A study was carried out on the forensic entomotoxicological evaluation of carrion insects of fishes poisoned with dichlorvos on the main campus of the University of Ibadan. Fishes (Clarias gariepinus) for the study were obtained from the fish farm on the University Campus. The fishes were then euthanized with 5ml of dichlorvos while the control was without poison. Adult carrion insects were collected from the fish carrion using a sweep net. The larvae were collected into a bowl by using a scoop, immobilized with hot water and later placed in sample bottles containing 70% ethanol. Pupae were collected using forceps. Carcass temperature was measured using infrared thermometer while relative humidity was recorded from a digital hygrometer. Calliphoridae and Muscidae were the initial pioneers of the decomposing carcass and were seen during the fresh stage, sarcophagidae was seen shortly after the fresh stage of decomposition. The highest mean temperature value for the fish treated with 5ml Dichlorvos was 31.30C while its lowest mean value was 22.60C. It was observed that the temperature on the ninth day was higher than the other days. This is attributed to the heat generated by the active maggots at that stage of decomposition. Dichlorvos was found to retard the growth of carrion larva as shown in Musca domestica larvae when compared with the control. Fast decomposition rate was recorded due to high ambient and carcass temperature. It can be concluded from this study that carrion insects can be used in solving crime puzzles through the extrication of post mortem intervals in conjunction with environmental variables. Since fish carrion in this study attracted a sizable number of carrion insects, it is recommended that fish be used in future forensic case and experimental studies.
Table of Contents
CHAPTER ONE
1.1 Entomotoxicology
1.2 Carrion Insects
1.3 Dichlorvos
1.4 Aims and Objectives
CHAPTER TWO
LITERATURE REVIEW
2.0. INTRODUCTION
2.1 URBAN FORENSIC ENTOMOLOGY
2.2 STORED-PRODUCT FORENSIC ENTOMOLOGY
2.3 MEDICO-LEGAL FORENSIC ENTOMOLOGY
2.4 Decomposition
2.4.1 Stages of decomposition
2.4.1.1. Stage 1: The living fish
2.4.1.2 Stage 2: Initial decay
2.4.1.3. Stage 3: Putrefaction
2.4.1.4. Stage 4: Black putrefaction
2.4.1.5 Stage 5: Butyric fermentation
2.4.1.6 Stage 6: Dry decay
2.5 Biology of Carrion insects
2.5.1. Types of Carrion Insect
2.5.1.1 Calliphoridae
2.5.1.2 Sarcophagidae
2.5.1.3 Muscidae
2.5.1.4 Piophilidae
2.5.1.5 Nitidulidae
2.5.1.6 Silphidae
2.5.2. The Utility of Carrion Beetles in Forensic Entomology
2.6. Effects of Temperature and Humidity
2.7. Review of Previous Literatures
CHAPTER THREE
MATERIALS AND METHODS
3.1 Study site
3.2.1 Preparation of fishes for setup
3.2.2 Mounting the fishes
3.2.3 Carrion insect collection and processing
3.2.3.1 Sampling for larvae
3.2.3.2 Sampling for pupae
3.3 Measurement of larval body length
3.4 Measurement of carcass temperature and humidity
CHAPTER FOUR
RESULTS
4.1 Abundance and species composition of carrion insects on fish carcass.
PICTURES OF CARCASS DECOMPOSITION STAGES IN THE STUDY
CHAPTER FIVE
DISCUSSION
5.1 Abundance and species composition of carrion insects on fish carcass
5.2 Carrion insect succession on fish carcass
5.3 Effects of Dichlorvos on the length and weight of larva
5.4 Variation in environmental variables at the field site
5.5 CONCLUSION
Research Objectives and Focus
This study investigates the forensic entomotoxicological impact of the suicide agent dichlorvos on the decomposition process and the associated larval development of *Clarias gariepinus* (catfish). The central research goal is to understand how such toxins influence the successional patterns and growth metrics of carrion-inhabiting insects, thereby affecting the estimation of post-mortem intervals (PMI) in forensic investigations.
- Entomotoxicological analysis of necrophagous insects on poisoned fish carcasses.
- Evaluation of larval growth inhibition caused by dichlorvos exposure.
- Observation of carcass colonization and insect succession stages.
- Correlation between temperature, carcass decomposition, and environmental variables.
- Validation of fish as suitable models for future forensic research studies.
Excerpt from the Book
1.1 Entomotoxicology
Entomotoxicology is derived from “entomo” which literally means insects and “toxicology” which means the study of toxins. Therefore entomotoxicology can simply be defined as the study of toxins or poisons in insects (Amendt et al, 2004).
Forensic entomology is the scientific study of the invasion and succession pattern of arthropods with their developmental stages of different species found on the decomposed cadaver during legal investigations. It is the application and study of insect and other arthropods, including insects, arachnids and centipedes to criminal or legal cases. It is primarily associated with investigations (Amendt et al, 2004).
Forensic entomotoxicology is most commonly used to estimate Post Mortem Interval (PMI) in cases involving homicide (Wallman,2003: Dadour and Morris,2009). The initial signs of soft tissue decay occurs within the first 72-98 hours after death. After the initial stages of decomposition are complete, the accurate determination of PMI is not possible but insects found on the deceased can enable entomologist to provide an estimation ranging from one day up to more than 2 months (Schoenly et al, 1992).
Summary of Chapters
CHAPTER ONE: Provides an introduction to the fields of entomotoxicology and forensic entomology, defines carrion insects, details the properties of Dichlorvos, and outlines the specific research objectives.
CHAPTER TWO: Reviews the literature regarding forensic entomology, its sub-fields, the stages of vertebrate decomposition, the biology of common carrion insects, and the historical evolution of the field.
CHAPTER THREE: Describes the methodology, including the study site, preparation of the *Clarias gariepinus* carcasses, mounting procedures, insect collection protocols, and measurement techniques for larva and temperature.
CHAPTER FOUR: Presents the primary results regarding the abundance and species composition of carrion insects, including comparative data on larval body length and carcass temperature fluctuations between poisoned and control groups.
CHAPTER FIVE: Discusses the findings related to insect succession and the inhibitory effects of Dichlorvos on larval growth, followed by a conclusion that emphasizes the importance of these findings for forensic case applications.
Keywords
Entomotoxicology, Dichlorvos, Clarias gariepinus, Carrion insect, Decomposition, Forensic Entomology, Post Mortem Interval, PMI, Musca domestica, Calliphoridae, Sarcophagidae, Larval growth, Carcass temperature, Species diversity, Insect succession.
Frequently Asked Questions
What is the primary focus of this research?
The study examines the forensic entomotoxicological evaluation of carrion insects on fish poisoned with dichlorvos, focusing on how this toxin affects the natural decomposition process and insect succession.
What are the primary fields covered in this document?
The research intersects forensic entomology, toxicology, and ecology, specifically investigating how insect development is used as a tool in medico-legal investigations.
What is the main objective of the study?
The primary goal is to assess the effect of the insecticide Sniper (containing dichlorvos) on the developmental stages of insect larvae and to evaluate the abundance and succession patterns of insects on decomposing *Clarias gariepinus*.
Which scientific methods were employed?
The researcher used a field-based experiment with *Clarias gariepinus* as a model, conducting comparative observations of insect colonization on poisoned versus control carcasses and performing larval growth measurements.
What does the main body address?
The main part of the text covers the foundational theory of forensic entomology, detailed procedural methodology, empirical results on insect abundance at different decomposition stages, and a detailed discussion on how dichlorvos inhibits larval growth.
Which keywords characterize this work?
Key terms include Entomotoxicology, Dichlorvos, *Clarias gariepinus*, Carrion insect, Decomposition, Post Mortem Interval (PMI), and forensic indicator species.
How does dichlorvos affect the rate of decomposition?
The study indicates that dichlorvos acts as an inhibitor, retarding the growth of carrion larvae, such as those of the *Musca domestica*, when compared to the natural growth observed in control groups.
What role does temperature play in this study?
Temperature is identified as a critical environmental variable; specifically, the study noted that higher temperatures accelerated decomposition, and that peak temperatures during the 9th to 11th days were linked to heat generated by active maggot masses.
What are the implications for forensic practice?
The study concludes that carrion insects are vital for estimating post-mortem intervals, and that because suicidal poisons alter insect diversity and colonization patterns, these factors must be accounted for in forensic investigations of questionable deaths.
- Arbeit zitieren
- Emmanuel Tyokumbur (Autor:in), 2023, Clarias Gariepinus Fish as a Suitable Culture for Carrion Insects in Forensic Investigations using Dichlorvos as a Suicide Agent. Forensics and Crime, München, GRIN Verlag, https://www.grin.com/document/1366996
