Corresponding author: Luc Bourguignon (
Academic editor: Daniel Whitmore
The calliphorid
We provide here the first data regarding pupal weight evolution during the pupal stage, female fertility and life expectancy of the species. At 22°C under a variable regime of temperatures, the egg-to-adult development time was an average of 18.05 ± 0.72 and 18.47 ± 0.67 days for females and males, respectively, in the control group. The pupal stage represented 56.7% of the total development. The development time from egg to adult and the duration of the pupal stage were significantly longer for males than for females. The measurement of pupal weight at the start of the pupal period revealed that female pupae were significantly lighter than male pupae by nearly 20%. This difference between the sexes was also observed for the dry weight of adults. An average decrease of 8.75% was observed throughout the first 8 days of the pupal stage, after which most adults started to emerge. The tested females produced an average of 176.13 ± 66.62 eggs throughout the egg-laying period. The average lifespan after emergence was 12.10 ± 4.09 days for females and 12.60 ± 2.95 days for males, with a median of 12.50 days for both sexes.
Blow flies (
Specimens for the laboratory colonies of
When eggs were required, a dish containing one piece of beef heart (around 10g) was placed into one or several mesh cages and removed 4 hours later. Each piece of meat with the newly laid eggs was transferred (for a maximum of 250–300 eggs) onto approximately 250g of fresh minced beef heart. Each portion of fresh minced beef heart was finally placed into home-made plastic rearing boxes (23cm x 17.5cm x 10cm). A 1cm thick layer of dry sand covered the bottom of the boxes to provide a pupation medium. The rearing boxes were then placed in an environmental chamber (SANYO Incubator MIR 553, Sanyo Electric Biomedical, Japan). To ensure a suitable relative humidity (> 85%), a container filled with water was also placed inside the environmental chamber.
The rearing treatments were maintained at a photoperiod of 16:8 (L:D; hours) and at a temperature gradually changing (over a 15 minute period) from 18°C to 24°C between the dark and light periods. This resulted in an average temperature of 22°C. A data logger (Testo 175-T1) was inserted into the incubator to monitor the temperature hourly.
From the eggs and larvae reared in the conditions described above, all the pupae were sampled for our analyses. The one-day old pupae (light brown in colour) were placed in 24-well plates (one pupa in each well), which were then placed back in the environmental chamber. All plates were divided into two batches. Weighing of the pupae began the day after the sampling and was undertaken on a Mettler-Toledo AB104-S balance (± 0.1 mg). The pupae of the first batch (Control group) were weighed only once and then replaced and left undisturbed in the incubator until the emergence of the adults. The pupae of the second batch (Test group) were weighed each day until the emergence of the adults, and immediately placed back in their individual well and in the incubator between two measurements. Successfully emerging adults were stunned with a small amount of CO2 before being removed from the rearing box. To avoid temperature bias, the rearing boxes were randomly replaced inside the incubator.
At emergence, the developmental time was recorded. The adults were sexed and dried for 15 days (at 40°C, RH: 0%) and then weighed. The change in pupal weight was recorded only during the first 8 days of the pupal stage. The last two days were not taken into account as the remnant number of pupae to emerge was very low.
Ten newly emerged couples were isolated in small plastic rearing boxes (12cm x 9cm x 5cm) and provided
Statistical analysis was performed using Microsoft® Excel 2010/XLSTAT©-Pro (Version 2013.5.08, Addinsoft, Inc., Brooklyn, NY, USA), the significance level was set at
The total number of pupae collected was 381 (Control: 189; Test: 192). The overall percentage of emergence was 81.89% (Control: 86.24%; Test: 77.60%). After elimination of the non-emerged pupae, as well as dead pupae or pupae presenting deformities, a total number of 309 pupae were studied and tested (Control: 161; Test: 148).
Among the retained pupae, the observed sex ratio was 1.70 males per female in the Control group and 1.59 males per female in the Test group. Maximum egg-to-adult development time was 20 days for the Control group with an average of 18.21 ± 0.73 days (18.05 ± 0.72 and 18.47 ± 0.67 days for females and males, respectively). For the Test group, the maximum egg-to-adult development time was 21 days with an average of 18.39 ± 0.91 days (18.23 ± 0.90 and 18.65 ± 0.89 days for females and males, respectively) (Table
Within each batch, the development time from egg to adult was significantly longer for males than for females (Table
The average pupal weight measured one day after sampling was 103.87 ± 14.66mg (95.2 ± 9.49mg for females, 117.72 ± 10.08mg for males) in the Control group and 101.51 ± 15.16mg (93.4 ± 9.29mg for females, 115.62 ± 12.9mg for males) for the Test group. The observed differences were not significant. In both groups, the female pupae were significantly lighter (80.87% of the weight of male pupae in the Control group, 80.78% in the Test group) (t test, <0.0001). This was also observed for the dry weight of adults, on average equal to 17.33mg for the Control group and 22.79mg for the Test group. In both batches, adult female flies presented a significantly lower dry weight than males (77.18% of the weight of adult males in the control group, 81.55% in the test group) (t test, <0.0001) (Table
Between the first day and the eighth day of weighing, an average decrease of 8.75% was observed in the Test group (8.40% for female pupae; 9.26% for male pupae) (Fig.
Ten pairs of
The average lifespan after emergence was 12.10 ± 4.09 days for females and 12.60 ± 2.95 days for males (Table
The lack of a significant difference between the Control group and the Test group indicates that the daily weighing of pupae in the test batch did not affect pupal development.
The observed sex ratio was an average of 1.65 males for every female. There were no significant differences between the Control group and the Test group regarding development time (egg-to-adult or pupa-to-adult). At 22°C, the pupal stage represented just over half of the total immature development period. The observed duration of the pupal stage of
During our tests, it appears that males of
The significant difference in mass between male and female
Despite the greater mass of the males, their longevity was barely higher than that of females (12.6 days vs. 12.1 days, respectively). This is contrary to what is observed in some other fly species (
These new data, while preliminary, bring some information on the development of
We wish to thank Michael Sharkey and Megan Critser for the correction of English and their suggestions. We also warmly thank the anonymous reviewers for their improvements and reviews.
YB, FH and LB designed and performed the experiments, and interpreted the results. YB wrote the manuscript and performed all statistical analyses. SV and VD reviewed the manuscript.
Change in pupal weight (mg) for males and females during the 8 days after sampling in the Test group experiment. The initial value of the pupal weight in the undisturbed group (Control group) is also shown for comparison with the initial value in the test group. The red cross represents the median. (Suppl. material
Number of oviposition events and of eggs laid after hatching of pupae. The red cross represents the median. (Suppl. material
Mass, developmental time (in days) and accumulated degree days (ADD) between the Control and the Test (daily weighing) for the retained pupae. (SD) = Standard deviation in brackets for each value. *: measure of the pupa was done one day after sampling. $: ADD was calculated for the egg–adult development time at 22°C using the lower threshold given by
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103.87 (14.66) | 17.33 (3.26) | 18.21 (0.73) | 10.32 (0.53) | 292.18 (12.68) |
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95.20 (9.49) | 15.56 (2.12) | 18.05 (0.72) | 10.22 (0.53) | 289.39 (12.53) | |
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117.72 (10.08) | 20.16 (2.73) | 18.47 (0.67) | 10.47 (0.50) | 296.65 (11.68) | |
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101.51 (15.16) | 22.79 (3.31) | 18.39 (0.91) | 10.41 (0.60) | 295.21 (15.93) |
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93.40 (9.29) | 21.05 (2.07) | 18.23 (0.90) | 10.35 (0.56) | 292.58 (15.62) | |
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115.62 (12.90) | 25.81 (2.88) | 18.65 (0.89) | 10.50 (0.67) | 299.79 (15.55) |
Lifespan (in days) of males and females for each rearing box with the corresponding amount of eggs laid by the female during its life. *: zero scores were not used in calculating the average, SD and median.
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17 | 14 | 139 |
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18 | 18 | 263 |
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13 | 13 | 196 |
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10 | 10 | 187 |
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7 | 9 | 121 |
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12 | 15 | 62 |
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15 | 15 | 192 |
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13 | 12 | 0* |
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11 | 11 | 249 |
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5 | 9 | 0* |
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12.10 (4.09) | 12.60 (2.95) | 176.13 (66.62) |
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12.50 | 12.50 | 189.50 |
Raw Data for Fig.1a & 1b
Datasheet
This file contains the values of the evolution of pupal weight (mg) for males and females during the 8 days after sampling in the Test group experiment. The initial value of the pupal weight in the Control group is also shown for comparison with the initial value of the pupal weight in the Test group.
File: oo_44311.xls
Raw Data for Fig 2
Datasheet
Number of oviposition events and of eggs laid after hatching of the pupae. The red cross represents the median.
File: oo_47177.xls