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Hajime Fugo - One of the best experts on this subject based on the ideXlab platform.
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Fenoxycarb levels and their effects on general and juvenile hormone esterase activity in the hemolymph of the silkworm, Bombyx mori
Pesticide Biochemistry and Physiology, 2002Co-Authors: Skarlatos G. Dedos, Ferenc Szurdoki, András Székács, Takahiro Shiotsuki, Bruce D. Hammock, Jun Shimada, Hajime FugoAbstract:Abstract We studied the relationship between Fenoxycarb levels and general esterase (GE) activity, juvenile hormone esterase (JHE) activity, and induction of permanent fifth instar (dauer) larvae in Bombyx mori . Fenoxycarb (1 μg/animal) was topically applied to B. mori at 0 h of the fifth instar. Hemolymph Fenoxycarb levels, as determined by an ELISA, reached a peak within 1 h, and then decreased to undetectably low at 42 h. After 48 h, the feces of these larvae contained 99% of the applied Fenoxycarb dose. The above Fenoxycarb treatment induces dauer larvae with persistently increased hemolymph GE and JHE activities for the rest of the fifth instar. Application of Fenoxycarb later in the fifth instar (48 h), when it still could induce dauer larvae, resulted in a similar pattern of elimination from the hemolymph and produced steadily elevated hemolymph GE and JHE activities for the rest of the fifth instar. Application of Fenoxycarb late in the fifth instar (132 h) did not prevent pupal ecdysis; it increased hemolymph JHE activity, but not GE activity. The latter treatment prevented the JHE activity decrease observed in control larvae before pupal ecdysis. In vivo, in control animals, the highest hemolymph JHE activity was observed 12 h after pupal ecdysis. At that developmental time, Fenoxycarb inhibited this enzyme in vitro ( IC 50 ≈2 μM ) . The combined results suggest: (1) Fenoxycarb is rapidly excreted from the larval body; (2) induction of dauer larvae and increased hemolymph GE and JHE activities are not directly associated with its presence in the larval body of B. mori .
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Induction of dauer pupae by Fenoxycarb in the silkworm, Bombyx mori.
Journal of insect physiology, 2002Co-Authors: Skarlatos G. Dedos, Ferenc Szurdoki, András Székács, Akira Mizoguchi, Hajime FugoAbstract:Abstract Topical application of Fenoxycarb (1 μg per animal) at 129 or 132 h of the fifth instar larvae of the silkworm, Bombyx mori, did not induce morphological abnormalities in the pupal stage, but these animals became dauer (permanent) pupae. This condition of B. mori and the endocrine events leading to permanent pupae are discussed in this work. Application of Fenoxycarb at 132 h of the fifth instar elicited a high ecdysteroid titre in the pharate pupal stage and a steadily high ecdysteroid titre in the pupal stage. The Fenoxycarb-induced permanent pupae had non-degenerating prothoracic glands that secreted low amounts of ecdysteroid and did not respond to recombinant prothoracicotropic hormone (rPTTH) late in the pupal stage. The Bombyx PTTH titre in the haemolymph, determined by a time-resolved fluoroimmunoassay, was lower than that of controls at the time of pupal ecdysis, but higher than controls later in the pupal stage in Fenoxycarb-treated animals. After application of Fenoxycarb, its haemolymph level, measured by ELISA, reached a peak at pupal ecdysis, then remained low. These results suggest that the Fenoxycarb-mediated induction of permanent pupae is only partially a brain-centred phenomenon. It also involves alterations in the hormonal interplay that govern both the initiation of pupal–adult differentiation and changes in the steroidogenic pathway of the prothoracic glands of B. mori.
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Acceleration of Pupal-Adult Development by Fenoxycarb in the Silkworm, Bombyx mori
Zoological Science, 2001Co-Authors: Skarlatos G. Dedos, Hajime FugoAbstract:Abstract Treatment by Fenoxycarb (> 0.1 μg/animal) during a short developmental period in the pharate pupal stage of the silkworm, Bombyx mori, induced alterations in the normal pupal-adult development. All Fenoxycarb-treated animals showed accelerated development and precocious adult cuticle deposition very early in the pupal stage. Various internal and external organs of the developing adults underwent abnormal differentiation and were extensively malformed. Consequently, pupal-adult development and adult eclosion behaviour were disturbed. Similar effects were induced by injections of high doses (≥ 4 μg/animal) of 20-hydroxyecdysone (20E) only around the time of pupal ecdysis. Treatment with 1 μg of Fenoxycarb in the pharate pupal stage did not affect haemolymph ecdysteroid titers early in the pupal stage. Our results, therefore, suggest that Fenoxycarb, a potent juvenile hormone mimic, can imitate the developmental effects of excess 20E and behave as an ecdysteroid mimic after its application during th...
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Induction of dauer larvae by application of Fenoxycarb early in the 5th instar of the silkworm, Bombyx mori.
Journal of insect physiology, 1999Co-Authors: Skarlatos G. Dedos, Hajime FugoAbstract:Abstract Fenoxycarb application from 0 h until 60 h of the 5th instar of Bombyx mori induced 100% dauer larvae. Between the 60 and 78 h, the ratio of Fenoxycarb-induced dauer larvae decreased, and the ratio of supernumerary instar moulting larvae increased. After application of Fenoxycarb at the 48 h of the 5th instar, the haemolymph prothoracicotropic hormone (PTTH) titer was higher in Fenoxycarb-treated larvae than in control larvae. Furthermore, brain–corpora cardiaca–corpora allata (Br–CC–CA) complexes from Fenoxycarb-treated larvae released higher amounts of PTTH in vitro than the Br–CC–CA complexes of control larvae. Prothoracic glands (PGs) of Fenoxycarb-treated larvae at the 48 h of the 5th instar exhibited basal and PTTH-stimulated secretory activities similar to that of control PGs until the 72 h of the 5th instar. After that time point, both basal and PTTH-stimulated secretory activity of PGs from Fenoxycarb-treated larvae significantly decreased and remained low for the rest of the investigated period. The combined results suggest that the application of Fenoxycarb affects the ability of the PGs to be stimulated by PTTH and the induction of dauer larvae in Bombyx mori is not due to inhibition of PTTH release from Br–CC–CA complexes.
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Downregulation of the cAMP signal transduction cascade in the prothoracic glands is responsible for the Fenoxycarb-mediated induction of permanent 5th instar larvae in Bombyx mori
Insect Biochemistry and Molecular Biology, 1999Co-Authors: Skarlatos G. Dedos, Hajime FugoAbstract:Abstract Fenoxycarb application at 48 h (day 2) of the 5th instar of Bombyx mori induced permanent larvae with prothoracic glands (PGs) exhibiting weak ecdysteroidogenic activity. Although glands from control and Fenoxycarb-treated larvae exhibited similar responses to dibutyl cAMP and forskolin on day 2, forskolin could not stimulate ecdysteroid secretion from PGs of Fenoxycarb-treated larvae on day 3. Glands from control larvae incubated with cholera toxin (CTX) on day 3 had increased cAMP content and enhanced ecdysteroid secretion. Cholera toxin did not stimulate ecdysteroid secretion and marginally increased cAMP content in day 3 PGs of Fenoxycarb-treated larvae. After application of Fenoxycarb on day 2, crude brain extracts (cBRAIN) could not increase the glandular cAMP content throughout the rest of the 5th instar of the treated larvae. Fenoxycarb did not affect the basal or cBRAIN-stimulated cAMP accumulation in control PGs on day 2 and day 3 in vitro. Application of Fenoxycarb on day 2 did not affect the recombinant PTTH (rPTTH)-stimulated ecdysteroid secretion on day 3, but reduced the cBRAIN-stimulated ecdysteroid secretion on day 3 to levels similar to that of rPTTH. The combined results suggest that the cAMP signalling cascade in the PGs of B. mori becomes nonfunctional after Fenoxycarb application on day 2 of the 5th instar.
Skarlatos G. Dedos - One of the best experts on this subject based on the ideXlab platform.
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Fenoxycarb levels and their effects on general and juvenile hormone esterase activity in the hemolymph of the silkworm, Bombyx mori
Pesticide Biochemistry and Physiology, 2002Co-Authors: Skarlatos G. Dedos, Ferenc Szurdoki, András Székács, Takahiro Shiotsuki, Bruce D. Hammock, Jun Shimada, Hajime FugoAbstract:Abstract We studied the relationship between Fenoxycarb levels and general esterase (GE) activity, juvenile hormone esterase (JHE) activity, and induction of permanent fifth instar (dauer) larvae in Bombyx mori . Fenoxycarb (1 μg/animal) was topically applied to B. mori at 0 h of the fifth instar. Hemolymph Fenoxycarb levels, as determined by an ELISA, reached a peak within 1 h, and then decreased to undetectably low at 42 h. After 48 h, the feces of these larvae contained 99% of the applied Fenoxycarb dose. The above Fenoxycarb treatment induces dauer larvae with persistently increased hemolymph GE and JHE activities for the rest of the fifth instar. Application of Fenoxycarb later in the fifth instar (48 h), when it still could induce dauer larvae, resulted in a similar pattern of elimination from the hemolymph and produced steadily elevated hemolymph GE and JHE activities for the rest of the fifth instar. Application of Fenoxycarb late in the fifth instar (132 h) did not prevent pupal ecdysis; it increased hemolymph JHE activity, but not GE activity. The latter treatment prevented the JHE activity decrease observed in control larvae before pupal ecdysis. In vivo, in control animals, the highest hemolymph JHE activity was observed 12 h after pupal ecdysis. At that developmental time, Fenoxycarb inhibited this enzyme in vitro ( IC 50 ≈2 μM ) . The combined results suggest: (1) Fenoxycarb is rapidly excreted from the larval body; (2) induction of dauer larvae and increased hemolymph GE and JHE activities are not directly associated with its presence in the larval body of B. mori .
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Induction of dauer pupae by Fenoxycarb in the silkworm, Bombyx mori.
Journal of insect physiology, 2002Co-Authors: Skarlatos G. Dedos, Ferenc Szurdoki, András Székács, Akira Mizoguchi, Hajime FugoAbstract:Abstract Topical application of Fenoxycarb (1 μg per animal) at 129 or 132 h of the fifth instar larvae of the silkworm, Bombyx mori, did not induce morphological abnormalities in the pupal stage, but these animals became dauer (permanent) pupae. This condition of B. mori and the endocrine events leading to permanent pupae are discussed in this work. Application of Fenoxycarb at 132 h of the fifth instar elicited a high ecdysteroid titre in the pharate pupal stage and a steadily high ecdysteroid titre in the pupal stage. The Fenoxycarb-induced permanent pupae had non-degenerating prothoracic glands that secreted low amounts of ecdysteroid and did not respond to recombinant prothoracicotropic hormone (rPTTH) late in the pupal stage. The Bombyx PTTH titre in the haemolymph, determined by a time-resolved fluoroimmunoassay, was lower than that of controls at the time of pupal ecdysis, but higher than controls later in the pupal stage in Fenoxycarb-treated animals. After application of Fenoxycarb, its haemolymph level, measured by ELISA, reached a peak at pupal ecdysis, then remained low. These results suggest that the Fenoxycarb-mediated induction of permanent pupae is only partially a brain-centred phenomenon. It also involves alterations in the hormonal interplay that govern both the initiation of pupal–adult differentiation and changes in the steroidogenic pathway of the prothoracic glands of B. mori.
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Acceleration of Pupal-Adult Development by Fenoxycarb in the Silkworm, Bombyx mori
Zoological Science, 2001Co-Authors: Skarlatos G. Dedos, Hajime FugoAbstract:Abstract Treatment by Fenoxycarb (> 0.1 μg/animal) during a short developmental period in the pharate pupal stage of the silkworm, Bombyx mori, induced alterations in the normal pupal-adult development. All Fenoxycarb-treated animals showed accelerated development and precocious adult cuticle deposition very early in the pupal stage. Various internal and external organs of the developing adults underwent abnormal differentiation and were extensively malformed. Consequently, pupal-adult development and adult eclosion behaviour were disturbed. Similar effects were induced by injections of high doses (≥ 4 μg/animal) of 20-hydroxyecdysone (20E) only around the time of pupal ecdysis. Treatment with 1 μg of Fenoxycarb in the pharate pupal stage did not affect haemolymph ecdysteroid titers early in the pupal stage. Our results, therefore, suggest that Fenoxycarb, a potent juvenile hormone mimic, can imitate the developmental effects of excess 20E and behave as an ecdysteroid mimic after its application during th...
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Induction of dauer larvae by application of Fenoxycarb early in the 5th instar of the silkworm, Bombyx mori.
Journal of insect physiology, 1999Co-Authors: Skarlatos G. Dedos, Hajime FugoAbstract:Abstract Fenoxycarb application from 0 h until 60 h of the 5th instar of Bombyx mori induced 100% dauer larvae. Between the 60 and 78 h, the ratio of Fenoxycarb-induced dauer larvae decreased, and the ratio of supernumerary instar moulting larvae increased. After application of Fenoxycarb at the 48 h of the 5th instar, the haemolymph prothoracicotropic hormone (PTTH) titer was higher in Fenoxycarb-treated larvae than in control larvae. Furthermore, brain–corpora cardiaca–corpora allata (Br–CC–CA) complexes from Fenoxycarb-treated larvae released higher amounts of PTTH in vitro than the Br–CC–CA complexes of control larvae. Prothoracic glands (PGs) of Fenoxycarb-treated larvae at the 48 h of the 5th instar exhibited basal and PTTH-stimulated secretory activities similar to that of control PGs until the 72 h of the 5th instar. After that time point, both basal and PTTH-stimulated secretory activity of PGs from Fenoxycarb-treated larvae significantly decreased and remained low for the rest of the investigated period. The combined results suggest that the application of Fenoxycarb affects the ability of the PGs to be stimulated by PTTH and the induction of dauer larvae in Bombyx mori is not due to inhibition of PTTH release from Br–CC–CA complexes.
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Downregulation of the cAMP signal transduction cascade in the prothoracic glands is responsible for the Fenoxycarb-mediated induction of permanent 5th instar larvae in Bombyx mori
Insect Biochemistry and Molecular Biology, 1999Co-Authors: Skarlatos G. Dedos, Hajime FugoAbstract:Abstract Fenoxycarb application at 48 h (day 2) of the 5th instar of Bombyx mori induced permanent larvae with prothoracic glands (PGs) exhibiting weak ecdysteroidogenic activity. Although glands from control and Fenoxycarb-treated larvae exhibited similar responses to dibutyl cAMP and forskolin on day 2, forskolin could not stimulate ecdysteroid secretion from PGs of Fenoxycarb-treated larvae on day 3. Glands from control larvae incubated with cholera toxin (CTX) on day 3 had increased cAMP content and enhanced ecdysteroid secretion. Cholera toxin did not stimulate ecdysteroid secretion and marginally increased cAMP content in day 3 PGs of Fenoxycarb-treated larvae. After application of Fenoxycarb on day 2, crude brain extracts (cBRAIN) could not increase the glandular cAMP content throughout the rest of the 5th instar of the treated larvae. Fenoxycarb did not affect the basal or cBRAIN-stimulated cAMP accumulation in control PGs on day 2 and day 3 in vitro. Application of Fenoxycarb on day 2 did not affect the recombinant PTTH (rPTTH)-stimulated ecdysteroid secretion on day 3, but reduced the cBRAIN-stimulated ecdysteroid secretion on day 3 to levels similar to that of rPTTH. The combined results suggest that the cAMP signalling cascade in the PGs of B. mori becomes nonfunctional after Fenoxycarb application on day 2 of the 5th instar.
Dirk Jungmann - One of the best experts on this subject based on the ideXlab platform.
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Chronic toxicity of Fenoxycarb to the midge Chironomus riparius after exposure in sediments of different composition
Journal of Soils and Sediments, 2009Co-Authors: Dirk Jungmann, Thomas Gildemeister, Cândida Shinn, Lennart Weltje, Thomas G. Preuss, Roland Nagel, Hans Toni Ratte, Cornelia Bandow, Hanna M. MaesAbstract:Background, aim, and scope Fenoxycarb is an insect growth regulator widely used to control a variety of pests. As a juvenile hormone analogue, it interacts with the natural hormones involved in insect development, inhibiting metamorphosis to the adult stage. Adverse effects of Fenoxycarb on non-target organisms have been repeatedly observed and its rapid dissipation from water to the organic fraction of the sediment is known. The aim of this work was to investigate the impact of Fenoxycarb on the development of sediment-dwelling larvae of the midge Chironomus riparius after exposure to spiked sediment. Materials and methods Three spiked-sediment toxicity tests were carried out based on OECD Guideline 218 using various sediment composition and food sources. Results The endpoints mean emergence time, development rate, and sex ratio were not influenced by Fenoxycarb exposure. The emergence ratio showed a concentration-dependent decrease in all experiments. The lowest no observed effect concentration (NOEC) value was calculated as 0.125 µg kg^−1. The results imply that food quantity and quality might influence the toxicity of Fenoxycarb to the midges. Discussion A comparison of the NOEC with predicted environmental concentration in sediments (PEC_sed) leads to toxicity exposure ratios between 0.3 and 7.8, depending on the chosen scenario, which is an indication that Fenoxycarb may be a risk for sediment-dwelling organisms. Recommendations and perspectives The findings are in contrast to results derived from risk assessment using effect data of water exposure and PEC_surface water. Therefore, the risk assessment for sediment-dwelling organisms needs further refinement.
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Chronic toxicity of Fenoxycarb to the midge Chironomus riparius after exposure in sediments of different composition
Journal of Soils and Sediments, 2009Co-Authors: Dirk Jungmann, Thomas Gildemeister, Cândida Shinn, Lennart Weltje, Thomas G. Preuss, Roland Nagel, Hans Toni Ratte, Cornelia Bandow, Hanna MaesAbstract:Background, aim, and scope Fenoxycarb is an insect growth regulator widely used to control a variety of pests. As a juvenile hormone analogue, it interacts with the natural hormones involved in insect development, inhibiting metamorphosis to the adult stage. Adverse effects of Fenoxycarb on non-target organisms have been repeatedly observed and its rapid dissipation from water to the organic fraction of the sediment is known. The aim of this work was to investigate the impact of Fenoxycarb on the development of sediment-dwelling larvae of the midge Chironomus riparius after exposure to spiked sediment.
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Long-term effects of Fenoxycarb on two mayfly species in artificial indoor streams.
Ecotoxicology and environmental safety, 2004Co-Authors: Oliver Licht, Dirk Jungmann, Kai-uwe Ludwichowski, Roland NagelAbstract:The effects of the juvenile hormone analog Fenoxycarb (CAS No. 72490-01-8) were investigated in artificial indoor streams. The results from aufwuchs and two mayfly species (Rhithrogena semicolorata and Ephemerella ignita) are presented. Four concentrations ranging from 0.05 to 50 microg/L (with a spacing factor of 10) were tested. Fenoxycarb disappeared rapidly from the water phase (DT(50) approximately 5 days in the highest concentration, less in the other concentrations). Physico-chemical parameters and aufwuchs were not affected by Fenoxycarb. The mayfly R. semicolorata, introduced at the start of the experiment, was affected by treatments of 5 and 50 microg/L. For the larvae in the streams a LC(50) of 3.3 microg/L and for the larvae in the enclosures a LC(50) of 2.5 microg/L were calculated. The second species (E. ignita) was introduced 72 days after the application, at which time no Fenoxycarb was detectable in the water of the streams (limit of detection of 0.5 ng/L). The emergence of E. ignita was affected in the highest treatment (50 microg/L). Ninety percent of the emerged imagoes showed morphological abnormalities at the abdomen.
Roland Nagel - One of the best experts on this subject based on the ideXlab platform.
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Chronic toxicity of Fenoxycarb to the midge Chironomus riparius after exposure in sediments of different composition
Journal of Soils and Sediments, 2009Co-Authors: Dirk Jungmann, Thomas Gildemeister, Cândida Shinn, Lennart Weltje, Thomas G. Preuss, Roland Nagel, Hans Toni Ratte, Cornelia Bandow, Hanna M. MaesAbstract:Background, aim, and scope Fenoxycarb is an insect growth regulator widely used to control a variety of pests. As a juvenile hormone analogue, it interacts with the natural hormones involved in insect development, inhibiting metamorphosis to the adult stage. Adverse effects of Fenoxycarb on non-target organisms have been repeatedly observed and its rapid dissipation from water to the organic fraction of the sediment is known. The aim of this work was to investigate the impact of Fenoxycarb on the development of sediment-dwelling larvae of the midge Chironomus riparius after exposure to spiked sediment. Materials and methods Three spiked-sediment toxicity tests were carried out based on OECD Guideline 218 using various sediment composition and food sources. Results The endpoints mean emergence time, development rate, and sex ratio were not influenced by Fenoxycarb exposure. The emergence ratio showed a concentration-dependent decrease in all experiments. The lowest no observed effect concentration (NOEC) value was calculated as 0.125 µg kg^−1. The results imply that food quantity and quality might influence the toxicity of Fenoxycarb to the midges. Discussion A comparison of the NOEC with predicted environmental concentration in sediments (PEC_sed) leads to toxicity exposure ratios between 0.3 and 7.8, depending on the chosen scenario, which is an indication that Fenoxycarb may be a risk for sediment-dwelling organisms. Recommendations and perspectives The findings are in contrast to results derived from risk assessment using effect data of water exposure and PEC_surface water. Therefore, the risk assessment for sediment-dwelling organisms needs further refinement.
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Chronic toxicity of Fenoxycarb to the midge Chironomus riparius after exposure in sediments of different composition
Journal of Soils and Sediments, 2009Co-Authors: Dirk Jungmann, Thomas Gildemeister, Cândida Shinn, Lennart Weltje, Thomas G. Preuss, Roland Nagel, Hans Toni Ratte, Cornelia Bandow, Hanna MaesAbstract:Background, aim, and scope Fenoxycarb is an insect growth regulator widely used to control a variety of pests. As a juvenile hormone analogue, it interacts with the natural hormones involved in insect development, inhibiting metamorphosis to the adult stage. Adverse effects of Fenoxycarb on non-target organisms have been repeatedly observed and its rapid dissipation from water to the organic fraction of the sediment is known. The aim of this work was to investigate the impact of Fenoxycarb on the development of sediment-dwelling larvae of the midge Chironomus riparius after exposure to spiked sediment.
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Long-term effects of Fenoxycarb on two mayfly species in artificial indoor streams.
Ecotoxicology and environmental safety, 2004Co-Authors: Oliver Licht, Dirk Jungmann, Kai-uwe Ludwichowski, Roland NagelAbstract:The effects of the juvenile hormone analog Fenoxycarb (CAS No. 72490-01-8) were investigated in artificial indoor streams. The results from aufwuchs and two mayfly species (Rhithrogena semicolorata and Ephemerella ignita) are presented. Four concentrations ranging from 0.05 to 50 microg/L (with a spacing factor of 10) were tested. Fenoxycarb disappeared rapidly from the water phase (DT(50) approximately 5 days in the highest concentration, less in the other concentrations). Physico-chemical parameters and aufwuchs were not affected by Fenoxycarb. The mayfly R. semicolorata, introduced at the start of the experiment, was affected by treatments of 5 and 50 microg/L. For the larvae in the streams a LC(50) of 3.3 microg/L and for the larvae in the enclosures a LC(50) of 2.5 microg/L were calculated. The second species (E. ignita) was introduced 72 days after the application, at which time no Fenoxycarb was detectable in the water of the streams (limit of detection of 0.5 ng/L). The emergence of E. ignita was affected in the highest treatment (50 microg/L). Ninety percent of the emerged imagoes showed morphological abnormalities at the abdomen.
Charles L Mckenney - One of the best experts on this subject based on the ideXlab platform.
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the influence of insect juvenile hormone agonists on metamorphosis and reproduction in estuarine crustaceans
Integrative and Comparative Biology, 2005Co-Authors: Charles L MckenneyAbstract:Comparative developmental and reproductive studies were performed on several species of estuarine crustaceans in response to three juvenile hormone agonists (pyriproxyfen, methoprene and Fenoxycarb). Larval development of the grass shrimp, Palaemonetes pugio, was greater than two orders of magnitude more sensitive to disruption by methoprene and Fenoxycarb than was embryonic development. Developing larvae of the mud crab, Rhithropanopeus harrisii, exhibited reduced metamorphic success at lower concentrations of methoprene and pyriproxyfen than grass shrimp larvae. These responses suggest that the more rigidly controlled metamorphic process in crabs is more sensitive to compounds acting as endocrine disruptors than is the more flexible metamorphic pattern in shrimp. The final crab larval stage, the megalopa, was more sensitive to methoprene and Fenoxycarb exposure than earlier zoeal stages. Mud crab larvae exposed to Fenoxycarb had reduced biomass and lipid content, particularly triglycerides and sterols. Concentrations of Fenoxycarb which reduced the reproductive capacity in single life-cycle exposures of the estuarine mysid, Americamysis bahia, were similar to those concentrations which inhibited metamorphosis in grass shrimp. Juvenile mysids released by exposed adults and reared through maturation without further exposure produced fewer young and had altered sex ratios (lower percentages of males) at lower parental-exposure concentrations than directly affected parental reproduction. These transgenerational responses may well be a product of irreversible effects during developmental exposures which become apparent following maturation and initiation of reproduction. These findings support using a functional approach as an appropriate screening procedure to evaluate potential environmental endocrine-disrupting chemicals in aquatic environments.
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Comparative Embryonic and Larval Developmental Responses of Estuarine Shrimp (Palaemonetes pugio) to the Juvenile Hormone Agonist Fenoxycarb
Archives of Environmental Contamination and Toxicology, 2004Co-Authors: Charles L Mckenney, G. M. Cripe, S. S. Foss, S. R. Tuberty, M. HoglundAbstract:Grass shrimp ( Palaemonetes pugio ) were reared separately through both embryonic and total larval development during exposure to Fenoxycarb at measured concentrations of 0.05) effect on complete embryonic development. Significantly fewer shrimp successfully metamorphosed to postlarvae when exposed through complete larval development to Fenoxycarb concentrations ≥4 μg L^−1. Larval development of grass shrimp was therefore >2 orders of magnitude more sensitive to this juvenile hormone agonist than was embryonic development. Viability of larvae developing in Fenoxycarb was concentration dependent. Development beyond third zoeal stage was significantly inhibited at Fenoxycarb concentrations ≥190 μg L^−1, whereas development beyond fourth zoeal stage was inhibited by a concentration of ≥45 μg L^−1. Fenoxycarb exposure of developing larvae did not alter either the duration of total larval development or the total number of larval stages before metamorphosis. Rearing of Fenoxycarb-exposed embryos through larval development without further exposure had no significant effect on number of larval stages, larval development rate, or metamorphic success of larvae. Similarities in the sensitivity of grass shrimp larvae and mosquito larvae to Fenoxycarb suggests that the use of a bioassay protocol measuring the metamorphic success of crustacean larvae would be a valuable adjunct to the hazard assessment of newly developed pesticides that target endocrine control of metamorphosis in insects and possibly other endocrine-disrupting xenobiotics as well.