Juvenile Hormone Antagonist Research Articles

NADPH–cytochrome P450 reductase knockdown decreases the response to precocene I in the migratory locust Locusta migratoria

Precocene I is a juvenile hormone antagonist that needs to be activated via oxidative biotransformation catalyzed by cytochrome P450 (CYP). NADPH–cytochrome P450 reductase (CPR) supplies CYP with electrons in the oxidation–reduction process; however, its functional role in the activation of precocene I remains unexplored. Here, the representative characteristics of CPRs were analyzed in the CPR gene of Locusta migratoria (LmCPR), the result of model docking indicated that the hydrogen bonds were formed between reduced nicotinamide adenine dinucleotide phosphate (NADPH), flavin adenine dinucleotide (FAD), flavin mononucleotide (FMN) and NADPH-, FAD-, FMN-domains of LmCPR, respectively. Treating the fourth-instar nymphs with precocene I decreased the juvenile hormone titers of nymphs to 0.55-fold of that in acetone-treated controls, and extended the interval time between fourth- and fifth-instar nymphs. 68.75% of the treated fourth-instar nymphs developed into precocious adults in the fifth-instar. LmCPR knockdown decreased the response to precocene I in the nymphs, the occurrence rate of precocious adults induced by precocene I treatment reduced by 23.11%. Therefore, LmCPR may be involved in the activation of precocene I in L. migratoria. In addition, we generated an active recombinant LmCPR protein using a prokaryotic expression system, its activity in reducing cytochrome c was 33.13 ± 11.50 nmol CytCred/min/μg protein. This study lays the foundation for further research on the role of LmCPR in precocene I activation.

Juvenile hormone antagonistic activity of secondary metabolites from Streptomyces lactacystinicus and their insecticidal activity against Plutella xylostella

• IMBL-1412 isolate showed high JHAN and insecticidal activity against P. xylostella . • IMBL-1823 isolate showed high JHAN and insecticidal activity against P. xylostella . • Both IMBL-1412 and IMBL-1823 were identified as Streptomyces lactacystinicus . • Ethyl acetate fraction of them showed high JHAN and insecticidal activities. Due to their specificity to target insects and low toxicity to non-target organisms, insect growth regulators (IGRs) have been promising alternatives to neurotoxic insecticides. Actinobacteria produce a wide range of secondary metabolites with insecticidal and insect growth regulatory activities. In this study, the culture media of 25 actinobacteria isolates showing high juvenile hormone antagonist (JHAN) activity were assessed for their insecticidal activity to identify novel IGR compounds toxic to Plutella xylostella . Among them, four isolates exhibited high insecticidal activity against 3rd instar larvae of P. xylostella . Two isolates of IMBL-1412 and IMBL-1823 showing relatively high insecticidal activities (greater than90% mortality) were identified as Streptomyces lactacystinicus based on colony color on various International Streptomyces Project (ISP) media and nucleotide sequences of the 16S rRNA gene. The ethyl acetate fractions of both isolates showed high JHAN and insecticidal activities against P. xylostella larvae at a concentration of 100 ppm when the culture media of these two isolates were extracted sequentially using hexane, ethyl acetate, and butyl alcohol. These results suggested that secondary metabolites of these actinobacterial isolates could be efficiently applied to develop novel IGR insecticides for the control of P. xylostella .

Juvenile hormone inhibitory and mosquito larvicidal substances derived from actinomycetes

AbstractMosquitoes are major pests that attack humans and spread pathogens. To control mosquito larvae, insect growth regulators such as methoprene and pyriproxyfen have been widely used. Juvenile hormone antagonists (JHAN) have the potential to act as an eco‐friendly insecticide with a novel mode of action. Actinomycetes are known as a producer of an enormous number of secondary metabolites. In this study, secondary metabolites of 232 Actinomycetes strains were screened for their juvenile hormone antagonist activity and their mosquito larvicidal activity. Among them, IMBL‐1939, 1952, 2005 and 2064 strains showed mosquito larvicidal activity with JHAN activity. These actinomycetes derived JHAN could be alternative sustainable vector control agents.

Methyl farnesoate regulatory mechanisms underlying photoperiod‐dependent sex determination in the freshwater crustacean Daphnia magna

Freshwater zooplankton Daphnia magna has been widely used in ecotoxicology studies. During the last 20 years, it has been demonstrated that the topical application of juvenile hormone (JH) or JH analogs to mother daphnids induce male offspring production. Based on this finding, an in vivo screening validation method for chemicals with JH agonistic effect has developed. Although this screening system successfully identified a number of JH-like chemicals, molecular mechanisms underlying the male sex-determining process remain largely unknown. To address this issue, we established a reliable male- or female-producing system using Daphnia pulex WTN6 strain by changing the rearing photoperiod. Taking advantage of this rearing system, we successfully found several factors involving male sex determination such as ionotropic glutamate receptors, protein kinase C and pantothenate. Here, we used two D. magna strains that can also control the production of female or male offspring by photoperiod differences as model species for ecotoxicology studies. We demonstrated that either treatment of antagonist of ionotropic glutamate receptors or inhibitor of protein kinase C strongly suppressed male offspring production even under male-producing conditions. Moreover, we revealed that male sex-determining processes are likely diverged between D. magna and D. pulex based on the current experiment. This study provides a fine experimental method for in vivo screening not only JH agonists but also JH antagonists. Moreover, using daphnids with photoperiod-dependent sex determination manner will hugely contribute to understanding the mode-of-action of JH in daphnids.

Insecticidal and insect growth regulatory activities of secondary metabolites from entomopathogenic fungi, Lecanicillium attenuatum

AbstractInsect growth regulators (IGRs) are effective alternatives to chemical insecticides because of their specificity and low environmental toxicity. Entomopathogenic fungi are an important natural pathogen of insects and have been developed as biological control agents. They produce a wide range of secondary metabolites such as antibiotics, pesticides, growth‐promoting or inhibiting compounds and insect attracting agents. In this study, to explore novel IGR substances from entomopathogenic fungi, culture extracts of 189 entomopathogenic fungi isolated from Korean soil samples were investigated for their juvenile hormone (JH)‐based IGR activities. Whereas none of the culture extracts exhibited JH agonist (JHA) activity, 14 extracts showed high levels of JH antagonist (JHAN) activity. Among them, culture extract of JEF‐145 strain, which was identified as Lecanicillium attenuatum, showed the highest insecticidal against Aedes albopictus and Plutella xylostella. At liquid culture condition, JHAN activity was observed in culture soup rather than mycelial cake, indicating that substances with JHAN activity are released from the JEF‐145 strain during culture. Furthermore, while extract from solid cultured JEF‐145 strain showed insecticidal activities against both A. albopictus and P. xylostella, that from liquid cultured fungi showed insecticidal activity only against A. albopictus, indicating that L. attenuatum JEF‐145 strain produces different kinds of secondary metabolites with JHAN activity depending on culture conditions. These results suggested that JHAN substances derived from entomopathogenic fungi could be usefully exploited to develop novel eco‐friendly IGR insecticides.

Mosquito larvicidal activities of farnesol and farnesyl acetate via regulation of juvenile hormone receptor complex formation in Aedes mosquito

Abstract Due to their target specificity and low-toxicity, insect growth regulators (IGRs) are regarded as promising alternatives to chemical insecticides. In this study, farnesol and farnesyl acetate exhibited juvenile hormone (JH)-based IGR activities. While farnesyl acetate showed JH agonist (JHA) activity in concentration-dependent manner, farnesol was identified as JH antagonist (JHAN) by interfering pyriproxyfen-mediated binding JH receptor complex. Both compounds showed mosquito larvicidal activities and caused retardation of ovarian growth of female Aedes albopictus by modulating the formation of JH receptor complex, expression of JH-inducible genes, and thereby disrupting JH-based endocrine regulations. These results suggested that farnesol and farnesyl acetate could be applicable for investigating underlying mechanisms of JH-regulated insect physiologies as well as developing novel eco-friendly insecticides.

Isolation and characterization of the insect growth regulatory substances from actinomycetes

Insect growth regulators (IGRs) are attractive alternatives to chemical insecticides. Since it has been reported that secondary metabolites from actinomycetes show insecticidal activities against various insect pests, actinomycetes could be a potential source of novel IGR compounds. In the present study, insect juvenile hormone antagonists (JHANs) were identified from actinomycetes and their insect growth regulatory and insecticidal activities were investigated. A total of 363 actinomycetes were screened for their insect growth regulatory and insecticidal activities against Aedes albopictus and Plutella xylostella. Among them, Streptomyces sp. AN120537 showed the highest JHAN and insecticidal activities. Five antimycins were isolated as active compounds by assay-guided fractionation and showed high JHAN activities. These antimycins also exhibited significant insecticidal activities against A. albopictus, P. xylostella, F. occidentalis, and T. urticae. Moreover, dead larvae treated with these antimycins displayed morphological deformities that are similar to those of JH-based IGR-treated insects. This is the first report demonstrating that the insecticidal activities of antimycins resulted from their possible JHAN activity. Based on our results, it is expected that novel JHAN compounds potentially derived from actinomycetes could be efficiently applied as IGR insecticides with a broad insecticidal spectrum.

Dissecting the Role of Juvenile Hormone Binding Protein in Response to Hormone and Starvation in the Cotton Bollworm, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae).

Juvenile hormone (JH) regulates many physiological processes in insect development, diapause, and reproduction. Juvenile hormone binding protein (JHBP), the carrier partner protein of JH, is essential for the balance of JH titer to regulate the metamorphosis and development of insect. In this study, two JHBP genes were identified from Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae), namely HaJHBP1 and HaJHBP2. The tissue and temporal expression pattern revealed that both HaJHBP1 and HaJHBP2 were dominantly expressed in larval fat body, and their high transcription stages were detected in fourth and fifth instars. The ingestion of methoprene, a JH analogue, significantly induced the expression of HaJHBP1 and HaJHBP2. However, both HaJHBP1 and HaJHBP2 mRNA levels were significantly downregulated after treated with a JH antagonist, precocene. When subject to starvation, larvae showed a marked suppressive effect in the expression of HaJHBP1 and HaJHBP2. These results indicate that JHBP plays a part in the JH-regulated metabolism, growth, or development in reaction to different nutritional conditions.

A plant diterpene counteracts juvenile hormone-mediated gene regulation during Drosophila melanogaster larval development

Many plant species possess compounds with juvenile hormone disruptor (JHD) activity. In some plant species, such activity has been attributed to diterpene secondary metabolites. Plant JHD diterpenes disrupt insect development by interfering with the juvenile hormone (JH)-mediated formation of JH receptor complexes. Here, we demonstrate that a plant extract and a diterpene from Lindera erythrocarpa (methyl lucidone) interfere with the formation of both methoprene-tolerant (Met)/Taiman and Germ cell-expressed (GCE)/Taiman heterodimer complexes in yeast two-hybrid assays in vitro. In addition to the in vitro JHD activity, the diterpene and the plant extract from L. erythrocarpa also disrupt the development of larvae and pupae in Drosophila melanogaster. Comparing the transcriptomes of juvenile hormone analog (JHA, methoprene)- and JHD (methyl lucidone)-fed wandering third-instar larvae revealed a large number of genes that were coregulated by JHA and JHD. Moreover, most (83%) of the genes that were repressed by methyl lucidone were significantly activated by methoprene, indicating that JHDs and JHAs have opposing effects on the transcriptional regulation of many JH-dependent genes. Gene ontology analysis also suggested that some of the genes activated-by-JHA/repressed-by-JHD play roles in spermatogenesis. Affymetrix microarray-based analysis indicated that the expression of genes activated-by-JHA/repressed-by-JHD was testis-specific. Together, these results suggest that JH is involved in testis-specific gene expression and that plant JHD diterpenes function as JH antagonists in such JHA-mediated gene regulation.

Insect growth regulatory and larvicidal activity of chalcones against Aedes albopictus

AbstractWidespread use of chemical insecticides has resulted in development of insect resistance and natural products with biological activities could become an attractive alternative to control insect pests. In order to find more effective insecticides for controlling mosquito, various mosquitocidal compounds are studied. Recently, juvenile hormone antagonists (JHANs) have been found to be to safe and effective insecticides for control of mosquito. In order to identify novel insecticidal compounds with JHAN activity, several chalcones were surveyed on their JHAN activities and larvicidal activities against Aedes albopictus larvae. Among them, 2′‐hydroxychalcone and cardamonin showed high levels of JHAN and mosquito larvicidal activities. These results suggested that chalcones with JHAN activity could be useful for control of mosquito larvae.

Mosquitocidal activity of penfluridol as juvenile hormone antagonist

Juvenile hormone antagonists (JHANs) are known to interfere with the formation of juvenile hormone (JH) receptor complex. JHANs might be effective for control of target pests in larval stages at which stages high level of endogenous JH titer is maintained. In order to identify novel insecticidal compounds, 2352 compounds were surveyed on their JHAN activities using the yeast-two hybrid system. Among 53 compounds with JHAN activities, penfluridol showed high level of insecticidal activity against larvae of Aedes albopictus. JHAN activity was increased in proportion to the concentration of penfluridol. Larvicidal activity of penfluridol was 1.3–2.0 folds higher than that of pyriproxyfen. These results suggested that penfluridol could be useful for control of mosquito larvae.

Conifer Diterpene Resin Acids Disrupt Juvenile Hormone-Mediated Endocrine Regulation in the Indian Meal Moth Plodia interpunctella.

Diterpene resin acids (DRAs) are important components of oleoresin and greatly contribute to the defense strategies of conifers against herbivorous insects. In the present study, we determined that DRAs function as insect juvenile hormone (JH) antagonists that interfere with the juvenile hormone-mediated binding of the JH receptor Methoprene-tolerant (Met) and steroid receptor coactivator (SRC). Using a yeast two-hybrid system transformed with Met and SRC from the Indian meal moth Plodia interpunctella, we tested the interfering activity of 3704 plant extracts against JH III-mediated Met-SRC binding. Plant extracts from conifers, especially members of the Pinaceae, exhibited strong interfering activity, and four active interfering DRAs (7α-dehydroabietic acid, 7-oxodehydroabietic acid, dehydroabietic acid, and sandaracopimaric acid) were isolated from roots of the Japanese pine Pinus densiflora. The four isolated DRAs, along with abietic acid, disrupted the juvenile hormone-mediated binding of P. interpunctella Met and SRC, although only 7-oxodehydroabietic acid disrupted larval development. These results demonstrate that DRAs may play a defensive role against herbivorous insects via insect endocrine-disrupting activity.

Identification of plant compounds that disrupt the insect juvenile hormone receptor complex

Insects impact human health through vector-borne diseases and cause major economic losses by damaging crops and stored agricultural products. Insect-specific growth regulators represent attractive control agents because of their safety to the environment and humans. We identified plant compounds that serve as juvenile hormone antagonists (PJHANs). Using the yeast two-hybrid system transformed with the mosquito JH receptor as a reporter system, we demonstrate that PJHANs affect the JH receptor, methoprene-tolerant (Met), by disrupting its complex with CYCLE or FISC, formation of which is required for mediating JH action. We isolated five diterpene secondary metabolites with JH antagonist activity from two plants: Lindera erythrocarpa and Solidago serotina. They are effective in causing mortality of mosquito larvae at relatively low LD50 values. Topical application of two diterpenes caused reduction in the expression of Met target genes and retardation of follicle development in mosquito ovaries. Hence, the newly discovered PJHANs may lead to development of a new class of safe and effective pesticides.

Effects of juvenile hormone antagonist KK-42 on temporal and spatial expressions of FAMeT in shrimp Penaeus schmitti

It has been demonstrated that the treatment of juvenile hormone antagonist KK-42 can significantly accelerate growth of Penaeus schmitti,which has been applied in P.schmitti aquaculture,but the mechanism of KK-42 is unclear.To provide the theory support involved in KK-42 application,the temporal and spatial expressions of farnesoic acid O-methyltransferase (FAMeT),a key synthesis enzyme of methyl farnesoate (MF) which is the important hormone regulating directly crustacean growth,was assayed and the effect of KK-42 on the enzyme was researched.The shrimps (Penaeus schmitti),3.5 5.0 cm long,were randomly divided into two groups,soaked in KK-42 solution at a concentration of 1.95×10-4 mol/L or in the solution without KK-42 for 1 min,respectively,and then cultured in normal way.The levels of FAMeT mRNA were determined using real-time PCR and hemolymph MF titer was analyzed by normal phase high-performance liquid chromatography.Results showed that the expression pattern of FAMeT derived from the muscle,eyestalk and mandibular organ (MO) tissues varied in control,of which,the mRNA levels in muscle and eyestalk tissues were not only relatively low but also little various during the experiment.However,an obvious fluctuation of mRNA level occurred in MO during the stage of experiment,more than 1-fold of increase in mRNA level was observed on days 2,6,7,and 8 comparing to that on day 0.The hemolymph MF content in control shrimps rose during the experiment.Administration of KK-42 resulted in the universal depression on FAMeT expression in three tissues mentioned above;the most significant inhibitory effect occurred in MO where the level of FAMeT mRNA was considerably lower than that in control group from day 1 to day 7;the level even decreased to 50.9% (P0.01),63.4% (P0.01) and 55.7% (P0.01) on day1,day 4 and day 6 after KK-42 treatment,respectively.Meanwhile,the amount of hemolymph MF fell in KK-42-treated shrimps compared to that in control ones during the duration of the experiment,which might be involved in famet transcription depression in the animal tissues,especially in the MO.Our present study demonstrates that KK-42 can significantly inhibit FAMeT expression in the MO and muscle as well as eyestalk tissues of the shrimp Penaeus schmitti and decrease the hemolymph MF titer,which may be one of the growth-promoting mechanisms of KK-42 on Penaeus schmitti.

Effects of KK‐42 on Expression of 3‐Hydroxy‐3‐Methylglutaryl‐Coenzyme A Reductase in Penaeus schmitti

Methyl farnesoate (MF) is an important hormone controlling crustacean growth. Our previous study has demonstrated that the treatment of juvenile hormone antagonist KK‐42 can accelerate growth of Penaeus schmitti. The expression of 3‐hydroxy‐3‐methylglutaryl‐coenzyme A reductase (HMGR), a key enzyme of MF precursor production, was assayed using real‐time PCR, and hemolymph MF titer was determined by high‐performance liquid chromatography. Shrimp, 3.5–5.0 cm long, were soaked for 1 min in KK‐42 solution at a concentration of 1.95 × 10−4 mol/L or in the solution without KK‐42 and then cultured in normal way. Results showed that the highest level of hmgr transcript occurred in mandibular organ (MO). Administration of KK‐42 resulted in HMGR expression to be notably depressed in the MO, even reduced by 80.2% (P < 0.01) and 90.7% (P < 0.01) on Day 1 and Day 7, respectively. The MF level showed a decline trend in KK‐42 treatment compared to that of corresponding control group. Our present study demonstrates that treatment of KK‐42 significantly inhibits HMGR expression in different tissues especially in the MO, which is likely one of KK‐42 growth‐promoting mechanisms on P. schmitti.

Synthesis and biological activity of novel anti-juvenile hormone agents

Ethyl 4-[2-(tert-butylcarbonyloxy)butoxy]benzoate (ETB) is a partial juvenile hormone (JH) antagonist which targets larval epidermis. We converted ETB to ethyl 4-(2-substituted alkyloxy)benzoates. These compounds induced precocious metamorphosis in the silkworm, Bombyx mori, which is a clear sign of JH deficiency, and their activity was completely counteracted by the simultaneous application of a JH agonist, methoprene. Among these novel compounds, ethyl 4-(2-benzylhexyloxy)benzoate (KF-13) showed high precocious metamorphosis-inducing activity at low doses, but its activity decreased with increasing dose, probably due to their JH-like activity. KF-13 is an enantiomeric compound. The (S)-enatiomer of KF-13 was more active than the (R)-enantiomer at low doses, but at high doses the activity was reversed (R>S). Hemolymph JH esterase activity, which is indispensable for the initiation of pupation in normal last-instar larvae, was induced in 4th-instar larvae by treatment with KF-13. 2-(6-Methyl-3-pyridyloxy)hexyl and 2-phenoxyhexyl analogs showed JH activity when topically applied to allatechtomized 4th-instar larvae.

A new and practical application of JH antagonist KK-42 to promoting growth of shrimp Penaeus schmitti

The shrimps ( Penaeus schmitti), 0.6–0.8 cm long, were soaked for 1 min in juvenile hormone antagonist KK-42 solution at a concentration of 1.95 × 10 − 4 mol/L, and then cultured in normal way. The body weight of animals rose with increasing culture time in all groups, but was higher in KK-42 treatment. The increase rate of body weight of treatment group was 167% and 68% higher than control group at 30th day and 60th day, respectively; the body weight rose by 42.5% at 90th day and 22.1% at 120th day. Histological observations showed that the number of acini of mandibular organ increased gradually as animals grew, and the diameter of acinus-forming cells was statistically bigger at 120th day than at other times. After KK-42 treatment, both the number of acini and the diameter of gland cells decreased in the entire experiment observed. The results indicated the inhibition of anti-juvenile hormone KK-42 on the development of mandibular organ in P. schmitti.

Synthesis and Anti-Juvenile Hormone Activity of Alkyl 4-(2-Phenoxyalkyloxy) benzoates and Related Compounds

Since juvenile hormone (JH) is involved in a wide range of physiological processes in both developing and mature insects (Riddiford, 1994), compounds that possess anti–JH activity are potentially useful not only as biochemical probes to assist in elucidating the role of JH in insect development and reproduction, but also as insect growth regulators (Staal, 1986). Several compounds including precocenes (Bowers et al., 1976), fluoromevalonate (Quistad et al., 1981), ethyl 4–[2–(tert–butylcarbonyloxy)butyloxy]benzoate (ETB) (Staal, 1982), dichloroallyl hexanoate (Quistad et al., 1985), 1,5–disubstituted imidazoles (Pratt et al., 1990) and brevioxime (Moya et al., 1997) have so far been found to have anti–JH activity. However, none of the compounds has been developed for practical use in pest control as yet. Among them, ETB is known to be a unique anti–JH agent. It shows anti–JH activity as well as JH activity for the tobacco hornworm, Manduca sexta (Staal, 1982) and the silkworm, Bombyx mori (Kiguchi et al., 1984), depending on the dose applied; low doses of ETB induced precocious metamorphosis, a clear JH–deficiency symptom, but at higher doses only JH–like activity was observed. Riddiford et al. (1983) have reported that ETB acts as a partial JH antagonist at the target tissue of the larval epidermis. No other anti–JH agents with such action have been found to date. In our previous studies (Ishiguro et al., 2003), we found that ethyl 4–[2–(6–methyl–3–pyridyloxy)butyloxy] benzoate (1), structurally derived from ETB (Fig. 1), showed stronger activity than ETB. Modifications of the ethyl side chain of 1 revealed that the butyl (2) and isobutyl (3) groups were optimal for high activity (Fujita et al., 2005). Further structure activity relationship studies on this series of compounds indicated that the phenyl analog 4 showed activity comparable to that of 2, suggesting that the 6–methyl–3–pyridyl moiety is not significant for activity (Furuta et al., 2006). Conversion of the 4–ethoxycarbonyl group of 2 and 4 to the corresponding carboxylic acids eliminated the activity, indicating that the ester moiety is responsible for the activity. We therefore synthesized additional analogs in which the ethoxycarbonyl group of 4 was modified, and evaluated their activity to induce precocious metamorphosis in B. mori larvae. We also examined the precocious metamorphosis–inducing activity of both optical isomers of ethyl 4–(4–methyl–2–phenoxypentyloxy) benzoate. We report here the structure–activity relationships of new phenyl ether analogs derived from compound 4. Synthesis and Anti–Juvenile Hormone Activity of Alkyl 4–(2–Phenoxyalkyloxy)benzoates and Related Compounds

Acid zeolites as catalysts in organic reactions. Highly selective condensation of 2-alkylfurans with carbonylic compounds

Condensation of 2-(3-acetoxypropyl)furan and 2-methylfuran with a series of aliphatic and aromatic carbonyl compounds, including formaldehyde, acetaldehyde, hexanal, cinnamaldehyde, benzaldehyde, anisaldehyde and acetone has been carried out in the presence of acid zeolites of medium and large pore size at different reaction temperatures. While H-ZSM-5 and H-MOR exhibited lower activity, we have found that tridirectional large pore zeolites Y and β are very convenient catalysts. In some cases, total conversion with complete selectivity could be achieved under our experimental conditions. Sulfuric acid was less active and selective for this type of Friedel-Crafts condensations. The resulting gem difurylalkanes with 3-hydroxypropyl substituent at the 2 position of the furan ring can be precursors of bis-spiroketals with potential activity as juvenile hormone antagonist for the Mediterranean fly.

Effect of reproductive toxicants on lipovitellin in female blue crabs, Callinectes sapidus

Changes in the concentration of lipovitellin, a lipoprotein that is the major protein in mature oocytes of crustaceans, were determined during ovarian development in female blue crabs, Callinectes sapidus. To test the effects of reproductive toxins on vitellogenesis, crabs were fed food containing cadmium or injected with the juvenile hormone antagonist, precocene II. Monoclonal antibodies prepared against one of the lipovitellin peptides (peptide A—107 kDa) were used in an enzyme linked immunosorbent assay to determine lipovitellin concentrations. Recently molted female crabs fed food containing cadmium (0.02 mg/g) for 18 days had oocytes with the same lipovitellin concentration as controls, but after 24 days the oocytes in cadmium treated crabs had significantly lower lipoprotein contents than controls (30 ± 4 ng/oocyte—cadmium treated; 45 ± 4 ng/oocyte—control). Precocene II-treated crabs had significantiy lower lipovitellin concentrations after 18 and 24 days. Diameters of oocytes were the same in both treated and control crabs. The results suggest that some pollutants may affect reproduction by acting during secondary vitellogenesis i.e., period when there is a large increase in lipovitellin synthesis. Since lipovitellins serve many of the nutritional needs of recently emerged crab embryos, poor larval survival may occur as a result of lower lipovitellin content.