Evaluation of the Morphology of the Female Reproductive System of the Grasscutter (thryonomys swinderianus, temminck 1827)
Evaluation of the Morphology of the Female Reproductive System of the Grasscutter (thryonomys swinderianus, temminck 1827).
ABSTRACT
Fifteen female grasscutters, obtained from David Mark Farms, Otukpo, Benue State, Nigeria, were used for the study. They were randomly assigned to 3 groups of 5 each according to their ages; 1-3 months, 4-6 months and 7-9 months.
They were acclimatized for 14 days. The live weights of the grasscutters were obtained. They were then euthanized with gaseous chloroform in an air-tight container. The female reproductive system (ovaries, uterine tubes, uterine horns, uterus duplex, cervix and vagina) were carefully dissected out and observed for gross features.
The morphometry was also obtained. Each segment was then fixed in 10% Bouin’s solution and 10% neutral-buffered formalin of equal volume for 24 hours and processed routinely for light microscopy. Photomicrographs of the sections were taken using Moticam MC 2001 digital camera.
The data were subjected to one way analysis of variance. Variant means were separated using Duncan’s multiple range test. Significance was accepted at p < 0.05. Grossly, the ovaries were spindle-shaped at 1-3 months, oval at 4-6 months and round at 7-9 months.
In all the age groups studied, the uterine horns had a firm consistency on palpation, the uterus presented the appearance of a double uterus, the cervix had a rubber-stopper consistency on palpation, and the vagina had a soft consistency on palpation.
The weight and length of each segment of the female reproductive system of the grasscutter increased as the animal attained puberty. Thus, the organ sizes and lengths may not be pre-determined pre-natally, but increased proportionately as the animal attained puberty.
There were significant (p < 0.05) variations between the means of the relative weight and length of the ovaries, uterine tubes, uterine horns, uterus duplex, cervix and vagina of all the age groups.
Histomorphologically, the oocyte was peripherally located in the Graafian follicle as well as corpora haemorrhagica and lutea in the cortex at 7-9 months.
An intensely eosinophilic vaginal plug that was absent in the lumen of the vagina at 1-3 and 4-6 months, was very conspicuous at 7-9 months. The female grasscutter could thus be said to attain puberty at 7 months of age.
TABLE OF CONTENTS
Title Page – – – – – – – – – – – i
Dedication – – – – – – – – – – – ii
Certification – – – – – – – – – – iii
Acknowledgment – – – – – – – – – iv
List of Tables – – – – – – – – – – vi
List of Plates – – – – – – – – – – vii
Table of Contents – – – – – – – – – x
Abstract – – – – – – – – – – – xvi
CHAPTER ONE – – – – – – – – 1
1.0 Introduction – – – – – – – – – 1
1.1 Statement of Problem – – – – – – – 2
1.2 Justification – – – – – – – – – 2
1.3 Objectives – – – – – – – – – 3
1.3.1 Main Objective – – – – – – – – 3
1.3.2 Specific Objectives – – – – – – – – 3
CHAPTER TWO – – – – – – – – 5
2.0 Literature Review – – – – – – – – 5
2.1 Grasscutter Taxonomy – – – – – – – 5
2.2 Grasscutter Dentition – – – – – – – 5
2.2.1 Temporary Dentition – – – – – – – 5
2.2.2 Permanent Dentition – – – – – – – 5
2.3 Detection Of Oestrous Cycle In Does – – – – – 6
2.4 Pregnancy Diagnosis in Does – – – – – – 6
2.5 Gestation Period in Does – – – – – – – 7
2.6 Imminent Parturition in Does – – – – – – 7
2.7 Oogenesis – – – – – – – – – 8
2.8 Oestrous Cycle – – – – – – – – 8
2.8.1 Proestrus – – – – – – – – – 8
2.8.2 Oestrus – – – – – – – – – 8
2.8.3 Metoestrus – – – – – – – – – 9
2.8.4 Dioestrus and Anoestrus – – – – – – – 9
2.9 Embryogenesis of the Female Reproductive Tract – – – – 9
2.9.1 Primordia Germ Cells – – – – – – – 9
2.9.2 Undifferentiated Stage of the Gonadal Formation – – – – 10
2.9.3 Differentiation and Maturation of the Ovaries – – – – 11
2.9.4 Differentiation of the Mammalian Female Duct System – – – 12
2.9.5 Formation of the Genital Fold – – – – – – 14
2.9.6 External Genitalia – – – – – – – – 15
2.9.7 Differentiation of the External Genitalia – – – – – 15
2.9.8 Influence of Hormones on Development of Genital Ducts and External Genitalia – – 15
2.9.9 Sexual Differentiation, Associated Brain Function and Subsequent Sexual Behaviour at Puberty 16
2.9.10 Ovarian Migration – – – – – – – – 16
2.10 Gross Studies of the Female Reproductive System – – – – 17
2.10.1 Ovary – – – – – – – – – 17
2.10.2 Uterine Tubes – – – – – – – – 18
2.10.3 Uterine Horns – – – – – – – – 18
2.10.4 Uterine Body – – – – – – – – – 18
2.10.5 Cervix – – – – – – – – – 19
2.10.6 Vagina – – – – – – – – – 19
2.11 Histology of the Female Reproductive System – – – – 20
2.11.1 Ovaries – – – – – – – – – 20
2.11.1.1 Cortex – – – – – – – – – 21
2.11.1.2 Medulla – – – – – – – – – 22
2.11.2 Uterine Tubes – – – – – – – – 23
2.11.2.1 Infundibulum- – – – – – – – – 23
2.11.2.2 Ampulla – – – – – – – – – 23
2.11.2.3 Isthmus – – – – – – – – – 23
2.11.3 Uterus – – – – – – – – – 24
2.11.4 Uterine Horns and Body – – – – – – – 25
2.11.4.1 Endometrium- – – – – – – – – 25
2.11.4.2 Myometrium – – – – – – – – – 25
2.11.4.3 Perimetrium – – – – – – – – – 26
2.11.5 Cervix – – – – – – – – 26
2.11.6 Vagina – – – – – – – – – 26
CHAPTER THREE – – – – – – 28
3.0 Materials and Methods – – – – – – – 28
3.1 Animal Source – – – – – – – – 28
3.2 Animal Management – – – – – – 28
3.3 Gross Studies – – – – – – – 29
3.4 Histological Studies – – – – – – – 30
3.5 Statistical Analysis- – – – – – – – 31
CHAPTER FOUR – – – – – – – 32
4.0 Results – – – – – – – – – 32
4.1 Gross Anatomy and Morphometry – – – – – 32
4.1.1 Ovaries – – – – – – – – – 32
4.1.1.1 Left Ovary- – – – – – – – – 32
4.1.1.2 Right Ovary – – – – – – – – 32
4.1.2 Uterine Tubes – – – – – – – – 33
4.1.2.1 Left Uterine Tube – – – – – – – – 33
4.1.2.2 Right Uterine Tube – – – – – – – 34
4.1.3 Uterine Horns – – – – – – – – 34
4.1.3.1 Left Uterine Horn – – – – – – – – 34
4.1.3.2 Right Uterine Horn – – – – – – – 35
4.1.4 Uterus Duplex – – – – – – – – 35
4.1.5 Cervix – – – – – – – – – 36
4.1.6 Vagina – – – – – – – – – 36
4.2 Histomorphology- – – – – – – – 37
4.2.1 Ovary – – – – – – – – 37
4.2.2 Tubular Organs – – – – – – – – 39
4.2.2.1 Uterine Tubes- – – – – – – – 39
4.2.2.2 Uterine Horns- – – – – – – – 40
4.2.2.3 Uterus Duplex – – – – – – – – 41
4.2.2.4 Cervix- – – – – – – – – 42
4.2.2.5 Vagina – – – – – – – – – 43
CHAPTER FIVE – – – – – – – 85
5.0 Discussion and Conclusion – – – – – – 85
5.1 General Consideration – – – – – – – 85
5.2 Ovary – – – – – – – – 85
5.2.1 Morphometry – – – – – – – – 85
5.2.2 Position of the Oocyte within the Ovarian Follicle – – – 86
5.2.3 Presence of Corpus Haemorrhagicum in the Ovarian Cortex – – 86
5.2.4 Presence of Corpus Luteum in the Ovarian Cortex – – – 86
5.3 Uterine Tubes- – – – – – – – – 87
5.3.1 Gross Anatomy – – – – – – – – 87
5.3.2 Morphometry – – – – – – – – 87
5.3.3 Apical Modification on the Mucosa of the Uterine Tubes – – 88
5.4 Uterine Horns – – – – – – – – 89
5.4.1 Morphometry – – – – – – – – 89
5.4.2 Number and Size of the Endometrial Glandular Acini of the Uterine Horns — 89
5.5 Uterus Duplex – – – – – – – – 90
5.5.1 Gross Anatomy – – – – – – – – 90
5.5.2 Morphometry – – – – – – – – 90
5.5.3 Number and Size of the Endometrial Glandular Acini of the Uterus Duplex – – – 90
5.6 Cervix – – – – – – – – – 91
5.6.1 Gross Anatomy – – – – – – – – 91
5.6.2 Apical Modification on the Endocervical Mucosa – – – 92
5.6.3 Mucosal Cells on the Externum of the Cervix – – – – 93
5.7 Vagina – – – – – – – – – 94
5.7.1 Morphometry – – – – – – – – 94
5.7.2 Apical Modification on the Tunica Mucosa of the Vagina- – – 94
5.7.3 Presence of Vaginal Plug in the Vaginal Lumen- – – – – 95
5.8 Summary – – – – – – – – – 95
5.9 Conclusion – – – – – – – – – 97
References
Appendix I
Appendix II
INTRODUCTION
Grasscutter (Thryonomys swinderianus, Temminck 1827) is a wild herbivorous rodent of the Sub-Order Hystricomorpha, found only in Africa (Baptist and Mensah, 1986).
Rodents (which the grasscutter is a part of) comprise the largest and most diverse group of mammals with over 1,700 different species (Besselsen, 2002; Annor and Djang-Fordjour, 2006).
In Nigeria where grass provides its main habitat and food, it is commonly called “grasscutter”. The Igbos of Eastern Nigeria call it “nchii”, Hausas of Northern Nigeria call it “jawji” or “jebji” (depending on the dialect spoken), Yorubas of Western Nigeria call it “ewuju” or “oya” (also depending on the dialect spoken), while the Idomas of North-C 1 l Nigeria (precisely Benue State) call it “obije”.
The Igalas of Kogi State call it “emi”. Other parts of Africa particularly South Africa, where it is closely associated with cane fields, it is called “greater cane rat” or simply “cane rat”.
French-speaking African countries call it “agouti”, which means “animal from the bush” (Ismail, 2008). Its distribution is therefore determined by the availability of adequate or preferred grass species for food (National Research Council-NRC, 1991; Songhai Centre, 2009).
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