Understanding the Morphology and Distribution of Nematocysts in Sea Anemones and Their Relatives
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Understanding the morphology and distribution of nematocysts in sea anemones and their relatives DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University By Abigail Julia Reft Graduate Program in Evolution, Ecology and Organismal Biology The Ohio State University 2012 Dissertation Committee: Dr. Marymegan Daly, Advisor Dr. John V. Freudenstein Dr. William Ausich Copyright by Abigail Julia Reft 2012 Abstract Cnidaria includes organisms diverse in body form, life-cycle, and ecology and includes corals, sea anemones, Hydra, and jellyfish. Despite this diversity, cnidarians are easily recognized by the presence of small intracellular stinging capsules called nematocysts. This structure, which consists of a tubule attached at one end that typically bears spines, are a synapomorphy for the group as all members of the phylum produce them. These structures are used in many aspects of everyday biology including defense against predators, attachment to substrate, capture of prey, and aggression against other cnidarians. Although the basic construct of the nematocyst is simple, high amounts of morphological variation in tubule and spine features are found throughout the phylum. This variation has been difficult to interperate for several reasons including the need for advanced microscopy techniques to visualize the morphology, disagreements among authors as to how to best circumscribe and organize the variation that is observed, and the lack of many broad, phylogenetically based analyzes to put this diversity in an evolutionary context. Because the interpretation of nematocyst diversity is so problematic, the utility of nematocyst as phylogenetic characters for cnidarians is unclear. To determine if nematocysts can be used phylogenetically requires a better understanding of the morphological variation itself and its distribution within cnidarians. To address these issues, I performed a morphological survey of nematocysts using advanced microscopy techniques (differential inference contrast, scanning and ii transmission electron microscopy). This work included assessing the distribution and morphology of a single nematocyst character, the apical structure, to determine if it contained any phylogenetic signal, fully documenting the diversity of a group of nematocyst morphologies that have been particularly confusing (the rhabdoids or nematocysts with a wider diameter basal tubule), placing this diversity on phylogenetic trees to look for patterns of evolution, and utilizing a multivariate approach to assess the morphological groups implied by qualitative characters. The apical structure study found that an individual morphological character does provide strong phylogenetic information. Three morphological states are present and they each represent a monophyletic group (Medusozoa, Anthozoa, and the anthozoan order Actiniaria). For the Actiniaria, this provides a morphological synapomorphy that this group has previously lacked. In fully describing the variation of rhabdoid nematocyst forms, I recognize nine distinct morphologies. Some of these morphologies (particularly some of the p-rhabdoid forms) agree closely with previously hypothesized morphological groupings. However, other morphologies are recognized as distinct for the first time. New names are given to these nematocyst morphologies to help clarify the exact distribution of variation. Placing this variation in a phylogenetic context reveals that the presence/absence of certain morphologies does define monophyletic groups. Clarifying the confusion over which cnidarians have each morphology results in a clearer pattern morphotypes shared amongst certain taxa (i.e. the p-rhabdoid B forms in the Metridiodea). iii Finally, using quantitative characters in a multivariate analysis reveals support for many groups of nematocyst morphology. Using qualitative features to group the variation is effective in finding groups of morphologies that share shape features as quantified by a multivariate analysis. iv Dedication Dedicated to my parents, Joyce A. and Chester S., for all their love and support, and Prof. Michael LaBarbera for introducing me to the wonderful world of invertebrates. v Acknowledgments A project such as this one is impossible to complete without the help and support of many people both professionally and personally. First and foremost, I would like to thank my advisor, Meg Daly for taking me under her wing while I was working on my masters and supporting me through the completion of my Ph.D. I know of no other scientist could nurture my love of all things invertebrate and Asian like she has; I could not have asked for a better academic mother. I also want to thank the other members of my committee, John Freudenstein and Bill Ausich. In and out of class, I have learned much about both systematics and being a scientist from both and have always enjoyed learning about the plant and paleontological perspectives on the field. Also, I thank those that assisted me in fieldwork and hosted me while I was in foreign countries. Specifically, I thank Dr. Shin Kubota of the Seto Marine lab of Kyoto University for his assistance (and for the onsen) during my time in Japan, Dr. Jun-Im Song and her lab at Ewha Womens University for their assistance during my time in South Korea (and for the lovely trip to Jeju), and Dr. Bernard Picton of the National Museums of Northern Ireland for his assistance (and for the warm hospitality of his family) in Northern Ireland. Others to thank in collecting material include Anthony vi Montgomery, Estefanía Rodríguez, Neil Blackstone, and Paulyn Cartright; thank you for providing some of the raw material needed to complete my project. The Daly lab has been my home for the last six years and I thank all members both past and present for their help and friendship. Specifically, thanks to Annie Lindgren for always providing perspective, Luciana Gusmaõ for the many long discussions about anything and everything, Estefanía Rodríguez for endless help and support, Paul Larson for fun atmosphere in lab, Nick Skomrock for the fun and gossip, and Jason Macrander for the events and parties. Finally, I would like to thank my family for being so supportive even if they do not completely understand what I am doing here. My parents in particular have always encouraged me to grow and explore the world around me and never discouraged me from trying new (and sometimes hard things). Thanks so much for all the love and support. vii Vita October 1980..................................................Born: Chicago, IL, USA 2002................................................................B.A. Biology, University of Chicago 2005................................................................M.A. Ecology and Evolutionary Biology, University of Kansas 2006 to present ..............................................Graduate Teaching Associate, Department of Evolution, Ecology and Organismal Biology, The Ohio State University Publications Voight JA, Lee RW, Reft AJ, Bates AE. 2012. Scientific gear as a vector for alien species at deep-sea hydrothermal vents. Conserv Biol DOI: 10.1111/j.1523-1739.2012.01864.x Reft AJ, Daly M. 2012. Morphology, distribution, and evolution of apical structure of nematocysts in Hexacorallians. J Morph. 273: 121-136. viii Daly M, Gusmao LC, Reft AJ, Rodriguez E. 2010. Phylogenetic Signal in Mitochondrial and Nuclear Markers in Sea Anemones (Cnidaria, Actiniaria). Integr Comp Biol 50: 371- 388. Reft, AJ, Westfall, JA, Fautin DG. 2009. Formation of the apical flaps in nematocysts of sea anemones (Cnidaria: Actiniaria). Biol Bull 217: 25-34. Reft AJ, Voight J. 2009. Sensory structures on the siphons of wood-boring bivalves (Pholadidae: Xylophagainae: Xylophaga). Nautilus 123:43-48. Sierwald P, Reft AJ. 2004. The Millipede Collections of the World. Fieldiana, Zoology New Series 103, Publication number 1532, 1-100. Fields of Study Major Field: Evolution, Ecology, and Organismal Biology ix Table of Contents Abstract............................................................................................................................... ii Dedication........................................................................................................................... v Acknowledgments.............................................................................................................. vi Vita...................................................................................................................................viii List of Tables .................................................................................................................... xv List of Figures................................................................................................................. xvii Chapter 1: Introduction.................................................................................................. 144 Overview of the chapters.........................................................................................3 References................................................................................................................6 Chapter 2: Morphology, distribution, and evolution of apical structure of nematocysts in Hexacorallia.........................................................................................................................8 Introduction..............................................................................................................8