Temperature requirements for the growth of immature stages of blowflies species, Chrysomya albiceps and Calliphora vicina, (Diptera:Calliphoridae) under laboratory conditions

Effects of ivermectin on development of Calliphora vicina, Robineau-Desvoidy 1830 (Diptera, Calliphoridae)

Ivermectin is one of the most widely used drugs for parasite control. Previous studies have shown a reduction in the abundance and diversity of "non-target" coprophilous organisms due to the presence of ivermectin (IVM) in bovine faecal matter (FM). Due to its breadth of behavioural habits, Calliphora vicina is a suitable dipteran species to evaluate the effects of IVM in FM. The aim of this work was to evaluate the effect of five concentrations of IVM in FM (3000, 300, 100, 30, and 3 ng/g) on the development of C. vicina. The following endpoints were evaluated: survival (between the first larval stage and emergence of new adults), larval development times to pupation and pupation times to adult, and adult emergence (% sex) and LC50. Sampling was performed from larval hatching at 60 and 120 min and at 3, 4, 5, and 12 h, and every 24 h specimens were weighed until pupae were observed. Data were analysed by ANOVA using a non-parametric Kruskal-Wallis test and as a function of elapsed development time and accumulated degree hours (ADH). Mortality at 3000 and 300 ng/g was 100% and 97%, respectively. There were statistically significant delays in adult emergence time (p = 0.0216) and in the ADH (p = 0.0431) between the control group (C) and 100 ng/g. The LC50 was determined at 5.6 ng/g. These results demonstrate the lethal and sub-lethal effects of IVM on C. vicina, while highlighting the usefulness of this species as a bioindicator for ecotoxicological studies.

A preliminary study of carrion insects in Greece and their attraction to three animal baits: a forensic entomology perspective

The current study provides data on the composition of the dipteran and coleopteran fauna attracted to three different animal baits (chicken stomach, beef liver, fish) in the urban ecosystem of Athens, Greece. An additional objective was to examine the effect of bait choice by the collected taxa. Three trap locations were established within the Agricultural University of Athens. At each location two different types of baited traps were used to capture and record the local dipteran and coleopteran biodiversity. During the sampling period, a total of 2416 dipteran and coleopteran specimens representing 43 species were collected and identified. The three most abundant dipteran taxa were Sarcophaga sp. (Diptera: Sarcophagidae), Calliphora vicina Robineau-Desvoidy, Lucilia sericata (Meigen) (Diptera: Calliphoridae). The results showed that the structure of the local insect community associated with the decomposition of animal baits depends on the bait used for sampling. This study reinforced the feasibility of using animal tissues as attractants to a wide diversity of medical, parasitological and forensically important taxa. Overall, beef liver attracted the most insects with Diptera preferring beef liver and Coleoptera preferring chicken stomach. Furthermore, this study revealed that baits of one animal tissue did not attract all species but in combination a much better understanding of this biodiversity was achieved. Finally, from a forensic entomology perspective this study highlights the lack of understanding of the value of entomological data related to case work in Greece.

Climate Change Helps Polar Invasives Establish and Flourish: Evidence from Long-Term Monitoring of the Blowfly Calliphora vicina

The isolated sub-Antarctic islands are of major ecological interest because of their unique species diversity and long history of limited human disturbance. However, since the presence of Europeans, these islands and their sensitive biota have been under increasing pressure due to human activity and associated biological invasions. In such delicate ecosystems, biological invasions are an exceptional threat that may be further amplified by climate change. We examined the invasion trajectory of the blowfly Calliphora vicina (Robineau-Desvoidy 1830). First introduced in the sub-Antarctic Kerguelen Islands in the 1970s, it is thought to have persisted only in sheltered microclimates for several decades. Here, we show that, in recent decades, C. vicina has been able to establish itself more widely. We combine experimental thermal developmental data with long-term ecological and meteorological monitoring to address whether warming conditions help explain its current success and dynamics in the eastern Kerguelen Islands. We found that warming temperatures and accumulated degree days could explain the species' phenological and long-term invasion dynamics, indicating that climate change has likely assisted its establishment. This study represents a unique long-term view of a polar invader and stresses the rapidly increasing susceptibility of cold regions to invasion under climate change.

Development of Chrysomya albiceps (Wiedemann, 1819) (Diptera: Calliphoridae) from the Jazan region of Southwest Saudi Arabia under different laboratory temperatures: applications in forensic entomology

Background

Chrysomya albiceps (Wiedemann, 1819) (blowflies), family Calliphoridae, is important in forensic entomology, where the minimum and maximum postmortem intervals (PMI) are estimated on the basis of the developmental stages of Diptera larvae that consume dead tissue. The present study was designed to estimate the effects of different ambient temperatures (20, 25, and 30 °C) under controlled laboratory conditions on the developmental stages of C. albiceps from the Jazan region, Saudi Arabia.

Results

The present study showed that the larval body weight and length were significantly increased when larvae were reared at 30 °C compared with corresponding values at 24 h, 48 h, and 72 h at rearing temperatures of 20 °C and 25 °C; however, the weight and length were significantly decreased compared with corresponding values at 96 h at 20 °C and 25 °C. The pupation time was inversely related to the rearing temperature, occurring at 144, 124, and 120 h at rearing temperatures of 20 °C, 25 °C, and 30 °C, respectively. The pupal weight and length were significantly increased in larvae reared at 30 °C compared with those reared at 20 °C and 25 °C. At 20 °C, 25 °C, and 30 °C, larval durations of 5.00, 5.00, and 4.00 days were recorded, respectively. Pupae and adults showed gradual decreases in life stage durations, at 6.00, 5.30, and 4.80 days in pupae and 20.00, 18.70, and 16.90 days in adults, with increasing rearing temperatures. Average adult longevity at 30 °C (194.40 h) was significantly less than adult longevity at 20 °C (216.00 h) and 25 °C (204.60 h). The results showed an inverse relation between durations of developmental stages and rearing temperatures.

Conclusions

Insect laboratory colonization for the determination of biological characteristics of insects is economically viable for forensic entomology and as a technique for evaluating insect evidence.

Body Size and Cuticular Hydrocarbons as Larval Age Indicators in the Forensic Blow Fly, Chrysomya albiceps (Diptera: Calliphoridae)

Chrysomya albiceps (Wiedemann 1819) is one of the most important insects in forensic entomology. Its larval developmental and survival rates are influenced by nutritional resources, temperature, humidity, and geographical regions. The present study investigated the possibility of relying on body size and cuticular hydrocarbon composition as indicators for age estimation of the different larval instars of C. albiceps. Larvae were maintained in standardized laboratory conditions at different experimental temperatures. All larval instars (first, second, and third) were randomly collected for measuring their body sizes and for estimating their cuticular hydrocarbons at different rearing temperatures (30, 35, 40, and 45°C) using gas chromatography-mass spectrometry (GC-MS). Results indicated that the duration of larval stage was temperature dependent as it gradually decreased on increasing the rearing temperature (30, 35, and 40°C) except 45°C at which larval development was ceased. In contrary, larval body size, in terms of length, width, and weight, was temperature dependent as it gradually increased with larval development on increasing rearing temperature except at 45°C at which larval development was ceased. The GC-MS showed a significant difference in the extracted components of cuticular hydrocarbons between different larval instars reared in the same temperature and between the same larval instar that reared at different temperatures. Furthermore, the highest and lowest amounts of cuticular hydrocarbons were detected at 35 and 40°C, respectively. Overall, larval body size and cuticular hydrocarbon components were temperature dependent within the range 30-40°C, which may suggest them as possible reliable age indicators for estimating the postmortem interval in the field of medicolegal entomology.

Post-Mortem Interval Estimation Based on Insect Evidence: Current Challenges

During death investigations insects are used mostly to estimate the post-mortem interval (PMI). These estimates are only as good as they are close to the true PMI. Therefore, the major challenge for forensic entomology is to reduce the estimation inaccuracy. Here, I review literature in this field to identify research areas that may contribute to the increase in the accuracy of PMI estimation. I conclude that research on the development and succession of carrion insects, thermogenesis in aggregations of their larvae and error rates of the PMI estimation protocols should be prioritized. Challenges of educational and promotional nature are discussed as well, particularly in relation to the collection of insect evidence.

Gene expression as age estimation marker in the larval stages of the forensic blowfly, Chrysomya albiceps, at different temperatures

The blowfly Chrysomya albiceps (Diptera: Calliphoridae) has been known to breed in both animal and human carcasses in different geographical regions and is considered an important post-mortem indicator in forensic entomology. Determining the age of its larvae is an essential tool for the accurate determination of post-mortem intervals (PMI). This study adopted a molecular-based approach for age determination of the immature stages of the blowfly, C. albiceps, by evaluating the genes 15_2, 2014192, EcdR, AR, hsp90, and Actin, during larval development at different temperatures. Targeted genes were amplified by real-time PCR (RT-PCR), and the resulting amplicons were normalized against the two housekeeping genes, rp49 and 19_2. Data showed that the expression profile of AR was constant throughout all larval developmental stages at all tested temperatures. 2014192 showed low expression levels throughout the 1st, 2nd, and 3rd larval stages. Hsp90 and EcdR showed different expression profiles. The expression of 15_2 was low at the tested temperatures and was undetectable on most days. Collectively, the results of this study indicate that larvae exhibit temperature-dependent and age-specific up- and down-regulation in the expression profile of the targeted genes. This may indicate a possibility to be utilized as age estimation markers for C. albiceps.

Modeling Temperature Variations Using Monte Carlo Simulation: Implications for Estimation of the Postmortem Interval Based on Insect Development Times*, †

The association between insect development and temperature is well established. Thermal summation using accumulated degree-day measures is commonly used. However, the time at which evidence is collected is important in these estimates. The aim of this study was to provide a simulated model of the effect of temperatures on six dipteran species commonly associated with cadavers, from the death scene to the refrigerator, and finally at the time of autopsy. Temperatures measurements were sampled over a 16-month period from the external environment (external to the mortuary), within the mortuary refrigerator, and within the mortuary autopsy suite. Monte Carlo simulation using accumulated degree-days (ADD) was used to estimate the variations based on the mean and standard deviation of the temperature measurements. It was found that there was a negative correlation between the base temperature of the fly species (lowest temperature at which the flies will survive) and developmental likelihood. Species with high base temperatures (Chrysomya albiceps, Chrysomya chloropyga, and Musca domestica) were less likely to continue development in refrigerators than species with lower base temperatures (Lucilia sericata and Piophila casei). The findings of this study highlight the importance of recording temperature measurements and the period of refrigeration on PMI estimation especially when continued development occurs in spite of a period of cooling of the insect evidence.