OTC and 84.6% were OTC sensitive. Oxytetracycline was generally not consistently quantifiable with liquid chromatography-mass spectroscopy technique in shrimp homogenates. The only peak detected was at the 32 mg/L dose of OTC at 96 h. Nevertheless, OTC had a significant biological effect on the bacterial population. Antibiotic resistance to five other antibiotics (penicillin G, sulfathiazole, trimethoprim, trimethoprim and sulfamethoxazole, and tetracycline) was strongly associated with OTC exposures. The present study indicates that OTC toxicity effects in P. pugio and changes in the shrimp microbial community would only be expected under special circumstances. [source] Critical period of sensitivity for effects of cadmium on frog growth and development,ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 6 2009Jackson A. Gross Abstract Cadmium is a ubiquitous pollutant in aquatic environments that can alter organismal physiology and ecology. Previous experiments found that ecological Cd exposures increased the growth and development of two North American anurans. However, the generality of these effects among species, the time period over which they occur, and the mechanisms responsible remain conjectural. The goal of the present study was to determine the critical period of sensitivity of Rana pipiens exposed to ecologically relevant levels of Cd. We exposed tadpoles to Cd (0 [control], 1.0, and 10.0 ,g/L) from Gosner stage (GS) 25 to metamorphic climax. We assessed effects of Cd on amphibian length, survival, and development during premetamorphosis (GS 25,30) and prometamorphosis (GS 31,42). After 14 d of exposure, we staged tadpoles and recorded snout-vent length. Tadpoles were then pooled according to treatment and stage (GS , 29 or GS , 30) and allowed to undergo metamorphic development. Tadpoles exposed to 10 ,g/L were significantly larger and more advanced in development by 14 d. Survival to forelimb emergence exceeded 90% in all treatments, and time to metamorphic climax was not different from that in controls. Body burdens of Cd were positively correlated with increasing treatment. Early amphibian development (premetamorphosis) was shown to be the critical period of sensitivity for growth and development. Whereas the freshwater criterion for Cd appears to be protective for survival, a lack of knowledge remains about the sublethal effects of chronic exposures of metal pollutants, especially as they relate to tissue concentrations at various stages of amphibian life history. [source] Risk assessment of Magnacide® H herbicide at Río Colorado irrigation channels (Argentina). tier 3: Studies on native speciesENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 1 2007Andrés Venturino Abstract We evaluated the potential environmental risk of the herbicide Magnacide® (Baker Petrolite, TX, USA) using native species from Argentina, representing the ecosystem at the Irrigation Corporation (CORFO) channels at the Colorado River mouth, Buenos Aires, Argentina. Six species including fish, toads, snails, crustaceans, and insects were selected to perform studies on acute toxicity and repeated exposure effects. Magnacide H susceptibility ranking was Bufo arenarum (lethal concentration 50 [LC50] = 0.023 mg/L), Onchorhynchus mykiss (LC50 = 0.038 mg/L), Heleobia parchappii (LC50 = 0.21 mg/L), Hyalella curvispina (LC50 = 0.24 mg/L), Simulium spp. (LC50 = 0.60 mg/L), and Chironomus spp. (LC50 = 2.83 mg/L). The risk limit of 10th percentile (0.013 mg/L) determined by probit analysis on sensitivity distribution was similar to the one calculated from literature data. Risk assessment based on field application data suggested lethal exposures for more than 70 to 90% of the species up to 20 km downstream from the application point. Repeated exposures to Magnacide H of amphibian larvae at the lowest-observed-effect concentration caused some effects during the first exposure, but without cumulative effects. Amphipods were insensitive to repeated exposures, showing no cumulative effects. Whether short-term exposures may result in long-term sublethal effects on the organism's life history was not addressed by these laboratory tests. In conclusion, tier 3 studies indicate that Magnacide H application schedule is extremely toxic for most native species at CORFO,Río Colorado channels, representing a high potential risk in the environment. The real environmental impact must be addressed by field studies at tier 4 giving more information on population effects and communities. [source] Dissolved copper triggers cell death in the peripheral mechanosensory system of larval fishENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 2 2006Tiffany L. Linbo Abstract Dissolved copper is an increasingly common non,point source contaminant in urban and urbanizing watersheds. In the present study, we investigated the sublethal effects of dissolved copper on the peripheral mechanosensory system, or lateral line, of larval zebrafish (Danio rerio). Zebrafish larvae were exposed to copper (0,65 ,g/L), and the cytotoxic responses of individual lateral line receptor neurons were examined using a combination of in vivo fluorescence imaging, confocal microscopy, scanning electron microscopy, and conventional histology. Dissolved copper triggered a dose-dependent loss of neurons in identified lateral line neuromasts at concentrations ,20 ,g/L. The onset of cell death in the larval mechanosensory system was rapid (<1 h). When copper-exposed zebrafish were transferred to clean water, the lateral line regenerated over the course of 2 d. In contrast, the lateral line of larvae exposed continuously to dissolved copper (50 ,g/L) for 3 d did not recover. Collectively, these results show that peripheral mechanosensory neurons are vulnerable to the neurotoxic effects of copper. Consequently, dissolved copper in non-point source storm-water runoff has the potential to interfere with rheotaxis, schooling, predator avoidance, and other mechanosensory-mediated behaviors that are important for the migration and survival of fish. [source] Acute and chronic toxicity of mercury to early life stages of the rainbow mussel, Villosa iris (Bivalvia: Unionidae)ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 5 2005Theodore W. Valenti Abstract Mercury (Hg) contamination is receiving increased attention globally because of human health and environmental concerns. Few laboratory studies have examined the toxicity of Hg on early life stages of freshwater mussels, despite evidence that glochidia and juvenile life stages are more sensitive to contaminants than adults. Three bioassays (72-h acute glochidia, 96-h acute juvenile, and 21-d chronic juvenile toxicity tests) were conducted by exposing Villosa iris to mercuric chloride salt (HgCl2). Glochidia were more sensitive to acute exposure than were juvenile mussels, as 24-, 48-, and 72-h median lethal concentration values (LC50) for glochidia were >107, 39, and 14 ,g Hg/L, respectively. The 24-, 48-, 72-, and 96-h values for juveniles were 162, 135, 114, and 99 ,g Hg/L, respectively. In the chronic test, juveniles exposed to Hg treatments ,8 ,g/L grew significantly less than did control organisms. The substantial difference in juvenile test endpoints emphasizes the importance of assessing chronic exposure and sublethal effects. Overall, our study supports the use of glochidia as a surrogate life stage for juveniles in acute toxicity tests. However, as glochidia may be used only in short-term tests, it is imperative that an integrated approach be taken when assessing risk to freshwater mussels, as their unique life history is atypical of standard test organisms. Therefore, we strongly advocate the use of both glochidia and juvenile life stages for risk assessment. [source] Altering cytochrome P4501A activity affects polycyclic aromatic hydrocarbon metabolism and toxicity in rainbow trout (Oncorhynchus mykiss)ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 9 2002Stephanie A. Hawkins Abstract The polycyclic aromatic hydrocarbons (PAHs) phenanthrene and retene (7-isopropyl-1-methyl phenanthrene) are lethal to rainbow trout (Oncorhynchus mykiss) larvae during chronic exposures. Phenanthrene is a low-toxicity, non-cytochrome P4501A (CYP1A),inducing compound that accumulates in fish tissues during exposure to lethal concentrations in water. Retene is a higher toxicity CYP1A-inducing compound that is not detectable in tissue at lethal exposure concentrations. The metabolism, excretion, and toxicity of retene and phenanthrene were examined in juvenile and larval rainbow trout during coexposure to the model CYP1A inducer ,-naphthoflavone (,NF), or to the inducer-inhibitor piperonyl butoxide to determine if modulating CYP1A activity affected PAH metabolism and toxicity. Phenanthrene metabolism, excretion rate, and toxicity increased with coexposure to ,NF. Piperonyl butoxide inhibited phenanthrene metabolism and reduced the excretion of all phenanthrene metabolites. As a consequence, embryo mortality rates increased but rates of sublethal effects did not. Coexposure of trout to retene and ,NF caused no change in retene metabolism and excretion, but retene toxicity increased, perhaps due to additivity. Piperonyl butoxide inhibited retene metabolism, decreased the excretion of some retene metabolites while increasing the excretion of others, and increased the toxicity of retene. These results support the role of CYP1A activity in PAH metabolism and excretion, and the role of the CYP1A-generated metabolites of PAHs in chronic toxicity to larval fish. [source] Lethal and sublethal effects of polychlorinated biphenyls on Rana sylvatica tadpolesENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 1 2002Wesley K. Savage Abstract In static experiments, we exposed tadpoles of the wood frog (Rana sylvatica) to sediment collected from a riverine wetland in the St. Lawrence River basin that is highly contaminated with polychlorinated biphenyls (PCBs). Significant mortality occurred early in the experiment and was not explained by a simple dose-dependent relationship. Direct sediment contact resulted in higher tadpole mortality compared with tadpoles suspended in mesh containers above the sediment. Sublethal effects of exposure were also apparent, characterized by behavioral abnormalities, including reduced activity levels and swimming speed, that differed depending on whether tadpoles were in contact with or suspended above the sediment. We demonstrate in this experiment that PCB-contaminated sediment induced significant mortality and behavioral dysfunction in early development, but the effects on natural populations existing in the contaminated region is not known. [source] Behavioral effects of ivermectin in a freshwater oligochaete, Lumbriculus variegatusENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 7 2001Jing Ding Abstract Ivermectin is a potent antiparasitic drug against nematode and arthropod parasites. In this study, we examined the lethal and sublethal effects of ivermectin in a freshwater oligochaete, Lumbriculus variegatus. The median lethal concentration (LC50) at 72 h after ivermectin exposure was 560 nM. Sublethal endpoints focused on several stimulus-evoked locomotor behaviors: escape reflexes controlled by giant interneuron pathways, swimming and reversal, and crawling. Swimming, reversal, and crawling are controlled by nongiant interneuron pathways. Ivermectin inhibited swimming, reversal, crawling frequency, and crawling speed in a time- and concentration-dependent manner with a mean inhibitory concentration (IC50) at 3 h of 1.1, 16, 91, and 51nM, respectively. Ivermectin at 0.3 nM also significantly decreased the frequency of helical swimming waves. Picrotoxin, a Cl, channel blocker, antagonized the ivermectin-induced decrease in swimming frequency, crawling frequency, and crawling speed. There were no adverse effects on escape reflex 3 h after exposure to 300 nM ivermectin. Electrophysiological recordings showed that ivermectin had no effects on the conduction velocity of giant fiber systems. The results indicated that locomotor behaviors controlled by nongiant locomotor pathways were more sensitive to ivermectin than pathways controlled by giant interneurons and that Cl, channels may be involved in mediating ivermectin's inhibitory effects. [source] Effects of Ultraviolet Radiation on Locomotion and Orientation in Roughskin Newts (Taricha granulosa)ETHOLOGY, Issue 3 2000Andrew R. Blaustein Environmental changes, including those associated with the atmosphere may significantly affect individual animals and ultimately populations. Ultraviolet (UV) radiation, perhaps increasing due to stratospheric ozone depletion, has been linked to mortality in a number of organisms, including amphibians. The eggs and larvae of certain amphibian species hatch at significantly lower rates when exposed to ambient ultraviolet light. Yet little is known about the sublethal effects of UV radiation. For example, UV radiation may affect specific behaviors of an animal that could alter its ability to survive. To examine if UV radiation affects amphibian behavior, we used roughskin newts (Taricha granulosa) as a model. Newts were exposed to low-level doses of UV in the laboratory and then tested in the field to examine if UV-exposed and control (no UV) newts differed in orientation towards water or in locomotor activity levels. UV-exposed and control newts both exhibited a significant orientation towards water in field tests but there was no significant difference in orientation between treatments. However, UV-exposed newts were significantly more active than control newts. Our results suggest that exposure to short-term low levels of UV radiation alters certain behaviors. Environmentally induced changes in behavior may have significant ecological and evolutionary consequences. [source] Amphibian defenses against ultraviolet-B radiationEVOLUTION AND DEVELOPMENT, Issue 1 2003Andrew R. Blaustein SUMMARY As part of an overall decline in biodiversity, amphibian populations throughout the world are disappearing. There are a number of potential causes for these declines, including those related to environmental changes such as increasing ultraviolet-B (UV-B) radiation due to stratospheric ozone depletion. UV-B radiation can kill amphibian embryos or can cause sublethal effects that can harm amphibians in later life stages. However, amphibians have defenses against UV-B damage that can limit damage or repair it after exposure to UV-B radiation. These include behavioral, physiological, and molecular defenses. These defenses differ interspecifically, with some species more able to cope with exposure to UV-B than others. Unfortunately, the defense mechanisms of many species may not be effective against increasing persistent levels of UV-B radiation that have only been present for the past several decades due to human-induced environmental damage. Moreover, we predict that persistent UV-B,induced mortality and sublethal damage in species without adequate defenses could lead to changes in community structure. In this article we review the effects of UV-B radiation on amphibians and the defenses they use to avoid solar radiation and make some predictions regarding community structure in light of interspecific differences in UV-B tolerance. [source] A review of the effects of catch-and-release angling on black bass, Micropterus spp.: implications for conservation and management of populationsFISHERIES MANAGEMENT & ECOLOGY, Issue 2 2007M. J. SIEPKER Abstract, This paper summarises recent peer-reviewed literature addressing the effects of catch-and-release angling on black bass, Micropterus spp., to facilitate management and conservation of these fish. Traditionally, the effects of catch and release have been evaluated by measuring mortality. Many recent studies have measured sublethal effects on physiology and behaviour. There is also greater emphasis on adding more realism to sublethal catch-and-release experiments through angler involvement in research activities and by conducting studies in the field rather than in laboratory environments. Owing to these advances, there have been a number of recent findings, which are summarised here, related to air exposure, gear (e.g. circle hooks) and the weigh-in procedure that are particularly relevant to black bass anglers, tournament organisers and fishery managers. Additional research is particularly needed for: (1) population-level effects of angling for nesting fish; (2) population-level effects of tournament-associated mortality; (3) effectiveness of livewell additives for enhancing survival; (4) consequences of fish displacement in competitive events; (5) effects of weigh-in procedures and other organisational issues on fish condition and survival; and (6) reducing barotrauma. [source] Lethal and non-lethal effects of multiple indigenous predators on the invasive golden apple snail (Pomacea canaliculata)FRESHWATER BIOLOGY, Issue 10 2004Nils Carlsson Summary 1. We investigated the individual and combined effects of two predators (the climbing perch, Anabas testudineus, and the wetland crab, Esanthelphusa nimoafi) indigenous to wetlands in Laos, on the behaviour and survival of the invasive South American golden apple snail (Pomacea canaliculata). The snail is considered a pest, consuming large amounts of rice and other aquatic vegetation in the region. 2. Snail avoidance reactions to released predator chemical cues were investigated in aquaria while the effects of predators on a mixed snail population were studied in field enclosures that contained native aquatic plants (Salvinia cucullata, Ludwigia adscendens and Ipomoea aquatica). 3. In the aquaria experiment, neonate (2,3 mm) and medium-sized snails (8,10 mm) responded to fish chemical cues by going to the surface, whereas adult snails (35,40 mm) went to the bottom. In contrast, no size class of snails reacted to chemical cues released by crabs. 4. In the field experiment, fish reduced the abundance of neonate snails, and crabs reduced the abundance of all size classes. The effect of the combined predators could not be predicted from the mortality rate observed in single predator treatments. The survival of neonate and medium-sized snails was greater and of adults less than expected. The presence of predators did not affect egg production. Snails consumed significant amounts of plants despite the presence of predators. 5. Our findings suggest that some indigenous Asian predators have lethal and sublethal effects on P. canaliculata that depend on snail size and predator type. When in the presence of several predators the response of snails to one predator may either increase or decrease the vulnerability of snails to the others. [source] Effects of a toxicant on population growth rates: sublethal and delayed responses in blowfly populationsFUNCTIONAL ECOLOGY, Issue 6 2001S. J. MOE Summary 1,Previous studies have shown that cadmium exposure of blowfly populations (Lucilia sericata[Meigen 1826]) results in reduced population growth rate, but also in higher individual mass, because of reduced competition for food. In this study, the discrepancy between the positive effect on individual growth and the negative effect on population growth is investigated, by measuring direct and delayed effects of cadmium in the adult stage. 2,Blowfly populations were exposed to cadmium through the diet in four treatment combinations: larval stage, adult stage, both stages or neither stage. The effects on accumulation of cadmium, survival, development time, mass and reproductive rate were measured. 3,Cadmium was accumulated from both stages. 4,Individuals exposed to cadmium in the larval stage had higher mean pupal and adult mass (because of reduced densities), but also reduced adult longevity and fecundity. 5,Adult longevity and fecundity were also reduced by cadmium exposure in the adult stage. 6,In stage-structured populations, the link between individual-level and population-level responses to a toxicant may be complicated by stage-specific sensitivities to the toxicant, by delayed responses in the adult stage to sublethal effects in the juvenile stage, and by density-dependent compensatory responses to toxicant-induced mortality. [source] The physiology of predator stress in free-ranging preyJOURNAL OF ANIMAL ECOLOGY, Issue 6 2009Evan L. Preisser M.J. Sheriff, C.J. Krebs & R. Boonstra (2009) The sensitive hare: sublethal effects of predator stress on reproduction in snowshoe hares. Journal of Animal Ecology, 78, 1249,1258. Ecologists have only begun to understand the physiological mechanisms underlying individual- and population-level responses of prey- to predator-related stress. Sheriff, Krebs and Boonstra advance this field by providing evidence that predator-induced increases in glucorticoid concentrations in wild female snowshoe hares (Lepus americanus) impact both litter size and offspring condition. They hypothesize that the glucocorticoid-mediated effects on reproduction provides an adaptive benefit: mothers ,programming' their offspring to be timid and risk-averse in high-risk environments should increase their survival probability. This research illuminates the connection between stress physiology and population-level changes and demonstrates the surprisingly far-reaching impact of predation risk. [source] The sensitive hare: sublethal effects of predator stress on reproduction in snowshoe haresJOURNAL OF ANIMAL ECOLOGY, Issue 6 2009Michael J. Sheriff Summary 1.,Prey responses to high predation risk can be morphological or behavioural and ultimately come at the cost of survival, growth, body condition, or reproduction. These sub-lethal predator effects have been shown to be mediated by physiological stress. We tested the hypothesis that elevated glucocorticoid concentrations directly cause a decline in reproduction in individual free-ranging female snowshoe hares, Lepus americanus. We measured the cortisol concentration from each dam (using a faecal analysis enzyme immunoassay) and her reproductive output (litter size, offspring birth mass, offspring right hind foot (RHF) length) 30 h after birth. 2.,In a natural monitoring study, we monitored hares during the first and second litter from the population peak (2006) to the second year of the decline (2008). We found that faecal cortisol metabolite (FCM) concentration in dams decreased 52% from the first to the second litter. From the first to the second litter, litter size increased 122%, offspring body mass increased 130%, and offspring RHF length increased 112%. Dam FCM concentrations were inversely related to litter size (r2 = 0·19), to offspring birth mass (r2 = 0·32), and to offspring RHF length (r2 = 0·64). 3.,In an experimental manipulation, we assigned wild-caught, pregnant hares to a control and a stressed group and held them in pens. Hares in the stressed group were exposed to a dog 1,2 min every other day before parturition to simulate high predation risk. At parturition, unsuccessful-stressed dams (those that failed to give birth to live young) and stressed dams had 837% and 214%, respectively, higher FCM concentrations than control dams. Of those females that gave birth, litter size was similar between control and stressed dams. However, offspring from stressed dams were 37% lighter and 16% smaller than offspring from control dams. Increasing FCM concentration in dams caused the decline of offspring body mass (r2 = 0·57) and RHF (r2 = 0·52). 4.,This is the first study in a free-ranging population of mammals to show that elevated, predator-induced, glucocorticoid concentrations in individual dams caused a decline in their reproductive output measured both by number and quality of offspring. Thus, we provide evidence that any stressor, not just predation, which increases glucocorticoid concentrations will result in a decrease in reproductive output. [source] Sublethal effects of chlorfluazuron on reproductivity and viability of Spodoptera litura (F. ) (Lep., Noctuidae)JOURNAL OF APPLIED ENTOMOLOGY, Issue 5-6 2000F. Perveen To clarify the sublethal effects of chlorfluazuron on reproductivity and viability of common cutworm, Spodoptera litura, some experiments were conducted under laboratory conditions. The LD50 was found to be 12.0 ng/larva when evaluated up to pupation and 9.9 ng/larva up to adult emergence. At lethal dosages the development of different instars, moulting to pupae and emergence into adults were found to be more affected. Reduction in the body weight was also observed in the larvae and pupae when treated with a sublethal dose (LD30 : 3.75 ng/larva) and in the adults when treated with sublethal doses (LD10 : 1.00 ng/larva; LD30 : 3.75 ng/larva) as newly moulted fifth instar larvae of S. litura, although the number of matings per female and life span of adult females and males remained unaffected by the same treatments. When sublethal doses were applied only to females or only to males, or both sexes, the average fecundity reduction was up to 35,44%. When only females were treated with sublethal doses, fertility was reduced by 49,58%; when only males were treated fertility was reduced by 65,81% and when both sexes were treated, fertility was reduced by 68,83%. Hatchability was reduced by 22,26% when only females were treated, by 44,66% when only males were treated and by 45,72% when both sexes were treated with LD10 or LD30 doses as newly moulted fifth instars. The results from these observations suggest that the fecundity was reduced to a similar degree when only females or only males or both sexes were treated with LD10 or LD30 doses as newly moulted fifth instars. However the fertility and hatchability were affected more when only males were treated with LD10 and much more when treated with LD30. Currently, work is in progress to find out the main reasons for the sublethal effects of chlorfluazuron on reproductivity and viability. [source] Effects of the toxic dinoflagellate, Alexandrium fundyense on three species of larval fish: a food-chain approachJOURNAL OF FISH BIOLOGY, Issue 1 2008J. C. Samson Sublethal behavioural effects of exposure to paralytic shellfish toxins (PST; saxitoxin and its derivatives) from the toxic dinoflagellate Alexandrium fundyense were investigated in newly settled winter flounder Pseudopleuronectes americanus, larval sheepshead minnow Cyprinodon variegatus and larval mummichog Fundulus heteroclitus through an A. fundyense,copepod,fish food chain. Consumption of as few as six to 12 toxin-containing copepods was lethal to the fishes. After consuming fewer toxin-containing copepods, all three fish species exhibited sublethal effects from vector-mediated exposure. Prey-capture ability of mummichogs was reduced in larvae that had consumed toxic copepods, Coullana canadensis. After consuming toxic C. canadensis or mixed copepods, mummichog larvae had reduced swimming performance. Swimming activity was also significantly reduced in winter flounder after consuming toxic copepods, including time spent in motion and distance travelled. Prey capture and predator avoidance were reduced in first-feeding sheepshead minnow larvae that had consumed toxic dinoflagellate cells. Adverse effects on prey capture or predator avoidance may reduce larval survival and facilitate the transmission of PST through the food web. This study provides baseline information on sublethal effects of PST exposure on fishes using a novel food-chain approach with zooplankton as vectors. [source] Effects of cassava processing methods on antinutritional components and health status of children,JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 3 2002Omorogieva Ojo Abstract This study was conducted to evaluate cassava processing methods in Nigeria, its antinutritional components and the possible impact on the health status of children. The traditional method of cassava processing involved peeling of cassava tubers with a knife, manual grating, dewatering with logs of wood and/or stones, sieving with a cane-woven sieve and frying in a local metal fryer on a wood fire. In contrast, the modern method involved the use of knives for peeling, a mechanical grater, a hydraulic press for dewatering, iron sieves for sieving and an improved metal fryer for frying on a coal fire. The products of both methods included gari (accounting for 70% of Nigeria's total cassava consumption) and lafun. The intake of gari and other foods in 129 3,5-year-old children in Benin City, Nigeria was also assessed based on a food frequency questionnaire. The children were classified into normal and protein-deficient groups using lower/middle/upper-arm circumference and clinical features of malnutrition. Based on the number of households in villages around Benin City who were involved in cassava processing, 90% used the traditional processing method compared with 10% using the modern method, although the latter controlled the commercial production and sale of gari. There were significantly (P,<,0.05) higher intakes of protein and energy in normal compared with protein-deficient children, but the latter group obtained higher percentages of protein and energy from gari. In addition, the correlation between the amount of gari consumed and clinical scores of malnutrition was low (R2,<,0.2). This may be due to the children consuming gari from both methods and also from different sources. The average gari intake for these children was 320,g,day,1 and HCN levels may be as high as 10.24,mg,day,1. Some children who are exposed to these levels with poor nutritional status and lack of access to food varieties may develop sublethal effects in the short term. The higher protein intake by the normal children may also reduce the toxicity of HCN. We conclude that methods of processing cassava have profound effects on HCN retention and chemical composition of cassava products. In addition, the modern processing method is more efficient than the traditional method, with significantly reduced processing losses, labour input and levels of HCN. The HCN content in combination with the quantity and quality of protein in the diet has significant impact on the health status of children. Therefore, in susceptible children with poor nutritional status who consume inadequately processed cassava products with limited food choice, these may predispose them to the effects of HCN and thiocyanate. © 2002 Society of Chemical Industry [source] Acute Toxicity and Sublethal Effects of Nitrite on Selected Hematological Parameters and Tissues in Dark-banded Rockfish, Sebastes inermisJOURNAL OF THE WORLD AQUACULTURE SOCIETY, Issue 2 2007In-Seok Park Acute toxicity and sublethal effects of nitrite in dark-banded rockfish, Sebastes inermis (83.3 ± 7.2 g), were studied under static conditions for a period of 96 h. The acute toxicity of nitrite evaluated for the 96-h lethal concentration (LC50) was 700 mg/L. The sublethal effects on selected hematological parameters of S. inermis, such as total erythrocyte count (TEC), hemoglobin, plasma glucose, and serum protein content, were measured after 0, 6, 12, 24, 48, 72, and 96 h of exposure to 0, 50, 100, 200, 400, and 700 mg/L of nitrite. Sublethal nitrite caused progressive reduction in the TEC, hemoglobin, and serum protein content in fish depending on the nitrite concentration and exposure period. The 96-h exposure resulted in a 14,42% reduction in TEC and 25,33% reduction in hemoglobin content for 100,700 mg/L of nitrite compared to the control. A dose-related reduction in plasma glucose (25.7,34.2%) was observed for concentrations of 200,700 mg/L of nitrite during 48 h of exposure, followed by an increase through 96 h. A significant reduction in serum protein (7.3,12.6%) was observed for 200,700 mg/L of nitrite after 96 h of exposure. Abnormal histological changes in skin, gill, liver, and kidney tissue were observed in fish exposed to 700 mg/L of nitrite after 96 h of exposure compared to the control. Although no mortality of S. inermis occurred at 500 mg/L of nitrite, all hematological parameters adversely responded to a nitrite dose of 200 mg/L for 96 h. These results showed that although acute toxicity concentration of nitrite in S. inermis is higher than 700 mg/L, sublethal concentrations of nitrite also negatively affect hematological parameters. [source] Systemic action of novel neonicotinoid insecticide IPP-10 and its effect on the feeding behaviour of Rhopalosiphum padi on wheatPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 7 2010Li Cui Abstract BACKGROUND: IPP-10 is a novel neonicotinoid insecticide recently developed in China and has good activity against sucking insects. Studies were carried out to investigate the activity of IPP-10 against Rhopalosiphum padi L. RESULTS: The results demonstrated that IPP-10 had both contact and systemic activity, including acropetal and basipetal translocation in wheat vascular bundles. Starved R. padi were allowed to stay on wheat treated with a sublethal dose of IPP-10. The results of studying their feeding behaviour from an electrical penetration graph (EPG) revealed a decrease in total time and bout duration of xylem and phloem ingestion, but the total time and bout duration of phloem salivation were significantly prolonged. The frequency (7.03 ± 0.49 Hz) of the xylem ingestion waveform produced by aphids on wheat treated with IPP-10 was significantly lower than that of blank control aphids (8.20 ± 0.30 Hz). Consequently, aphids born on wheat treated with IPP-10 were obviously lighter and less fecund than the control aphids. CONCLUSION: These tests indicated that IPP-10 had both contact and systemic activity, with sublethal effects resulting in reduction in R. padi feeding behaviour, growth rate and fecundity. Copyright © 2010 Society of Chemical Industry [source] Larvicidal and oviposition-altering activity of monoterpenoids, trans -anithole and rosemary oil to the yellow fever mosquito Aedes aegypti (Diptera: Culicidae),PEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 3 2009Ranil Waliwitiya Abstract BACKGROUND:Aedes aegypti L. is the major vector of dengue fever and dengue hemorrhagic fever. In an effort to find effective tools for control programs to reduce mosquito populations, the authors assessed the acute toxicities of 14 monoterpenoids, trans -anithole and the essential oil of rosemary against different larval stages of Ae. aegypti. The potential for piperonyl butoxide (PBO) to act as a synergist for these compounds to increase larvicidal activity was also examined, and the oviposition response of gravid Ae. aegypti females to substrates containing these compounds was evaluated in behavioral bioassays. RESULTS: Pulegone, thymol, eugenol, trans -anithole, rosemary oil and citronellal showed high larvicidal activity against all larval stages of Ae. aegypti (LC50 values 10.3,40.8 mg L,1). The addition of PBO significantly increased the larvicidal activity of all test compounds (3,250-fold). Eugenol, citronellal, thymol, pulegone, rosemary oil and cymene showed oviposition deterrent and/or repellent activities, while the presence of borneol, camphor and ,-pinene increased the number of eggs laid in test containers. CONCLUSIONS: This study quantified the lethal and sublethal effects of several phytochemical compounds against all larval stages of Aedes aegypti, providing information that ultimately may have potential in mosquito control programs through acute toxicity and/or the ability to alter reproductive behaviors. Copyright © 2008 Society of Chemical Industry [source] | ||||||||||||||||