Acanthocephala from Lake Fishes in Wisconsin: Neoechinorhynchus robertbaueri n. sp. from Erimyzon sucetta (Lacepede), with a Key to Species of the Genus Neoechinorhynchus Hamann, 1892, from North American Freshwater Fishes

Neoechinorhynchus robertbaueri n. sp. , the twentieth species of the genus from freshwater fishes in North America, was described from Erimyzon sucetta (Lacepede) (Catostomidae) in Silver Lake, southeastern Wisconsin. The species was distinguished from Neoechinorhynchus venustus Lynch, 1936 by having smaller eggs, longer lemnisci and proboscis hooks in the middle not equal to those of the anterior circle in size. A key further distinguishing it from other North American species from fish is presented. It was also separated from similar species infecting fish elsewhere in the world as well as from those infecting North American turtles. The life history of N. robertbaueri in E. sucetta was very brief (April to July). Juveniles were established in anterior intestinal locations by April but moved posteriorly with maturation and with earlier loss of males by July. Seasonal concurrent infections primarily with 3 other helminth species (a cestode, a trematode and an acanthocephalan) are also discussed. The description of Fessisentis tichiganensis by Amin (1980) from Tichigan Lake constitutes the first report of acanthocephalans from lake fishes in southeastern Wisconsin. The continuation of these studies begins with the present report on a a new species of the genus Neoechinorhynchus Hamann, 1892, from Erimyzon sucetta (Lacepede) in Silver Lake. Nineteen species of Neoechinorhynchus are presently known from various species of freshwater fishes in North America. The presence of an additional species, Neoechinorhynchus robertbaueri, in collections made from certain southeastern Wisconsin lakes since 1977 is herein reported. Ecological and life history information and a key distinguishing the new species from others infecting North American freshwater fishes are included along with the description. MATERIALS AND METHODS Seasonal parasitological collections yielding the reported material from Silver Lake (Kenosha County) were conducted during 1978, 1979, and 1984. The 188 ha lake (revised from 200 ha reported in earlier papers) is an eutrophic natural land-locked lake of glacial origin lying within the lateral moraine of the Lake Michigan lobe of the Wisconsin glacier. A small outlet historically permitted the intermittent discharge of overflow waters (until dammed in 1932) into the Fox River, a tributary of the Mississippi River drainage system. The Received 15 October 1984; revised 25 January 1985; accepted 28 January 1985. lake was probably originally populated by fish and parasite faunas of Mississippi River origin. Fishes were collected by electro-shocking and routinely examined within 24 hr. Recovered worms were refrigerated in distilled water overnight or until proboscides everted, then fixed in cold AFA, stained in Mayer's acid carmine, cleared in terpineol, and mounted in Canada balsam. Description is based on mature males with sperm in their sperm ducts and females with eggs at some stage of development. Width measurements refer to maximum width. Proboscis length is exclusive of the neck. Hooks were measured only in profile. The length of the reproductive system in males is the distance from the anterior margin of the anterior testis to the posterior end of the trunk and in females from the anterior end of the uterine bell to the genital pore. Ripe eggs squashed ut of gravid females as well as in body cavity were measured from fixed and stained preparations. All measurements are in micrometers, with averages in parentheses, unless otherwise noted. Mean per host is the number of parasites recovered/number of fishes examined. The site of infection was determined in the following 6 host alimentary regions (see fig. 2 in Amin, 1975b): stomach (A), first straight post-gastric limb (B), the second limb (C-1), two coils (C-2, 3), and the posteriormost limb leading to the vent (C-4); the C regions were usually similar in size. This system is preferred over the percentile method, used by some authors, as it takes into account regional differences in intestinal topography and biochemistry. Illustrations are made by the author using a carbon arc projector. RESULTS AND DISCUSSION Of 861 fishes of 8 families (Amiidae, 1 species; Catostomidae, 2; Centrarchidae, 9; Cyprinidae, 2; Esocidae, 2; Ictaluridae, 3; Lepisosteidae, 1;