296
AUGUST EPPLE
IV. THE PHYSIOLOGICAL ROLE OF THE ISLETS IN FISHES
A. Islet Changes under Normal Conditions
1. ISLET CHANGES WITH AGE
Apparently, a study on the embryonic development of the endocrine
pancreas of fishes with modern methods is lacking. The literature on the
development of the pancreas of the cyclostomes is well covered by
Ermisch (1966). The literature on the ontogenesis of the islets in higher
fishes is found in the papers of Siwe (1926), Baron (1934), Vorstmann
( 1948), and in the review of Bargmann ( 1939),
During the metamorphosis from the larval to the adult form in Petromyzon planed there is a conspicuous change in the islets. The islets of the
larva contain only B cells and a few agranular elements; during the metamorphosis a second type of granular cell appears in large numbers (see
Section 11, D, 1). As pointed out by Ermisch ( 1966,1967), this may well
be associated with the end of food uptake of the adult animals and the
subsequent utilization of lipid reserves (see also Bentley and Follett,
1965).
Senile, castrated Pacific salmon, Oncorhynchus nerka kennerlyi, which
had survived 1 to almost 4 years beyond the normal life span showed
marked hyperplasia and hypertrophia of the islets (Robertson and Wexler, 1!362). This closely resembles the picture in the spawning salmon
(see Section IV, A, 3).
2. SEASONAL ISLET VAFUATIONS
Pallot and associates (cf. Schatzle, 1954) report very striking alterations of the exocrine and endocrine pancreas of several teleosts. In the
carp, CypTinus carpio, they describe a change from a prevalent B-cell
activity in summer to an A-cell hypertrophy in winter. This was not seen
in Italian (cf. Mosca, 1959) or in Japanese (Watanabe, 1960) specimens
of the same species. Dancasiu (1960) finds islet neoformation in Roumanian carps during May and June; yet this takes place in a way quite different from the islet alterations described by Pallot and associates. Ghittino
( 1961) reports seasonal changes in the relative proportions of “A” and
“B’a cells in the islets of another cyprinide, Leuciscus sufi muticellus.
Honma and Tamura (1968) observe no seasonal changes in the islet composition of Salvelinus leucomaenis pluvius, but an increase in the number
of small islets after the breeding season. In a sedentary population of
Salmo trutta, Schneider and Epple (1969) did not observe clear signs of
AUGUST EPPLE
IV. THE PHYSIOLOGICAL ROLE OF THE ISLETS IN FISHES
A. Islet Changes under Normal Conditions
1. ISLET CHANGES WITH AGE
Apparently, a study on the embryonic development of the endocrine
pancreas of fishes with modern methods is lacking. The literature on the
development of the pancreas of the cyclostomes is well covered by
Ermisch (1966). The literature on the ontogenesis of the islets in higher
fishes is found in the papers of Siwe (1926), Baron (1934), Vorstmann
( 1948), and in the review of Bargmann ( 1939),
During the metamorphosis from the larval to the adult form in Petromyzon planed there is a conspicuous change in the islets. The islets of the
larva contain only B cells and a few agranular elements; during the metamorphosis a second type of granular cell appears in large numbers (see
Section 11, D, 1). As pointed out by Ermisch ( 1966,1967), this may well
be associated with the end of food uptake of the adult animals and the
subsequent utilization of lipid reserves (see also Bentley and Follett,
1965).
Senile, castrated Pacific salmon, Oncorhynchus nerka kennerlyi, which
had survived 1 to almost 4 years beyond the normal life span showed
marked hyperplasia and hypertrophia of the islets (Robertson and Wexler, 1!362). This closely resembles the picture in the spawning salmon
(see Section IV, A, 3).
2. SEASONAL ISLET VAFUATIONS
Pallot and associates (cf. Schatzle, 1954) report very striking alterations of the exocrine and endocrine pancreas of several teleosts. In the
carp, CypTinus carpio, they describe a change from a prevalent B-cell
activity in summer to an A-cell hypertrophy in winter. This was not seen
in Italian (cf. Mosca, 1959) or in Japanese (Watanabe, 1960) specimens
of the same species. Dancasiu (1960) finds islet neoformation in Roumanian carps during May and June; yet this takes place in a way quite different from the islet alterations described by Pallot and associates. Ghittino
( 1961) reports seasonal changes in the relative proportions of “A” and
“B’a cells in the islets of another cyprinide, Leuciscus sufi muticellus.
Honma and Tamura (1968) observe no seasonal changes in the islet composition of Salvelinus leucomaenis pluvius, but an increase in the number
of small islets after the breeding season. In a sedentary population of
Salmo trutta, Schneider and Epple (1969) did not observe clear signs of