DISEASES OF MARINE FISHES
5
hypertrophic diseases. Lymphocystis disease and certain papillomas
have long been felt to be of viral origin, based on epizootiological and
transmission studies, and on the presence of inclusions in affected cells.
Lymphocystis is probably the best known virus disease of marine
and fresh-water fishes. First described from the European flounder,
Pleuronectes jlesus (L.),* by Lowe (1874), and soon after from other
species (McIntosh, 1884, 1885 ; Sandeman, 1892 ; Woodcock, 1904), the
disease has since been reported from the orange filefish, Alutera schepfi
(Walb.), by Weissenberg (1938) and Nigrelli and Smith (1939); the
killifish, Fundulus heteroclitus L., by Weissenberg (1939a) ; the red
mullet, Mullus surmuletus (L.), by Alexandrowicz (1951) ; and from
other marine and fresh-water species (Smith and Nigrelli, 1937; Weissenberg et al., 1937; Weissenberg, 1945). Recently several cases of
presumed lymphocystis in striped bass, Roccus saxatilis (Walb.), have
been observed (Anonymous, 1951 ; Sindermann, unpublished). The
disease was originally thought to be caused by parasitic protozoa or
eggs of another animal laid under the skin of fish (Sandeman, 1892;
Woodcock, 1904). Weissenberg (1914, 1920) and Joseph (1918) were
the first to recognize lymphocystis cells as hypertrophied fibroblasts.
Transmission studies (Ragin, 1927, 1928; Weissenberg, 1939b, 196lb;
Wolf, 1962) have demonstrated the infectious nature of the disease and
have suggested some degree of host specificity. Definitive evidence that
a virus is responsible for lymphocystis was obtained by electron microscopy (Walker, 1962; Walker and Wolf, 1962) and by transmission of
the disease with ultracentrifugates and bacteria-free filtrates (Weissenberg, 1951a; Wolf, 1962). Manifestations of lymphocystisinclude whitish
nodules on body and fins caused by hypertrophy of fibroblasts and
osteoblasts (Fig. la). The connective tissue cells grow to enormous size
(5 mm in some cases) and become surrounded by a thick hyaline capsule.
In severe cases most of the body surface may be involved. Weissenberg
(1921a) reported that in some areas up to one-third of a population of
fish could be affected. A great body of literature has accumulated on
lymphocystis, and much of the early work was well summarized by
Nigrelli and Smith (1939). A history of research on the disease has just
been published (Weissenberg, 1965).
A recent and apparently sharply defined outbreak of lymphocystis
* Throughout the paper an attempt has been made to give common and scientific
names of fishes when they are first mentioned, and only the common name thereafter.
In some cams this is not possible, aa for example when the =me common name ia
applied to several different species in different geographical are-, or when a species
m y have a different common name in different areas. Scientific names of fishes from
North American watera follow the recommendations of the American Faeries Society
(1960).
5
hypertrophic diseases. Lymphocystis disease and certain papillomas
have long been felt to be of viral origin, based on epizootiological and
transmission studies, and on the presence of inclusions in affected cells.
Lymphocystis is probably the best known virus disease of marine
and fresh-water fishes. First described from the European flounder,
Pleuronectes jlesus (L.),* by Lowe (1874), and soon after from other
species (McIntosh, 1884, 1885 ; Sandeman, 1892 ; Woodcock, 1904), the
disease has since been reported from the orange filefish, Alutera schepfi
(Walb.), by Weissenberg (1938) and Nigrelli and Smith (1939); the
killifish, Fundulus heteroclitus L., by Weissenberg (1939a) ; the red
mullet, Mullus surmuletus (L.), by Alexandrowicz (1951) ; and from
other marine and fresh-water species (Smith and Nigrelli, 1937; Weissenberg et al., 1937; Weissenberg, 1945). Recently several cases of
presumed lymphocystis in striped bass, Roccus saxatilis (Walb.), have
been observed (Anonymous, 1951 ; Sindermann, unpublished). The
disease was originally thought to be caused by parasitic protozoa or
eggs of another animal laid under the skin of fish (Sandeman, 1892;
Woodcock, 1904). Weissenberg (1914, 1920) and Joseph (1918) were
the first to recognize lymphocystis cells as hypertrophied fibroblasts.
Transmission studies (Ragin, 1927, 1928; Weissenberg, 1939b, 196lb;
Wolf, 1962) have demonstrated the infectious nature of the disease and
have suggested some degree of host specificity. Definitive evidence that
a virus is responsible for lymphocystis was obtained by electron microscopy (Walker, 1962; Walker and Wolf, 1962) and by transmission of
the disease with ultracentrifugates and bacteria-free filtrates (Weissenberg, 1951a; Wolf, 1962). Manifestations of lymphocystisinclude whitish
nodules on body and fins caused by hypertrophy of fibroblasts and
osteoblasts (Fig. la). The connective tissue cells grow to enormous size
(5 mm in some cases) and become surrounded by a thick hyaline capsule.
In severe cases most of the body surface may be involved. Weissenberg
(1921a) reported that in some areas up to one-third of a population of
fish could be affected. A great body of literature has accumulated on
lymphocystis, and much of the early work was well summarized by
Nigrelli and Smith (1939). A history of research on the disease has just
been published (Weissenberg, 1965).
A recent and apparently sharply defined outbreak of lymphocystis
* Throughout the paper an attempt has been made to give common and scientific
names of fishes when they are first mentioned, and only the common name thereafter.
In some cams this is not possible, aa for example when the =me common name ia
applied to several different species in different geographical are-, or when a species
m y have a different common name in different areas. Scientific names of fishes from
North American watera follow the recommendations of the American Faeries Society
(1960).