DISEASES O F MARINE FISHES
21
species (Kudo, 1920), are of widespread occurrence in marine fishes.
Heavy infections may cause enlargement, discoloration and disruption
of function of the organ. Fantham and Porter (1912), who examined
the widespread occurrence of gall bladder parasites in elasmobranchs
and teleosts from the English and French coasts, found that myxosporidean parasitization caused inflammation of the organ, excess
secretion of mucus and increase in viscosity of bile, enlarged livers and
emaciation of the host.
Gill-invading Myxosporidea are not usually of serious consequence
to marine fishes. However, Shulman (1957) described an epizootic of
Myxobolus exiguus in the gills of mullet, Mugil cephalus (L.), from the
Black Sea in which 500-600 kg of fish per kilometer were washed up
on the western shore of the Crimean Peninsula during the spring of
1949. Mechanical disruption of gill function, caused by heavy infection
with myxosporidean cysts, was considered the cause of death. No
abnormalities were noted in the viscera.
Several species of Myxosporidea invade the cranial cartilages of
fishes. One, Myxobolus aeglejini (Auerbach), occurs in plaice, Pleuronectes
plntessa (L.), hake, Merluccius merluccius (L.), and haddock, Gadus
aeglefinus L., of the North Sea (Johnstone, 1906 ; Auerbach, 1906, 1912 ;
Kabata, 1957b). Erosion and in some instances hypertrophy of head
cartilage results. Effects of M . aeglefini do not seem as severe as those
caused by Myxosoma cerebralis (Hofer) in salmonid fishes. Myxosoma,
a highly infectious disease agent acquired early in life in fresh water,
causes " whirling disease " of juvenile salmon and trout, as well as
gross skeletal abnormalities (Bogdanova, 1960 ; Hoffman ef al., 1962).
The disease has long been known in central Europe, and has recently
been found in Russia and United States. Dannevig and Hansen (1952)
have reported symptoms indicating M . cerebralis infections in very
young herring reared in aquaria.
3. Microsporidea
Several serious diseases of marine fishes result from microsporidean
invasion. Smelts, Osmerus eperlanus, from Europe (Weissenberg, 191 Ic)
and Osmerus mordax from North America (Schrader, 1921 ; Fantham
et al., 1941) are often parasitized by Glugea hertwigi Weissenberg,
which produces varying degrees of visceral involvement, to the extreme
condition in which the body cavity is packed full of microsporidean
cysts up to 9 mm in diameter. Heavy infections have been reported
to prevent reproduction by mechanical occlusion of the vent (Haley,
1954 ; Sindermann, 1963) and lesser infections destroy areas of digestive
tract and gonad and impair other metabolic functions. Haley found
21
species (Kudo, 1920), are of widespread occurrence in marine fishes.
Heavy infections may cause enlargement, discoloration and disruption
of function of the organ. Fantham and Porter (1912), who examined
the widespread occurrence of gall bladder parasites in elasmobranchs
and teleosts from the English and French coasts, found that myxosporidean parasitization caused inflammation of the organ, excess
secretion of mucus and increase in viscosity of bile, enlarged livers and
emaciation of the host.
Gill-invading Myxosporidea are not usually of serious consequence
to marine fishes. However, Shulman (1957) described an epizootic of
Myxobolus exiguus in the gills of mullet, Mugil cephalus (L.), from the
Black Sea in which 500-600 kg of fish per kilometer were washed up
on the western shore of the Crimean Peninsula during the spring of
1949. Mechanical disruption of gill function, caused by heavy infection
with myxosporidean cysts, was considered the cause of death. No
abnormalities were noted in the viscera.
Several species of Myxosporidea invade the cranial cartilages of
fishes. One, Myxobolus aeglejini (Auerbach), occurs in plaice, Pleuronectes
plntessa (L.), hake, Merluccius merluccius (L.), and haddock, Gadus
aeglefinus L., of the North Sea (Johnstone, 1906 ; Auerbach, 1906, 1912 ;
Kabata, 1957b). Erosion and in some instances hypertrophy of head
cartilage results. Effects of M . aeglefini do not seem as severe as those
caused by Myxosoma cerebralis (Hofer) in salmonid fishes. Myxosoma,
a highly infectious disease agent acquired early in life in fresh water,
causes " whirling disease " of juvenile salmon and trout, as well as
gross skeletal abnormalities (Bogdanova, 1960 ; Hoffman ef al., 1962).
The disease has long been known in central Europe, and has recently
been found in Russia and United States. Dannevig and Hansen (1952)
have reported symptoms indicating M . cerebralis infections in very
young herring reared in aquaria.
3. Microsporidea
Several serious diseases of marine fishes result from microsporidean
invasion. Smelts, Osmerus eperlanus, from Europe (Weissenberg, 191 Ic)
and Osmerus mordax from North America (Schrader, 1921 ; Fantham
et al., 1941) are often parasitized by Glugea hertwigi Weissenberg,
which produces varying degrees of visceral involvement, to the extreme
condition in which the body cavity is packed full of microsporidean
cysts up to 9 mm in diameter. Heavy infections have been reported
to prevent reproduction by mechanical occlusion of the vent (Haley,
1954 ; Sindermann, 1963) and lesser infections destroy areas of digestive
tract and gonad and impair other metabolic functions. Haley found