The Life Cycle and Larval Development of Octospinifer macilentis (Acanthocephala: Neoechinorhynchidae)

Abstract

The acanthocephalan, Octospinifer macilentis Van Cleave, is an intestinal parasite of the common sucker, Catostomus commersoni (Lac6pede). Ostracods, Cyclocypris serena (Koch), Physocypria pustulosa, and Cypridopsis sp., along with other arthropods, were fed infective ova. Only C. serena susstained infections until cystacanth larvae developed. Eggs hatched inside the intermediate host within 4 hr and liberated spindle-shaped acanthors with anterior spines. Attempts to induce hatching artificially by proteolytic enzymes failed. Motile acanthors penetrated the gut within 24 hr. After 4 days in tissues dorsal to the gut, acanthors moved into the hemocoel and by the 5th day lost their spines and became immotile. Acanthella stages revealed changes in the entoblast: the anterior section gave rise to the brain, proboscis receptacle, and proboscis muscles; the posterior section formed the genital complex; between the two sections the pseudocoel appeared. The epidermis, formed from the peripheral cytoplasm, contained nine giant nuclei-six remained in the epidermis and three moved into the lemnisci after 25 days. The octamerous nature of the proboscis became apparent after 20 days when the hooks, in three rows of eight each, developed from the dermis. Differentiation of the genital apparatus distinguished the sexes by day 20 when two testes appeared within a single ligament sac and ovarian masses differentiated within two ligament sacs. By day 30 the proboscis of the cystacanth was capable of inversion and protrusion, epidermal nuclei were in their characteristic sites, and the gonads were distinct. No transport host was required to carry the cystacanth to a definitive host. In this respect, 0. macilentis differs from Neoechinorhynchus cylindratus and N. emydis. Catostomus commersoni was successfully infected by force-feeding with parasitized ostracods. Moxostoma aureolum and Notropis dorsalis failed to acquire infections. In the definitive host, worms were established in the intestine within 4 hr. Maturity was reached after approximately 8 to 10 weeks for males and 16 weeks for females. Octospinifer macilentis (order Eoacanthocephala, family Neoechinorhynchidae) was described as an intestinal parasite of the common sucker, Catostomus commersoni (Lacepede), from Douglas Lake, Michigan (Van Cleave, 1919). The species has since been reported from numerous localities in the Great Lakes Region of the United States and Canada, in Saskatchewan, in northeastern United States (Van Cleave, 1947), and in Florida (Bangham, 1940). Hosts for the adult stage belong to the family Catostomidae and include, in addition to the type host, the following species: Catostomus catostomus, Moxostoma aureolum, Erimyzon oblongus, and Carpiodes carpio. Received for publication 10 August 1964. *Portion of a thesis for the degree Doctor of Philosophy submitted to the Graduate School, University of Minnesota, Minneapolis, 1962. t Present address: Department of Biology, Tabor College, Hillsboro, Kansas 67063. 206 The other member of the genus is 0. torosus Van Cleave and Haderlie from C. occidentalis and C. tahoensis in California. Goslin (1936) reports 0. macilentis from C. macrocheilus and Salmo lewisi in Glacier National Park, Montana. The current identification of the parasites he found, however, is open to question. A comparison of Goslin's illustration with the description by Van Cleave and Haderlie (1950) indicates that he may have collected 0. torosus. All known acanthocephalans require an arthropod as an intermediate host and a vertebrate as a definitive host. In addition, a transport host (vertebrate or invertebrate), in which essentially no development occurs, may be intercalated into the life cycle. Species of the family Neoechinorhynchidae whose life cycles have been elucidated, at least in part, are Neoechinorhynchus rutili (Miiller) by Robin (1877), Villot (1885) and Levander (1905); N. cylindratus (Van Cleave) by Ward This content downloaded from 157.55.39.78 on Thu, 23 Jun 2016 06:26:53 UTC All use subject to http://about.jstor.org/terms HARMS-LIFE CYCLE AND LARVAL DEVELOPMENT OF OCTOSPINIFER (ACANTHOCEPHALA) 287 (1940); and N. emydis (Leidy) by Hopp (1946, 1954) and Lincicome and Whitt (1947). MATERIALS AND METHODS The intermediate host, Cyclocypris serena (Koch), an ostracod, was collected primarily from two sites: the Mississippi River, Clearwater County, Minnesota; and Little Long Lake, Hennepin County, Minnesota. A modified Birge cone was used to collect plankton and benthos which was taken to the laboratory, where ostracods and other arthropods were removed with a pipette. Cultures were kept in finger bowls under controlled lighting (17 hr per day) and at 21 C. Boiled timothy hay was supplied as food and at no time were cultures aerated artifically. To obtain infective eggs of 0. macilentis, mature females from the intestines of common suckers were dissected in sterile lake water. Eggs from 5 to 20 females were concentrated by centrifugation and stored in 10 ml water at 4 C. Arthropods were exposed to infective eggs for 12 to 24 hr after being isolated from their source of food for 1 day. Hosts were examined for infection by making squash-preparations in Nile blue sulfate-saline (1:2,500). Larvae of O. macilentis were studied alive and drawings of all stages were made with the aid of a camera lucida. Cystacanths were also stained with combination hematoxylin (Van Cleave, 1953) and mounted in toto. Sections for microscopic study of infected ostracods were made after embedding in paraffin (melting point 60 C) containing 10% bayberry wax. Naturally infected common suckers were taken from the headwaters of the Mississippi River, Clearwater County, Minnesota. Those fish selected for laboratory experimentation measured 3 to 7 inches in length and were collected from streams in the vicinity of Minneapolis, Minnesota or purchased from bait dealers in that city. Fish were kept up to 9 months in tanks with 92 to 275 gallons of aerated water at approximately 15 C. Fish were fed three times a week on oatmeal and once every 2 weeks on chopped beef liver. Two to five infected ostracods were force-fed to fish with a polyethylene tube (2.5 mm diameter). Autopsies were made at scheduled intervals. EXPERIMENTAL DETERMINATION