Paramoebidae

Abstract: An amoeba resembling Paramoeba has been cultured from tissues of diseased sea urchins. Cultures containing the amoeba produced signs of the disease when injected into the coelom of healthy urchins. Control treatments lacking the amoeba did not cause the disease. The amoeba was cultured from radial nerve fragments and seen in tissue sections from experimentally infected urchins. Cultures of the amoeba from these experimentally infected urchins reproduced the disease in healthy urchins by both injection and water-borne routes. These observations suggest involvement of Paramoeba in recent mass mortalities of sea urchins in Nova Scotia.

Abstract: Paramoeba invadens is a pathogenic marine amoeba responsible for mass mortalities of sea urchins (Strongylocentrotus droebachiensis) along the Atlantic coast of Nova Scotia in the early 1980's. The amoeba has been maintained in vivo in S. droebachiensis for five years in the laboratory without observable loss of virulence. Paramoeba invadens was cultured polyxenically (on mixed marine bacteria) and monoxenically (on a single strain of Pseudomonas nautica) on non-nutrient agar for 58 weeks and 19 weeks respectively. Pathogenicity tests showed some loss of virulence in monoxenic culture after 15 weeks and in polyxenic culture after 58 weeks. Polyxenic culture is recommended for long-term culture of P. invadens although periodic passage of the amoeba through the sea urchin host may be required to maintain virulence for periods exceeding one year.

Abstract: Two new species of Korotnevella Goodkov, 1988, Korotnevella hemistylolepis n. sp. and Korotnevella monacantholepis n. sp., are described from mesohaline ecosystems. The amoebae are characterized on the basis of light and electron microscopy with special emphasis on the structure of the basket scales, which have species-specific architecture. The two new species are the second and third ones recovered from environments other than freshwater. In terms of scale morphology they most closely resemble a freshwater species, Korotnevella bulla (Schaeffer, 1926) Goodkov, 1988. Two genus names, Dactylamoeba Korotnev, 1880 and Korotnevella Goodkov, 1988, are in current use. The latter name is preferred, pending rediscovery and characterization of Dactylamoeba elongata Korotnev, 1880, the type species of the genus. Korotnevella species can be divided into three groups on the basis of scale morphology, suggesting that the genus may not be monophyletic. A key to species is provided.