The immune response of wild rainbow trout, Salmo gairdneri Richardson, to naturally acquired plerocercoid infections of Diphyllobothrium dendriticum (Nitzsch, 1824) and D. ditremum (Creplin, 1825)

Natural infections of rainbow trout with two species of Diphyllobothrium result in a host inflammatory response encapsulating the plerocercoid. The encapsulating cyst, observed by light and electron microscopy, comprises leucocytes, fibroblasts and collagenous connective tissue and is infiltrated with a blood vascular network. An indirect immunofluorescence technique and enzyme-linked immunosorbant assay (ELISA) have shown that specific antibodies are elicited by the fish host to these Diphyllobothrium spp. These antibodies have been semi-quantitatively measured by ELISA and correlated with worm burdens in individual fish.     

Functional units in rainbow trout (Salmo gairdneri, Richardson) liver: III. Morphometric analysis of parenchyma, stroma, and component cell types

Hepatic stroma and parenchyma with its component cell types were quantitatively described in adult male and female actively-spawning 5-year-old rainbow trout (Salmo gairdneri, Richardson). Point-count morphometry of glycol methacrylate sections estimated volume compartments for stroma and parenchyma. Veins composed 85% of the stroma while arteries and bile ducts occupied approximately 6-7% each. Parenchyma accounted for 95% of hepatic volume. Point-count morphometry of transmission electron micrographs estimated volume compartments as well as numerical and surface density measurements for parenchymal components. Within the hepatic parenchymal compartment, hepatocytes occupied 85% and showed significant sex differences. Female hepatocytes were significantly more numerous but were smaller, only 60% of the volume of male hepatocytes. Since hepatocyte nuclear volume was equal in both sexes, differences were due to reduced cytoplasmic volume in females. Perisinusoidal macrophages of females occupied larger volumes of their respective parenchymal compartments, and their larger mean cytoplasmic volumes suggested activation. Biliary epithelial cells of preductules and ductules were numerous. Ratios of numerical density of hepatocytes to biliary epithelial cells were consistent with a tubular arrangement of hepatocytes. Factors possibly mediating the sexual dimorphism are discussed.     

Postembryonic ontogeny and functional anatomy of the ligamentum mandibulo-hyoideum and the ligamentum interoperculo-mandibulare,with notes on the opercular bones and some other cranial elements in Salmo gairdneri Richardson, 1836 (Teleostei: Salmonidae)

This study deals with the development of the opercular bones the ligamentum mandibulo-hyoideum, the ligamentum interoperculo-mandibulare and with some aspects of the development of the ceratohyale and the cartilago meckeli during postembryonic ontogeny of Salmo gairdneri (rainbow trout). It is stated that the ligamentum mandibulo-hyoideum is present from hatching onward, while the development of the ligamentum interoperculo-mandibulare appears during the period of active feeding. Some functional reasons are proposed to explain these facts. It is further suggested that the opercular bones develop under influence of the opercular muscles.