The relationship between dung quality and oocyte resorption in laboratory and field populations of Lucilia cuprina

Abstract

Oocyte resorption in Lucilia cuprina (Wiedemann) (Diptera: Calliphoridae) is indicative of protein shortages during ovarian development. It is commonplace in field populations and is thought to reflect the species’ dependence on sheep dung as its primary source of protein. To test this proposition, resorption was monitored in flies fed with sheep dung collected when pastures varied from lush to drought affected. Laboratory assays showed that the proportion of females that became gravid, their rate of ovarian development, and the size and number of oocytes matured all decreased significantly as the protein content of the food source decreased. Conversely, the number of oocytes resorbed increased as dung protein decreased. However, estimates of dung quality (DQ), as derived from a pasture growth–DQ model, were not informative in explaining the seasonal or regional prevalence of resorption in flies collected over several years in three widely disparate sheep‐grazing areas. Recalibration of the DQ model to provide daily estimates of dung protein, which were then used to predict the incidence of oocyte resorption at different times of the year, also failed to show any systematic effects. There was, however, a clear tendency for this model to underestimate the extent of resorption in field populations. Because wild flies would have ready access to a wide variety of food sources, many of which would have been more nutritious than sheep dung, this finding is contrary to expectation and hence the nutritional role of sheep dung merits further study.

Effects of Floral Scent, Color and Pollen on Foraging Decisions and Oocyte Development of Common Green Bottle Flies

“…Secondly, the physiological stage of flies alters their foraging response and preference [ 65 , 66 ]. Recently eclosed flies need protein and carbohydrates to mature their oocytes [ 16 , 67 ] and respond well to a bi-modal cue complex of floral color (e.g., yellow) and floral odor (e.g., daisy odor) that is indicative of pollen protein and nectar (this study). Gravid flies, in turn, that seek oviposition sites respond better to a cue complex of carrion odor and dark color than to a complex of carrion odor and white or yellow color [ 30 ].…”

“…Although of high quality, carrion protein is ephemeral and thus less dependable as a nutritional resource [ 12 , 13 ]. In comparison, animal feces has a low protein content (0.5–7%) [ 10 , 11 , 14 – 16 ] and, as such, represents a poor diet for the rapid maturation of fly oocytes prior to oviposition. Flower pollen, in contrast, has a protein content of 7% to 80% and contains low-molecular-weight proteins [ 17 ], which are essential for oocyte development [ 18 , 19 ].…”

“…Frequent protein meals are crucial for gravid blow fly females to develop and maintain their reproductively mature oocytes, which they otherwise resorb [ 16 , 20 ]. When protein-deprived females of the flesh fly Sarcophaga bullata Parker (Diptera: Sarcophagidae) are given a food choice between an amino acid-sugar mix and sugar, they feed on the former suggesting that these females detect the amino acids and exhibit a nutrition-based feeding preference [ 21 , 22 ].…”

Pollinator nutrition and its role in merging the dual objectives of pollinator health and optimal crop production

“…Evidence suggests that the nutritional value of these resources can vary, and this may impact the health of non-bee pollinators. For example, in Diptera that visit manure for adult protein needs, dung protein content which is influenced by livestock forage quality, can impact egg maturation [ 66 , 67 ]. Veterinary medicines used for livestock management may also contaminate manure, with off-target impacts on beneficial coprohilic insects including Diptera [ 68 ].…”