Animal Research International (2020) 17( 3 ): 3869 – 3877 3869 ARTHROPOD SUCCESSION ON EXPOSED AND SHADED MAMMALIAN CARCASSES IN NSUKKA, NIGERIA ONYISHI, Grace Chinenye , OSUALA, Fredrick, AGUZIE, Ifeanyi Oscar , OKWUONU , Elijah Sunday and ORAKWELU, Chinemerem Hodges Department of Zoology and Environmental Biology, U niversity of Nigeria, Nsukka, Enugu State, Nigeria. Corresponding Author: Onyishi, G. C. Department of Zoology and Environmental Biology, University of Nigeria, Nsukka, Enugu State, Nigeria. Email: grace.ony [email protected] Phone: +234 7064609656 Received February 26, 2020 ; Revised March 08, 2020; Accepted October 26, 2020 ABSTRACT Ten Wistar rats were used as model to study arthropod succession on carcass under shade and exposed conditions . Carcass decomposition took longer periods under shade than on the exposed site . Four decomposition stages ( fresh, bloated, decay and dry ) were observed. A total of 164 arthropods were c ollected belonging to three classes : Insecta, Arachnida and Crustacean. I nsects formed 95.1 2 %, arachnids 1.22 % and crustaceans 3.66 %. Large numbers of arthropods were found on the exposed carcass than the shaded carcass . C alliphorids and S arcophagids were the primary colonizers observed breeding on the carcasses. The most abundant insects include Chrysomya albiceps (13.4 %) and Lucilia serricata (10.3 7 %). Other dipterans including Muscidae, Phoridae, Sepidae, Fannidae and A nthomyiidae were found during the bloated and decay stages. Famil ies of the coleopterans including; Dermestidae, Silpgidae, Staphylinidae and H isteridae were observed during the bloated to the dry stages and fed on the immature dipterous maggots and carrion remains. Hymenopterans were observed throughout the process of decomposition and played a vital role in carcass decomposition. Other arthropods arrived mostly during the decay stage. Species richness on the carcasses peaked during the decay stage. The rate of decomposition of carcasses is affected by environmental fac tors such as temperature, relative humidity, precipitation and insect abundance. Keywords: Post mortem interval, Carcass decomposition, Insect abundance, Forensic entomology INTRODUCTION According to Bornemissza (1957), the decomposer community of a carcass goes Decomposition is a natural and necessary through a process of ecological succession. The process responsible for the return of organic in sects arrive in a determined sequence, material to the environment through the producing an addition or substitution of species. breakdown of dead plant or animal matter. It The potential of insects as forensic indicators represents a temporary and changing food has stimulated detailed research regarding the source for varied and distinct community of role of fauna in carcass decomposition in organisms (Putman, 1983). Insects, especially various regions and countries (Tomberlin and coleopteran s and dipteran s are the major Alder, 1998; Centeno et al. , 2002; Kočárek , components of insect community which are 2003 ; Okiwelu et al. , 2008). The basic reason primarily involved in the decomposition process for using insects in criminal investigations ( Kočárek , 2003 ). resides in the fact that insects are usually the ISSN: 1597 – 3115 ARI 2020 17( 3 ): 3869 – 3877 www.zoo - unn.org Onyishi et al . 3870 first organisms to detect and find a cadaver and later reappear in the course of decomposition are involved in all stages of decomposition. (Wolff et al. , 2001). It is important to observe Furthermore, some insect species are specific that not all the i nvertebrates found near a for certain areas and seasons (Carvalho et al. , corpse are fe eding on it. Based on this, four 2000). Also, it has been o bserved that ecological categories have been recognized for oviposition can occur minutes after death the insect community found around corpses. (Smith, 1986). The knowledge of this succession These include: (i) necrophagous species which pattern as well as their preference for the are flesh feeding species. They constitute the di fferent stages of decomposition, and the m ost important category to establish the time of meteorological data ( temperature and death. (ii) Predators and parasites of humidity), have been applied in forensic science necrophagous species , (i ii ) omnivorous species to determine the post mortem interval (PMI) of and the (iv) a dventitious species that use the a corpse ( Kočárek, 2003; Okiwelu et al. , 2008 ) . cadaver like an extension of their ecological This field of forensic entomology involves the niche (Smith, 1986). use of the knowledge of insects in investigation The stud y of the entomofauna of crimes or even ci vil disputes. I t also includes associated with cadavers has been an extremely the application of the study of insects and other effective tool to clarify numerous cases of arthropods to legal i ssues, especially in the homicides, sexual abuses and traffic of organs court of law (Okiwelu et al. , 2008). Some (Catts and Haskell, 1990 ). The types of insect examples of criminal cases where forensic present in a decomposing corpse are specific for entomology was successful in determining the c ertain areas and seasons. Invariably , certain outcome includes, one involving a young groups will colonize first, such as blowflies prostitute and a thirty - year - old member of the ( Calliphoridae) and flesh flies (S arcophagidae), Army ( Lord and Rodriguez, 1989 ) . Her family but the species involved will usually vary. It is members had informed the police of her therefore necessary , to study each region for vanishing approximately four days before her arthropods associat ed with mammalian body was found. She had last been seen in the carcasses. This is a major factor that has company of this military man on May 31. A hindered the application of forensic entomology number of adult flies and maggots were noticed in Nigeria, as only few studies has been carried and gath ered inside and around the wounds of out in the different geographical location of the the young girl. A number of these maggots country which include works by Okiwelu et al. were kept and grown to be adult flies, and (2 008) in Rivers State, Ekanem and Dike (2010) others were taken in their present state. in Uyo, Ekrakene and Iloba (2009) in Benin City Pictures were taken and enlarged showing the and Abajue et al. (2014) in Okija. Therefore, it flies around the body when it was found. Using is necessary to carry out this study, as this will this evidence along with associating weather add to the available data on entomofauna conditions known to be current around the time, present in mammalian c arcasses in Nigeria. The an entomologist was able to give a PMI . The objective of this study was to investigate insects evidence showed that the flies had arrived on visiting exposed and shaded decomposing rat May 31, which implied a time period of four carcasses to establish relationship between days since she had died. This information insect s and carcasses which may be of forensic indicated the army man to be the last person to importance in Nsukka, Enugu State, Nigeria. be with the girl. When presented with the evidence the authorities were able to get a MATERIALS AND METHODS confession out of the man. The use of forensic entomology was a strong factor in this case S ite D escription : The study was carried out ( Lord and Rodrigue z, 1989 ). within the University of Nigeria, Nsukka Invasion time of the corpse is usually environs. The climate in Nsukka is tropical with considered important since some insect species monthly temperatures ranging between 24 ° C are always present, while others disappear and and 29 ° C (Inyang, 1978 ). There are two Animal Research International (2020) 17( 3 ): 3869 – 3877 Arthropod succession on exposed and shaded ma mmalian carcasses 3871 seasons: the dry and rainy seasons. The dry RESULTS season is from November to March , while the rainy season is from April to October. Two sites, Phases of Carcass Decomposition : During an open grass area filled with Pennisetum the observation periods, the ambient purpureum (elephant grass), and abandoned temperature for both sites ranges from 25 ° C to building, 50 m apart opposite the maize 28 ° C (26.8 ± 0.53 ° C) on the exposed site and farmland o f the Faculty of Agriculture, University 25 ° C to 29 °C (26.9 ± 1.05 ° C) on the shaded of Nigeria, Nsukka were used . site. Relative humidity ranges from 80 to 100 % (98 ± 5.05) on both sites, and a total of 5550 Study Design : Ten carcasses of laboratory rats mm 2 of precipitation was recorded. ( Rattus norvegicus : Berkenhout 1769) each Decomposition period lasted for 23 days weighing ~ 200 g were used as model . The rats on the exposed carcasses and 25 days on the were sacrificed by strangulation and shaded carcasses. Fou r carrion decomposition immediately transported to the study area. Five phases , namely fresh, bloated, decay and dry carcasses were placed on each site in a cage were observed. The fresh stage lasted for less (120 mm x 100 mm x 30 mm). The cages were than 24 hours on the exposed carcasses, while covered with a 5 cm mesh to allow colonization on the shaded carcasses it was about 30 hours. of carcasses by insects, while preventing Bloating occurred on the second day on both scavengers attack (Sukon tason et al. , 2003 ) . carcasses. It was characterized by the swelling Samples were collected twice a day of the abdomen and this lasted for two days on (9:00 and 13:00) during the first (fresh) and the exposed carcasses while on the shaded second (bloated) stages of decomposition and carcasses it lasted for three days. The decay thereafter once a day for up to the end of stage started on the 5 th day, with the breaking - decomposition according to Mabika et al. up of the skin at the eye and anal region. The (2014). Flying insects were caught using an abdomen later began to tear - up and the i nsect net, while the immature insects and other carcasses were relaxing a strong foul odour.