Forensically Important Flies Associated with Decomposing Rabbit Carcasses in Mangrove Forests in Kuching, Sarawak, Malaysia Robin Maramat a, Nor Aliza Abdul Rahim b a Department of Forensic Medicine, Sarawak General Hospital, Kuching, Sarawak b Department of Paraclinical Sciences, Faculty of Medicine and Health Sciences, Universiti Malaysia Sarawak, 94300 Kota Samarahan, Sarawak. ABSTRACT: In Malaysia, researches on insect fauna associated with decomposition of carcass at different geographical locations have been conducted in several areas in peninsular Malaysia. However such data from East Malaysia; Sarawak and Sabah are currently lacking. This study aims to provide the first checklist of forensically important insect fauna species found in mangrove forest in Kuching, Sarawak. Two decomposing rabbits, (Oryctolagus cuniculus) carcasses were used as animal model and they were placed at two mangrove forest sites at Sungai Loba Kora, Jalan Sultan Tengah, Petra Jaya and Sungai Stutong, Stutong, Kuching. A total of 236 and 218 individual insects were collected from rabbit carcasses throughout the decomposition processes at Sungai Loba Kora and Sungai Stutong mangrove forests, respectively. The adults and immature insects identified were mostly blowflies from the genus Chrysomya including Chrysomya megacephala, Chrysomya rufifacies, Chrysomya nigripes and Chrysomya villeneuvi. Chrysomya megacephala and Chrysomya rufifacies were found to be dominant species on the decomposing rabbit carcasses at both locations. Adults of other dipterans from the genus Muscidae, Sarcophagidae and Tachinidae, and several species of hymenopteran were also found visiting the carcasses. There were five decomposition stages of rabbit carcasses observed which include fresh, bloated, active decomposition, advanced decay and dry remains. The decomposition process of both carcasses at both mangrove forest took nine days to complete. From this study we concluded that Chrysomya megacephala and Chrysomya ruffifacies may serve as forensically important flies at mangrove forest in Kuching, Sarawak because both species were dominant and active carcass decomposers. Keywords: Chrysomya sp., mangrove forest, forensic entomology, decomposition process Introduction The challenge to apply forensic entomology is increased because of the fact that the pronounced geographic variability of the carrion insect community does not allow the use of the available data from one biogeographic area to another [1]. Taxa can vary greatly at different locality, thus it is important to identify the forensically important insects that are specific to an area for estimation of postmortem interval (PMI) [2]. Study on forensically important insect in Sarawak, Malaysia is still very scarce and most study has done in Peninsular Malaysia. Due to the importance of geo-location and diversity of insects, more studies on forensic entomology in Sarawak are needed for references in cases involving decomposition of bodies. According to Mahat and Jayaprakash [3], in Malaysia, researches on species compositions and development of necrophagous insects recovered from dead bodies as well as infesting animal models 79 decomposing in various conditions have been conducted in several states as Selangor, Kuala Lumpur, Penang, Kedah and Kelantan. However such data from the other states within peninsular Malaysia as well as from East Malaysia which is Sarawak and Sabah are currently lacking. We hypothesize that the insects collected during the rabbit carcasses decomposition may be of different species from other sites in Malaysia due to difference in geographic location. Materials and methods This study was conducted at two sites of mangrove forest in Kuching, Sarawak. First site field work was carried out at mangrove forest along Sungai Loba Kora, Jalan Sultan Tengah, Kuching (1⁰37.909 N 110⁰20.691 E), from 8 th to 16 th of February 2012. The second field site of mangrove forest was along Sungai Stutong, Jalan Stutong (1⁰30. 258 N 110⁰ 22.912 E), from 2 nd to 10 th of March 2012. Rabbits (Oryctolagous cuniculus) weighing
from 1.5 to 1.6 kg were used as experimental animals. Freshly killed rabbits were used as they are an internationally accepted substitute for human bodies. The rabbits were different colors but comparable in size. At the study site a rabbit placed inside a metal cage size (60 cm x 40 cm x 42 cm) to prevent the carcasses from being disturbed by scavengers during the experiment. The cage with the rabbit carcass was be placed on top of the grass in the two different site of mangrove forest, thus the carcass were exposed to the surrounding environment. Immediate after placement rabbit carcass temperature reading were taken twice per day, first visit are in the morning around 8.00 am and second visit are in the afternoon 5.00pm, until the rabbit carcass are completely decomposed and dried. Daily visual observation and written brief notations of the habitat of the surrounding site are also taken. All collected larvae (immature) and adult flies bring into laboratory for identification process. Results and discussion There were two orders; Diptera and Hymenoptera recorded from both study sites (Table 1). Among the Diptera are Family Calliphoridae, Muscidae, Sarcophagidae and Tachinidae which includes 11 species. The Humenopteran recorded were Formicidae and Apidae. Two major important forensic flies found at both mangroves sites were C. megacephala and C. rufifacies which is similar to finding of other studies conducted in the Peninsular Malaysia [4, 5, 6]. In fact these two species have always been strongly associated with forensic medico-legal investigations [7, 8]. Overall 236 and 218 insects were collected from Sg. Loba Kora and Sg. Stutong, respectively. Table 1: Species of insects collected from rabbit carcasses in Sungai Loba Kora and Sungai Stutong, mangrove forest. Sg. Loba Kora Sg. Stutong Order Family Genus/Species Number of Number of species & species & Percentages Percentages Diptera Calliphoridae Chrysomya megacephala 101 (42.8%) 85 (39%) Chrysomya rufifacies 21 (8.9%) 26 (11.9%) Chrysomya nigripes 1 (0.4%) 1 (0.5%) Hemipyrellia liggurriens 1 (0.4%) 2 (0.9%) Muscidae Musca sorbens 1 (0.4%) 1 (0.5%) Musca domestica 3 (1.3%) 2 (0.9%) Hydrotaea spinigera 1 (0.4%) 1 (0.5%) Fannia sp. 4 (0.4%) 7 (3.2%) Sarcophagidae Parasarcophaga sp. 1 (0.4%) 2 (0.9%) Tachnicidae Archytas sp. 5 (2.1%) 5 (2.3%) Hymenoptera Formicidae Oceophylla smaradgina 53 (22.5%) 47 (21.6) Anomalomyrma sp 23 (9.7%) 21 (9.6%) Crematogaster sp 19 (8.1%) 17 (7.8%) Odontomachus sp 1 (0.4%) 1 (0.5%) Apidae (Bee) Unidentified 1 (0.4%) - TOTAL 236 (100%) 218 (100%) Throughout the study, five decomposition stages were observed and the duration of the decomposition processes lasted for nine days at both sites (Table 2). The five decomposition stages follows the description by De Jong and Chadwick (1999) [9].The earliest flies recorded attending the carcasses was C. megacephala and C. rufifacies which arrived on the second and third day during bloated stage. During this period, the immatures were also recovered. Ant visited the carcasses as early as the first day during fresh stage. Formicidae (ants) are common visitors of rabbit carcasses although they are not decomposers. Ants have recently gain importance because they predated on fly eggs, maggots and pupae [10]. The maggot mass temperature, carcass temperature, ambient temperature and soil temperature changes were not significantly different throughout the decomposition process (Fig. 1 and Fig. 2). 80
Table 2: Species of insect associated with each stage of decomposition of rabbit carcass. Mangrove forest: Sungai Loba Kora, Jalan Sultan Tengah, Kuching Mangrove forest: Sungai Stutong, Kuching Stages Stages Order Species Genus/Species Dry Bloated Active Dry Fresh Bloated Active Advance Fresh Advance (Day (Day (Day (Day (Day 1) (Day 2-3) (Day 4-6) (Day 7) (Day 1) (Day 7) 8-9) 2-3) 4-6) 8-9) Diptera Calliphoridae Chrysomya - I, A I, A I, A - - I, A I, A I, A - megacephala Chrysomya rufifacies - I, A I, A I, A - - I, A I, A I, A - Chrysomya nigripes - - I, A - - - - I, A - - Chrysomya - - A - - - - I, A - - villeneuvi Hemipyrellia - - A - - - - A - - liggurriens Muscidae Musca sorbens - - A - A - - A A A Musca Domestica - - A - A - - A - A Hydrotaea Spinigera - - A A - - - A - A Fannia sp. - - A - A - - A A A Sarcophagidae Parasarcophaga sp. - - A - - - A - - - Tachnicidae Archytas sp. - - A A - - - A A - Hymenoptera Formicidae Oceophylla A A A - - A A A - - Smaradgina Anomalomyrma sp A A A - - - A A - - Crematogaster sp A A A A A A A A A A Odontomachus sp - A A - - - - - - - Apidae (Bee) Unidentified - - A - - - - A - - (Note: A Adult; I Larva) 81
Fig. 1: Daily body temperature, ambient temperature, soil temperature, maggot mass temperature and relative humidity in relation to the decomposition stages of rabbit carcass at Sg. Loba Kora mangrove forest Fig. 2: Daily body temperature, ambient temperature, soil temperature, maggot mass temperature and relative humidity in relation to the decomposition stages of rabbit carcass at Sg. Stutong mangrove forest 82
There were significant changes for relative humidity at both study sites however from this study; it cannot be determined weather these changes affect the duration of the decomposition process of carcasses. It is important to record environmental parameters because changes in temperature and humidity will affect the decomposition duration [11, 12]. Conclusion In this study, we found that the dominant blowfly species decomposing rabbit carcasses at two mangrove forest sites in Kuching Sarawak were C. megacephala and C. rufifacies. There were also Muscidae, Sarcophagidae and Tachinidae that arrived at a later stage. Among the Hymenoptera found attracted to the carcasses was several species of Formicidae. These insect groups were also reported in studies done in peninsular Malaysia. There were five decomposition stages of rabbit carcass identified. Since the body surface temperature, ambient temperature, soil temperature and maggot mass temperature were consistent throughout the study, the effect on the decomposition process cannot be determined. A significant change in the relative humidity between the two sites also may or may not affect the decomposition process. References 1. Anderson, G.S (2010). Factors that influence insect succession on carrion. In:J.H., Byrd and J.L., Castner, eds. Forensic Entomology: The utility of Arthropods in Legal Investigation 2 nd edition. Boca Raton, Florida:CRC Press. Pp 201-250 2. Tabor, K.L., Fell, R.D and Brewster C.C (2005). Insect fauna visiting carrion in Soutwest Virginia. Forensic Science International. 150 (1):73-80. 3. Mahat N.A and Jayaprakash P.T, ( 2013). Forensic Entomology in Malaysia: A Review. Malaysian Journal of Forensic Sciences. Vol. 4, No. 1:1-6. 4. Heo, C.C., Sulaiman, S., Othman, H., Jeffery, J., Kurahashi, H. & Omar, B. (2010). Insect succession associated with a hanging pig carcass placed in an oil palm plantation in Malaysia. Sains Malaysiana 39 (6): 921-926. 5. Kumara, T., Disney, R.H.L.H. & Ahmad, A.H. (2010). First records of two species of Oriental scuttle flies (Diptera: Phoridae) from forensic cases. Forensic Science International 195: e5-e7. 6. Wahizatul A.A and Wuen, J.C.T (2011). Comparative study of dipteran diversity and their succession on rabbit carrion in two different hilly areas. Proceedings of the Universiti Malaysia Terengganu 10 th International Annual Symposium. 11-13 July 2011, Permai Hotel, Terengganu, Malaysia, pp 48-53. 7. Heo, C.C., Marwi, M.A., Jeffery, J. & Omar, B. (2008a). Insect succession on a decomposing piglet carcass placed in a man-made freshwater pond in Malaysia. Tropical Biomedicine 25(1): 23-29. 8. Heo, C.C., Marwi, M.A., Mohd. Salleh, A.F., Jeffery, J., Kurahashi, H. & Omar, B. (2008b). Study of insect succession and rate of decomposition on a partially burned pig carcass in an oil palm plantation in Malaysia. Tropical Biomedicine 25(3): 202 208. 9. De Jong, G.D. & Chandwick, J.W. (1999). Decomposition and arthropod succession on exposed rabbit carrion during summer at high altitudes in Colorado, USA. Entomological Society of America, 36(6), 833-845. 10. Heo, C.C., Marwi, M.A., Hashim, R. Abdullah, N.A., Chen C.D., Jeffrey, J. Kurahashi, H. & Omar, B. (2009). Ants (Hymenoptera: Formicidae) associated with pig carcasses in Malaysia. Tropical Biomedicine. 26(1)106-109. 11. Campbasso, C.P., Vella, G.D. & Introna F. (2001) Factors affecting decomposition and Diptera colonization. Forensic Science International. 120, 18-27. 12. Azwandi, A & Abu, H.A. (2009). A preliminary study on the decomposition and dipteran association with exposed carcasses in an oil palm plantation in Bandar Baharu, Kedah, Malaysia. Tropical Biomedicine. Additional information and reprint request: Robin Maramat Email: robinmaramat@yahoo.com.sg Department of Forensic Medicine, Sarawak General Hospital, Kuching, Sarawak, Malaysia. Tel: 082-276 666 Ext 6021 Fax: 082 276 794 83