Locating Craspedacusta Sowerbii Polyps

Locating Craspedacusta sowerbii polyps Taylor L. Brandt1 INTRODUCTION There are few freshwater cnidarians, and even fewer that can be found within the freshwaters of North America. The most common freshwater cnidarian in North America are those in the genus Hydra, the second being the non-native Craspedacusta sowerbii, or the freshwater jellyfish. Found throughout North America, the common name of C. sowerbii is a misnomer as it belongs to the group hydrozoa, along with the hydra, and is not a true jellyfish (Peard 2017). Craspedacusta sowerbii has two main body forms that can be studied: the more commonly known bell-shaped medusa and the smaller, harder to locate polyp. Craspedacusta sowerbii medusas were found in Otsego Lake in the late summers of 2014 and 2016 (P. Lord, personal communication). The polyp has not previously been located in Otsego Lake. Locating the polyp in Otsego Lake could help in better understanding the dynamics of the presence of the medusa body form. To positively identify C. sowerbii polyps, morphological differences and DNA sequencing will be necessary. METHODS Samples of aquatic vegetation, substrate, and the surrounding water were taken by collection of water in a bucket, rake tosses, snorkeling, and SCUBA diving from Otsego Lake. The locations of the samples were taken from Rat Cove, Peggs Point, and Blackbird Bay. Of these samples, 50 subsamples were examined in white trays under a dissecting microscope. Potential C. sowerbii polyps found, as well as some hydra samples for comparison, were preserved using the following technique of hydra preservation. Cnidarians were placed in 10% ethanol for 1 to 2 minutes, then placed in formalin for 24 hours, and finally transferred to 70% ethanol (Thorp and Rogers 2014). “Possible” polyps and selected hydra were stained and mounted on permanent whole mount slides to view using light microcopy. The “possible” polyps were examined for cnidocytes by comparing these cells with preserved hydra cnidocytes, which would assist in identifying the potential polyp as C. sowerbii. RESULTS Of the 50 trays examined, four contained potential Craspedacusta sowerbii polyps, giving a total of four “possible” polyps. Images were captured of these “possible” polyps 1 SUNY Oneonta Biological Field Station Intern, summer 207. Current affiliation: SUNY Oneonta. after they were prepared for light microcopy (Figure 1). Hydra were present within the trays examined. Hydra were enumerated in 12 of the trays, with 147 hydra counted in total. Cnidocyte cells on hydra were morphologically compared to those on the “possible” polyps (Figure 2). The use of light microscopy was inconclusive for morphological identification. TEM microscopy would be necessary to determine if the four possibly polyps are in fact Craspedacusta sowerbii polyps. Figure 1. Images of “possible” polyps taken using light microscopy. Figure 2. Top row: magnified cnidocytes found on a hydra. Bottom row: magnified cnidocytes found on a potential hydra. Four C. sowerbii polyps may have been found, although the “possible” polyps could merely have been deformed hydra or some other aquatic organism. DNA sequencing would allow for a more conclusive determination but would require an increase in the number of samples and polyps. DNA sequencing would be the next step in determining if the “possible” polyps are C. sowerbii polyps. REFERENCES Peard, T.L. http://freshwaterjellyfish.org Thorp, J.H., and Rodgers D.C., eds. Thorp and Covich’s Freshwtaer Invertebrates: Ecology and General Biology. Vol. 1. 176-177. Elsevier, 2014. .

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