Influences of temperature, fly size and protein‐feeding regime on ovarian development rates in the Australian bush fly, Musca vetustissima

Abstract

A reproductive age‐grading system is presented for female Musca vetustissima based on length and yolk content of developing follicles. Ovarian development rate models are also presented for estimating reproductive and chronological ages of females under laboratory and field conditions. Maturation rates are determined primarily by temperature, but are also influenced by protein‐availability and fly size (adult headwidth). Females of average size (2 mm headwidth) require 70 and 38 day degrees above 8 °C respectively to mature their first and subsequent egg complements. Under suboptimal protein‐feeding regimes in the laboratory, females experienced variable periods of arrested development prior to vitellogenesis. These females also resorbed part of their egg complements, but their ovarian development rates were unaffected by oocyte resorption. Under field conditions, females develop their ovaries at near expected rates, requiring only 5 and 2 day degrees more than expected, respectively, to complete their first and each subsequent ovarian cycle. Résumé Influences de la température, de la taille de l'adulte et de l'alimentation en protéines sur les taux de développement ovarien de Musca vetustissima Une échelle de classement est élaborée d'après l'âge des femelles de Musca vetustissima, en se basant sur la longueur et la teneur en vitellus des follicules en croissance. Des modèles de développement ovarien sont proposés pour évaluer les âges chronologique et reproductif, dans les conditions de laboratoire et de la nature. La vitesse de maturation est déterminée avant tout par la température, mais elle est aussi influencée par la disponibilité en protéines et la taille de l'adulte (largeur de la tête). Des femelles de taille moyenne (2 mm de largeur de tête) ont besoin de 70 et 38 degrés/jours au‐dessus de 8°C pour conduire successivement à maturité leur premier et leur second lots d'oeufs. Au laboratoire, avec une alimentation protéique inférieure à l'optimum, le développement des femelles est interrompu pendant des durées variables avant le début de la vitellogenèse. Ces femelles résorbent aussi une fraction de leur lot d'oeufs, mais les vitesses de développement ovarien n'ont pas été modifiées par cette résorption. Dans la nature, le développement ovarien s'effectue à peu près à la vitesse prévue, demandant seulement 5 jours de plus que les prévisions pour accomplir leur premier cycle ovarien, et ensuite 2 jours de plus que prévu pour accomplir chaque cycle supplémentaire.

Potential and realised fecundity in the bush fly, Musca vetustissima under favourable and unfavourable protein‐feeding regimes

“…Under field conditions, females of field origin consistently matured 87~ or more of their egg complements (Table 3). The latter confirms the conclusion of Vogt & Walker (1987) that female M. vetustissima cannot be primarily dependent on cattle dung for ovarian development (Table 4). In keeping with their pestiferous habits, they probably derive most of their dietary protein from animal discharges and secretions.…”

“…Following oviposition, females were provided with water, dry sucrose and liver exudate until gravid for the second time and the procedure repeated. At oviposition, females usually ingest dung, which is a low quality protein source for ovarian development (Vogt & Walker, 1987). To ensure a maximal protein intake, females were therefore forced to ingest high-quality protein shortly before oviposition by depriving them of water and sucrose for 16 h and then offering the protein in combination with sucrose.…”

“…Two additional sibling cohorts were given limited (24 h) access to diluted liver exudate 1.5 days after emergence. These females were given whole liver exudate 1 and 2 days later, when examination of their yolk and follicle lengths indicated that they were in respective early and middle stages of vitellogenesis (Vogt & Walker, 1987). Water was again removed (24 h) to enhance protein ingestion.…”

“…Follicles had developed beyond the resting stage 24 h later and had attained a mean length of 0.5 mm. Females of equivalent size require 45.3 day degrees above 8 ~ to reach this stage of ovarian development in the absence of arrested development (Vogt & Walker, 1987). These females had ac-121 cumulated 47.5 day degrees at the time of dissection, indicating that their development was not arrested during the resting stage.…”

Laboratory environment effects on the reproduction and mortality of adult screwworm (Diptera: Calliphoridae)

“…Oogenesis and survival are affected by temperature (Vogt & Walker 1987), and photoperiod (Cunha-e-Silva et al 1992). The percentage of total time (hours to complete the 1 st cycle of oogenesis) for each stage of egg development was not affected signifi cantly when screwworm females were held at 24°C and 30°C (Adams & Reinecke 1979).…”