SHELL GROWTH AND ECOLOGY OF RECENT BRACHIOPODS FROM SCOTLAND AND NEW ZEALAND BY GORDON BARRETT CURRY, B.A.(Mod.); (T.C.D.). September 1979 A thesis submitted for the degree of Doctor of Philosophy of the University of London and for the Diploma of Membership of the Imperial College. Department of Geology, Royal School of Mines, Imperial College, London, SW7. 1 SHELL GROWTH AND ECOLOGY OF RECENT BRACHIOPODS FROM SCOTLAND AND NEW ZEALAND by Gordon B. Curry. ABSTRACT The ecology, growth rate, and population structure of the Recent articulate brachiopod Terebratulina retusa (Linnaeus) are described. The specimens studied are pred- ominantly attached to the mussel Modiolus modiolus, (Linnaeus), which occur in dense beds around the margins of a deep (220 metres) depression off the west coast of Scotland. Length-frequency histograms prepared from large represent- ative samples collected at regular intervals during 1977 - 1979 are unimodal and right-skewed. Prominent modes within the overall unimodal length-frequency histograms correspond to biannual settlement cohorts. Spawning occurs regularly in late spring and late autumn, and is initiated at temperatures of 10°C - 11°C; the available evidence indicates that the entire reproductive cycle, from spawning to settlement, occurs within 3 weeks. Newly-settled specimens grow rapidly to a length of 2.75mm within 3 months; the animals grow (initially by 4mm per year) throughout life at a progressively reduced rate. Growth slows or ceases during winter in all but recently settled specimens. The maximum life-span is 7 years. Mortality rate remains constant from the first year of life onwards; the causes of death are not apparent. Growth-lines form biannually, at times of pronounced envir- onmental disturbance. In Part II the results of growth-line analyses of numerous Recent and fossil brachiopod populations are des- cribed. In temperate-latitude, shallow-water habitats growth-lines form biannually or annually - alternate large and small increments representing 'summer' and 'winter' growth are diagnostic of the former strategy; the latter is a special case of the former due to the cessation of growth in winter because of unfavourable conditions. Regularly- spaced growth-lines in brachiopod populations from polar and abyssal habitats are thought to form annually; the reduced growth-rate in such habitats is attributed primarily to the lower temperatures and reduced food availability. Preliminary growth-line analyses of fossil brachiopod pop- ulations are encouraging; the great potential of growth- line analysis as a source of precise palaeoecological data is discussed. 2 ACKNOWLEDGEMENTS I am greatly indebted to my joint supervisors, Dr. C.H.C.Brunton, Dept. of Palaeontology, British Museum (Natural History), London, and Dr.P.Wallace, Dept. of Geology, Imperial College, London, for their advice, guid- ance, and encouragement; their willingness to discuss the subject at all times was greatly appreciated. Dr. H.W.Ball kindly granted me space and use of facilities within the Dept. of Palaeontology; many other members of this Dep- artment also contributed greatly by discussing various prob- lems and giving freely of their academic and technical exp- ertise, in particular Dr. R. Cocks, Mr. E. Owen, Mr. A. Rissone, Dr. M. Howarth, and Mrs.P.P. Hamilton-Waters. Miss L. Cody kindly helped with the typing, and arranged for German translations by Mrs. 0. Ferguson. I also gratefully acknowledge the help of Mr. D.Claugher and the technical staff of the Electron Microscopy Unit, B.M.(N.H.), for instruction in the techniques of specimen preparation and the use of the Scanning Electron Microscopes. Dr. A. Fincham, Dept. of Zoology, B.M.(N.H.), kindly agreed to the installation of an aquarium system within a constant temperature room under his charge. Mr. J. Hoar of the Photographic Studios, B.M.(N.H.), expertly re-photographed the plates. I am very grateful to many members of staff of the Dunstaffnage Marine Research Laboratory, Oban, Scotland, for their willing co-operation, and for the collection of regular samples during my absence in New Zealand and USA; in 3 particular I would like to thank the Director, Mr R.Currie, for granting me space and use of facilities, Dr.A.Ansell, Mr. C.Comely, Mrs. L.Robb, Miss F.Newman, Mr.. S.Knight, and the Captains and crews of the R/V 'Calanus' and 'Seol Mara'. My visit to New Zealand and USA would not have been possible without the co-operation and encouragement of Dr. G.A.Cooper, Dept. of Paleobiology, N.M.N.H., Washington, DC, and Dr. D.I.Mackinnon, Dept. of Geology, Univ. of Canterbury, Christchurch; their consideration and academic expertise greatly alleviated the many problems associated with such a venture. Professor R.Crawford, Christchurch, and Dr, P. Kerr, Washington, kindly granted me space and the use of facilities during my visits. I also wish to acknowledge the help of Dr.P.Andrews, N.Z. Geological Survey; Professor J.Jellitt, and the Captain and Crew of R/V 'Munida', Portobello Marine Research Laboratory, Dunedin; Dr J.Richardson, N.Z. Oceanographic Institute, Wellington; and Dr.P.Redfern, N.Z. Dept. of Agriculture and Fisheries, Wellington. Dr. A. Williams, Principal's Lodgings, Univ. of Glasgow, suggested the topic of this thesis, and his continuing interest, support, and encouragement is a great stimulus, and is gratefully acknowledged. Finally, I wish to express my appreciation to the Dept. of Education, (Northern Ireland), for a Postgraduate Studentship, and to the British Council for a Commonwealth University Interchange Scholarship which provided the travel funds for the trips to New Zealand and USA. 4. CONTENTS PAGE ABSTRACT . 1 ACKNOWLEDGEMENTS . 2 LIST OF CONTENTS . 4 LIST OF TABLES . 7 LIST OF TEXT-FIGURES . 8 FRONTISPIECE . 10 PART I ASPECTS OF THE ECOLOGY AND BIOLOGY OF TEREBRATULINA RETUSA (LINNAEUS) CHAPTER I.1. Introduction . 11 I.2. Materials . 16 Section I.2.1. Collection . 16 1.2.2. Aquaria . 19 CHAPTER I.3. Ecology of T.retusa . 26 Section I.3.1. Distribution . 26 1.3.2. Depth . 30 1.3.3. Temperature . 33 1.3.4. Substrate . 42 1.3.5. Current . 47 I.3.6. Salinity . 49 I.3.7. Associated fauna . • 51 CHAPTER 1.4. Population structure and dynamics of T.retusa . 53 Section I.4.1. Introduction . 53 I.4.2. Size-frequency diagrams . 54 I.4.3. Growth rate . 71 I.4.4. Mortality . 88 5 Section I.4.5. Life-history . 92 I.4.6. Comparison with theoretical model. 96 I.4.7. Comparison with other studies . 99 CHAPTER I.5. Biology of T.retusa . 113 Section I.5.1. Lophophore and feeding . 113 I.5.2. Reproduction . 124 Subsection 1.5.2.1. Introduction . 124 1.5.2.2. Gonad development . 125 1.5.2.3. Spawning season . 132 1.5.2.4. Fertilisation 138 1.5.2.5. Larval development • 140 I.5.2.6. Settlement . 143 PART II GROWTH OF RECENT AND FOSSIL BRACHIOPODS CHAPTER II.1. Introduction . 149 I1.2. Materials . 151 II.3. Methods . 152 Section 11.3.1. Electron microscopy . 152 11.3.2. Growth-line measurement techniques 154 CHAPTER II.4. Microscopic growth-lines . 171 CHAPTER I1.5. Analysis of Macroscopic growth-lines 181 Section II.5.1. Recent temperate latitude brachiopods - N.Hemisphere . 181 Subsection II.5.1.1. Terebratulina septentrionalis (Couthouy). 181 II.5.1.2. Laqueus californicus (Koch) . 185 Section 1I.5.2. Recent temperate latitude brachiopods - $.Hemisphere . 190 Subsection 1I.5.2.1. Terebratella inconspicua (Sowerby) . 190 ▪• 6 Subsection I2.5.2.2. Notosaria nigricans (Sowerby) . 199 I2.5.2.3. Neothvris lenticularis (Deshayes) . 204 II.5.2.4. Liothvrella neozelanica, Thomson . 207 11.5.2.5. Magellania venosa (Solander) . 211 I2.5.2.6. Gvrothvris mawson& antipodesensis, Foster . 214 Section II.5.3. Recent polar brachiopods . 217 Subsection IL5.3.1. Liothvrella uva notorcadensis (Jackson) 217 1I.5.3.2. Magellania fragilis, Smith . 223 Section II.5.4. Recent abyssal brachiopods . 226 Subsection II.5.4.1. Macandrevia baveri, Cooper . 226 Section II.5.5. Fossil brachiopods . 230 Subsection II.5.5.1. Magadina sp. 230 1I.5.5.2. Bouchardia antarctica, Buckman . 233 I1.5.5.3. Pachvmagas sp. 237 CHAPTER II.6. Discussion . 239 PART III. Appendices 243 Appendix I. The N.Atlantic species of Terebratulina 243 II.Free-lying brachiopods - the evolutionary implications 246 III.Comments on the function of Caeca 250 IV.BRITISH BRACHIOPODS (with C.H.C. Brunton) . 252 PART IV. REFERENCES . • . • . 253 PART V. PLATES 1 - 17 • . 264 7 TABLES PAGE I - SAMPLE STATIONS . • 27 II - SUBSTRATE OF ATTACHMENT . 41 III - ANALYSIS OF MARCH 1977 LENGTH-FREQUENCY HISTOGRAM 68 IV - AGE-GROUPS IN MARCH 1977 SAMPLE . 70 V - ANNUAL GROWTH RATE OF T.RETUSA . 73 VI - MODE PROGRESSION - 4th and 5th YEAR-GROUPS. 75 VII - MODE PROGRESSION - JUVENILES 75 VIII - GROWTH-LINE ANALYSIS - T.RETUSA . 76 IX - GROWTH RATE ANALYSIS OF R.ROSTRATA 110 X - GROWTH RATE ANALYSIS OF T.SEPTENTRIONALIS . 181 XI - GROWTH RATE ANALYSIS OF T.INCONSPICUA . 191 XII - GROWTH RATE ANALYSIS OF T.INCONSPICUA . 194 XIII - GROWTH RATE ANALYSIS OF G. MAWSONI ANTIPODESENSIS . • . • • 214 XIV - GROWTH RATE ANALYSIS OF MAGADINA SP . • 230 8 FIGURES PAGE 1 - Internal and external shell features of T.retusa 15 2 - Distribution Map . 28 3 - Brachiopod aquaria . .. 32 4 - Temperature graphs - Firth of Lorne and aquaria . 35 5 - (A) % of mussels with attached brachiopods; (B) correlation of modes in length-frequency and width-frequency histograms- March 1977 . 45 6 - Population structure - March 1977 -T-. 60 7 - Length-frequency histograms - May, July, August, 1977 . 64 8 - Length-frequency histogram - January 1979,(A); Age pyramid (B.); Growth curve (C); Survivorship curve (D). 67 9 - Sexual dimorphism in growth rate . 80 10 - Stylised growth rate, survivorship, and size-frequency curves .