The sicklefin redhorse, Moxostoma sp. (Cypriniformes: Catostomidae), is an innominate imperiled catostomid endemic to the Hiwassee and Little Tennessee river basins, which has been restricted to a few tributaries of these systems by impoundments. During collections to propagate sicklefin redhorse for reintroduction, a myxozoan, described herein, was observed infecting sicklefin redhorse in the Little Tennessee River Basin, North Carolina. Myxobolus naylori Ksepka et Bullard sp. n. infects the stratum spongiosum covering the scales of sicklefin redhorse. Myxospores of the new species differ from all congeners by the combination of having a mucous envelope, intercapsular process, and sutural markings as well as lacking an iodinophilic vacuole in the sporoplasm. and A phylogenetic analysis of the 18S rDNA gene recovered the new species in a polytomy with Myxobolus marumotoi Li et Sato, 2014 and a clade comprised of species of Myxobolus Bütschli, 1882; Thelohanellus Kudo, 1933, and Dicauda Hoffman et Walker, 1973. Histological sections of infected sicklefin redhorse skin revealed myxospores within a plasmodium in the stratum spongiosum dorsal to scales, encapsulated in collagen fibres, and associated with focal erosion of scales directly beneath the plasmodium; in some instances, the scale was perforated by the plasmodium. The specificity of the new species to sicklefin redhorse may make it a useful biological tag to differentiate sicklefin redhorse from morphologically similar species. The new species is the first parasite reported from sicklefin redhorse, a species of concern to the United States Fish and Wildlife Service. No species of Myxobolus has been reported from species of Moxostoma in the Southeast United States. As it was observed that Myxobolus minutus Rosser, Griffin, Quiniou, Alberson, Woodyard, Mischker, Greenway, Wise et Pote, 2016 is a primary junior homonym of Myxobolus minutus Nemeczek, 1911, we propose the replacement name Myxobolus diminutus (Rosser, Griffin, Quiniou, Alberson, Woodyard, Mischker, Greenway, Wise et Pote, 2016).
Nomasanguinicola canthoensis gen. et sp. n. infects the branchial vessels of bighead catfish, Clarias macrocephalus Günther (Siluriformes: Clariidae), in the Mekong River near Can Tho, southern Vietnam. Nomasanguinicola differs from all other genera of fish blood flukes (Digenea: Aporocotylidae) by the combination of lacking body spines and by having an anterior sucker with two flanking columns of large denticles, an intestine comprising several short papilla-like caeca, an inverse U-shaped uterus, and an ootype located near the separate genital pores. The new species has an ootype that is posterior to the level of the female genital pore. That feature most easily differentiates it from the only other putative aporocotylid species having an anterior sucker with two flanking columns of large denticles, Plehniella dentata Paperna, 1964 and Sanguinicola clarias Imam, Marzouk, Hassan et Itman, 1984, which have an ootype that is lateral (P. dentata) or anterior (S. clarias) to the level of the female genital pore. These two species apparently lack extant type materials, infect North African catfish, Clarias gariepinus (Burchell), and herein are considered incertae sedis, but likely comprise species of Nomasanguinicola. An updated list of hosts, sites of infection and geographic localities for the six species and three genera of blood flukes that mature in catfishes is provided. The new species is the first fish blood fluke recorded from Vietnam and only the third reported from a walking catfish (Clariidae).
Cardicola langeli n. sp. (Digenea: Aporocotylidae) infects the heart of sheepshead, Archosargus probatocephalus (Walbaum, 1792) (Perciformes: Sparidae) in the northern Gulf of Mexico off Horn Island (type locality), Mississippi, USA. The new species is described herein using light and scanning electron microscopy of adult specimens and can be most easily distinguished from the other 24 accepted species of Cardicola Short, 1953 by the combination of having (i) an ovovitelline duct that extends anteriad and that (ii) is posterior to the ootype, (iii) a male genital pore that is lateral to the oviducal seminal receptacle and (iv) a female genital pore lateral to the ootype. The new species is the only member of Cardicola so-far reported to have tegumental spines that are distally flattened and broad, rather than pointed. The new species generally resembles the two other species of Cardicola that infect sparids, i.e. Cardicola cardiocolum (Manter, 1947) (type species) from jolthead porgy, Calamus bajonado (Block et Schneider), in the Gulf of Mexico and Cardicola aurata Holzer, Montero, Repullés, Sitja-Bobadilla, Alvarez-Pellitero, Zarza et Raga, 2008, from gilthead seabream, Sparus aurata Linnaeus, in the Mediterranean Sea, by having a spheroid anterior sucker with concentric rows of minute spines anterior to the mouth and by having a similar general arrangement of the vitellarium, gonads and genitalia. However, it differs from them by having the combination of the aforementioned five features plus asymmetrical posterior caeca and a dextral posterior caecum that extends beyond the posterior margin of the ovary. Probable eggs of C. langeli n. sp. that contain a ciliated miracidium infect gill epithelium and are spheroid. An updated list of hosts, infection sites and geographic localities for the 25 accepted species of Cardicola is provided.
Eggs of Huffmanela markgracei sp. n. infected one of three Atlantic sharpnose sharks, Rhizoprionodon terraenovae (Richardson) (Carcharhiniformes: Carcharhinidae) captured by bottom long-line in the northwestern Gulf of Mexico off Padre Island, Texas. Eggs in the skin formed sinuous tracks (1-8 eggs wide; 1-4 eggs deep; 150 eggs/mm2) occupying a swath of the skin 22 cm × 2 cm on the tongue, branchial arches and the dorsal surface of the buccal cavity. Eggs had transverse eggshell ridges (branching and non-branching), had shells that were clear, amber or brown, and measured 90-113 µm (x = 102 ± 4; n = 190) long, 38-54 µm (43 ± 3; 190) wide, 3-5 µm (4 ± 0; 190) in eggshell thickness with protruding polar plugs 8-12 µm (10 ± 1; 190) wide. Apparently fully developed larvae in eggs were 255-335 µm (299 ± 26; 30) long, 8-10 µm (9 ± 1; 30) wide, and in-folded 5-6 (6 ± 0; 30) times. Some of these larvae were emerging from eggs in the skin. The new species differs from congeners by the combination of having a large, spindle-shaped egg, transverse eggshell ridges, an envelope that is smooth, tightly-apposed to the eggshell and surrounds the entire eggshell inclusive of the polar plugs, and a large larva. This is the first report of a species of Huffmanela Moravec, 1987 from a chondrichthyan in the Gulf of Mexico and from a shark not assigned to Carcharhinus.
Psettarium anthicum sp. n. (Digenea: Sanguinicolidae) infects the myocardium and atrial wall of the cobia Rachycentron canadum (Linnaeus, 1766) (Rachycentridae) in the northern Gulf of Mexico off Mississippi, USA. It is the first member of Psettarium Goto et Ozaki, 1930 reported from other than the Indian Ocean or Pacific Ocean and the second species of the genus reported from cobia. It differs from its congeners by the combination of having posterior caeca with lateral projections appearing as thorns in lateral view and the male pore anterior to the oötype. The species of Psettarium, P. japonicum (Goto et Ozaki, 1929) (type species), P. tropicum Manter, 1940, P. sebastodorum Holmes, 1971, P. rachycentri (Lebedev et Parukhin, 1972) comb. n. (syn. Psettarioides rachycentri Lebedev et Parukhin, 1972) and P. anthicum sp. n., differ from other sanguinicolids by the combination of having an elongate body with a sinistral posterolateral protuberance, minute, straight tegumental body spines in ventrolateral transverse rows, posterior caeca greater than seven time the anterior caeca length, the oötype near the posterior end of the body, a uterus primarily between the ovary and oötype and an oviduct and vitelline duct extending posteriad primarily between the uterus and dextral body margin. We emend Psettarium and provide a diagnostic key to the species. Psettarioides is regarded as a junior synonym of Psettarium because herein we return its type species, P. tropicum, to Psettarium. Regarding the three other sanguinicolids formerly of Psettarioides, we suspect that P. pseudupenei Lebedev et Parukhin, 1972 belongs to Psettarium but include it only tentatively pending an examination of type or other material; we tentatively place P. kurochkini Parukhin, 1976 in Cardicola Short, 1952; and we designate P. grandis (Lebedev et Mamaev, 1968) as incertae sedis pending examination of type or other appropriate material.