2014 Northeastern Naturalist Notes Vol. 21, No. 3 N18 J.R. Flowers and M.A. Matsche Notes on the Fish Parasite Nitzschia (Monogenoidea: Capsalidae) in North America James R. Flowers1,* and Mark A. Matsche2 Abstract - We review and revise the taxonomic history of Nitzschia sturionis parasitizing North American Acipenser spp. (sturgeon), and provide data regarding its anatomy. The currently accepted diagnostic character of speciation (hamuli lengths) is unreliable, suggesting the synonymy of Nitzschia superba and Nitzschia monticelli under N. sturionis, resulting in two recognized species of Nitzschia spp. in North America—N. sturionis along the Atlantic coast and Nitzschia quadritestes along the Pacific coast. Introduction. The late Dr. Emmett W. Price’s (1935, 1939) study of North American capsalid monogeneans is well known to all who have studied these piscine parasites. Price studied the US National Parasite Museum (USNPC; Beltsville, MD) specimens (USNPC 4873, 7153, 7742, 35639, 35640, 35641) of the genus Nitzschia Baer. Many researchers studying these parasites of Acipenser spp. (sturgeon) have cited and repeated information from his study. Recently, M.A. Matsche et al. (2010) studied Nitzschia sturionis (Abildgaard) Krøyer 1852 from Chesapeake Bay Acipenser oxyrinchus Mitchill (Atlantic Sturgeon). That investigation examined the historical literature as well as the same museum specimens studied by Price and found both historical and morphological discrepancies, which we report here. Methods for specimen collection and processing are described in Matsche et al. (2010). We use monogenean morphological terminology developed by Hendrix (1994), and Kearn’s (1999) and Whittington’s (2004) terminology for haptoral morphology and sclerites. Host names follow Nelson et al. (2004). We examined paratype and voucher specimens of nominal species of Nitzschia from the USNPC (Nitzschia superba MacCallum—4873, 7153, 7742, 35639, 35640, 35641; N. sturionis— 73135, 101671, 101672; Nitzschia quadritestes Pratt and Herrmann—38905) and from the HW Manter Laboratory of Parasitology (HWML) (Nitschia [sic] sp. [identified as N. quadritestes]—42837) for comparison. Specimens of Entobdella hippoglossi (O.F. Müller) Johnston 1856 (USNPC 7151) were also examined. There have been 9 primary reports (Table 1) of Nitzschia spp. from North American sturgeon. Like Appy and Dadswell (1978), Beverley-Burton (1984), Bychowsky (1957), and Choudhury and Dick (2001), we consider Nitzschia superba to be a synonym of N. sturionis and discuss proposed synonymy later in this report. Verrill’s location. Price (1935, 1939) and Sproston (1946) listed Block Island, RI, as a locality record for N. sturionis, presumably in reference to Verrill’s (1875b) report. However, Verrill (1875b) gave no specific locality. When we examined Verrill’s contemporaneous publications (1873, 1875a, 1875b, 1875c, 1875d, 1885, Verrill and Smith 1874) and other pertinent Fish Commission reports (Sumner et al. 1911), we found no mention of the locality from which the host sturgeon was collected. In the first US Fish Commission report, Baird (1873) listed many fish species—Tetrapturus albidus Poey (Bill-fish), Atlantic Sturgeon, 3 sciaenid species (drum-fish), Ceratacanthus aurantiacus (Mitch.) Gill. 1Department of Population Health and Pathobiology, College of Veterinary Medicine, North Carolina State University, 1060 William Moore Drive, Raleigh, NC 27607. 2Maryland Department of Natural Resources, Cooperative Oxford Laboratory, 904 South Morris Street, Oxford, MD 21654. *Corresponding author - james_flowers@ncsu.edu. Manuscript Editor: Jay Stauffer Notes of the Northeastern Naturalist, Issue 21/3, 2014 N19 2014 Northeastern Naturalist Notes Vol. 21, No. 3 J.R. Flowers and M.A. Matsche (Orange File-fish), Raja spp. (skates), etc.—collected at Woods Hole, MA, that were also reported by Verrill (1875b, 1885) as hosts for other monogeneans and lernæans (subclass Copepoda). It is reasonable to suspect that Commissioner Baird, head of the Fish Commission, shared specimens with Verrill, his deputy for the study of invertebrates (Goode 1883, 1988). Nevertheless, due to a lack of definitive evidence, we agree with Lawler (1981) in listing the “New England coast,” Verrill’s US Fish Commission study area, as the locality for N. sturionis (as N. elegans) of Verrill (1875b). Verrill’s specimen. In addition to reading the historical literature, we queried pertinent natural history museums. We consulted the Yale Peabody Museum (New Haven, CT) and National Museum of Natural History (Washington, DC; later the Smithsonian Institution) regarding specimens or records of Verrill’s specimens associated with the US Fish Commission during Professor Verrill’s tenure. Respectively, the responses were: “I checked the USNM catalog and ledger series, and the specimen of Nitzschia elegans Baer, 1826 as reported by Verrill, 1875 is not in our catalog or ledger. ... Catalog numbers nearby, USNM 13292–13296, are specimens of the genus Tristoma and are marked in the ledger as being with Stiles (on) April 9, 1908.” (William Moser, 2010, Smithsonian Institution, Washington DC, pers. comm.) and, “Although I managed to find the Tristoma (YPM IZ 39794) you list (dried) I have not seen the other species in our collection. According to records of an audit (~1906) of US Fish Commission specimens, we should have one specimen and the National Museum should have one specimen. … It is possible that amongst our dried USFC samples there might be a vial containing this specimen, but we have hundreds of these old vials and they are only partially arranged by taxon. Furthermore, we still Table 1. Primary reports of Nitzschia spp. from Acipenser hosts in North America. Species Synonym Reported host Locality Reference N. sturionis N. elegans A. oxyrinchus* New England Coast Verrill 1875b N. elegans A. sturio† Delaware River, PA Leidy 1887 N. elegans A. sturio Woods Hole, MA Linton 1898‡ N. superba A. brevirostrum New York, NY MacCallum 1921 A. oxyrinchus NB, Canada Appy and Dadswell 1978 Nitzschia spp.§ A. oxyrinchus NY and NJ Fast et al. 2009 A. oxyrinchus Chesapeake Bay, MD Matsche et al. 2010 N. quadritestes A. transmontanus Columbia River, OR Pratt and Herrmann 1962 A. medirostris Columbia River, OR Pratt and Herrmann 1962 A. medirostris WA and CA Foley et al. 1989 A. transmontanus San Pablo Bay, CA Hanson et al. 1992 *For the spelling of the name of the Nearctic Atlantic sturgeon (A. oxyrinchus), we follow Nelson et al. (2004). †Per Nelson et al. (2004), the sturgeon host (A. sturio) of Leidy (1887) and Linton (1898) were likely A. oxyrinchus. ‡Linton (1898) reported Nitzschia papillosa from Gadus callarias (Cod) from Woods Hole, MA. Price (1938) determined this species to be Udonella caligorum Johnston 1835. §We were allowed access to specimens and data collected by Mark Fast, University of Prince Edward Island, Charlottetown, PEI, Canada and Mark Sokolowski Stony Brook University, Stony Brook, NY, USA (unpubl. data). Specimens proved to be N. sturionis and were deposited in the USNPC (105133, 105134, 105135). 2014 Northeastern Naturalist Notes Vol. 21, No. 3 N20 J.R. Flowers and M.A. Matsche have about 5000 microscope slides that did not get databased … it is possible the specimen exists on a slide. Chances are very slim, however, that we could actually find it.” (Eric A. Lazo-Wasem, 2010, Peabody Museum of Natural History, New Haven CT, pers. comm.) USNPC 7153. Many specimens (USNPC 7151, 7164, 7168–7181, 7184–7191, 7193–7194, 7196–7197, etc.) that were deposited or cataloged contemporaneous with the N. superba specimen USNPC 7153, are from the US Fish Commission. These specimens include Entobdella hippoglossi Müller specimens (USNPC 7151) and anasakids (USNPC 7152) collected by N.P. Scudder who was studying Hippoglossus hippoglossus L. (Atlantic Halibut) and Gadus morhua L. (Atlantic Cod) banks of Davies Straits for the US Fish Commission (Collins and Rathbun 1887; Goode 1883, 1988; Rathbun 1887). Although unverifiable, we suspect that specimen USNPC 7153, regarding which Price (1939) reported: “the host of which was not given” (nor host locality or collection date), is likely from the US Fish Commission collection, deposited contemporaneously with Scudder’s specimens, and possibly the lost specimen of Verrill (1875b). Stafford 1904. Following Price (1939), many authors including Pratt and Herrmann (1962), Sproston (1946), and Yamaguti (1963) have listed “Stafford (1904)” as reporting N. sturionis (as N. elegans) from “Canada (Gulf of St. Lawrence).” However, none of Stafford’s contemporaneous publications (1900, 1902, 1904, 1905, 1907a, 1907b) reported Nitzschia spp. or other parasites from any anadromous sturgeon. Further, Miller’s (1941) critical study of Stafford’s work also lacks any mention of Nitzschia spp. Also, Margolis and Arthur (1979) did not list Nitzschia spp. for any of Stafford’s publications in their synopsis of Canadian piscine parasites. Beverley-Burton (1984) and Lawler (1981) noted this erroneous record previously. With exclusion of “Stafford (1904)” and “Canada (Gulf of St. Lawrence)” from the nitzschian historical record; the earliest Canadian reports of Nitzschia spp. include Nitzia [sic] superba listed in a marine fauna/flora checklist by Linkletter et al. (1977) via personal communications with Dr. R.G. Appy, who later, with Dr. M.J. Dadswell, reported N. sturionis from Atlantic Sturgeon collected from New Brunswick, Canada (Appy and Dadswell 1978). We presume that Linkletter et al. (1977), which we consider secondary literature, listed the (then soon to be published) primary record of Appy and Dadswell. Cecal confluence. While most authors did not report on the cecal conformation of Nitzschia spp., Beverly-Burton (1984:68) and Hendrix (1994:figure 17) used cecal diverticula as a taxonomic key characteristic for Nitzschia spp. Both authors indicated in illustrations and text that the caeca are “not confluent posteriorly”. During our study, cecal branches, extending anteriorly from the pharynx, as well as a posterior confluence, were observed in sectioned N. sturionis specimens from Woods Hole, MA (USNPC 4873; slides 102-15, 102-16) (Fig. 1a, c), and Potomac River, MD (USNPC 101672; slide 304A-8) (Fig. 1b, d) sturgeons. Our findings support Bychowsky’s (1957:188) description of the larval N. sturionis, which reported a “small ring-shaped intestine emerges from the pharynx”, and Blanchard’s (1847:330) study of the nitzschian digestive system: “… alors j'ai pu suivre après le bulbe buccal, … un oesophage court, se divisant bientôt en deux longues branches, qui se rejoignent en avant de la ventouse, et forment ainsi une ellipse.” Translated as: “… so I could follow after the buccal bulb, … a short esophagus, dividing soon into two long branches, which meet in front of the sucker, and thus form an ellipse.” N21 2014 Northeastern Naturalist Notes Vol. 21, No. 3 J.R. Flowers and M.A. Matsche Haptoral sclerites. In general, the posterior haptor of capsalids possess: a membranous marginal valve, 14 marginal hooklets, 1 pair of central accessory sclerites, 1 pair of anterior hamuli, and 1 pair of posterior hamuli (Kearn 1999, Whittington 2004, Whittington et al. 2001). The anterior hamulus has a relatively dull tip and variable shape (blunt, straight, or curved), but is most often not in the form of a sharp recurved button-hook, and is slightly Figure 1. Cecal branches and confluence of N. sturionis. a. Primary cecal branches of N. sturionis (USNPC 4873) showing anterior cecal branch (black arrows), posterior cecal branch (white arrows), pharyngeal lumen (P), and cirrus (C); scale bar = 200 μm. b. Primary cecal branches of N. sturionis (USNPC 101672) showing anterior cecal branch (black arrows), posterior cecal branch (white arrows), pharynx (P), and cirrus (C); scale bar = 200 μm. c. Posterior cecal confluence of N. sturionis (USNPC 4873) showing cecal confluence (arrow), haptor (H); scale bar = 200 μm. d. Posterior cecal confluence of N. sturionis from Potomac River, MD showing cecal confluence (arrow); scale bar = 200 μm. 2014 Northeastern Naturalist Notes Vol. 21, No. 3 N22 J.R. Flowers and M.A. Matsche more medial to the posterior hamulus. The more lateral posterior hamulus consistently has a tip in the form of a sharp recurved button-hook. This same general hamuli arrangement and morphology is retained in N. sturionis and N. quadritestes—sharp recurved button-hooked posterior hamuli lateral to the dull-tipped anterior hamuli (Fig. 2a–d and Fig. 3b, c). The first detailed description and illustrations of the hamuli of the North American N. sturionis (as N. superba) were imprecisely reported and labeled by Price (1935, 1939). We have found that subsequent interpretations of Price’s illustration by Beverly-Burton (1984) and Sproston (1946) are also mislabeled. As indicated above, and verified by microscopic study, the posterior hamuli are sharp and recurved, and the anterior hamuli often have dull, non-recurved tips. Price’s (1935, 1939) illustration correctly shows that the sharp recurved-hamulus is indeed positioned as the most posterior hamulus; however, the caption labels this hamulus as the anterior hamulus. Unfortunately, while their hamuli measurements in the text description of Nitzschia quadritestes are correct, Pratt and Herrmann (1962) also mislabeled their hamuli illustrations. Finally, although Price (1935, 1937) reported finding the marginal hooklets of Nitzschia sp., the present report is the first to clearly illustrate the location of these tiny hooklets (Fig. 3a, e). Morphologic speciation. Price (1939) proposed 3 species of Nitzschia based on the length of the haptoral hamuli and accessory sclerites: N. sturionis—European species with hamuli and sclerites of equal length; N. monticelli Price 1935—European species with neither hamuli nor sclerites equal in length; and N. superba—North American species with anterior and posterior hamuli of equal lengths, but not equal in length with the accessory sclerites. Dawes (1947), Hoffman (1999), Sproston (1946), and Yamaguti (1963) accepted Price’s conclusions. Bychowsky (1957), without explanation, considered N. monticelli and N. superba to be synonyms of N. sturionis. Appy and Dadswell (1978) and Beverley-Burton (1984) accepted Bychowsky’s synonymy of N. superba under N. sturionis, but did not address the validity Figure 2. Natural position of hamuli of Nitzschia spp. specimens (scale bars = 50 μm). a. Anterior hamuli of N. sturionis (USNPC 7153). b. Posterior hamuli of N. sturionis (USNPC 7153). c. Anterior hamuli of N. quadritestes (HWML 42837). d. Posterior hamuli of N. quadritestes (HWML 42837). N23 2014 Northeastern Naturalist Notes Vol. 21, No. 3 J.R. Flowers and M.A. Matsche of N. monticelli. Hendrix (1994) acknowledged the possible synonymy of N. superba, but suggested that more work was needed to clarify the validity of this species. In their biogeographical study of sturgeon parasites, Choudhury and Dick (2001) did not recognize Figure 3. Haptor and haptoral accessories of Nitzschia sturionis from Atlantic Sturgeon in Chesapeake Bay. a. Haptor (scale bar = 500 μm); marginal hooklets (arrow heads). b. Posterior, sharp hamulus (scale bar = 20 μm). c. Anterior, blunt hamulus (scale bar = 20 μm). d. Accessory sclerite (scale bar = 20 μm). e. Marginal hooklet (scale bar = 20 μm). 2014 Northeastern Naturalist Notes Vol. 21, No. 3 N24 J.R. Flowers and M.A. Matsche N. superba or N. monticelli, but Whittington (2004), possibly unaware of N. quadritestes (or more likely by misprint), listed N. sturionis and N. superba as the only two valid species. There is no evidence that Price (1939) examined any European specimens; rather, he likely based his conclusion of 3 Nitzschia species on the text and illustrations of Monticelli’s (1908) report. Brinkman (1952) and Price (1939) both questioned the accuracy of the illustrated measurements of the “forma giovane” hamuli of Monticelli (1908). We suspect that Monticelli’s illustration of the elongate “2nd pair” of hamuli includes the hamuli tendon, which Kearn (1999) has shown to function in haptoral attachment for Entobdella soleae (van Beneden and Hesse) Johnston. Hamuli tendons can be observed extending anteriorly from hamuli of some N. sturionis specimens, e.g., USNPC 4873. Although Price (1935, 1939) proposed that equal hamuli lengths are the defining character for the North American species N. superba, we found the hamuli of most North American specimens to be unequal (Table 2). Further, during compression and mounting of specimens, hamuli often become deformed, folded, and/or too poorly positioned (distinctly angled or perpendicular to the focal plane) to allow for accurate measurements. Consequently, we suggest that the inability to reliably measure hamuli length invalidates this sole distinguishing morphologic character, as well as the two species (N. monticelli and N. superba) that this character would authenticate; based on testes number, our proposal leaves N. sturionis and N. quadritestes (26+ and 4 testes, respectively) as the only two valid species. Molecular work would be extremely valuable in determining species validity and relationships. Acknowledgments. We gratefully acknowledge assistance with specimen acquisition and analysis of specimen records by Patricia A. Pilitt of US National Parasite Collection, Animal Parasitic Diseases Laboratory, United States Department of Agriculture, Beltsville, MD. Gratitude is also extended for the acquisition of specimens to Drs. Scott Gardener and Gabor Racz of Harold W. Manter Laboratory of Parasitology W 529 Nebraska Hall, University of Nebraska-Lincoln, Lincoln, NE. We are also grateful to Dr. Mark Fast, of the Department of Pathology and Microbiology, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, PEI, Canada and Mark Sokolowski of the Marine Disease Pathology and Research Consortium, School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, NY for access to their data and specimens. Table 2. Measurements of accessory sclerites and hamuli of Nitzschia spp. specimens studied by Price (1935, 1939). Voucher USNPC 7742 is a longitudinally sectioned specimen, making sclerite and hamuli measurements unfeasible. Syntypes USNPC 35640 are three specimens mounted on the same microscope slide. Due to compression of the large specimen of syntypes 35640, the hamuli are highly folded, making measurements unfeasible. Accessory Anterior Posterior Nominal USNPC Total body sclerite blunt hamulus sharp hamulus species accession no. length (mm) length (μm) length (μm) length (μm) N. superba 4873 15 107 172 131 7153 12 110 203 189 7742 n/a n/a n/a n/a 35639 15 111 151 147 35640 7.8 101 180 164 35640 9 85 170 127 35640 11 87 n/a n/a 35641 9 104 173 161 N25 2014 Northeastern Naturalist Notes Vol. 21, No. 3 J.R. Flowers and M.A. Matsche Literature Cited Appy, R.G., and M.J. Dadswell. 1978. Parasites of Acipenser brevirostrum LeSueur and Acipenser oxyrhynchus Mitchill (Osteichthyes: Acipenseridae) in the Saint John River Estuary, NB, with a description of Caballeronema pseudoargumentosus sp. n. (Nematoda: Spirurida). Canadian Journal of Zoology 56:1382–1391. Baird, S.F. 1873. XX. List of Fishes collected at Woods Hole. Pp. 823–827, In S.F. Baird (Ed.). Report on the Condition of the Sea Fisheries of the South Coast of New England in 1871 and 1872. 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