Reproductive styles of Osteoglossomorpha with emphasis on Notopterus notopterus and Osteoglossum bicirrhosum DISSERTATION Zur Erlangung des akademischen Grades Doctor rerum agriculturarum (Dr. rer. agr) Eingereicht an der Landwirtschaftlich-Gärtnerischen Fakultät der Humboldt-Universität zu Berlin von Honesty Yanwirsal (M.Sc Fishery Science and Aquaculture) Präsident der Humboldt-Universität zu Berlin Prof. Dr. Jan-Hendrik Olbertz Dekan der Landwirtschaflich-Gärtnerischen Fakultät Prof. Dr. Dr. h. c. Frank Ellmer Gutachter: 1. Prof. Dr. Frank Kirschbaum 2. Prof. Dr. Ralph Tiedemann 3. Dr. Peter Bartsch Tag der mündlichen Prüfung: 16 Mai 2013 Dedicated to Prof. Dr. Frank Kirschbaum & Dr. Peter Bartsch Thousand words are never enough to express my gratitude. It’s been a long journey, a precious and unforgettable experience in my life. ii LIST OF CONTENTS LIST OF FIGURES ......................................................................................................... VI LIST OF TABLES ........................................................................................................... IX SUMMARY ..................................................................................................................... X ZUSAMMENFASSUNG ............................................................................................... XII 1 INTRODUCTION ........................................................................................................ 1 1.1 General overview on Osteoglossomorpha ........................................................... 1 1.2 Reproduction in Osteoglossomorpha .................................................................. 4 1.2.1 Influence of environmental factors on gonad development and spawning season ...................................................................................... 4 1.2.1.1 Family Osteoglossidae .............................................................. 4 1.2.1.2 Family Notopteridae ................................................................. 4 1.2.1.3 Family Mormyridae .................................................................. 5 1.2.1.4 Family Gymnarchidae ............................................................... 5 1.2.1.5 Family Pantodontidae ............................................................... 5 1.2.1.6 Family Hiodontidae .................................................................. 5 1.2.2 Breeding behaviour ................................................................................. 6 1.2.2.1 Family Osteoglossidae .............................................................. 6 1.2.2.2 Family Notopteridae ................................................................. 7 1.2.2.3 Family Mormyridae .................................................................. 7 1.2.2.4 Family Gymnarchidae ............................................................... 8 1.2.2.5 Family Pantodontidae ............................................................... 8 1.2.2.6 Family Hiodontidae .................................................................. 8 1.2.3 Early ontogeny and objectives of the study ............................................ 8 2 MATERIALS AND METHODS ................................................................................ 10 2.1 Mormyridae ....................................................................................................... 10 2.1.1 Petrocephalus soudanensis ................................................................... 10 2.1.2 Petrocephalus catostoma ...................................................................... 10 2.2 Pantodontidae .................................................................................................... 11 2.2.1 Pantodon buchholzi ............................................................................... 11 2.3 Notopteridae ...................................................................................................... 13 2.3.1 Notopterus notopterus ........................................................................... 13 2.3.1.1 Specimens and breeding tanks ................................................ 13 2.3.1.2 Rearing .................................................................................... 14 2.3.2 Xenomystus nigri ................................................................................... 15 2.3.2.1 Specimens and breeding tanks ................................................ 15 2.4 Osteoglossidae ................................................................................................... 16 2.4.1 Osteoglossum bicirrhosum .................................................................... 16 2.4.1.1 Location and fishes ................................................................. 16 2.4.1.2 Collection of samples .............................................................. 16 iii 2.4.1.3 Rearing and documentation .................................................... 18 2.5 Variation and measurement of environmental parameters ................................ 19 2.6 Behaviours ......................................................................................................... 19 2.7 Maturity coefficient (MC) ................................................................................. 19 2.8 Hormonal treatment ........................................................................................... 20 2.9 General photography ......................................................................................... 20 2.10 Terminology ...................................................................................................... 20 3 RESULTS ................................................................................................................... 21 3.1 Family Mormyridae ........................................................................................... 21 3.1.1 Petrocephalus soudanensis ................................................................... 21 3.1.2 Petrocephalus catostoma ...................................................................... 23 3.2 Family Pantodontidae, Pantodon buchholzi ...................................................... 26 3.3 Family Notopteridae .......................................................................................... 30 3.3.1 Xenomystus nigri ................................................................................... 30 3.3.2 Notopterus notopterus ........................................................................... 33 3.3.2.1 Reproduction ........................................................................... 33 3.3.2.2 In situ condition of mature and immature (F1) specimens ................................................................................ 39 3.3.2.3 External features of the egg .................................................... 40 3.3.2.4 Development ........................................................................... 41 3.3.2.4.1 The embryonic period ....................................................... 41 3.3.2.4.1.1 The cleavage phase ....................................................... 41 3.3.2.4.1.2 The embryonic phase ................................................... 43 3.3.2.4.1.3 The eleutheroembryonic phase ..................................... 49 3.3.2.4.2 The larval period ............................................................... 52 3.3.2.4.3 The juvenile period ........................................................... 54 3.3.2.4.4 The adult period ................................................................ 57 3.4 Osteoglossidae ................................................................................................... 61 3.4.1 Osteoglossum bicirrhosum .................................................................... 61 3.4.1.1 External morphology and in situ condition of dissected gonads...................................................................... 61 3.4.1.2 Gonad of Silver Arowana and Blue Arowana ........................ 63 3.4.1.3 Egg of Silver Arowana............................................................ 64 3.4.1.4 Development ........................................................................... 65 3.4.1.4.1 The embryonic period ....................................................... 65 3.4.1.4.1.1 The embryonic phase ................................................... 65 3.4.1.4.1.2 The eleutheroembryonic phase ..................................... 71 3.4.1.4.2 The juvenile period ........................................................... 76 4 DISCUSSION ............................................................................................................. 81 4.1 Overview of environmental triggers of gonad development ............................. 81 4.1.1 Family Mormyridae .............................................................................. 81 iv 4.1.2 Family Notopteridae ............................................................................. 81 4.1.3 Family Pantodontidae ........................................................................... 82 4.1.4 Family Osteoglossidae .......................................................................... 83 4.2 Modes of reproduction in Notopterus notopterus and Osteoglossum bicirrhosum with comparison to other osteoglossomorphs ............................................................................................ 83 4.2.1 Reproductive guilds .............................................................................