R. A. Khan

Prevalence and Influence of Loma branchialis (Microspora) on Growth and Mortality in Atlantic Cod (Gadus morhua) in Coastal Newfoundland

A study was conducted to determine the prevalence, geographical distribution, and effects of a microsporan parasite, Loma branchialis, in Atlantic cod in coastal Newfoundland. The parasite was identified microscopically as opaque, ovoid xenomas, primarily in the gills, heart, and spleen. Although widely distributed in young fish inhabiting 7 coastal localities, prevalence was 1–7% in general, <0.01% in older and large fish, but 78% in market-size cod from a commercial farm. Some of the latter fish were emaciated, and ∼2 mo after the parasite was detected, 63% succumbed with a massive infection. Condition factor and blood values were significantly lower than those in reference fish. An experimental study conducted over 2 yr revealed that mass gained and condition factor were significantly lower in infected cod than in controls at the termination of the study. Feed consumption, mass gained, feed conversion efficiency, and condition factor also were significantly lower in another group of infected cod of marketable size studied over 12 wk. Xenomas also were observed in the heart and gills of year class II cod reared in a hatchery. Loma branchialis is considered to be a potential pathogen in both hatchery-reared and net pen–cultured cod in Newfoundland.

EFFECT, DISTRIBUTION, AND PREVALENCE OF GLUGEA STEPHANI (MICROSPORA) IN WINTER FLOUNDER (PLEURONECTES AMERICANUS) LIVING NEAR TWO PULP AND PAPER MILLS IN NEWFOUNDLAND

A study was conducted to determine the effects, geographical distribution, and prevalence of a microsporan parasite, Glugea stephani, in winter flounder (Pleuronectes americanus) in Newfoundland. Fish were captured by SCUBA divers in several coastal areas, including 2 embayments where pulp and paper mill effluent was discharged, as well as a number of pristine sites. Fish health was assessed by comparing histological profiles, condition factors (K), organosomatic indices and blood values between infected and uninfected samples. Multifocal xenomas of G. stephani were observed in several organs of fish taken near contaminated sites, whereas infected samples captured at a pristine site harbored the cysts only in the wall of the digestive tract. Proliferative inflammation, granuloma formation, and focal necrosis were associated with the infection primarily in the liver and kidney. Condition factors and blood values were lower and ovarian development inhibited or delayed in infected flounder. The multifocal infection occurred only in flounder in 2 embayments in western Newfoundland where pulp and paper mill effluent was discharged. Prevalence varied seasonally, with a peak in autumn and a low in spring. It is likely that the multifocal infection was associated with immunodepression after exposure to the contaminant.

SPECIES COMPOSITION OF ASSEMBLAGES OF CERATOMYXA (MYXOZOA), PARASITES OF LINGS GENYPTERUS (OPHIDIIDAE) IN THE SOUTHEASTERN PACIFIC OCEAN: AN ECOMORPHOMETRIC APPROACH

Studies on Myxozoa have emphasized their potential impact on aquatic animal health but less on ecological aspects. In this investigation, we assess the importance of host and latitudinal variations in the morphometry of spores of Ceratomyxa Thélohan, 1892 (Myxozoa) from the gall bladder of 3 ling Genypterus (Pisces; Ophidiidae) species. Discriminant analyses indicated that several morphospecies of Ceratomyxa coexist in these hosts, despite the fact that the specific level of taxonomic resolution of each spore was not attempted. At least 4 species, i.e., Ceratomyxa hokarari Meglitsch, 1960; Ceratomyxa inversa Meglitsch, 1960; Ceratomyxa laxa Meglitsch, 1960; and Ceratomyxa elongata Meglitsch, 1960 occur in the study area, and at least 2 species co-occur in each host and geographical location. The most widespread pattern found is that spores are larger in golden ling (Genypterus blacodes) and spore size decreases with increasing latitude; this may be associated with the species composition of these assemblages, as well as with the habitat and diet segregation of the host species.

Cryptobia neghmei sp. n. (Protozoa: Kinetoplastida) in two species of flounder, Paralichthys spp. (Pisces: Paralichthydae) off Chile

Se describe a Cryptobia neghmei sp.n., un protozoo sanguineo de dos especies de lenguados, Paralichthys microps y P. adspersus, habitantes de la costa de Chile en el sur-este del oceano Pacifico. Los protozoos flagelados son de forma elongada, delgados con dos flagelos y una membrana ondulante conspicua. Esta especie se distingue de aquellas descritas previamente en base a su forma y dimensiones inusuales. Los 97 lenguados revisados estaban infectados. Se observaron otros estados de desarrollo de protozoos kinetoplastidos en la sanguijuela Glyptonotobdella sp. que parasitaba a los lenguados y que probablemente sea el vector del protozoo

Comparison of metazoan parasites of Atlantic cod, Gadus morhua, from three geographical areas of coastal Newfoundland.

Abstract This study compared metazoan parasites in the digestive tract of Atlantic cod, Gadus morhua, captured from 3 geographical areas off the northeastern (NE), southeastern (SE), and southwestern (SW) coasts of Newfoundland. Samples were obtained by line trawl and frozen after capture, and the digestive tract was subsequently examined for metazoan parasites following conventional parasitological methods. Mean abundance of nematodes, but not the trematodes, and an acanthocephalan was significantly greater in cod taken from the NE than from the SE or SW areas, which were generally similar. Four species of trematodes, 3 nematodes, and an acanthocephalan, Echinorhynchus gadi, were the dominant parasites observed. Differences in mean abundance among samples from different areas might be related to the types of prey consumed rather than to environmental factors. The dominant parasites were probably acquired by cod on the NE coast after feeding on capelin, Mallotus villosus, which serve as paratenic hosts for several helminth species. Previous studies on tagging, feeding, and prevalence of 3 parasites have revealed differences in the populations of cod from the NE than from the SW or SE areas. Results from the present study, indicating geographical differences in parasite mean abundance and prevalence from the digestive tract of Atlantic cod between SW and NE areas, support the view of distinct coastal cod stocks off Newfoundland.

Two Species of Commercial Flatfish, Winter Flounder, Pleuronectes americanus, and American Plaice, Hippoglossoides platessoides, as Sentinels of Environmental Pollution

Two species of marketable-size flatfish, winter flounder (Pleuronectes americanus) and American plaice (Hippoglossoides platessoides) from a fjord, were examined as sentinels for the effects of effluent discharged by a pulp and paper mill in Newfoundland, Canada. Reference samples for comparison were obtained from a pristine fjord. Condition factor, lymphocyte levels and the abundance of two intestinal parasites were significantly greater in flounder and plaice sampled at the reference site while macroscopic and microscopic lesions, and hepatic somatic indices were greater in flatfish taken from the contaminated site. These results suggest that both species of commercial flatfish are useful as sentinels for studying environmental pollution.

Two new protist species, Trypanoplasma ojedae sp. n. (Mastigophora: Kinetoplastida) and Trichodina lascrucensis sp. n. (Ciliophora: Peritrichida) in a blenniid fish, Scartichthys viridis, from the coast of Chile

Two new protistan species were observed in a blenniid fish, Scartichthys viridis, inhabiting tide pools at Las Cruces, central Chile. Trypanoplasma ojedae sp. n. (Mastigophora: Kinetoplastida) in the blood is characterized by its small size (29.8 ± 5.0 x 5.1 +1.2 im), short anterior flagellum (4.9 ± 0.6 im), anterior located kinetoplast (2.4 ± 0.2) and a prominent undulating membrane. All of 18 fish were infected and 67% were parasitized on the gills by an unidentified piscicolid leech that harbored developing and infective biflagellated stages. Trichodina lascrucensis sp. n. (Ciliophora: Peritrichida) parasitized the gill fillaments of all fish. The ciliate is characterized by its body size (70.8 ± 8.4 im), adhesive disc (53 ± 5.4 im), denticular ring (33 ± 3.1 im), mean number of denticles (32.8 ± 3.0), mean number of denticular pins (9.5 ± 1.0) and ovoid micronucleus located near to one of the macronuclear arms. Since none of the two parasites was similar to any species described from marine tide pool habitats as well as from the Pacific Ocean, both are considered new species with the characteristics described herein.