Performance of bean bruchids Callosobruchus maculatus and Zabrotes subfasciatus (Coleoptera: Bruchidae) reared on resistant (IT81D-1045) and susceptible (Epace 10) Vigna unguiculata seeds: relationship with trypsin inhibitor and vicilin excretion

Callosobruchus maculatus (Cm) and Zabrotes subfasciatus (Zs) were reared on resistant (IT81D-1045) and on susceptible (Epace 10) cowpea seeds. The emergence of adult insects, total developmental period (TDP) and excretion of trypsin inhibitor and vicilin were determined for both bruchid populations. Parameter evaluation showed that the Zs populations emerged from both seeds had no significant differences in emergence and TDP. The Cm population raised from resistant seeds had lower emergence (5.6+/-1.3%) and delayed TDP (46+/-1.25 days) than those emerged from susceptible seeds. The excretion of defense proteins showed that Zs reared in resistant seeds excreted 1.7 times more trypsin inhibitor, but this did not affect emergence or TDP. Furthermore, Cm population emerged from resistant seeds excreted 7 times higher vicilin and 0.4 times less trypsin inhibitor than that emerged from susceptible seeds. These results indicate that vicilins from resistant seeds are involved to significantly longer TDP (46 days) and also drastic reduction of insect emergence ( approximately 5%) of C. maculatus.     

Intra-specific variation in female remating in Callosobruchus chinensis and C. maculatus

The effects of mating duration on female remating (exp. 1) and under different male densities (exp. 2) were examined in two strains of the adzuki bean beetle, Callosobruchus chinensis and in one strain of the bruchid beetle, C. maculatus. In experiment 1, the frequency of female remating was markedly different between the two strains of C. chinensis. Females of the jC strain, reared long-term in the laboratory, did not remate after being allowed to mate freely (=monogamy), whereas females of the isC strain, recently established from the field, showed high remating frequencies (=polyandry). In both strains, the frequency of female remating increased after the duration of the first mating was deliberately shortened. The relation between mating duration and remating frequency was significantly different, however, between the two strains. In a closely related species, C. maculatus, which manifests polyandry, this relation was more similar to that of the field-derived (=isC) than to that of the laboratory-derived (=jC) strain of C. chinensis. The reasons for the inter-strain variation observed in the remating frequencies of C. chinensis are also discussed. In experiment 2, the mating duration of the three strains was compared under different male densities. Only the lab-derived strain demonstrated a significantly shorter mating duration when one female was placed together with five males than when paired with one male. The shorter mating duration (approximately 26 s) was similar to that of females allowed to remate in the monogamous strain in experiment 1.     

Evaluation of the effectiveness of conventional insecticides against the cowpea weevil, Callosobruchus maculatus (Coleoptera: Bruchidae), on four different substrata surfaces

在害虫治理中,在消费或贮藏粮食加工产品的建筑设施或场所进行害虫防治需要将杀虫剂施用在各种基质表面上.为了测定不同基质表面上杀虫剂的药效,将四纹豆象Callosobruchus maculatus(F.)成虫接触田间推荐剂量的阿维菌素、溴氰菊酯和毒死蜱.结果表明:施用在玻璃、瓷砖、塑料和纸盘表面上,阿维菌素对四纹豆象成虫的致死率分别为63.33％,22.41％,12.9％和11.9％,而溴氰菊酯在这4种基质表面上对四纹豆象成虫的致死率分别为55％,44.2％,41.3％和37.4％.在所有基质表面上接触毒死蜱,四纹豆象成虫的死亡率均为100％.对数据进行的Probit分析表明,毒死蜱制剂在玻璃、瓷砖、塑料和纸盘上对四纹豆象成虫的LC50值分别为8.66,13.6,29 16和56.5 μg/mL,阿维菌素制剂的相应数值分别为119.4,446.2,774.2和836.4μg/mL,溴氰菊酯制剂的相应数值分别为1008,1131,1210和1336 μg/mL.据此推断,毒死蜱对四纹豆象的毒性最强,且在玻璃、瓷砖、塑料和纸盘表面上的毒性依次降低.     

Effect of trypsin inhibitor from Crotalaria pallida seeds on Callosobruchus maculatus (cowpea weevil) and Ceratitis capitata (fruit fly)

A proteinaceous trypsin inhibitor was purified from Crotalaria pallida seeds by ammonium sulfate precipitation, affinity chromatography on immobilized trypsin-Sepharose and TCA precipitation. The trypsin inhibitor, named CpaTI, had M(r) of 32.5 kDa as determined by SDS-PAGE and was composed of two subunits with 27.7 and 5.6 kDa linked by disulfide bridges. CpaTI was stable at 50 degrees C and lost 40% of activity at 100 degrees C. CpaTI was also stable from pH 2 to 12 at 37 degrees C. CpaTI weakly inhibited chymotrypsin and elastase and its inhibition of papain, a cysteine proteinase, were indicative of its bi-functionality. CpaTI inhibited, in different degrees, digestive enzymes from Spodoptera frugiperda, Alabama argillacea, Plodiainterpunctella, Anthonomus grandis and Zabrotes subfasciatus guts. In vitro and in vivo susceptibility of Callosobruchus maculatus and Ceratitis capitata to CpaTI was evaluated. C. maculatus and C. capitata enzymes were strongly susceptible, 74.4+/-15.8% and 100.0+/-7.3%, respectively, to CpaTI. When CpaTI was added to artificial diets and offered to both insect larvae, the results showed that C. maculatus was more susceptible to CpaTI with an LD(50) of 3.0 and ED(50) of 2.17%. C. capitata larvae were more resistant to CpaTI, in disagreement with the in vitro effects. The larvae were more affected at lower concentrations, causing 27% mortality and 44.4% mass decrease. The action was constant at 2-4% (w/w) with 15% mortality and 38% mass decrease.     

FUNCTIONAL INCOMPATIBILITY BETWEEN THE FERTILIZATION SYSTEMS OF TWO ALLOPATRIC POPULATIONS OF CALLOSOBRUCHUS MACULATUS (COLEOPTERA: BRUCHIDAE)

Abstract Recent studies indicate that postcopulatory sexual selection may represent an important component of the speciation process by initiating reproductive isolation via the evolutionary divergence of fertilization systems. Using two geographically isolated populations of the polyandrous beetle Callosobruchus maculatus, we investigated divergence in fertilization systems by determining the extent of postcopulatory functional incompatibility. Through reciprocal, cross‐population matings we were able to separately estimate the effects of male and female population origin and their interaction on the extent of last‐male sperm precedence, female receptivity to further copulation and female oviposition. Our results indicate partial incompatibility between the fertilization systems of the two populations at all three functional levels. Males derived from the same population as females outcompete rival, allopatric males with respect to sperm preemption, sperm protection, and ability to stimulate female oviposition. This pattern is reciprocated in both populations indicating that postcopulatory, prezygotic events represent important mechanisms by which between‐population gene flow is reduced. We suggest the partial gametic isolation observed is a by‐product of the coevolution of male and female fertilization systems by a process of cryptic female choice. Our results are consistent with a mechanism akin to conventional mate choice models although they do not allow us to reject antagonistic sexual coevolution as the mechanism of cryptic female choice.     

Contest and scramble competitions inCallosobruchus maculatus (Coleoptera: Bruchidae) II. Larval competition and interference mechanisms

Competition between contest and scramble strategists was examined using two strains of Callosobruchus maculatus, the contest strain (iQ) and the scramble strain (tQ). The direct larval interference experiment within each strain showed that the contest strain performed strong direct interference throughout its larval stage against the conspecific opponent(s). The scramble strain also performed its interference, but only during the 3rd and the 4th larval stages. The inter-strain larval competition experiments inside a large and small mung bean (Vigna radiata) showed that the contest strain was, in general, superior to the scramble strain in competition, but the competition results were density- and frequency-dependent. In the large beans, the proportion of adult emergence of the contest strain increased with the increase of its own initial density but decreased as the initial density of the scramble strain increased. The shape of the proportion of adult emergence became nonlinear in the small beans. The cause of the complexity of inter-strain competition results was discussed in the light of the difference in larval interference ability between the two strains.     

Distribution and microhabitat use by flatfishes in a Louisiana estuary

We used a 1 m beam trawl to characterize microhabitat use of flatfishes in monthly samples collected in Barataria Bay, Louisiana. Six strata were established along a salinity gradient from the nearshore zone along the Gulf of Mexico to approximately 30 km inland. Randomized sampling within strata characterized flatfish distributions and environmental conditions throughout the bay. Microhabitats were characterized by salinity, temperature, dissolved oxygen, depth, distance from shore, and substrate type. In 594 short-duration, beam-trawl samples collected from October 1992 through September 1994, we identified seven flatfish species from 7046 specimens, most of which were juveniles. Four species accounted for 98.3% of all flatfishes. The two most abundant, offshore tonguefish and bay whiff, were euryhaline and widely distributed over the salinity gradient; however, offshore tonguefish were concentrated in the lowermost stratum where bay whiff were uncommon. The third species, fringed flounder, was more abundant in middle and lower bay strata at higher salinities. The fourth species, blackcheek tonguefish, was most common in middle and upper bay strata and declined in abundance in coastal strata. A rotated factor analysis resolved six environmental variables into three major axes that explained 69 percent of the variance and were characterized as seasonal, depth-distance, and substrate-salinity axes. Separation of species and life history intervals in three-dimensional factor space reflected temporal and spatial segregation. Within the four common flatfishes, 14 of 24 variable comparisons showed clear ontogenetic trends in which at least two size-class means differed significantly. Among the common species, temporal differences were reflected by mean temperatures and dissolved oxygen concentrations and spatial differences were reflected by other environmental variables, including depth, distance, substrate, and salinity. This revised version was published online in July 2006 with corrections to the Cover Date.