The parasite community of yellow perch (Perca flavescens) from Canadarago Lake Kerianne Engesser 1, Heidi Gorton 1, Byron Peregrim 1, Victoria Pigott 1, Jessica Schoeck 1, Timothy Pokorny 2, and Florian Reyda 3 INTRODUCTION Parasites are commonly a forgotten yet important part of any ecosystem (Roberts et al., 2012). There are multitudes of parasitic species that dwell in a variety of different hosts, or that are free-swimming organisms. Yellow perch (Perca flavescens), which inhabit much of the lakes in central New York, have a wide ranged diet consisting of other fish, insects, and plant material, as well as other organisms. In correlation with their diets they interact with many trophic levels in the ecosystems of these lakes (Wilkins et al. 2002). They are common prey of larger fish, birds, and mammals, which hunt around or in these lake environments. Due to these organisms interactions with both predator and prey in their environment, they serve as both intermediate and definitive hosts to more than a dozen parasitic species (Hoffman 1999). Many of the parasites that can be found in these fish have complex life cycles that require intermediate hosts. Fish will pick up these parasites through the food they eat, through the water (if it is a freeswimming parasite), or from contact with other organisms throughout their aquatic environment (Johnson et al. 2004). This year we performed a follow-up of a study conducted in 2016 (Doolin et al. 2017), in which P. flavescens were collected from 2 different lakes, Otsego Lake and Canadarago Lake. The authors in that study compared the presence of parasites within fish from two different bodies of water. They then performed full necropsies, resulting in the acquisition of 18 different species of parasites. The parasite faunas of both lakes overlapped for the most part, though there were a few differences (Doolin et al. 2017). For example, during that study it was found that "ick" was present in Otsego Lake but not in any of the P. flavescens examined in Canadarago Lake. The goal of the current study is to compare results from the 2016 survey (Doolin et al. 2017) with our own 2017 survey. However, due to inadequate ice build up on Otsego Lake last winter, the fish used in this study were only caught from Canadarago Lake. Full necropsies of 32 P. flavescens, obtained from Canadarago Lake were performed, and all parasites that were encountered were documented. METHODS Perca flavescens were collected via ice fishing. A total of 32 were collected from Canadarago Lake between the dates of 19 January and 18 February 2017. All fish collections were conducted under the guidelines issues to F. Reyda by the NYS DEC (permit #1647). Fish were kept alive in aquaria at the SUNY Oneonta Biological Field Station until the time of 1 SUNY Oneonta undergraduate student, Biology Department, SUNY Oneonta. 2 Aquatic Biologist 1, Region 4, New York State Department of Environmental Conservation. 3 Associate Professor and Researcher, Biology Department and Biological Field Station, SUNY Oneonta.
dissection. Approximately 15 minutes before dissection, fish were anesthetized in a water solution containing Tricaine Methanosulfate and tap water (.3g/L) following SUNY Oneonta IACUC Protocol 201303. Once fully sedated, the anesthetized specimens were measured to the nearest millimeter, photographed alongside their appropriate label for laboratory record, and then examined. Full necropsies beginning with a ventral incision were performed. External surfaces were scraped and the scrapings were mounted upon glass slides which were then examined using a compound light microscope. Organs, body cavities, and external structures such as fins were examined under a stereoscope. A saline solution (7.5g NaCL / 1L H2O) was used to prevent organs from drying out during examination. If any parasites were found during dissection, they were extracted and placed in clean dishes filled with saline solution. Parasites were separated according to taxon and the host organ in which they were found. They were then preserved in 17x60mm screw thread glass vials filled with preservative fluids that varied depending on the parasites taxon and the purpose of their preservation. Parasites that were to be stained and further examined were kept in 70% ethanol (leeches and large nematodes), hot formalin (cestodes, trematodes, monogenes, and small nematodes), or tap water that was later replaced with formalin as was the case for acanthocephalans. Specimens from Phylum Ciliata were not preserved due to the difficulty of preserving them, but were rather photographed using a Leica DSC295 camera mounted on a Leica DM2500 compound microscope. Specimens that were to be used for DNA sequencing were preserved in 100% molecular-grade ethanol and kept at 4 C. Following preservation, specimens that were to be mounted permanently upon glass slides were hydrated with a graded ethanol/water treatment, stained with Delafield s hematoxylin, and then dehydrated with a graded ethanol/water treatment. Specimens were then washed with methyl salicylate and mounted in Canada balsam on 25x75mm glass slides with glass coverslips (22x22mm). Parasites were identified with the aid of taxonomic reference literature (Amin 2002; Bray et al. 2008; Caira et al. 2012; Hoffman 1999; Kuchta et al. 2007; Moravec 1998; Schell 1985) RESULTS A total of 16 species of parasites were found in P. flavescens in this study (Table 1). The sixteen species of parasites encountered included representatives of the animal phyla Acanthecephala, Nematoda, Annelida and Platyhelminthes as well as two species of protists. Specimens of Phylum Acanthocephala were the most commonly encountered in this study. Leptorhynchoides thecatus was commonly found in the intestine and the pyloric caeca. The prevalence (percentage of animals examined infected with a given parasite) of L. thecatus was 56.25%. The stomach-dwelling specimens of the trematode genus Azygia were the next most commonly found, with 53.13% prevalence. Neoechinorhynchus tenellus was another acanthecephalan found in the intestines, 12.5% prevalence. Species belonging to the phylum Nematoda were found often encysted in the body cavity. Eustrongylides tubifex, also known as "red worm," were found in 31.25% of the P. flavescens analyzed, and adults of Dichelyne cotylophora were found in the intestines of 15.63% of fish examined. Additional Platyhelminthes found were two species of gill monogenean, Urocleidus aspectus and a second unidentified species of monogenean, as well as metacercaria of the body cavity or external surface-dwelling trematode Clinostomum marginatum, also known as "yellow grub." Urocleidus aspectus was found in 34.38% of the fish dissected. Other platyhelminthes encountered included
three species of cestodes (tapeworms), two of which (a species of Bothriocephalus and a species of Proteocephalus) occurred as adult worms in the intestine, and one (Triaenophorus sp.) as a juvenile worm in the body cavity and liver. The two species of protists encountered were a species of Trichodina, a species that is an ectoparasite (or perhaps an ectocommensal) found on the external surfaces of the scales and on the gills, with 37.5% prevalence, and another unidentified protozoan from the skin. The organ that was most parasitized was the intestine. There were twenty-two fish that contained parasites of the intestine. The stomach was also very common in hosting parasites; nineteen fish had parasites of the stomach. Table 1. Records of parasite prevalence from 32 Canadarago Lake P. flavescens. Parasites encountered are separated according to phyla and other major taxonomic categories and identified to as specific of a taxon as possible. Percentages listed represent prevalence of the parasite in the fishes examined from each lake (# of fish infected / # of fish examined). Acanthocephala (thorny-headed worms) Neoechinorhynchus tenellus 12.50% Leptorhynchoides thecatus 56.25% Platyhelminthes (flatworms) Cestoda (tapeworms) Bothriocephalus sp. (adult) 3.13% Proteocepalus sp. (adult) 25.00% Tiraenophorus sp. (juvenile) 15.63% Monogenea (monogenes) Urocleidus aspectus 34.38% Unknown 3.13% Trematoda (flukes) Azygia sp. 53.13% Bunodera sacculata 6.25% Clinostomum marginatum (juvenile) 6.25% Trematoda sp. (other juveniles) 3.13% Nematoda (round worms) Dichelyne cotylophora 15.63% Eustrongylides tubifex 31.25% Annelida (leeches) Piscicolaria sp. 9.38% Protista Trichodina sp. 37.50% Unknown 6.25%
DISCUSSION We found 16 species of parasites in the 32 individual P. flavescens that we examined in this study. This is contrasted with the 18 species that Doolin et al. (2017) encountered in 18 individual P. flavescens in Canadarago Lake in 2016. Doolin et al. (2017) encountered four species that we did not find in our study, an unidentified species of cestode and nematode, the trematode Crepidostomum cornutum, and a species of myxozoan. Conversely, we found two species that were not reported by Doolin et al. (2017) for Canadarago Lake, a second monogenean, and the trematode species Bunodera sacculata. During the 2016 survey (Doolin et al., 2017), C. marginatum or "yellow grub" was found inside the mouth and eyes; however, during our survey, C. marginatum was only found in the body cavity. In the 2016 survey, metacercaria (a juvenile stage of trematodes) and myxozoans were found in the eye of P. flavescens. This differed from our study as we did not encounter any parasites within the eye. Last year s study found that Ichthyophthirius multifiliis was not present in Canadarago Lake, and was only found in Otsego. This held true to our study as well for we did not encounter ick in Canadarago Lake. In both studies, L. thecatus was found in the intestine and pyloric caeca. Perca flavescens acquired each of the 16 species of parasites shown in Table 1 via its diet or simply by being colonized by free-swimming stages of the parasites. The following are examples of parasites that were encountered by P. flavescens via its diet: The two species of acanthocephalans, L. thecatus and N. tenellus would have been introduced to P. flavescens when it ingested amphipods and ostracods, their respective intermediate hosts. Each of the three cestode species were most likely encountered by P. flavescens via consumption of the copepod intermediate host. The presence of red worm (E. tubifex) in the body cavity of P. flavescens is evidence that the fish had consumed the oligochaete intermediate host of that worm. For the life cycle of E. tubifex to be completed, however, an infected P. flavescens would have to be preyed upon by a kingfisher, the definitive host of the nematode. Examples of parasites that would have actively colonized P. flavescens include the ectoparasites encountered, such as the two monogeneans and the leech. In addition, each of the digenean species found to infect the fish would have colonized it via the cercaria free-swimming stage. We consider the differences observed in the parasites enountered in P. flavescens in our survey and the previous year survey to be relatively minor. These differences could be artefacts of the relatively low sample sizes of both surveys (18 fish in 2016 versus 32 fish in our 2017 survey) rather than indicators of a real parasitological change in the lake from one year to the next. We note, however, the importance of continued survey work in order to document longer term trends. CONCLUSION A total of 16 species of parasites were found in P. flavescens in Canadarago Lake in 2017. This is two fewer than was found in P. flavescens the previous year. This number of parasites is relatively in line with parasitological data for P. flavescens elsewhere. The
occurrence of these parasites in Canadarago Lake serves as an indicator that P. flavescens is a part of multiple trophic pathways in Canadarago Lake. REFERENCES Amin, O. 2002. Revision of Neoechinorhynchus Stiles & Hassall, 1905 (Acanthocephala: Neoechinorhynchidae) with keys to 88 species in two subgenera. Systematic Parasitology. 53: 1 18. Caira, J. N., K. Jensen, E. Barbeau. 2012. Global Cestode Database. World Wide Web electronic publication. University of Connecticut, Storrs, CT, USA. Available from: http://www.tapewormdb.uconn.edu (Accessed 26 February 2018). Doolin, M., Darpino, J., Iwanyckyj, E., Macchiarelli, S., Piper,Z., Vandemark, S., Pokorny, T., and Reyda, F. 2017. Comparison of parasite communities of yellow perch (Perca flavescens) from Otsego and Canadarago Lake. In 49 th Ann. Rept. (2016). SUNY Oneonta Biol. Fld. Sta., SUNY Oneonta. Bray, R. A., Gibson, D. J., A. Jones, Eds. 2008. 3: Keys to the Trematoda. CABI, 1st Edition. 848 pp. Hoffman, G.L. 1999. Parasites of North American Freshwater Fish 2 nd Edition. Kuchta, R., Vlčková, R., Poddubnaya, L.G., Gustinelli, A., Dzika, E., Scholz, T. 2007. Invalidity of three palaearctic species of Triaenophorus tapeworms (Cestoda: Pseudophyllidea): Evidence from Morphometric Analysis of Scolex Hooks. Folia Parasitologica. 54: 34-42. Johnson, M.W., Nelson, P.A., Dick, T.A. 2004. Structuring mechanisms of yellow perch (Perca flavescens) parasite communities: Host age, diet, and local factors. Canadian Journal of Zoology. 82: 1291-1301. Moravec F. 1998. Nematodes of freshwater fishes of the neotropical region. Academia. 464 pp. Roberts, L., Janovy Jr, J., Nadler, S. 2012. Foundations of parasitology (Botany, Zoology, Ecology, and Evolution) 9 th Edition. Schell, S. C. 1985. Trematodes of North America. Moscow, ID: University Press of Idaho Wilkins, J.L., T.J. DeBates, and D.W. Willis. 2002. Food habits of yellow perch, Perca flavescens, in West Long Lake, Nebraska. Transactions of the Nebraska Academy of Sciences 28: 49-56.