An Evolutionary-Morphological Study
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FACULTY OF SCIENCES Department of Biology Evolutionary Morphology of Vertebrates Structural diversity in the cranial musculoskeletal system in Anguilliformes: an evolutionary-morphological study Part 1 - Text Soheil Eagderi Thesis submitted to obtain the degree Academic year 2009-2010 of Doctor in Sciences (Biology) Rector: Prof. Dr. Paul van Cauwenberge Dean: Prof. Dr. Herwig Dejonghe Promoter: Prof. Dr. Dominique Adriaens FACULTY OF SCIENCES DEPARTMENT OF BIOLOGY EVOLUTIONARY MORPHOLOGY OF VERTEBRATES Structural diversity in the cranial musculoskeletal system in Anguilliformes: an evolutionary morphological study Part 1 - Text Soheil Eagderi Thesis submitted to obtain the degree Academic year 2009-2010 of Doctor in Sciences (Biology) Rector: Prof. Dr. Paul van Cauwenberge Dean: Prof. Dr. Herwig Dejonghe Promoter: Prof. Dr. Dominique Adriaens Cover image: CT scan image of the skull of Simenchelys parasiticus Members of the Examination Committee Prof. Koen Sabbe, Chairman (Ghent University) Prof. Dr. Dominique Adriaens, Promoter (Ghent University) Dr. Eric Parmentier (University of Liège) Dr. Natalie De Schepper Dr. Sam Van Wassenbergh (University of Antwerp) Prof. Dr. Ann Huysseune (Ghent University) Dr. Tom Geerinckx (Ghent University) Dr. Emmanuel Vreven (Royal Museum for Central Africa) Prof. Dr. Luc Lens (Ghent University) Reading committee Dr. Eric Parmentier (University of Liège) Dr. Natalie De Schepper Dr. Sam Van Wassenbergh (University of Antwerp) TABLE OF CONTENTS Chapter 1 - Introduction 1.1. General context ……………………………………………………………………………………………………………….… 1 1.1.1. Adaptation and diversity …………………………………………………………….…..... 1 1.1.2. Taxonomical history of Anguilliformes ………………………………………………. 4 1.1.3. Introduction of studied taxa …………………………………………………………….… 5 1.1.3.1. Anguillidae …………………………………………………………………………………….. 5 1.1.3.2. Nettastomatidae ……………………………………………………………………………. 7 1.1.3.3. Heterenchelyidae ………………………………………………………………………….. 7 1.1.3.4. Synaphobranchidae ………………………………………………………………………. 7 1.1.3.5. Muraenidae ……………………………………………………………………………………. 8 1.1.3.6. Congridae ………………………………………………………………………………………. 9 1.1.3.7. Eurypharyngidae …………………………………………………………………………… 9 1.2. Aims and thesis outlines ………………………………………………………………………………………………….. 9 1.2.1. General aim of this study ………………………………………………………………….. 9 1.2.2. Outline of thesis ……………………………………………………………………………….. 11 Chapter 2 – Aims and Structure of the thesis 2.1. Material examined ………………………………………………………………………………………………………. 15 2.2. Methods19 2.2.1. Preparation of specimens …………………………………………………………………. 17 2.2.1.1. Anaesthesia, sacifice and fixation ………………………………………………. 17 2.2.2. Morphology ……………………………………………………………………………………….. 17 2.2.2.1. In toto clearing and staining ……………………………………………………..17 2.2.2.2. Dissections ………………………………………………………………………………… 18 2.2.2.3. Histological sections …………………………………………………………………. 19 2.2.2.4. Shape analysis ………………………………………………………………………….. 22 2.2.2.5. Visualization ……………………………………………………………………………… 23 2.2.3. Terminology …………………………………………………………………………………….. 23 Chapter 3 –Head Morphology of the Duckbill Eel I Table of contents 3.1. Abstract …………………………………………………………………………………………….... 25 3.2. Introduction ……………………………………………………………………………………….. 26 3.3. Material and methods ………………………………………………………………………... 27 3.4. Results ………………………………………………………………………………………………... 27 3.4.1. Cranial Osteology of Hoplunnis punctata …………………………….…….… 27 3.4.2. Cephalic lateral system …………………………………………………………….….. 31 3.4.3. Cranial myology of Hoplunnis punctata ………………………………………. 32 3.4.4. Shape analysis ………………………………………………………………………………. 34 3.5. Discussion ……………………………………………………………………………………………. 35 3.5.1. Morphological changes towards jaw elongation ……………………………. 35 3.5.1.1. Osteology …………………………………………………………………………………. 35 3.5.1.2. Myology ……………………………………………………………………………………. 36 3.5.1.3. Jaw elongation …………………………………………………………………………. 37 3.5.2. Functional consideration of snout elongation ……………………………….. 38 Chapter 4 – Cephalic Morphology of Pythonichthys macrurus 4.1. Abstract ………………………………………………………………………………………………. 43 4.2. Introduction ……………………………………………………………………………………….. 43 4.3. Material and methods ………………………………………………………………………… 45 4.4. Results ………………………………………………………………………………………………… 46 4.4.1. Cranial Osteology of pythonichthys macrurus …………………………….. 46 4.4.2. Cranial myology of pythonichthys macrurus ……………………………….. 51 4.4.2.1. Muscles of the cheek ……………………………………………………………... 51 4.4.2.2. Ventral muscles of the head …………………………………………………… 52 4.4.2.3. Body muscles …………………………………………………………………………… 53 4.5. Discussion ……………………………………………………………………………………………. 53 4.5.1. Cranial specializations related to head-first burrowing ………………… 53 4.5.1.1. Eye reduction ……………………………………………………………………………. 54 4.5.1.2. Widened cephalic lateral line canals ………………………………………… 55 4.5.1.3. Gill opening ………………………………………………………………………………. 55 4.5.1.4. Different orientation of the anterior section of the adductor mandibulae muscle complex ……………………………………………………………………………………………. 55 Table of contents 4.5.1.5. Skull shape and large insertion sites of body muscles on the neurocranium .................................................................................................... 56 4.5.2. Variable degree of head-first burrowing specializations in Anguilliformes ............................................................................................................................ 57 Chapter 5 – Cephalic Specialization in a Parasitic Eel, Simenchelys parasiticus 5.1. Abstract …………………………………………………………………………………………...… 61 5.2. Introduction ……………………………………………………………………………………...…61 5.3. Material and methods ………………………………………………………………………….62 5.4. Results ………………………………………………………………………………………………… 64 5.4.1. Cranial osteology of Simenchelys parasiticus ……………………………… 64 5.4.2. Cranial myology of Simenchelys parasiticus ……………………….…..…. 69 5.4.3. Cranial myology of Ilyophis brunneus ..................................... 72 5.4.4. Cranial myology of Synaphobranchus brevidorsalis …………………… 75 5.5. Discussion ………………………………………………………………………………………….. 77 5.5.1. Variation in cranial morphology of Synaphobranchidae ............. 77 5.5.1.1. Osteology ……………………………………………………………………………….. 78 5.5.1.2. Myology ........................................................................ 79 5.5.2. Cranial specializations in relation to parasitism ........................ 80 Chapter 6 – Cephalic Specializations in Relation to a Second Set of Jaws in Muraenids 6.2. Abstract …………………………………………………………………………………………….. 85 6.2. Introduction ………………………………………………………………………………………. 85 6.3. Material and methods ………………………………………………………………………. 86 6.4. Results ………………………………………………………………………………………………. 86 6.4.1. Cranial osteology: Arisoma gilberti ........................................ 86 6.4.2. Cranial myology: Arisoma gilberti ........................................... 92 6.4.3. Cranial osteology: Gymnothorax prasinus and Anarchias allardicei (Muraeninae and Uropterygiinae: Muraenidae) ....................................................... 95 6.4.4. Cranial Myology: Gymnothorax prasinus and Anarchias allardicei 100 6.5. Discussion ………………………………………………………………………………………… 104 Table of contents Chapter 7 – Head Morphology of the Pelican Eel, Eurypharynx pelecanoide 7.1. Abstract ……………………………………………………………………………………………… 109 7.2. Introduction ……………………………………………………………………………………….. 109 7.3. Material and methods ………………………………………………………………………… 111 7.4. Results ……………………………………………………………………………………………….. 112 7.4.1. Cranial Osteology …………………………………………………………………………. 112 7.4.2. Cranial myology …………………………………………………………………………… 115 7.5. Discussion …………………………………………………………………………………………… 115 Chapter 8 - General Discussion 8.1. Evolutionary pattern of structural changes in the head musculoskeletal System …………………………………………………………………………………………………………………………….….… 121 8.2. Adaptive versus non-adaptive morphological evolution ………...………..130 8.3. Some concluding remarks ……………………………………………………………….… 132 8.4. Insights for further research …………………………………………………………….. 133 Summary ……………………………………………………………….…………………………………………………….. 135 Litrature cited ………………………………..……………………………………………………………………….. 137 Publication list………………………………..……………………………………………………………………….. 157 c Acknowledgments Acknowledgments I wish to express my genuine and sincere gratitude to those who contributed to the process that led to this dissertation, as without their help I could not have fulfilled this task. Infinite thanks go to my supervisor and promoter Prof. Dr. Dominique Adriaens, who gave me the opportunity to start and complete my doctoral thesis in his research group. He not only greatly increased my insight in biology, especially in the wonderful world of vertebrate morphology, but he also is a truly inspiring scientist and person. His corrections and comments, that filled all spaces between my double-lined manuscripts with different colors, not only brought my writing to a higher level, but also gave more color to my personal and scientific experience. His unfailing enthusiasm and patience could always motivate me and I truly find it hard to find proper words to express my gratitude to him. “Thank you very much, best teacher I ever had.” I am deeply indebted to Prof. Dr. Walter Verraes for his help, especially when I arrived in Belgium. I wish to express my thanks to Prof. Dr. Ann Huysseune for increasing my knowledge of histology. My sincere thanks go to my colleagues in the research group ‘Evolutionary Morphology of Vertebrates’, Dr. Tom Geerinckx, Dr. Natalie De Schepper, Dr. Frank Huysentruyt, Dr. Stijn Devaere, Barbara De Kegel, Joachim Christiaens,