ADDIS ABABA UNIVERSITY SCHOOL OF GRADUATE STUDIES DEPARTMENT OF BIOLOGY Chromosome Study of Some Fish Species from rift valley Lakes and some other water bodies of Ethiopia A Thesis Submitted to School of Graduate Studies, Addis Ababa University, in Partial Fulfillment of the Requirements for the Degree of Master of Science in Biology (Applied Genetics). By FEKADU WORKU G/MARIAM July, 2008 Addis Ababa ACKNOWLEDGEMENTS I am really indebted to Dr. Kifle Dagne for his enthusiastic and genuine guidance from the beginning of project selection to the completion of the study in developing protocol, analyzing slides and editing the final thesis. I would also like to acknowledge Dr Abebe Getahun, who helped me in contacting fishery research personnel at collection sites, morphological identification, provision of relevant literature and critical edition of the thesis. I would like to acknowledge Development Innovative Fund through Dr. Abebe Getahun for covering the financial expenses of this study. The Arba-Minch preparatory and Secondary School, and Ziway Fish Research Center are thanked for allowing me their laboratory rooms. My thanks go to Biology Department for accepting me as postgraduate student, the provision of laboratory facilities and financial support. Last, but not least I would like to appreciate Higher 23 preparatory School for their adjustment of appropriate time to pursuit my study; and my wife for her patience and understanding. I TABLE OF CONTENTS ACKNOWLEDGEMENTS -------------------------------------------------- i TABLE OF CONTENTS ----------------------------------------------------- ii LIST OF FIGURES ------------------------------------------------------------ iv LIST OF TABLES ------------------------------------------------------------- v ABBREVIATIONS ------------------------------------------------------------- vi ABSTRACT ---------------------------------------------------------------------- vii 1. INTRODUCTION ------------------------------------------------------ 1 2. GENERAL DESCRIPTION OF THE RIFT VALLEY LAKES-- 4 2.1. The diversity of fish fauna in the Ethiopian rift valley lakes- 5 2.2. General description of fish species under study---------------- 5 2.2.1. Family Cichlidae------------------------------------------- 5 2.2.1.1. Tilapia zilli --------------------------------------- 6 2.2.1.2. Oreochromis niloticus -------------------------- 7 2.2.2. Family Claridae -------------------------------------------- 7 2.2.2.1. Clarias gariepinus ------------------------------ 8 2.2.3. Family Mochokidae -------------------------------------- 8 2.2.3.1. Synodontis schall ------------------------------- 8 2.2.4. Family Cyprinidae ---------------------------------------- 9 2.2.4.1. Carassius auratus ------------------------------- 9 2.3. Chromosome cytology --------------------------------------------- 9 2.3.1. Reports on fish chromosome ------------------------------ 10 2.3.2. Variation in chromosome number ------------------------ 12 2.3.3. Variation in genome size ---------------------------------- 13 2.3.4. Variation in chromosome morphology ------------------ 14 2.3.4.1. Centro mere --------------------------------------- 14 2.3.4.2. Secondary constrictions ----------------------- 15 2.3.4.3. Variation in chromosome size-------------- 16 2.3.4.3.1. Relative chromosome size--------- 16 II 2.3.4.3.2. Absolute chromosome size-------- 16 2.3.5 Chromosome banding pattern-------------------------- 16 2.3.6 The significance of cytogenetics and cytotaxonomy in systematics and evolution--------------------------- 18 3. OBJECTIVE OF THE STUDY --------------------------------------------- 20 3.1 General objective ------------------------------------------------- 20 3.2 Specific objectives ------------------------------------------------ 20 4. MATERIALS AND METHODS -------------------------------------------- 21 4.1 Specimen collection ---------------------------------------------- 21 4.1.1. Collection sites -------------------------------------------- 21 4.1.2. Collection method ---------------------------------------- 22 4.2 Specimen identification and preservation --------------------- 24 4.3 Chromosome preparation ------------------------------------------ 24 4.4 Slide preparation and staining------------------------------------ 24 4.5 Methods of chromosome analysis ------------------------------ 25 5. RESULTS ---------------------------------------------------------------------- 26 6. DISCUSSION ----------------------------------------------------------------- 30 7. CONCLUSION ---------------------------------------------------------------- 33 8. RECOMMENDATIONS ---------------------------------------------------- 34 REFERENCES -------------------------------------------------------------------- 35 III LIST OF FIGURES Figure1. Photographs of fish Specimens-----------------------------------------------------------------23 Figure2a. Photographs of diploid chromosome number of Tilapia zilli from LakeZiway .-------26 Figure2b. Photographs of diploid chromosome number of Tilapia zilli from Lake Babogaya -----------------------------------------------------------------------------------------------26 Figure3a. Photographs of diploid chromosome number of oreochromis niloticus from Lake Ziway----------------------------------------------------------------------------------------27 Figure3b. Photographs of diploid chromosome number of oreochromis niloticus from Lake Babogaya.-----------------------------------------------------------------------------------27 Figure4. Photographs of diploid chromosome number of Clarias gariepinus from Lake Chamo -----------------------------------------------------------------------------------------28 Figure5. Photographs of diploid chromosome number of Synodontis schall from Lake Chamo .-------------------------------------------------------------------------------------------28 Fiure6. Photographs of diploid chromosome number of Carassius auratus from Sebeta artificial pond.-------------------------------------------------------------------------------------29 IV LIST OF TABLES Page Table1. Chromosome number (2n) and fundamental number (FN) of some freshwater fish species ----------------------------------------------------------------------------------------11 Table2. Specimens collection sites with their coordinates, altitude, specimen number, and species name----------------------------------------------------------------------------22 V ABBREVIATIONS BG-oreo = Oreochromis specimens from LakeBabogaya BG-zil = Zilli specimens from Lake Babogaya Cha-syn = Synodontis specimens from LakeChamo Cha-cla = Clarias specimens from LakeChamo Cha-oreo = oreochromis specimens from Lake Chamo Cha-hydro = Hydrocynus specimens from Lake Chamo Cha-bar = Barbus specimens from Lake Chamo Seb-oreo = Tilapia specimens from Sebeta artificial pond Seb-goldfish = Goldfish specimens from Sebeta artificial pond Zw-oreo = oreochromis specimens from Lake Ziway ZW-zil = Zilli specimens from Lake Ziway VI ABSTRACT Fishes are the most diverse of the major vertebrate groups. However, cytogenetic studies in fish have not been well studied globally as well as here in Ethiopia. Five species belonging to four families were sampled randomly from rift valley lakes and some water bodies; and their mitotic chromosomes have been studied or determined using splashing method. For chromosome preparation, each live fish specimen was injected with colchicine (0.5% of 0.8/100 gm body weight) and kept alive for 6-8 hours. The gill filaments were removed and kept in hypotonic solution (0.75M KCL) for about 30 minutes and then were fixed in 3:1(methanol: glacial acetic acid) for 30 minutes. Gill filaments were grinded with 1-1.5 ml of fixative solution and filtered with gauze. Finally the cell solution centrifugation for 5 minutes and air-dry slide preparation was made and stained in Giemsa. Photographs were taken from the best metaphase plates of each specimen and chromosome numbers were determined. The result showed that, the chromosome numbers of (2n) obtained for Tilapia zilli (2n=44), Oreochromis niloticus (2n=44), Clarias gariepinus (2n=56), Synodontis schall (2n=54), and Carassius auratus (2n= 94) all except the last fish specimen are in agreement with the previous reports. Since karyotypic analysis could not be given to all species under the present study, it is better to carry out further cytological study in the future to get more reliable chromosome data for better understanding about their taxonomic and evolutionary relationships. Key Words: - Fish, Tilapia, Oreochromis, Clarias, Synodontis, Carassius, diploid chromosome number, Rift Valley lakes, Ethiopia. VII 1. INTRODUCTION Fishes are the most numerous and diverse of the major vertebrate groups. They dominate the waters of the world through a marvelous variety of morphological, physiological, and behavioral adaptations. Nelson (1994) has described over 24500 extant fish species and the number may eventually increase to about 28500. About 28,900 species of fish were listed in Fish Data Base in 2005, but some experts feel that the final total may be considerably higher. Freshwater fishes comprise until now, almost 13,000 species and 2,513 genera (including only freshwater and strictly peripheral species), or about 15,000 if all species occurring from fresh to brackish waters are included (Springer, 2007). Noteworthy is the fact that the estimated 13,000 strictly freshwater fish species live in lakes and rivers that cover only 1% of the earth’s surface, while the