The parasitic fauna of the Seminole killifish, Fundulus seminolis, from Lake George, Florida

A total of 140 Fundulus seminolis were collected from Lake George (29° 17' 12” N 81° 35' 53” W) in Volusia County Florida, USA on three separate occasions from March through May 2007. Fish were transported back to a laboratory for biopsies of intestine, skin, fin, and gills. Biopsies were analyzed and parasites were identified and enumerated. Thirteen distinct taxa were identified as parasites of F. seminolis. The most common parasitic group encountered in this survey were members of the subclass Digenea. Responsible for the highest prevalence recorded in this study, 95% in the intestine, digeneans were found in all four of the tissues examined. Skin and gill biopsies yielded the greatest diversity of parasites with 8 taxa represented in each. Gyrodactylus sp. exhibited the greatest prevalence (14%) within skin biopsies. Dactylogyrus sp. (46% prevalence) was the most prevalent of parasites among gill biopsies. Hirudinea were the most common of all parasites found on the fin, with a prevalence of 39%. The maximum mean intensity recorded was 5.00 for Ichthyobodo sp. on the fin and 5.00 for Piscinoodinium sp. on the gill. Trichodina sp. found on the gill biopsies demonstrated the broadest intensity range, 1-12 organisms per specimen analyzed. The largest calculable mean abundance of 0.73 was displayed by Dactylogyrus sp. on the gill biopsies analyzed. This is the first comprehensive parasitic survey of F. seminolis from the Lake George region. Eight parasitic taxa never before recorded on F. seminolis were elucidated. *Corresponding author’s E-mail: [email protected]; [email protected] Introduction The Seminole Killifish, Fundulus seminolis, is an endemic Florida killifish with a geographic range within peninsular Florida from the St. Johns and New River drainage basins to just south of Lake Okeechobee (Page & Burr, 1991). Populations reaching as far south as NineMile Bend have been reported by Tabb and Manning (1961). This species, commonly referred to as a “bullminnow” or “mudminnow”, is one of the largest members of the genus, reaching lengths of 16 cm (Page & Burr, 1991). Its popularity as a local baitfish for Largemouth Bass, Micropterus salmoides, and other piscivorous game fish has generated interest in this species as a potential candidate for aquaculture. Relatively little is known regarding the life history of F. seminolis, with only one publication by DuRant et al. (1979) devoted entirely to the species. It has been referenced anecdotally or as a component in a larger study or survey in several publications (McLane, 1955; Phillips & Springer, 1960; Tabb & Manning, 1961; Gunter Bull. Eur. Ass. Fish Pathol., 28(6) 2008, 239 & Hall, 1963; Gunter & Hall, 1965; Foster, 1967; Griffith, 1974; Nordlie, 2006). To date there are no publications that have extensively examined the parasitic fauna of Fundulus seminolis. While Bangham (1940) did include F. seminolis in his parasite survey, his sample size was only 14 individuals and most of the specimens were preserved in formalin prior to examination, likely altering the detectable parasite burden. Dillon’s (1966) effort at compiling a list of parasites occurring on Fundulus spp. merely referenced Bangham’s work with no new additions. The most recent and extensive checklist of parasites occurring on Fundulus spp. compiled by Harris & Vogelbein (2006) excluded F. seminolis altogether. Therefore, the objective of this study was to elucidate and enumerate the various protozoan and metazoan parasites found within a population of Seminole Killifish from Lake George, FL. Methods A total of 140 Fundulus seminolis were collected from the eastern shore of Lake George (29° 17' 12” N 81° 35' 53” W) in Volusia County Florida. Fish were collected with a seine net (24.4 m X 1.2 m, 0.8 cm mesh) on three separate occasions from March through May 2007. A sample size of 100 fish was determined to be suitable for our experiment based on previous work by Ossiander & Wedemeyer (1973) and Simon & Schill (1984). This sample size would allow us to detect with a 95% confidence level one carrier fish in a population greater than 1,000,000 with a 3% incidence of disease (Ossiander & Wedemeyer, 1973). Fish were captured with a seine net and transported to the laboratory alive in water obtained from the collection site. A dissolved oxygen saturation of approximately 90% was maintained during transport. Water samples were collected prior to seining and were stored for later analysis. Water temperature was determined at collection sites. Dissolved oxygen (DO) and pH were both measured using Hach’s HQ-20 meter while total ammonia nitrogen (TAN), nitrite, total hardness, total alkalinity, CO2, and free and total chlorine were measured using standard techniques (Hach Co., Loveland, Colorado). Salinity was determined using a refractometer. Upon arrival fish were individually weighed and measured and subsequently examined externally for gross signs of parasitism. If no gross signs of parasitism were evident, skin biopsies were collected from the entire length of the left lateral body wall of the fish, a gill biopsy (~3mm2) was collected from the specimens left second gill arch and a fin biopsy (~5mm2) was collected from the specimen’s caudal fin. Active lesions, erosions, erythemic tissues, and visible parasites were given precedence and the area in question was biopsied instead. Wet mounts of all biopsied tissues were prepared for further analysis. Fish were subsequently euthanized in buffered tricaine methanesulfonate (MS-222, Argent Laboratories, Finquel, C-FINQ-UE-100G) and each specimen’s intestine was excised. Wet mounts of the complete intestine were prepared for further inspection. Skin, fin, gill, and intestinal biopsies were performed utilizing techniques described by E.J. Noga (1996). All wet mounts were prepared within 24 hours of capture and examined immediately thereafter. Bull. Eur. Ass. Fish Pathol., 28(6) 2008, 240 All parasitological terminology utilized adhere to the recommendations of Bush et al. (1997). Parasites were identified utilizing previously published literature (Stoskopf, 1993; Woo, 1995; Noga, 1996) and with the help of B. Denise Petty, DVM. Slide preparations were examined using light microscopy at three different magnifications (40x, 100x, and 400x). Parasites were enumerated individually with the exceptions of Nematoda, Digenea, Myxobolus sp., and sessile ectocommensal ciliates of the order Table 1. Classification of parasite intensity per field of view at predetermined magnifications on the skin, fin, gill and intestine of Fundulus seminolis. a – Parasite descriptors per field of view (Table 1). L = Light; M = Moderate; H = Heavy. Table 2. Parasite fauna observed on 100 intestinal biopsies of Fundulus seminolis. a – Parasite descriptors per field of view (Table 1). L = Light; M = Moderate; H = Heavy. Table 3. Parasite fauna observed on 100 skin biopsies of Fundulus seminolis. Parasite # of Fields of view (FOV) Magnifi‐ cation Light (Per FOV) Moderate (Per FOV) Heavy (Per FOV) Digenea 5 40x 1-10 Adult/ Metacercaria 11-25 Adult/ Metacercaria ≥ 26 Adult/ Metacercaria Myxobolus sp. 5 400x 1 Xenoma or individual Myxosporea 2-10 Xenomas ≥ 11 Xenomas Nematoda 5 40x 1-10 11-25 ≥ 26 Sessile Ectocommensal Ciliates (SEC) 5 400x 1-10 11-25 ≥ 26 Parasite Prevalence (%) Mean abundance Intensity range Mean intensity Cestoda 2 0.03 1-2 1.50