HISTOLOGICAL INTESTINAL DEVELOPMENT of AFRICAN LUNGFISH (Protopterus Aethiopicus Heckel 1851) LARVAE DURING FIRST FEEDING
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HISTOLOGICAL INTESTINAL DEVELOPMENT OF AFRICAN LUNGFISH (Protopterus aethiopicus Heckel 1851) LARVAE DURING FIRST FEEDING RONALD NTANZI Student number: 01700940 Promoters i. Prof. Dr. Gilbert Van Stappen ii. Dr.Ir. Nancy Nevejan iii. Prof. Dr. Wim Van den Broeck Supervisors I. Prof. Dr. Wim Van den Broeck II. Martin Sserwadda A dissertation submitted to Ghent University in partial fulfilment of the requirements for the degree of Master of Science in Aquaculture Academic year: 2017 - 2019 COPYRIGHT The author and promoters give permission to put this thesis to disposal for consultation and to copy parts of it for personal use. Any other use falls under the limitation of copyright, thus the obligation to explicitly mention the source when citing parts of this thesis. Promoters i) Prof.Dr. Gilbert Van Stappen ii) Dr.Ir. Nancy Nevejan …………………………………………………………………… ……………………………………………………….. iii) Prof.Dr. Win Van den Broeck ………………………………………………………………………. Supervisor ii) Martin Sserwadda …………………………………………………………… Author Ntanzi Ronald …………………………………………………………………….. i ACKNOWLEDGEMENT I would like to extend my sincere thanks to my promoters Prof. Gilbert Van Stappen and Dr Nancy Nevejan and supervisor Mr Martin Sserwadda of the Aquaculture Research and Development Centre (ARDC) Ghent University for the guidance rendered to me during the process of preparing this work. Special thanks also go to my third promoter Prof. Wim Van den Broeck of the department of morphology, faculty of veterinary medicine Ghent University and other members from this faculty including Prof. Pieter Cornillie and technicians Lobke De Bels and Bert De Pauw for the technical and practical guidance in preparation this work. I would like to give gratitude to the VLIR – UOS (Vlaamse Interuniversitaire Raad – The Flemish Interuniversity council) for the financial support rendered for my studies, I am grateful, and it has been a life changing experience. Thanks to my family members and friends who believed in me from the start and have been with me throughout the journey, your courage and guidance has brought me this far. Lastly, I give gratitude to God for all He has done for me. ii TABLE OF CONTENTS COPYRIGHT…………………………………………………………………………………………………………………………………….i ACKNOWLEDGEMENT……………………………………………………………………………………………………………………ii TABLE OF CONTENTS…………………………………………………………………………………………………………………….iii LIST OF FIGURES…………………………………………………………………………………………………………………………….v LIST OF TABLES………………………………………………………………………………………………………………………….…vii LIST OF ABBREVIATIONS……………………………………………………………………………………………………………..viii ABSTRACT…………………………………………………………………………………………………………………………………….ix CHAPTER 1: INTRODUCTION ............................................................................................................. 1 CHAPTER 2: LITERATURE REVIEW ..................................................................................................... 5 2.1 The state of world aquaculture ............................................................................................... 6 2.2 Air-breathing fishes and climate change ................................................................................. 7 2.3 Aquaculture in Africa .............................................................................................................. 9 2.4 Research on domestication of African lungfish ..................................................................... 10 2.5 Biology of African lungfish .................................................................................................... 12 2.5.1 Taxonomy and morphology ............................................................................................. 12 2.5.2 Habitat distribution of African lungfish ............................................................................ 14 2.5.3 The reproductive life cycle of African lungfish ................................................................. 16 2.6 Freshwater fish larval feeding strategies and live feeds ........................................................ 17 2.6.1 Larval feeding.................................................................................................................. 17 First feeding ......................................................................................................................... 17 Weaning .............................................................................................................................. 18 2.6.2 Live feeds ........................................................................................................................ 20 Rotifers ................................................................................................................................ 20 Artemia................................................................................................................................ 21 Microalgae ........................................................................................................................... 21 Other live feed organisms .................................................................................................... 22 2.7 Freshwater fish larval gastro-intestinal tract (GIT) ontogeny and histology .......................... 23 2.7.1 General gastro-intestinal tract ontogeny ......................................................................... 23 2.7.2 Buccal cavity and oesophagus ......................................................................................... 24 2.7.3 Stomach .......................................................................................................................... 26 2.7.4 Intestines ........................................................................................................................ 27 2.7.5 Liver and pancreas .......................................................................................................... 28 iii CHAPTER 3: MATERIALS AND METHODS......................................................................................... 30 3.1 Sampling and histological procedures ................................................................................... 31 3.1.1Tissue processing ............................................................................................................. 31 3.1.2 Tissue sectioning ............................................................................................................. 31 3.1.3 Staining and cover slipping .............................................................................................. 31 3.1.4 Histological analysis ........................................................................................................ 32 3.2 3D Reconstruction ................................................................................................................. 32 3.2.1 Selection of slides for reconstruction .............................................................................. 32 3.2.2 2D image acquisition protocol ......................................................................................... 32 3.2.3 Reconstruction procedure ............................................................................................... 33 Image import and alignment of image slices ........................................................................ 33 Image segmentation ............................................................................................................ 33 Surface generation, editing and visualisation ....................................................................... 33 CHAPTER 4: RESULTS....................................................................................................................... 35 4.1 Summary of histological and morphological landmarks between 17 and 26 DPH.................... 36 4.2 3D Reconstruction ................................................................................................................. 38 4.3 Histological observations between 17 and 26 DPH ................................................................. 40 4.3.1 Buccal cavity ................................................................................................................... 40 4.3.2 Pharynx ........................................................................................................................... 41 4.3.3 Oesophagus .................................................................................................................... 42 4.3.4 Spiral valve ...................................................................................................................... 44 4.3.5 Cloaca and anal opening ................................................................................................. 47 4.3.6 Liver and pancreas .......................................................................................................... 48 CHAPTER 5: DISCUSSION ................................................................................................................. 51 5.1 Larval digestive ontogeny ...................................................................................................... 52 5.2 Morphological development .................................................................................................. 52 5.3 Histological development....................................................................................................... 54 5.3.1 Buccal and pharyngeal cavities .......................................................................................