DISEASES OF MARINE FISHES
35
with the fishing ground, and heaviest infestations are off the North
American coast, where up to 10% of fish carry the parasite.
Another interesting parasitic copepod is Lermeenicus sprattae
(Sowerby) which occurs embedded in the eye or occasionally in the
dorsal body muscles of sprat and sardines in Europe (Baudouin, 1904,
1905; Wilson, 1917). According to Baudouin, the parasite is called
" pavillon " by sardine fishermen, because it has three distinct body
parts, showing the three colors of the French tricolor, called " pavillon "
by sailors. The long thin body and egg cases of the parasite trail posteriorly as the host swims.
Among the largest of the tissue-invading copepods are members
of the genus Pennella. P. exocoeti (Holten) from flying fish, Parexocoetus
brachypterus (Richardson), and Penriella jilosa (L.) from swordfish and
ocean sunfish, Mola rnola (L.), may reach a length of 20 cm. The adult
female of this and other members of the genus may be found almost
anywhere on the host's body, with the head and neck embedded in
the host organs, where large hard cysts are formed (Gnanamuthu,
1957).
Parasitic copepods other than the tissue-invading forms may
occasionally damage marine fish. Surface abrasions and lesions caused
by the parasites can be of serious consequence to the fish host directly
or as a route of entry for secondary invaders. Salmonids in the North
Pacific and the North Atlantic are often parasitized by Lepeophtheirus
salnionis ( K r ~ y e r ) ,
an ectoparasite which causes severe skin erosion,
and may even kill the fish host in heavy infestations (White, 1940,
1942 ; Margolis, 1958). Several members of the lernaeopodid genus
Glavella, parasitic on the fins and in the branchial and buccal cavities
of gadoid fishes, may cause lesions and tumors (Poulsen, 1939; NunesRuivo, 1957; Kabata, 1960, 1 9 6 3 ~ ) . Liiling (1953) has described an
instance of tissue damage in tuna, Thunnus thynnus (L.), caused by
the caligid Elytrophora brachyptera.
IV. GENETIC AND ENVIRONMENTALLY INDUCED ABNORMALITIES
I n addition to abnormalities which can be associated with particular
disease-causing organisms, marine fishes offer numerous examples of
physiological or structural defects, or conditions which may have
genetic or other causes. A number of inherited abnormalities of fishes
have been studied, including defective spinal columns, pigmented
tumors, cataracts, kidney tumors and association of certain pigmentproducing genes with physiological disturbances (Gordon, 1954). On
the basis of his review, Gordon felt that abundant evidence existed
for genetic control of certain diseases and abnormalities of fishes,
35
with the fishing ground, and heaviest infestations are off the North
American coast, where up to 10% of fish carry the parasite.
Another interesting parasitic copepod is Lermeenicus sprattae
(Sowerby) which occurs embedded in the eye or occasionally in the
dorsal body muscles of sprat and sardines in Europe (Baudouin, 1904,
1905; Wilson, 1917). According to Baudouin, the parasite is called
" pavillon " by sardine fishermen, because it has three distinct body
parts, showing the three colors of the French tricolor, called " pavillon "
by sailors. The long thin body and egg cases of the parasite trail posteriorly as the host swims.
Among the largest of the tissue-invading copepods are members
of the genus Pennella. P. exocoeti (Holten) from flying fish, Parexocoetus
brachypterus (Richardson), and Penriella jilosa (L.) from swordfish and
ocean sunfish, Mola rnola (L.), may reach a length of 20 cm. The adult
female of this and other members of the genus may be found almost
anywhere on the host's body, with the head and neck embedded in
the host organs, where large hard cysts are formed (Gnanamuthu,
1957).
Parasitic copepods other than the tissue-invading forms may
occasionally damage marine fish. Surface abrasions and lesions caused
by the parasites can be of serious consequence to the fish host directly
or as a route of entry for secondary invaders. Salmonids in the North
Pacific and the North Atlantic are often parasitized by Lepeophtheirus
salnionis ( K r ~ y e r ) ,
an ectoparasite which causes severe skin erosion,
and may even kill the fish host in heavy infestations (White, 1940,
1942 ; Margolis, 1958). Several members of the lernaeopodid genus
Glavella, parasitic on the fins and in the branchial and buccal cavities
of gadoid fishes, may cause lesions and tumors (Poulsen, 1939; NunesRuivo, 1957; Kabata, 1960, 1 9 6 3 ~ ) . Liiling (1953) has described an
instance of tissue damage in tuna, Thunnus thynnus (L.), caused by
the caligid Elytrophora brachyptera.
IV. GENETIC AND ENVIRONMENTALLY INDUCED ABNORMALITIES
I n addition to abnormalities which can be associated with particular
disease-causing organisms, marine fishes offer numerous examples of
physiological or structural defects, or conditions which may have
genetic or other causes. A number of inherited abnormalities of fishes
have been studied, including defective spinal columns, pigmented
tumors, cataracts, kidney tumors and association of certain pigmentproducing genes with physiological disturbances (Gordon, 1954). On
the basis of his review, Gordon felt that abundant evidence existed
for genetic control of certain diseases and abnormalities of fishes,