Reproductive Behavior Of Bactrocera Dorsalis(Hendel)

The oriental fruit fly,Bactrocera dorsalis（Hendel）,is subordinate to Diptera,Tephritidae,Dacinae,Bactrocera Macquart.Native to tropical and subtropical Asia,the oriental fruit fly is now found in at least 65 countries,including part of American and Oceania,as well as most region of African continent.In China,it is distributed widely in southern provinces.Female lay eggs inside fruits,its ovipositor can puncture peel and cause damage due to microorganism infection.Larvae eat hosts which result in decay and abscission of fruit.The pest has great reproductive ability,short life cycle,great fly ability,wide host range（42 family 124 species）.It spread swiftly as soon as invasion occurred,and has been high ranked as quarantine pest worldwide.The existence of this pest in a country or a region serious damaged its economy.Besides,the trade freedom of various commercial crops influenced,the fees associated with quarantine and control methods are also cost high.What is more,the application of chemical and biological measurements will cause serious impact to the environment.The actual loss and potential damage allow no neglectable.The integrate pest control requires the master of biology and ecology of target pests,thus various kinds of measures can be taken effectively.In this paper,I aimed at the reproduction behavior of B.dorsalis,reported its mating and oviposition rhythm and the influence of weight and multiple mating on reproductive fitness.Using sterile technique by thiotepa,research was conducted on male-male sperm competition.1.Mating and oviposition rhythm of B.dorsalisMature time:female of B.dorsalis mature earlier than male.Mating peak of female occur 7and 8 days later after emergence,accumulated 76%individuals mated on the 8th day.Mating peak of male happened on the 8th and 9th days after emergence,63%individuals mated on the9th day.The mating rate of female and male reached 100%on the 13th and 14th day respectively.Daily mating rhythm and mating duration:mating behavior of male and female B.dorsalis stimulated by dim light.During the dim period immediately after the light off,mating pairs reached peak of 20 pairs mated in total,accounting for 39.22%of total mating pairs.During the period of 1 hour before light off,24 pairs mated accounting for 47.06%of the total mating number.Mating duration of B.dorsalis lasted 630 min on average,the longest lasted 730 min with the shortest of 580min.Daily oviposition rhythm:Result showed that overwhelming majority eggs laid during the light period.A total of 6948 eggs laid from 34 females in 72 hours,6780 of them laid during the light period account for 97.58%of total eggs.Merely 168 eggs laid during the dark period,accounting for 2.42%of total eggs.Oviposition peak occurred during the 5th and 9th hour after light on with average eggs of 7.41 and 6.52 respectively.During the dark period,there were also two oviposition peak which occurred during the 3th and 8th hours after the light off with average eggs of 0.45 and 0.21 respectively.Lifetime mating potential:A total of 15 males were tested,result showed that males were able to acquire 16 matings on average with mated up to 34 times and lowest to 6 times.The longest male was with survival of 135 days and the shortest was 41 days.Of the 18 females tested,half of them remated twice or more with 2 of them mated 3 times.Mating intervals were uneven between 1 to 20 days.Lifetime oviposition observation:Female oviposition eggs mainly in the earlier period.Though oviposition period lasted to more than 30 days,female laid 50%of eggs in 10 days after oviposition.There were 2 obvious oviposition peaks during the period,the first one was on the 5th day account 25.1%accumulated eggs laid.The second one was on the 13th day.Hatchability peaked on the 4th day of 88.48%with another peak at 84.42%on the 9th day.2.Effect of body size on reproductive fitness of B.dorsalisWe investigated how adult body weight and hind-tibial length were correlated in each sex and how body size of each sex affected lifetime reproductive fitness.We show that body weight and hind-tibial length were significantly positively correlated in both sexes,indicating that either trait can be used as an index of body size.However,the weight–tibial length relationships were sex specific,with females gaining disproportionally more weight than males with the increase of hind-tibial length.Body size was not significantly correlated with longevity of either sex,but males lived significantly longer than females.Larger females laid significantly more eggs regardless of body size of the male partner,suggesting that male size has no effect on fecundity.However,body size of both sexes had a significant effect on fertility.Fertility rate significantly increased with the increase of male body size before reaching median size,after which,fertility rate significantly decreased.The effect of female body size on fertility rate significantly interacted with that of male body size,i.e.,the decrease in fertility rate significantly accelerated with the increase of body size of both sexes.We conclude that selection on body size–reproductive fitness relations operates in different directions for the two sexes of B.dorsalis,with larger females and average males having highest reproductive fitness.3.Effect of multiple mating on female and its offspring fitnessIn order to explore the influence of multiple mating on reproductive fitness of B.dorsalis,I set three treatments for parental generation and collected offsprings of double mated female to observe its reproductive fitness.in the parental generation,single mated female not significantly（M-1）produce fewer eggs than double mated ones（those with the same male and those with different males）with fecundity of 1472.04 eggs,1669.61 eggs and 1613.44 eggs.Hatchability（63.68%,65.64%and 64.10%）and longevity（47.70 d,47.93 d and 46.65 d）between three treatments were also not significant.About offspring fitness of the double mated female,results showed that fecundity,hatchability and longevity between offspring of female that mated with the same male（OSM）and female with different males（ODM）.The average fecundity of OSM and ODM were 1404.28 and1547.71 respectively.4.Post-copulatory sexual selection of B.dorsalisIn this section,I fed newly emergence male adult using diet dipped with thiotepa water solution for three days to obtain sterile males.Test of 6 dose indicated that the dose of 1%were able to sterilize males and that 2%thiotepa water solution resulted death.Artificially interrupted mating pairs showed that no significant difference detected between mating duration and hatchability,with 11 periods separated in total.The hatchability was lowest of 56.72±9.31%when mating duration lasted one and a half hours,and highest of 72.48±12.63%when mating duration lasted 9 hours.This means that mating duration of 1 hour is able to transfer enough sperm for female fertilize eggs of the whole life.Sperm competition experiment of B.dorsalis indicated the last male precedence with P₂ value of 70.34%.