W&M ScholarWorks Dissertations, Theses, and Masters Projects Theses, Dissertations, & Master Projects 1974 Hydroids of the Pelagic Sargassum Community of the Gulf Stream and Sargasso Sea David Holland Rackley College of William and Mary - Virginia Institute of Marine Science Follow this and additional works at: https://scholarworks.wm.edu/etd Part of the Marine Biology Commons, and the Oceanography Commons Recommended Citation Rackley, David Holland, "Hydroids of the Pelagic Sargassum Community of the Gulf Stream and Sargasso Sea" (1974). Dissertations, Theses, and Masters Projects. Paper 1539617456. https://dx.doi.org/doi:10.25773/v5-waa7-4e36 This Thesis is brought to you for free and open access by the Theses, Dissertations, & Master Projects at W&M ScholarWorks. It has been accepted for inclusion in Dissertations, Theses, and Masters Projects by an authorized administrator of W&M ScholarWorks. For more information, please contact [email protected]. HYDROIDS OF THE PELAGIC SARGASSUM COMMUNITY OF THE GULF STREAM AND SARGASSO SEA A Thesis Presented to The Faculty of the School of Marine Science The College of William and Mary in Virginia In Partial Fulfillment of the Requirements for the Degree of Master of Arts by David Rackley * 1974 APPROVAL SHEET This thesis is submitted in partial fulfillment the requirement for the degree of Master of Arts in Marine Science \A ________ David Holland Rackley Approved, July 1974 Donald F./Boesch, Ph.D \QaJU CaJLJm . Dale R. Calder, Ph.D. C-Jci— ^ Frederick Y. Kazama, Ph.D Franklyn D/ Marvin L. Wass, Ph.D TABLE OF CONTENTS Page ACKNOWLEDGMENTS ........... iv LIST OF TABLES ............. v LIST OF FIGURES. vi ABSTRACT ......... ............ ....................... ix INTRODUCTION................... ............ 2 METHODS AND MATERIALS. ......... 6 RESULTS AND DISCUSSION .............. 11 Key.......................... ...... ............... 11 Systematic Account.......... .......... 14 APPENDIX ........... .......... 62 FIGURES. ............................ 76 LITERATURE CITED ............... 86 VITA ............. 94 AC KNOWLEDGMENTS I wish to express my appreciation to Dr. Dale R. Calder and Dr. Donald F. Boesch, under whose guidance this investigation was conducted, for their patience and criticism. I am also indebted to Dr. Victor G. Burrell, Jr. for his aid in the collection of samples, Dr. Harold J. Humm for his aid in the identification of Sargassum, Mr. Robert J. Diaz for his aid in statistical analysis and to Mrs. Linda Jenkins and Miss Melissa Forrest for typing the manuscript. Special thanks is extended to Mr. James P. Amon and to my wife, Mary, for their continuous moral support. LIST OF TABLES Table Page 1. Hydroid species represented in these Sargassum collections ........................ 9 2 . The dominant hydroid species and their relative frequency for each Sargassum form collected. 58-59 v LIST OF FIGURES Figure Page A. Station locations for pelagic Sargassum collections .................... 1. Rhizogeton fusiformis . ............. 76 2. Cladocorvne pelagica ....... ........... 76 3. C. pelacrica. .............. ........ 76 4. Coryne sp. ........... ....... 76 5. Zanclea costata ......... ....... 76 6. Garveia humilis ......... ...........76 7. Pennaria disticha ................ ....... 77 8. Halecium nanum.................... ........... 77 9. Halecium nanum............. .. ........... 77 10. Halecium sp. A. * . ........... 77 11. Halecium sp. A. ........... .. ........... .. 77 12. Halecium sp. B .................... ............. 77 13. Halecium sp. B. .............. ............. 77 14. Clytia cylindrica ............... ....... 78 15. Clytia cylindrica ............. 16. Clytia fragilis ........... .. 17. Clvtia hemisphaerica............. ............. 78 18. Clytia hemisphaerica............. ............. 78 19. Clytia noliformis ............... ............. 78 List of Figures (continued),*. Figure Page 20. Clytia noliformis............... ............. 78 21. Clytia noliformis . ......... 79 22. Campanularia sargassicola ......... 79 23. Campanularia sargassicola .................... 79 24. Qbelia hyalina. ................ 79 25. Obelia hyalina........... 79 26. Cuspidella humilis............... 79 27. Scandia mutabilis ............................... 80 28. Dynamena mayeri ........... 80 29. Dynamena quadridentata. 80 30. Sertularia inf lata. ............. 81 31. Sertularia inf lata.................... 81 32. Sertularia stookeyi .............. 81 33. Sertularia stookeyi . 81 34. Sertularia parvula.................... 81 35. Antennella secundaria ........ 82 36. Antennella secundaria ...................82 37. Halopteris diaphana ...... ................ 82 Halopteris diaphana ............. 82 39. Plumularia margaretta ........ ......... 83 40. Plumularia margaretta ........... 83 41. Plumularia strictocarpa ........................ 83 v i i List of Figures (continued). Figure Page 42. Plumularia strictocarpa . .................. 84 43. Plumularia strictocarpa ............ 84 44. Plumularia sp. .................... 85 45. Plumularia s p . ........... 85 46. Aglaophenia latecarinata............. 84 47. Aglaophenia latecarinata. .................... 84 48. Aglaophenia latecarinata. ........... 84 ABSTRACT Pelagic Sargassum was collected during late spring, ■>. early summer, late summer, and late winter from stations in the Gulf Stream and Sargasso Sea. Collections were analyzed for the presence of hydrozoan polyps, hydroid affinity for particular Sargassum, their microhabitat distribution on the Sargassum, and their relative abundance. A total of 29 hy­ droid species was found, including 3 species not previously recorded from Sargassum. Three additional species are ap­ parently new. Detailed descriptions, illustrations, recent taxonomic nomenclature, and a key to the species found during this investigation are provided. i x HYDROIDS OF THE PELAGIC SARGASSUM COMMUNITY OF THE GULF STREAM AND SARGASSO SEA INTRODUCTION North American Atlantic hydroids have received almost continuous study since Stimpson's (1854) synopsis of the invertebrates of Grand Manan Island, New Brunswick (Fraser, 1944). This has been the result of a relatively small num­ ber of scientist, yet despite their extensive contributions, the hydroid fauna of many areas or particular habitats remains poorly known. Such a habitat is the pelagic Sargassum com­ munity of the Gulf Stream and Sargasso Sea of the North At­ lantic. Burkenroad (in Parr, 19 39) presented the only detailed study involving the hydroids associated with Sargassum. In it he identified sixteen hydroids from pelagic Sargassum in the Gulf Stream, Sargasso Sea, and Gulf of Mexico. Hydroid dominance and specificity were also determined for the differ­ ent Sargassum species or types distinguished by Parr (1939). Burkenroad observed that Clytia noliformis (McCrady) is the usual dominant associated with the narrow leafed Sargassum nataris (L.) Meyen types I, II, and IX; another dominant hydroid, Aglaophenia latecarinata Allman, is usually associated with the broader leafed Sargassum fluitans type III and natans type VIII. Burkenroad also noted that the hydroid fauna Sargassum v. Winge (tentitively identified as the benthic 2 alga Sargassum ramifolium) was dominated by either Clava sp. Gmelin (RhizOgeton fusiformis ? Agassiz) or Syncoryne sp. Ehrenberg. Other dominants occasionally appeared such as Sertularia mayeri Nutting on S. natans IX, or Sertularia flowersi Nutting on S^. natans IX and -S_. natans II. The other broad leafed form, Sargassum fluitans VIII was reported on occasion to be overgrown with S. flowersi, 53. mayeri, S_. inflata Versluys, S. turbinata Lamouroux, Dynamena quad- ridentata Ellis and Solander or Plumularia margaretta (Nutting). Morris and Megelberg (1973) compiled a checklist, with descriptions and illustrations, of 43 hydroids which have been reported from Sargassum. Fraser*s (1912, 1944) publica­ tions were the principal sources used for their checklist, and unfortunately most of the taxonomic changes put forth since those publications are not included. Also not included were the improved illustrations of many tropical hydroids since Fraser's monographs, such as those by Vervoort (1968) and Van Gemerden-Hoogeveen (1965) from the Caribbean, which have greatly facilitated hydroid identification. Furthermore, only brief remarks are given by Morris and Mogelberg concern­ ing hydroid occurrence on specific Sargassum species. Bennitt (1922) surveyed the hydroids of Bermuda, report­ ing 18 species from Sargassum, but like Fraser, did not dis­ cuss the Sargassum types from which the hydroids were found. Also at this time, Hentschel (1922) studied the epifauna of Sargassum, which included several hydroids. He estimated specificity based on the number of polyps found on Sargassum 4 thali 10 cm long and noted that there was always a dominant species (usually Aglaophenia on S. fluitans Bbrgesen and Clytia on £3. natans) . Hentschel also mentioned succession among the attached forms in which the growing apexes of the Sargassum are colon­ ized first by hydroids followed by the bryozoan Membranipora Ctuberculata (Bush);?] which establish on the older portions of the alga. Ryland (19 74) made similar observations on S. natans and attributed such behavior to the presence of tannins in the apical portions of the stems (Conover and Sieburth, 19 64; Sieburth and Conover, 1965) which inhibit the establishment of surface microfauna necessary for the settlement of larger epibionts. Wingess (19 23) study of the Sargasso Sea made during