摘要:

Susceptible juvenile chinook salmon (Oncorhynchus tshawytscha) were protected from otherwise lethal challenges with the haemoflagellateCryptobia salmositicaby acclimation to an elevated water temperature (20 °C). Following challenge at temperatures advantageous to the haemoflagellate (9–11 °C), surviving fish had plasma with enhanced acquired lytic activity against the parasite. In contrast, most coho salmon (Oncorhynchus kisutch) from a resistant stock survived up to three challenges withC.salmositica, without "immunization" at elevated temperatures. However, they acquired little or no lytic activity against the parasite, which survived in low numbers in some fish. Also, the chinook and coho salmon did not have innate plasma factors that lysed the parasite under in vitro conditions like those demonstrated in other salmonids. Thus, the mechanism(s) that protect the resistantO.kisutchfrom the pathogenic affects ofC.salmositicaare different from those identified in other fishes that are resistant toCryptobiaspp. A challenge of 105flagellates per fish was suggested to be representative of the number ofC.salmositicainoculated into a fish by one infected leech vector (Piscicola salmositica).

ISSN:0706-652X    

DOI:10.1139/f95-501

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

Myxobolus rhinichthidisFantham, Porter and Richardson, 1939 (Myxosporea) is redescribed from longnose dace (Rhinichthys cataractae) in Maryland. Large round plasmodia occurred in the connective tissue of the skin covering the head and opercular regions. Fixed spores are oval in front view and measure 11.5–14.5 μm long, 9.0–10.5 μm wide, and 6.0–7.0 μm thick. The polar capsules are 5.5–7.0 μm long and 3.0–3.5 μm wide. Photomicrographs of formalin-fixed spores document variation in spore size and shape. The report is the first forM.rhinichthidissince the species was described from blacknose dace (Rhinichthys atratulus) in Quebec. An updated list of species ofMyxobolusBütschli, 1882 reported from freshwater fishes in North America is provided.Myxobolus jahnriceiLandsberg and Lom, 1991 is considered a junior synonym ofMyxobolus filamentusGrinham and Cone, 1990; andMyxobolus liiDesser, 1993 andMyxobolus gibbosusLi and Desser, 1985 are junior synonyms ofMyxobolus uvuliferusCone and Anderson, 1977.

ISSN:0706-652X    

DOI:10.1139/f95-502

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

Proliferative kidney disease (PKD), caused by the PKX myxosporean, was observed in kokanee salmon (non-anadromous sockeye salmon) (Oncorhynchus nerka) and chinook salmon (O.tshawytscha) collected from the Puntledge River, Vancouver Island, British Columbia in July 1993. This is the first report of a natural infection of PKX in either captive or wild sockeye salmon. All 14 underyearling kokanee salmon and the one underyearling chinook salmon exhibited numerous PKX organisms and associated chronic inflammation in the renal interstitium. Thirty-eight percent of sexually mature kokanee salmon collected in the autumn of 1993 from Comox Lake (which drains into the Puntledge River) were infected withSphaerospora oncorhynchi, Kent, Whitaker and Margolis, 1993 in the renal tubules, while immature cutthroat trout (O.clarki) and coho salmon (O.kisutch) from the same collection did not exhibit myxosporean spores in the kidney. The kidneys of threespine stickleback (Gasterosteus aculeatus) and prickly sculpin (Cottus asper) collected from the Puntledge River during the summer were all infected with aMyxobilatussp., but no organisms suggestive of PKX orSphaerosporawere observed. This study further supports the hypothesis that PKX is a developmental stage ofS.oncorhynchi, which may sporulate only in sexually mature salmonids.

ISSN:0706-652X    

DOI:10.1139/f95-503

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

Chum salmon (Oncorhynchus keta) juveniles, experimentally infected with the bodonid flagellateIchthyobodo necator(Henneguy, 1883), were reared in 18-L tanks at three densities (300, 600, and 1200 fish) for 5 weeks. Water inflow rates were adjusted to give five combinations of crowding and flow rate. The parasite density on the fish body surface increased to 2700–4100 parasites-mm−2over the course of the experiment and did not differ significantly among the groups. Total mortality was 76–90% in infected groups kept under the most unfavorable conditions (crowding or low water supply) but 11–15% in the other infected groups. The former groups also showed apparent growth reductions. In the uninfected controls, mortality was low (0.7–2.6%) and the degree of crowding or water supply had no significant effect on growth or mortality. Infected salmon were also much less resistant to seawater challenge; all fish kept at high stocking density or low inflow rate died in seawater. These results indicate thatIchthyobodoinfections have marked effects on both host growth and survival when infections are combined with environmental stress induced by overcrowding and (or) inadequate water supply, although the parasite density is not affected by these factors.

ISSN:0706-652X    

DOI:10.1139/f95-504

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

Comment on the origin(s) of a group of parasites requires an awareness of the paleogeology of the region and historical records – phylogenies of both hosts and their parasites. The paleogeology of the Nearctic Region is described briefly and 11 families of Nearctic freshwater fishes for which phylogenetic information is available are considered: Acipenseridae, Polyodontidae, Catostomidae, Ictaluridae, Fundulidae, Poeciliidae, Cyprinodontidae, Percidae, Centrarchidae, Moronidae, and Percopsidae. A previous hypothesis that the Nearctic ancyrocephalids are of mixed origins is supported and the phenomena of vicariance, dispersal, host-switching, and co-evolution are demonstrated.

ISSN:0706-652X    

DOI:10.1139/f95-505

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

On the basis of data obtained from the literature, an attempt is made to synthesize current knowledge on the oncomiracidial osmoregulatory system of the Monogenea and its evolution during post-larval development. At the oncomiracidial level, two types characteristic respectively of the Monopisthocotylea and Polyopisthocotylea are defined. In each type, many states are recognized, based on the number and disposition of protonephridia. In the Monopisthocotylea these states appear to be in harmony with the ontogenic complication of the system. The development of the osmoregulatory system ofDiplectanum aequans(Wagener, 1857) is considered representative of the Monopisthocotylea. In the Polyopisthocotylea, a difference is pointed out between the post-larval development of the osmoregulatory system of the Microcotylidae and the Gastrocotylidae. The results of this synthesis add new support to the hypothesis of the polyphyletic origin of the Monopisthocotylea and the monophyletic origin of the Polyopisthocotylea.

ISSN:0706-652X    

DOI:10.1139/f95-506

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

This paper discusses probable causes for the origin and evolution of groups of monogenean congeneric sibling species infecting one fish host species, with special reference to freshwater fishes. These causes comprise strict specificity, topological differentiation of parasite micropopulations in microniches (microhabitats), ecological and geographic isolation of various parasite and host populations, paleogeographic or geomorphologic (butnotpaleogeologic) changes during the late Tertiary and Quaternary periods, with alternating marine transgressions and regressions acting upon continents which, after the Miocene, have been less affected by continental drift, orogenesis, and climatic fluctuations. Co-evolving with their hosts, Monogenea usually diverge faster than their hosts.

ISSN:0706-652X    

DOI:10.1139/f95-507

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

The analysis of population phenetics to study some of the polymorphic characters inPolystoma integerrimum(Froelich, 1791) from two populations in the Moscow and Novgorod regions, Russia, revealed discrete variations of these characters, defined as phenes, which are discrete, usually alternative, simple features reflecting the peculiarities of a given genotype. The studies demonstrate that the frequencies of phenes B1, B2, and B3, characterized by peculiarities of the serrations on the lower basal part of the marginal hooks, define the differences in genetic structure of the populations studied. Besides these structural differences, the two populations ofPolystomadiffer in intrapopulational phenetic diversity, whose index was higher in the Novgorod population. It is suggested that variations in the number of chitinous hooks of the copulatory organ i.e., 5, 6, 7, 9, and 10 hooks, characterize the complex of East-European populations ofP.integerrimum.

ISSN:0706-652X    

DOI:10.1139/f95-508

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

The monogeneanBenedenia epinepheli(Yamaguti, 1937) Meserve, 1938 is redescribed and reported for the first time from the fins, eyes, and body surface of cultured marine fishes of Japan. Because of close similarity in the general morphology of the reproductive system and median sclerites, comparable morphometrics, and the presence of a flap slightly left of the common genital aperture,Benedeniella congeriYamaguti, 1958 (=Neobenedeniella congeri(Yamaguti, 1958);Benedenia congeri(Yamaguti, 1958)) andBenedeniasp. of Tsutsumi and Ito, 1965 are synonimized with this species. Twelve new hosts are presented, bringing the total number of known hosts to 25 (11 Tetraodontiformes, 9 Perciformes, 3 Scorpaeniformes, 1 Pleuronectiformes, and 1 Anguilliformes). The ability ofB.epinephelito cause death of cultured fishes during heavy infection, and its low host specificity, ubiquitous distribution in western Japan, and the high susceptibility of marine aquarium fishes are indicative of the parasite's great potential to become a disease problem.

ISSN:0706-652X    

DOI:10.1139/f95-509

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

Steringophorus margolisin.sp., described from the ophidiidSpectrunculus grandis, is distinguished by its elongate vitelline fields and long caeca.Steringophorus(=Occultacetabulum)dorsolineatum(Reimer, 1985) n.comb. is described from the chlorophthalmidBathypterois dubius. It is suggested that the genusOccultacetabulumis synonymous withSteringophorus, and evidence is presented to show that the withdrawal of the ventral sucker into the body is a temporary condition.Steringophorus thuliniBray and Gibson, 1980 is partly redescribed from the macrouridsCoryphaenoides(Chalinura)mediterraneus,C. (Chal.)brevibarbis,C. (Chal.)leptolepis,C. (Chal.)profundicolus, andTrachyrincus murrayi.Steringophorus blackeriBray, 1973 is reported from the alepocephalidXenodermichthys copei.

ISSN:0706-652X    

DOI:10.1139/f95-510

出版商:NRC Research Press    

年代:1995

数据来源: NRC