Genetic and molecular investigations on the endogenous mobile elements of non-drosophilid fruitflies

A syndrome of abnormal genetic effects, resembling Drosophila hybrid dysgenesis, occurs in Ceratitis capitata when strains of different origin are mated. The pattern of abnormal traits observed appears to be the phenotypic expression of a complex interacting dysgenic system of inducer and suppressor effects; probably more than one system is activated in the crosses. This suggests that different systems of mobile elements occur in different strains and populations of C. capitata. Using a PCR primer specific to the ITR sequence of a deleted element, full length mariner elements were isolated from C. capitata, Ceratitis rosa, and Trirhithrum coffeae. Very high similarities were found in inter- and intraspecific comparisons of the elements. The majority of these elements contained deletions and frame-shifts. However, one clone Ccmar1.18, from C. capitata, was found to possess an uninterrupted ORF coding for 338 amino acids with ∼60% similarity to the Mos1 element of Drosophila mauritiana. Database searches and phylogenetic analyses showed that the mariner elements isolated in the present study are representatives of Robertson's mellifera mariner subfamily. The copy numbers of the elements within each species are very different, ranging from about 10 in T. coffeae to 5000 in C. rosa. This revised version was published online in August 2006 with corrections to the Cover Date.     

Determination of host status of citrus fruits against the Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae)

Abstract  The Mediterranean fruit fly (Medfly), Ceratitis capitata (Wiedemann) is a pest of citrus in parts of Western Australia. Three citrus cultivars: Valencia oranges, Eureka lemons and Imperial mandarins, as well as non-citrus control fruits, were examined for attractiveness and suitability to Medfly in the field and in the laboratory using choice and no-choice experiments. Oranges were more susceptible to Medfly than mandarins and lemons. Punctures in the skin had a significant impact on the degree of infestation in both citrus and non-citrus control fruit. Artificial infestation and larval survivorship were used to investigate the suitability of each cultivar to Medfly under laboratory conditions. Oranges and mandarins were suitable for the development of Medfly, but lemons were a poor host. When each cultivar was in season, field cage trials demonstrated that infestation occurred in oranges and mandarins but not in lemons.     

Are citrus species favorable hosts for the Mediterranean fruit fly? A demographic perspective

We studied, under laboratory conditions, demographic parameters of adult Mediterranean fruit flies, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) (medfly), obtained from three sweet orange varieties, lemon, and bitter oranges. These data were combined with immature developmental rates and survival on the same hosts to estimate host‐specific population parameters. Pairs of newly emerged adults from each citrus variety were held individually in transparent plastic cages, and females were allowed to oviposit in either red domes (artificial, pre‐punctured plastic oviposition devices), or intact, whole citrus fruits. We found strong effects of larval host (citrus fruits) on adult longevity and fecundity. In all five citrus varieties, females did not manage to deposit eggs into fruit pulp. The proportion of eggs laid in either the flavedo or albedo area of the fruit peel differed depending on the citrus variety. In all cases except bitter oranges, females oviposited fewer eggs in citrus fruits than in the artificial oviposition substrates, suggesting that most citrus fruits cause a significant reduction in the reproductive potential of medflies. Negative correlations were found between fecundity and (a) the density of oil glands, and (b) the amount of essential oils in the flavedo area of citrus fruits. There was no correlation between fecundity and other fruit physical characteristics, such as resistance of fruit peel to pressure and thickness of the flavedo. Apparently, resistance of citrus fruits to medfly infestation is directly related to citrus essential oils. The intrinsic rate of increase (r) was higher in bitter oranges than in the three sweet orange varieties tested. A negative r was estimated for flies that developed and oviposited in lemons, indicating a tendency for population decrease in this host. The suitability of citrus fruits for medfly development and the practical implications of our findings for management of medflies in citrus orchards are discussed.     

Copula duration and sperm storage in Mediterranean fruit flies from a wild population

In the Mediterranean fruit fly (Ceratitis capitata Weidemann, ‘medfly’), a lekking tephritid, evidence from laboratory studies of flies from laboratory strains suggests that copulation is shorter, and sperm storage more abundant, if males are large or protein‐fed, and that copulation is longer when females are large. In addition, sperm tend to be stored asymmetrically between the female’s two spermathecae and this asymmetry declines with abundance of stored sperm. The primary objective of this study was to investigate whether these trends persist in other experimental contexts that bear closer resemblance to nature. Accordingly, we carried out experiments in a field‐cage using males derived as adults from a wild population and virgin females reared from naturally infested fruit. The results of this study were consistent with laboratory studies in that copula duration increased with female size, that sperm were stored asymmetrically between the females’ spermathecae, and that this asymmetry declined with number of sperm stored. However, we also found some previously unreported effects of female size; large females stored more sperm and stored sperm more asymmetrically between their two spermathecae than did small females. Unlike the laboratory studies, copula duration and sperm storage patterns were unaffected by male size and diet. This may be due to overwhelming variation from other sources in the wild‐collected males used, as well as environmental variability in the semi‐natural setting.     

Factors affecting behavioural responses to visual stimuli in the tomato fruit fly, Neoceratitis cyanescens

Responses of Neoceratitis cyanescens (Bezzi) (Diptera: Tephritidae) females to visual stimuli were studied in a laboratory flight chamber. A bright orange sphere was used to investigate the effects of age, mating status and time of day on their responses. In no-choice assays, four parameters were considered: mean time before leaving the release vial, percentage of flies that visited the sphere, mean number of flights and mean time before landing on the sphere. Naive mated females first became strongly responsive to the orange sphere 6 days post-adult emergence (> 40%). The percentage of females that visited the sphere increased significantly with egg load. There were no significant differences in behavioural responses between virgin and mated mature females. In a choice situation between a yellow and an orange sphere, starved females displayed a greater propensity than well-fed females to land on the yellow sphere. Mature females were more responsive to the orange sphere when tested in the afternoon than earlier in the day. In a no-choice situation, females visited the yellow sphere as often as the orange sphere. However, the mean delay before landing was significantly greater for the yellow sphere. The results emphasize the importance of physiological condition on responses of N. cyanescens females to host-simulating visual stimuli.     

Mediterranean Fruit Fly leks: factors affecting male location

1. The mating system of Mediterranean Fruit Flies ( Ceratitis capitata , Diptera: Tephritidae) is based on male leks which form within the canopies of certain trees. In this study the following hypotheses are tested: (a) fly location depends on microclimate and illumination and (b) larger and heavier males occupy preferred locations in leks. Accordingly, systematic quantitative observations of diel three-dimensional (3-D) locations of lekking C. capitata males were performed in field and field cage studies.
2. Fly locations were found to vary significantly during the activity hours.
3. Medflies were generally found calling from highest and most exterior locations during early morning and late afternoon hours. During the hottest hours (1200–1500) flies occupied lower locations within the tree canopy, and interior locations from 1000 to 1500.
4. Fly location (from 1000 to 1700) was correlated with the azimuth of the sun. However, the mean azimuth range of fly location was limited to 85° (59·45°–143·94°).
5. Both in the field and in the field cage the temperature, relative humidity and light intensity beneath the leaves on which the males perched were closer to the microclimate beneath fully shaded leaves than to microclimates beneath leaves exposed to direct sunlight.
6. It is concluded that male medflies occupy locations which confer suitable microclimates for calling and copulating, and suitable 3-D locations within the canopy which provide protection from predators, wind, direct sunlight and water loss.     

Performance and feeding behavior of Ceratitis capitata: comparison of a wild population and a laboratory population

Experiments were carried out to test the performance and some aspects of feeding behavior in two populations of Ceratitis capitata (a population reared in the laboratory for 16 years, i.e., approximately 160 generations, and a wild one obtained from infested coffee, Coffea arabica grains). Two types of food were used in the experiment: an artificial yeast diet used for laboratory rearing and papaya (Carica papaya), a natural host of the fly. The performance parameters tested were percent emergence, time to emergence, adult female size, and egg production during the pre-oviposition phase (first five days of adult life). The behavioral aspects tested were food preference by newly hatched larvae, induction, estimated ingestion of the two diets, whether the larvae placed on one diet stayed there or moved to the other diet, and acceptance of food for oviposition. The results indicated that the performance of the wild population was superior when the flies fed on papaya, whereas the performance of the laboratory population was similar with the two diets; the wild population showed a strong preference for papaya in all choice experiments, whereas the laboratory population showed no diet preference; the females of the wild population only oviposited on pieces of papaya that had not been peeled, and did not oviposit in the artificial diet; the females of the laboratory population oviposited indiscriminately on unpeeled and peeled papaya and on the artificial diet.     

Host-specific demographic studies of the Mediterranean fruit fly Ceratitis capitata

Abstract. 1. This study was conducted in Greece using a wild strain of medflies ( Ceratitis capitata [Weidemann]) to assess age-specific vital rates in adults, and development and survival in pre-adults when reared on different host fruit. The results were used to construct life tables.
2. The demographic analyses suggested that there are basically four aspects of the medfly's life history which are of major importance: (i) multiple, highlyoverlapping generations; (ii) high net reproduction while young; (iii) high larval fitness in certain hosts; (iv) lack of diapause.
3. Reasons why these characteristics are felt to be important are briefly discussed.     

地中海实蝇及其近缘种基因芯片检测研究

本研究选择线粒体DNA (mtDNA) 细胞色素氧化酶Ⅰ基因（COⅠ）为分子标记基因,以双翅目实蝇科昆虫DNA序列为目标,建立了我国进境植物检疫害虫地中海实蝇Ceratitis capitata、芒果小条实蝇C. cosyra和纳塔尔小条实蝇C. rosa等生物芯片检测方法。地中海实蝇及其近缘种检测芯片由检测探针（实蝇科通用探针1条,小条实蝇属通用探针1条,地中海实蝇、芒果小条实蝇和纳塔尔小条实蝇近缘种探针2条和种特异探针4条）、质控探针（定位点探针、阳性质控、阴性质控和空白对照探针各1条）组成。芯片检测结果表明,检测探针特异性强,能实现上述3种实蝇的种类快速区分和准确鉴定; 检测方法稳定性好,地中海实蝇不同虫态（卵、幼虫、蛹和成虫）和不同地理种群检测结果完全一致。地中海实蝇生物芯片检测技术将为我国进口果蔬中检疫性实蝇快速筛查和种类鉴定提供检测方法,同时,还可应用到其他属的实蝇以及相关害虫的检疫中,为有害生物的快速鉴定提供了新方法。