The Micro Nucleus, Haematology and Toxicity effects of Glyphosate-based Herbicide 'Glysate' on post juveniles of African Catfish (Clarias Gariepinus) Burchell 1822

Glyphosate (N-phosphonomethyl glycine) is a broad spectrum systemic herbicide used extensively in weed control. The present study was designed to evaluate the toxicity effect of glyphosate on 300 post juveniles (50g±0.96g; 22cm±0.02) of Clarias gariepinus (Burchell, 1822) after exposure to acute concentration levels of 31, 33, 35, 37 and 39 mg glyphosate/L of clean water. The experiment was completely randomized as each treatment were all replicated thrice. Glyphosate toxicity (96 hr LC50) to Clarias gariepinus was determined at 35 mgL-1 after exposure by probit analysis. Based on the LC50 value, three sublethal test concentrations of 3.5, 7, 17.5mgL-1 corresponding to 1/10 LC50=3.5mgl-1, 1/5 LC50=7mgl-1, ½ LC50=17.5mgl-1 were selected for sub lethal experiment. A set of fish were also maintained simultaneously in water as a control experiment during the exposure periods. Blood samples were taken at intervals of day 1, 4 and 8 for assessment of hematology and micronucleus frequency. The results showed that glyphosate is toxic to Clarias gariepinus and fish generally though dose dependent as it significantly (p<0.05) enhanced, modulated and altered the parameters of analysis when compared to the control experiments The mean values of Micronucleus frequency in the treatments ranged from 375.66±8.01 – 406.66±5.03 which is about x5 higher than that of the control experiment 73.33±2.93. The hematological parameters were also affected by glyphosate toxicity as it reduced the PCV value in the treatments (ranging from 20.00±0.19 – 23.33±0.55) which is lower than the value 28.33±0.61 of the control experiment. Also, the RBC, WBC, Hb/dl and Platelets with ranges of 8.58±0.21 - 10.06±0.03; 12934.00±544.68 - 13700.00±485.72; 7.43±0.09 – 7.96±0.10; and 13866.66±449.41 respectively, were also significantly (p<0.05) altered from the control experiment which had values of 10.06±0.03; 9466.66±96.86; 8.73±0.05 and 15633.33±181.89 in the above parameters respectively. Mortality increased with increase in concentration of glyphosate and duration/time of exposure.  Glyphosate is a toxicant so should be judiciously and carefully used in both terrestrial and aquatic ecosystems to avoid ecotoxicological hazards.

TABLE OF CONTENTS

Title Page i

Certification ii

Dedication iii

Acknowledgements iv

Abstract v

Table Of Contents vi

List Of Tables ix

List Of Figures x

CHAPTER ONE 1

1.0 Introduction 1

1.1 Aim Of Study: 2

1.2 Objectives Of Study: 3

1.3 Justification Of The Study 3

CHAPTER TWO 4

2.0 Literature Review 4

2.1 Pesticide Toxicology 4

2.2 Glyphosate 5

2.2.1 Properties And Formulations 5

2.2.2 Mode Of Action 7

2.2.3 Glyphosate Toxicity 7

2.2.4 Effect Of Glyphosate On Fish 8

2.2.4.1 Behavioural Responses 9

2.2.4.2 Alterations In Tissues Of Exposed Fishes 10

2.2.4.2.1 Gills: 10

2.2.4.2.2 Liver: 10

2.2.4.3 Genotoxicity And Mutagenicity 10

2.2.4.4 Hematological Effects 12

2.3 The African Catfish (Clarias Gariepinus) 12

CHAPTER THREE 15

Materials And Methods 15

3.1 Materials 15

3.1.1 Herbicide 15

3.1.2 Experimental Fish 15

3.1.3 Equpments 16

3.2 Methods 16

3.2.1 Range Finding Test 16

3.2.2 Acute Toxicity Test 16

3.2.2.1 Percentage / Cummulative Mortality 17

3.2.2.2 Estimation Of Slope Function; F Consant, Upper And Lower Confidence Limits Of Lc50 17

3.2.3 Sub-Acute Toxicity Test 17

3.2.4 Micro Nucleus Assay 18

3.2.5 Hematological Assay 18

3.2.5.1 Blood Analysis 18

3.2.5.1.1 Determination Of The Red Blood Cells (Rbc) Count 19

3.2.5.1.2 Determination Of The White Blood Cells (Wbc) Count 19

3.2.5.1.3 Determination Of The Packed Cell Volume (Pcv) 20

3.2.5.1.4 Determination Of The Haemoblobin (Hb) Concentration 20

3.2.5.2 Determination Of Condition Factor (K) And Hepatosomatic Indices (HSI): 21

3.2.6 Water Quality Parameter 21

3.2.6.1 Dissolved Oxygen (Mg/L-1) 21

3.2.6.2 Temperature (0c) 21

3.2.6.3 pH 22

3.3 Statistical Analysis 22

CHAPTER FOUR 23

4.0 Results 23

4.1 Water Quality Parameters 23

4.2 Percentage/ Cummulative Mortality 25

4.3 Genotoxicity Potential /Assessment 29

4.4 Hematological Analysis 31

CHAPTER FIVE 33

Discussions, Conclusion And Recommendation 33

5.1 Discussion 33

5.2 Conclusion 34

Recommendations 35

References 36