Dennis J. Richardson

The Genus Centrorhynchus (Acanthocephala) in North America with Description of Centrorhynchus robustus n. sp., Redescription of Centrorhynchus conspectus, and a Key to Species

Reexamination of the type series of Centrorhynchus wardae Holloway, 1958, and Centrorhynchus conspectus Van Cleave and Pratt, 1940, revealed no consistent difference between the 2 purported species; therefore, C. wardae is considered a junior synonym of C. conspectus. Specimens from additional collections are consistent with this view and provided adequate material for redescription of the species. Centrorhynchus robustus n. sp. resembles C. conspectus in the number of hooks per Salient differences between the 2 species are size and body shape, with C. robustus having a robust trunk with the widest diameter anteriad and C. conspectus being elongate with no region of the trunk consistently widest. Additionally, a conspicuous posteriad swelling exhibited by females of C. conspectus is lacking in C. robustus. Centrorhynchus kuntzi is reported for the first time from Montana and Nebraska, and C. conspectus is reported for the first time from an eastern screech owl, Otus asio.

Copulation and sexual congress of Leptorhynchoides thecatus (Acanthocephala).

Pairs of the acanthocephalan Leptorhynchoides thecatus from laboratory infections were observed copulating at 21 days, 5 wk, and 12 wk postinfection (PI) in green sunfish, Lepomis cyanellus. Additionally, copulating pairs of worms from natural infections were observed. In each instance of paired males and females, the male was in 1 pyloric cecum of the fish and the female in another. Each had its posterior end protruding into the intestinal lumen at the point from which the ceca arise. The completely extruded bursa of the male fully enclosed the posterior end of the female in a firm attachment. In 1 instance at 5 wk PI, 2 males were observed in copula. One male had its copulatory bursa completely retracted, and the copulatory bursa of the other male was positioned just as though the mate were a female. Based on these and previous findings, it is concluded that male acanthocephalans mate indiscriminately and often throughout their lives. Habitation of ceca maximizes sexual congress because individuals often are positioned with their posterior ends extending into the intestinal lumen within the small area from which ceca originate. Emigration to find a mate is unnecessary.

Prevalence of Agglutinating Antibodies to Sarcocystis neurona in Skunks (Mephitis mephitis), Raccoons (Procyon lotor), and Opossums (Didelphis virginiana) From Connecticut

Equine protozoal myeloencephalitis is the most important protozoan disease of horses in North America and is usually caused by Sarcocystis neurona. Natural cases of encephalitis caused by S. neurona have been reported in skunks (Mephitis mephitis) and raccoons (Procyon lotor). Opossums (Didelphis spp.) are the only known definitive host. Sera from 24 striped skunks, 12 raccoons, and 7 opossums (D. virginiana) from Connecticut were examined for agglutinating antibodies to S. neurona using the S. neurona agglutination test (SAT) employing formalin-fixed merozoites as antigen. The SAT was validated for skunk sera using pre- and postinfection serum samples from 2 experimentally infected skunks. Of the 24 (46%) skunks 11 were positive, and all 12 raccoons were positive for S. neurona antibodies. None of the 7 opossums was positive for antibodies to S. neurona. These results suggest that exposure to sporocysts of S. neurona by intermediate hosts is high in Connecticut. The absence of antibodies in opossums collected from the same areas is most likely because of the absence of systemic infection in the definitive host.

EXPERIMENTAL INVESTIGATION OF PHYSIOLOGICAL FACTORS THAT MAY INFLUENCE MICROHABITAT SPECIFICITY EXHIBITED BY LEPTORHYNCHOIDES THECATUS (ACANTHOCEPHALA) IN GREEN SUNFISH (LEPOMIS CYANELLUS)

Representatives of Leptorhynchoides thecatus (Acanthocephala) inhabit ceca of green sunfish but cannot survive in the anterior intestine. The influence of elevated cecal protein concentrations, pH, and amounts of lumenal materials on the microhabitat specificity of L. thecatus was investigated. An attempt was made to alter the distribution of worms in starved fish, in fish of which cecal pH was reduced, and in fish of which intestinal protein concentration was elevated. Protein concentration and pH showed no effect on worm distribution. Starving hosts had no effect on worm number or distribution but resulted in retardation of worm growth and development, providing a mechanism by which worms may overwinter and by which peak egg production may coincide with abundance of the amphipod intermediate host. None of the factors investigated is solely responsible for the microhabitat specificity of L. thecatus. It is suggested that helminth site specificity is characterized by long histories of adaptation to specific habitats with many physiological adaptations being facilitated synergistically. Maximization of sexual congress may exert an important selective pressure favoring this establishment of microhabitat specificity.

Prevalence of Agglutinating Antibodies to Toxoplasma gondii in Striped Skunks (Mephitis mephitis), Opossums (Didelphis virginiana), and Raccoons (Procyon lotor) From Connecticut

The prevalence of agglutinating antibodies to Toxoplasma gondii was examined in striped skunks (Mephitis mephitis), opossums (Didelphis virginiana), and raccoons (Procyon lotor) from 8 cities in Connecticut. Ten (42%) of the 24 striped skunks, 2 of 7 (29%) opossums, and 12 of 12 (100%) raccoons were positive at dilutions of 1:50 or greater. These results suggest that T. gondii is prevalent in the environment, or prey items, or both, of these omnivores in Connecticut.

Acanthocephala of the bald eagle (Haliaeetus leucocephalus) in North America.

Examination of bald eagles (Haliaeetus leucocephalus) collected from several locations in North America contributed new information concerning the acanthocephalan fauna of this host. Representatives of Arythmorhynchus brevis, representing a new host record, were collected from eagles in Florida, New Hampshire, and Wisconsin. Plagiorhynchus sp. was collected from an eagle in Florida. Corynosoma strumosum was collected from an eagle in Alaska. Andracantha phalacrocoracis, representing a new host record, was collected from an eagle in Alaska. Southwellina hispida, representing a new host record, was collected from eagles in Maine and Virginia. The occurrence of gravid or mature females of A. brevis, Plagiorhynchus sp., and S. hispida suggests that the bald eagle may serve as a competent definitive host for these species.

Gastric Evacuation and Movement of Materials through the Alimentary Canal of Green Sunfish

Abstract Pyloric ceca, the function of which is unclear, often harbor large numbers of helminths. Ceca may provide a sheltered region for worms or provide a region of sequestered nutrients. Adults of the acanthocephalan parasite Leptorhynchoides thecatus are restricted to the seven pyloric ceca in green sunfish Lepomis cyanellus. Gastrointestinal motility of green sunfish was investigated to determine if ceca provide a sheltered or nutrient-sequestering region for L. thecatus. Gastric evacuation and the movement of materials through the alimentary canal were determined by monitoring the movement of meals containing dye, accomplished by inserting gelatin capsules containing dye into the body cavity of American cockroaches Periplaneta americana, which were fed to the sunfish, and recording observations at various time intervals postfeeding. Gastric evacuation occurred 24–32 h postfeeding. Approximately 25% of the stomach contents were evacuated by 4 h and 50% were by 12 h. Rate of gastric evacuation was hig...

Physiological attributes of the pyloric caeca and anterior intestine of green sunfish (Lepomis cyanellus) potentially influencing microhabitat specificity of Leptorhynchoides thecatus (Acanthocephala)

Abstract Pyloric caeca are present in some species of fish and serve as a habitat for many helminth parasites. Physiological and biochemical attributes of luminal contents of the caeca and proximal intestine of green sunfish, Lepomis cyanellus, were compared to determine factors that could account for localization of Leptorhynchoides thecatus (Acanthocephala) in caeca after initial establishment in caeca and anterior portion of the intestine. Caecal protein concentrations were significantly higher. The anterior intestine exhibited significantly higher levels of proteolytic activity; however, caeca exhibited higher levels of aminopeptidase activity. The pH of caeca was significantly higher than that of the proximal portion of the intestine. Caeca contained greater total amounts of materials, and therefore contained greater total amounts of proteins, free amino acids, lipids, carbohydrates, and bile salts. A significant time–place interaction was detected regarding total free amino acids, suggesting that enzymatic activity in the caeca was responsible for increased amounts of intestinal amino acids. Physiological factors that might influence microhabitat specificity of L. thecatus include inadequate levels of intestinal protein, different levels of proteolytic activity (perhaps resulting from differences in pH), such as aminopeptidase activity, and lack of sufficient quantities of anterior intestinal nutrients to sustain worms. These results demonstrate subtle spatial and temporal complexities intrinsic to the environment of helminths inhabiting the teleost enteric system.