52
C A R L J. SINDERMANN
young individuals, are replaced by parasites typical of adult hosts,
due to lack of association of juveniles and adults, change in habitat
from inshore to offshore, and change in feeding habits and diet.
Studies of Atlantic herring (Sindermann, 1963) have further
demonstrated age-associated changes in parasite fauna. The body
wall overlying the visceral cavity of post-larvae is sometimes infected
with a species of Plistophora which has not been found in juveniles
over 6 months old. Juvenile herring between 6 months and 1 year old
harbor an adult cestode not seen in older fish. Juveniles between
9 months and 3 years are infected with the myxosporidean Kudoa
clupeidae, which is absent in adults. Larval trematodes, Cryptocotyle
lingua, are characteristic of juvenile herring because the young fish
live during the warmer months in close proximity to intertidal snail
populations (Sindermann and Farrin, 1962). Adult herring, which are
only lightly infested, remain farther offshore except during spawning.
Other parasites-larval cestodes (Trypanorhyncha) and larval nematodes (Anisakinae)-make their first appearance in juveniles about
1 year old and, depending on geographic area, gradually increase in
abundance with increasing age.
Disease may begin to exert effects very early in the life history of
the fish. Eggs of marine fishes are often coated with microorganisms ;
Oppenheimer (1955) found that hatching percentages of cod, turbot
and sardine eggs were increased in bacteria-free media. Ahlstrom (1948)
found abnormalities, some of which may have been disease-induced,
in as many as 45% of developing Pacific sardine eggs.
VII. IMMUNITY
Resistance to fish diseases involves a complex of interacting factors,
including individual variability, species characteristics, seasonal
influences and nutritional effects. Immunity has both cellular and
humoral aspects and extends from obvious phagocytic, lytic and
agglutinating activity to include such factors as the role of skin and
mucus barriers and the role of gastric secretions. Some of the
mechanisms of natural and acquired resistance to disease in fish have
been summarized by Bissett (1947a, 1947b), Dreyer and King (1948)
and Snieszko (1958) ; McDermott (1956) and Hirsch (1959) have
reviewed the cellular and humoral mechanisms of immunity.
A number of papers have appeared recently which clearly substantiate earlier findings (Blake and Anderson, 1930; Toth, 1932 ;
Nybelin, 1935a ; Schaperclaus, 1938 ; Snieszko et al., 1938 ; Smith, 1940)
of specific immunological competence in fish. Clem and Sigel (1963),
Sigel et al. (1963), and Sigel and Clem (1965) studied immune responses
C A R L J. SINDERMANN
young individuals, are replaced by parasites typical of adult hosts,
due to lack of association of juveniles and adults, change in habitat
from inshore to offshore, and change in feeding habits and diet.
Studies of Atlantic herring (Sindermann, 1963) have further
demonstrated age-associated changes in parasite fauna. The body
wall overlying the visceral cavity of post-larvae is sometimes infected
with a species of Plistophora which has not been found in juveniles
over 6 months old. Juvenile herring between 6 months and 1 year old
harbor an adult cestode not seen in older fish. Juveniles between
9 months and 3 years are infected with the myxosporidean Kudoa
clupeidae, which is absent in adults. Larval trematodes, Cryptocotyle
lingua, are characteristic of juvenile herring because the young fish
live during the warmer months in close proximity to intertidal snail
populations (Sindermann and Farrin, 1962). Adult herring, which are
only lightly infested, remain farther offshore except during spawning.
Other parasites-larval cestodes (Trypanorhyncha) and larval nematodes (Anisakinae)-make their first appearance in juveniles about
1 year old and, depending on geographic area, gradually increase in
abundance with increasing age.
Disease may begin to exert effects very early in the life history of
the fish. Eggs of marine fishes are often coated with microorganisms ;
Oppenheimer (1955) found that hatching percentages of cod, turbot
and sardine eggs were increased in bacteria-free media. Ahlstrom (1948)
found abnormalities, some of which may have been disease-induced,
in as many as 45% of developing Pacific sardine eggs.
VII. IMMUNITY
Resistance to fish diseases involves a complex of interacting factors,
including individual variability, species characteristics, seasonal
influences and nutritional effects. Immunity has both cellular and
humoral aspects and extends from obvious phagocytic, lytic and
agglutinating activity to include such factors as the role of skin and
mucus barriers and the role of gastric secretions. Some of the
mechanisms of natural and acquired resistance to disease in fish have
been summarized by Bissett (1947a, 1947b), Dreyer and King (1948)
and Snieszko (1958) ; McDermott (1956) and Hirsch (1959) have
reviewed the cellular and humoral mechanisms of immunity.
A number of papers have appeared recently which clearly substantiate earlier findings (Blake and Anderson, 1930; Toth, 1932 ;
Nybelin, 1935a ; Schaperclaus, 1938 ; Snieszko et al., 1938 ; Smith, 1940)
of specific immunological competence in fish. Clem and Sigel (1963),
Sigel et al. (1963), and Sigel and Clem (1965) studied immune responses