Terry A. Dick

A rapid method to determine the isotype and specificity of coproantibodies in mice infected with Trichinella or fed cholera toxin

A method was developed to isolate and test coproantibodies from mice infected with Trichinella or mice fed cholera toxin. It was rapid as results were obtained within 3 h, and it was applicable to a single faecal pellet. It reduced the number of experimental animals required 7-fold, and reduced variability, since samples were obtained from the same experimental animal over time. As it was noninvasive, it did not alter normal gut physiology, nor the course of the parasitic infection. The immune response was monitored over time in individual mice, and specific sIgA and IgG isotypes were detected for both Trichinella and cholera toxin by ELISA.

HELMINTHS AND FOOD HABITS OF LAKE STURGEON ACIPENSER FULVESCENS FROM THE LAKE WINNEBAGO SYSTEM, WISCONSIN

-Eight species of helminths were recovered from 45 summer (June-August) and 29 winter (February) lake sturgeon adults and juveniles, from Lake Winnebago, Wisconsin. Eighteen young-of-the-year (YOY) sturgeon collected from the Wolf River were uninfected. Both summer and winter helminth communities were dominated by host specific parasites such as Crepidostomum auriculatum, Skrjabinopsolus manteri, Capillospirura pseudoargumentosa and Truttaedacnitis clitellarius. Examination of stomach contents indicated that chironomids were the most important food items and comparison with past records on lake sturgeon diet suggests an unchanged use of the benthos of Lake Winnebago. The eutrophic nature of Lake Winnebago is probably responsible for the absence of Hexagenia spp., an important component of the diet of lake sturgeon from other systems, which would explain the absence of a host specific nematode, Spinitectus acipenseri. Although the trophic status of the lake may modify the helminth community, some host specific endo-helminths (C. auriculatum, C. pseudoargumentosa) appear to be transmitted in riverine environments (deeper downstream channels) used as feeding areas by older (2 yr+) sturgeon. Differences in habitat and diet of YOY sturgeon in the Wolf River and the absence of any host specific helminths in these juveniles also indicate that the community of host specific helminths is not recruited until YOYjuveniles enter deeper downstream channels to feed.

Influence of Genotype and Temperature on the Relationship between Specific Growth Rate and Size of Rainbow Trout

Abstract The relationship between specific growth rate and fish size (weight) was influenced by temperature and genotype in two strains of rainbow trout Oncorhyncus mykiss (formerly Salmo gairdneri) and their hybrid. Heterogeneity among the regression slopes for strains (genotype) as well as interaction with temperature invalidated the use of analysis of covariance to adjust for initial fish size differences. Regression slopes ranged from –0.74 ± 0.21 (SE) to –0.01 ± 0.16 among fish families reared at 7°C and from –0.41 ± 0.03 to –0.24 ± 0.09 among fish families reared at 15°C. The use of a particular slope value as a universal constant to compare specific growth rates offish is questionable.

Role of Predation and Parasitism in Growth and Mortality of Yellow Perch in Dauphin Lake, Manitoba

Abstract Total mortality, mortality due to predation, and the contribution of parasite-induced mortality were estimated for yellow perch Perca flavescens infected with the nematode Raphidascaris acus. Total annual natural mortality of yellow perch in Dauphin Lake, Manitoba, was approximately 61%; predation by northern pike Esox lucius accounted for 19% and 45% of natural mortality for female and male yellow perch, respectively. Yellow perch harbored 18 species of parasites, of which R. acus was the most abundant; 95% of all R. acus larvae inhabited the liver. The number of free and encapsulated larvae and nodules in the liver of yellow perch varied seasonally and with fish gender, but it was not correlated with water temperature or fish habitat. Mean intensity but not recruitment increased with age of yellow perch. Density of R. acus (larvae per gram of liver) was highest in young, immature yellow perch and decreased with age in mature yellow perch. Yellow perch with high-density infections had lower cond...

Genetic and morphological variability in a population of Diphyllobothrium dendriticum (Nitzsch, 1824)

Plerocercoids of Diphyllobothrium dendriticum were isolated from whitefish (Coregonus clupeaformis) from McGregor Lake, Alberta. Adult D. dendriticum were obtained by infection of golden hamsters (Mesocricetus auratus). Analysis of morphological variables indicated high variability and some overlap with D. latum. Correlations in morphology were due to the covariance of shape variables. Isozyme analysis also showed high variability, with two thirds of the enzymes studied being polymorphic. Correlations with morphology indicate a relationship between rare patterns for malate dehydrogenase and esterase and increased size of adults. Southern hybridisation with ribosomal gene probes produced two common patterns and a rare intermediate form, indicating that the species is variable even within a local population. Correlations between rDNA pattern type and morphological variables supported the hypothesis of a genetic base for the morphological variability.

HELMINTHS OF STOCKED RAINBOW TROUT (SALMO GAIRDNERI) WITH SPECIAL REFERENCE TO CLINOSTOMUM COMPLANATUM

Rainbow trout (Salmo gairdneri) stocked into a small prairie dug-out were examined for helminths at harvest time. Five species of helminths were found (Diplostomum sp., Diplostomulum scheuringi, Clinostomum complanatum, Crepidostomum farionis and Pomphorhynchus bulbocolli); C. farionis and P. bulbocolli mature in fish while the remaining species utilize fish-eating birds as definitive hosts. Examination of stomach contents indicated that all invertebrate hosts required for the life-cycles of these helminths were present in the dug-out. The most conspicuous and prevalent helminth was C. complanatum as fish were “wormy” and unmarketable due to the presence of high numbers of metacercariae. Metacercariae of C. complanatum were recovered from most organs of rainbow trout. The low survival of stocked fish suggests that C. complanatum may cause some host mortality, but the condition of infected and uninfected fish was similar. It appears that a community of ichthyoparasites can become established in a population of stocked fish in a single growing season in north temperate regions.

Use of confidence ellipses to detect effects of parasites on the growth of yellow perch, Perca flavescens

Determining the causes of mortality in populations of fish is inherently difficult. To simplify the determination of whether parasite-induced mortality occurs, parasitologists have relied on 3 types of subjective analyses of graphs. Peaked host age-parasite intensity curves concomitant with a decrease in the degree of dispersion (measured by variance-to-mean ratio) of parasites in older age-classes of fishes, a slope of less than 2.0 for a log-log graph of variance versus mean intensity of infection, and differences between truncated and nontruncated forms of a theoretical frequency distribution for the parasite are considered indicators of parasite-induced mortality in fishes. The nematode Raphidascaris acus causes significant parasite-induced mortality in natural populations of yellow perch (Perca flavescens) in Dauphin Lake, Manitoba, Canada. Using this fish-parasite system we present a comparison of some of the graphical techniques used by parasitologists to detect parasite-induced mortality and show how confidence ellipses based on the parameters beta 0 and beta 1 of a linear model for growth of yellow perch (weight = beta 0 + beta 1 x age) can be used to compare many growth curves simultaneously. When plotted in a bivariate fashion (beta 0 vs. beta 1), vertical displacement of confidence ellipses along the ordinate (beta 1) are due to sublethal effects on growth of fishes in response to parasites, whereas lateral shifts along the abscissa (beta 0) are suggestive of parasite-induced mortality.(ABSTRACT TRUNCATED AT 250 WORDS)

Diclybothrium atriatum n. sp. (Monogenea:Diclybothriidae) from North American acipenserid fishes with observations on Diclybothrium armatum and Diclybothrium hamulatum.

Diclybothrium atriatum n. sp. is described from North American acipenserid fishes, Acipenser fulvescens Rafinesque (lake sturgeon) and Acipenser brevirostrum Le Sueur (shortnose sturgeon). Diclybothrium atriatum is distinguished from other diclybothriids by the presence of a unique preovarial structure that we name the ventral atrial organ. This structure possesses a ventral orifice leading to a deep groove that widens internally as a crypt, bordered by densely staining granular bodies and more deeply situated glandular cells. Previous records of Diclybothrium armatum Leuckart, 1835 examined in this study from North American acipenserids are referable to D. atriatum. Studies on the anatomy of this and other species of Diclybothrium Leuckart, 1835, D. armatum and Diclybothrium hamulatum (Simer, 1929), reveal the presence of paired multichanelled sperm ducts that are shown to be characteristic of the Diclybothriidae Bykhovskii and Gusev, 1950. Paired sperm ducts, while common in Turbellaria with multiple testes, are unusual amongst Monogenea. The endemicity of Diclybothrium atriatum and specificity for A. fulvescens and A. brevirostrum suggests that speciation of this parasite may have occurred following the isolation of Acipenser L. spp. in central and eastern North America.

Spinitectus acipenseri n. sp. (Nematoda: Cystidicolidae) from the lake sturgeonAcipenser fulvescens (Rafinesque) in Canada

Spinitectus acipenseri is described as a new species from the muscular stomach of the lake sturgeonAcipenser fulvescens from Manitoba and Saskatchewan. This new species closely resemblesS. gracilis Ward & Magath, 1917, but the major differences are the arrangement and larger size of spines (circlets and semicirclets of spines reaching to the anus in females ofS. acipenseri). Other differences include total body dimensions of adults (length and width relationships) and a 1:4–1:5 ratio of oesophagus to body length.

Evaluation of gill nets, fyke nets, and mark-recapture methods to estimate the number of Hirudinea and Crustacea on fish.

Twenty species of fishes (n = 20,759) were collected from Dauphin Lake, Manitoba, Canada, to determine the types and numbers of ectoparasites they harbored. Counts of ectoparasites on fishes collected with different gear were compared to evaluate different methods of collection and to estimate rates of recruitment of ectoparasites by fishes. Ectoparasites were found on 11 species of fishes and the majority of these were parasitic leeches (Myzobdella moorei, Cystobranchus verilli, and Placobdella montifera) and parasitic Crustacea (Argulus appendiculosus and Lernaea cyprinacea). Some fishes also were infested by neascus-type metacercariae (blackspot) or had tumors (lymphocystis). The prevalence of ectoparasites was correlated with the abundance, feeding habits, and spatial distribution of fish species. Argulus appendiculosus and blackspot were more prevalent on benthic fishes, whereas M. moorei and tumors were more prevalent on limnetic fishes. Mark-recapture records showed that fishes occupying shallow (less than or equal to 1.5 m) water had a higher prevalence of infestation and 28 of 29 infected fishes caught by gill nets were captured in shallow water. Placobdella montifera was the only ectoparasite found on fishes from deep (1.5-3.5 m) water and the only species that was acquired by fishes previously released with no ectoparasite (2 of 239 fishes). The littoral zone (less than or equal to 1.5 m) comprises only 14% of the surface area and 3% of the volume of Dauphin Lake, yet 72% of all gill-netted fishes harboring ectoparasites were collected there. Intensities of ectoparasites estimated from gill net and pound net samples were similar, but prevalence of ectoparasites estimated from samples obtained with gill nets was lower.