Wollschlager Thesis
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Nematocysts of the Invasive Species Cordylophora caspia THESIS Presented in Partial Fulfillment of the Requirements for the Degree Master of Science in the Graduate School of The Ohio State University By Jennifer Wollschlager, B.S. Graduate Program in Evolution, Ecology and Organismal Biology The Ohio State University 2011 Master's Examination Committee: Meg Daly, Advisor John Freudenstein Norman Johnson Copyright by Jennifer Wollschlager 2011 Abstract Although there is significant genetic diversity within the hydroid Cordylophora caspia, the species has not been formally split into genetically defined distinct species. This is due in part to the physiological and morphological plasticity of C. caspia : all morphological characters used to distinguish species in Cordylophora are phenotypically plastic in this species and unreliable for classification. One potential source of characters not yet explored in C. caspia are nematocysts. Nematocysts have been widely used in taxonomy of Cnidaria, and in some cases, have a strong functional component and so may be subject to or correspond with ecotype. Elucidating the cnidom of lineages of C. caspia will help determine whether or not nematocysts are good indicators for different genetic lineages of this group, and whether nematocysts are functionally differentiated in populations from different habitats. A one-way ANOVA was used to determine if means between populations differed for euryteles or desmonemes, the two types of nematocysts found in C. caspia. Means between populations differed for euryteles (p<0.001) and desmonemes (p<0.001), although no correlation could be found between clade or salinity. This indicates that nematocysts within C. caspia are not phenotypically plastic or taxonomically informative. Nematocysts may be correlated to another environmental factor, such as prey type, size, and abundance in the location of each population. These morphological characters may still aid in distinguishing more distantly related species such as Cordylophora japonica. Further study of reproductive compatibility and ii morphometric features (e.g., branching pattern, hydrocaulus length) may provide some means of separating lineages in this cosmopolitan invasive species. iii Acknowledgments Thanks are due to Meg Daly, Paul Larson, Anthony D’Orazio, and Jennifer Yi for collection aid, Abby Reft for Scanning Electron Micrographs and collection aid, Nadine Folino-Rorem for providing animals, Meg Daly, Norman Johnson, and John Freudenstein for input on my thesis, and The Ohio State University. iv Vita May 2008…………………………..B.S. Marine Science, Biology Track, Eckerd College 2008 to present……………………..Graduate Teaching Associate, Department of Evolution, Ecology, and Organismal Biology, The Ohio State University Fields of Study Major Field: Evolution, Ecology and Organismal Biology v Table of Contents Abstract ............................................................................................................................... ii Acknowledgments............................................................................................................ ivv Vita ...................................................................................................................................... v List of Tables ................................................................................................................... viii List of Figures .................................................................................................................... ix Introduction ......................................................................................................................... 1 Diversity and Systematics of Cordylophora caspia ........................................................ 7 A Potential Solution for this Species Complex ............................................................. 12 Methods............................................................................................................................. 18 Sample Collection ......................................................................................................... 18 Nematocyst Measurement ............................................................................................. 18 DNA Extraction, Amplification, and Sequencing ......................................................... 20 Statistical Analysis of Nematocyst Sizes ...................................................................... 21 Results ............................................................................................................................... 23 Discussion ......................................................................................................................... 38 vi References ......................................................................................................................... 43 vii List of Tables Table 1. Amplification primers ........................................................................................ 21 Table 2. P-values from a one-way ANOVA testing between polyp averages ................. 24 Table 3. Summary of statistical groups............................................................................ 30 Table 4. Summary of eurytele data .................................................................................. 31 Table 5. Summary of desmoneme data ............................................................................ 37 viii List of Figures Figure 1. Sketch of a Cordylophora colony....................................................................... 2 Figure 2. Phylogenetic tree based on mtDNA ................................................................... 5 Figure 3. Global distribution of Cordylophora lineages .................................................... 6 Figure 4. Scanning electron microscope image of a discharged eurytele capsule ........... 15 Figure 5. Scanning electron microscope image of a discharged desmoneme capsule ..... 16 Figure 6. Stained euryteles and desmonemes .................................................................. 17 Figure 7. Normal quantile plot of residuals of euryteles ................................................. 26 Figure 8. Boxplot of eurytele lengths by polyp and population ...................................... 27 Figure 9. Boxplot of eurytele lengths by population ....................................................... 28 Figure 10. Boxplot of eurytele lengths by groups ............................................................. 29 Table 11. Normal quantile plot of residuals of desmonemes ........................................... 33 Table 12. Boxplot of desmoneme lengths by polyp and population................................ 34 Table 13. Boxplot of desmoneme lengths by population ................................................ 35 Table 14. Boxplot of desmoneme lengths by groups ....................................................... 36 ix Introduction The Ponto-Caspian invasive hydrozoan Cordylophora caspia is one of only a handful of cnidarians that live in fresh rather than marine waters (Janowski et al. 2008). It can tolerate a range of salinities, from brackish (~ 15 ‰) to freshwater, giving it a wide range of suitable habitat (reviewed in Roos 1979; Folino 2000). In a laboratory setting, C. caspia can survive at salinities as high as 30 ‰ (Kinne 1958). It is a clonal organism that also reproduces sexually, allowing it to be able to spread over substrate rapidly and spread planulae to new substrate locations. It grows by adding more hydranths to hydrocauli, the upright branches, or by extending the attached stolon (hydrorhiza) for more hydrocauli (Fig. 1) (Kinne 1958; Fulton 1962; Jormalainen et al. 1994). Gonophores, the reproductive structures, branch from the hydranths (Fig. 1) (Jormalainen et al. 1994). Cordylophora caspi a is often associated with zebra mussels ( Dreissena polymorpha ), another Ponto-Caspian invasive species, and, like D. polymorpha , it is also biofouling, causing industrial and ecological problems (Folino 2000; Musko et al. 2008). The spread of C. caspia is difficult to control because colonies are able to “die back” to structures called menonts, in which the tissue shrinks back into the stolon (Fig. 1). Menonts are ecologically resilient and allow a colony to survive stressful and changing environments, because a colony can regenerate from a menont when environmental 1 conditions are right (Roos 1979; Folino 2000). This diversity of growth and reproductive mechanisms and its broad salinity tolerance enhance the capacity of C. caspia to invade. Figure 1. A. Part of a Cordylophora colony with gastrozooids, female gonophores, and epiphauna. Scale is 5 mm. Camera lucida drawing (Roos 1979). B. A drawing of the anatomy of an upright stalk and hydrorhiza of Cordylophora (Folino 2000 re-drawn from Marcum and Dichl 1978). C. Menonts in hydrorhiza and base of hydrocaulus. Scale is 1 mm. Camera lucida drawing (Roos 1979). Although its success as an invader comes largely from being clonal and phenotypically plastic (Roman and Darling 2007), there is also evidence for multiple invasions of C. caspia into different localities throughout the world (Folino-Rorem et al. 2009). Multiple invasions greatly increase genetic diversity of the invader species in the new habitat, and thus are thought to increase invasion success (Roman and Darling 2007). Multiple invasions can even increase the genetic diversity of an invasive 2 population to higher