Chrysomya megacephala (Fab. 1794) (Diptera: Calliphoridae) is a very important species for forensic entomology, mainly contributing estimations of the postmortem interval (PMI) in judicial investigations. There are some doubts about the nocturnal oviposition of these flies, which could lead to errors in the PMI calculation. This study aimed to monitor the nocturnal oviposition behavior of this species through four experimental conditions carried out in laboratory. Ten cages, each containing five males and females (n = 100), were kept in a fume hood and subjected to total darkness or to artificial light for 11 consecutive hours. Two verifications were performed to determine whether the females deposited eggs on the substrate of ~20 g of chicken gizzards per cage. The first verification occurred at 9:00 pm in nocturnal experiments and at 09:00 am in diurnal experiments. The second verification occurred at 05:00 am in nocturnal experiments and at 05:00 pm in diurnal experiments. Each experiment lasted 5 d. Chrysomya megacephala deposited eggs at night under artificial light and in total darkness, but the amount of eggs was significantly lower when compared with the daytime experiments in dark conditions and under natural light. Oviposition occurred when the average temperature was around 25°C (± 2°C) and relative humidity around 73% (± 6%). Night oviposition is a possibility which should not be ruled out. Thus, future experiments are recommended.
Terapia Larval é uma bioterapia que utiliza larvas de moscas necrobiontófogas previamente esterilizadas para desbridar feridas necrosadas. Há um gradual aumento de aceitabilidade desta terapia, principalmente nos casos de feridas crônicas, como pé diabético, que cursa com o risco de amputação. O objetivo do estudo foi avaliar o peso médio de trinta larvas de segundo ínstar (L2) de Chrysomya megacephala, após esterilização pelo Glutaraldeído. As etapas de esterilização dos ovos ocorreram a partir da obtenção de duas massas de ovos de 0,15 g imersas em solução salina estéril (5 mL) e dissociadas com pincel No. 0. Foram submetidas ao processo de esterilização por 15 minutos em Glutaraldeído (Glutacin 28®), ativada com Solução de Bicarbonato de Sódio a 12 %, atingindo pH 8,3-8,5. Após filtração, o material foi rinsado com 30 mL de Caldo Soja Tripticaseína (TSB), em Cabine de Segurança Biológica Classe I. As massas de ovos foram postas em placas de Ágar Sangue e após 72 horas, já em L2, transferidas para um bécher e lavadas com água destilada. Trinta larvas L2 foram transferidas individualmente para uma Coluna Spin (750 µL) com Tubo de Coleta (2 mL) para extração/purificação de DNA (Norgen®), contendo água destilada. Com o auxílio de uma microcentrífuga, o excesso de água destilada foi removido da coluna para avaliação do peso das larvas, realizada em balança analítica em dez repetições. A temperatura média registrada durante os três dias de experimento foi de 27 ºC (dia) e 20 ºC (noite). A média do peso para 30 L2 de C. megacephala foi de 0,129 g, com peso mínimo de 0,09 g e o peso máximo de 0,18 g. Para o biodesbridamento do tecido necrosado, é necessária a aplicação de cinco a dez larvas por cm² da ferida. Desta forma, ao conhecer o peso médio referente a 30 L2, é possível calcular a quantidade de larvas a serem usadas em qualquer ferida necrótica.
Forensic Entomology uses arthropods to aid in legal investigations. This study checked the biological response of Chrysomya putoria pupae to submersion in fresh water for up to 6 d, evaluating the critical submersion time, survival rate, and development time of the flies. Adults were collected using fish baits in two typical traps. Seven hundred and twenty fourth-generation pupae with 2 d of development were used and separated into submergence intervals: 24, 48, 72, 96, 120, and 144 h. An additional 120 pupae were used as a control. Each treatment was done in triplicate, consisting of 40 pupae distributed in four tulle-sealed test tubes containing 10 pupae each. All tubes of each treatment were co-adhered in test tube racks and were submerged in mineral water in a container with constant oxygenation, except those of the control group, which were not submerged. The tubes were removed from the water according to their respective submersion interval, until 144 h was completed. The control group had a survival rate of 90%, while the 24-h treatment had 85% and the 48-h treatment had 35.8%. The critical submersion time for pupae was 72 h, with 100% mortality by 144 h. The average development time for the control group was 3.2 d, while the 24- and 48-h treatments developed in 4.3 and 6.3 d, respectively. The longer the individuals were submerged, the lower the survival rate was, while the development time increased. The data obtained in this study have potential in applications to estimate the interval of submersion of a cadaver.
This is the first study in Brazil that monitored the nocturnal oviposition behavior of Chrysomya putoria, a species of forensic importance, in order to verify if individuals of this species oviposit at night. Groups of 10 flies (5 male and 5 female) distributed in ten cages were kept in a fume hood and submitted to total darkness or exposed to artificial light for eleven consecutive hours through four experimental conditions in the laboratory. Two verifications were made to see if the females oviposited in the offered substrate of about 20 g of chicken gizzard per cage. Verification 1 occurred at 09:00 pm in the evening experiments and at 09:00 am in the daytime experiments. Verification 2 occurred at 05:00 am in the night experiments and at 05:00 pm in the daytime experiments. Each experiment lasted 5 d. C. putoria laid eggs at night (with or without light) and the quantity of eggs was significantly similar to those produced during the day under natural light or in total darkness. Only the amount of eggs produced during the day in the absence of light was considerably greater than in the typical daytime period. The females oviposited in greater quantity in the nights when the average temperature was between 23 and 24.8°C and relative humidity above 81%. Ovipositions only occurred at temperatures above 21°C and humidity above 56% during the day. Finally, it is necessary that more evaluations on the effect of variables on blowfly behavior are performed to better understand nocturnal oviposition.
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