82
J. N. BALL AND BRIDGET I. BAKER
after Aliz B and is distributed throughout the gland. Type 2 is orangeophilic and is confined to the posterior region. Presumably these cells
secrete prolactin and growth hormone. Three types of basophils occur.
Type 1 and Type 2 both have the typicabstaining reactions of basophils
(PAS + ve, AB + ve, A F + ve, Aniline blue + ve), but can be separated
by details of shape, distribution, and granulation. Type 3 basophils are
restricted to the anterior tip of the gland and are violet after Aliz By
PAS + ve but AF - ve and AB - ve. The Type 1 basophil appears very
early in development and may be a thyrotrop. The Type 3 basophil
appears later in ontogeny, and strongly resembles the amphibian LH cell
in location and staining properties. The Type 2 basophils are found only
in adult fish, in which they may be very abundant, and are possibly FSH
cells (Kerr and van Oordt, 1966). As far as one can compare the descriptions, Godet (1964) suggested a similar functional identification on the
basis of the tinctorial properties of the cells. He observed that all three
basophils regress during estivation, and correlated this with regression
of the thyroid, cessation of spermatogenesis, and atrophy of sex
accessories.
The pars intermedia and neurohypophysis are closely associated to
form a dorsal neurointermediate lobe, separated from the pars distalis by
the neurohypophysial cleft. Protopterus has a thick intermedia, composed
of hollow tubules interdigitating with the neurohypophysial processes.
The cavities of the intermedia tubules often communicate with the hypophysial cleft, from which they are probably ultimately derived, but in
the adult many are closed. In Neoceratodus the hypophysial cleft also
sends diverticuli into the pars distalis, as in Acipenser (Wingstrand,
1966a), and in Lepidosiren the pars intermedia is just a thin layer of cells
(Kerr, 1933). Two pars intermedia cells occur in Protopterms: one is
weakly PAS + ve and AB + ve but strongly AF + ve, while the other is
strongly PAS + ve but AB - ve (Kerr and van Oordt, 1966). The latter
cell type is more abundant in younger fish. There is some indirect
evidence that MSH is secreted by this region as in other fishes. Total
hypophysectomy leads to melanin concentration, but removal of the pars
distalis alone causes melanin dispersion together with hypertrophy of the
pars intermedia ( Godet, 1961a,b, 1963). This hypertrophy together with
persistent skin darkening suggests an enhanced secretion of MSH, and it
is possible that as in many other vertebrates the pars intermedia is innervated by inhibitory hypothalamic nerve fibers which are damaged
when the pars distalis is removed.
Adaptation to aerial life in the cocoon during estivation is accompanied by melanin dispersion in P. aethiopicus, and by degranulation of
the pars intermedia cells, although no histological details were given
J. N. BALL AND BRIDGET I. BAKER
after Aliz B and is distributed throughout the gland. Type 2 is orangeophilic and is confined to the posterior region. Presumably these cells
secrete prolactin and growth hormone. Three types of basophils occur.
Type 1 and Type 2 both have the typicabstaining reactions of basophils
(PAS + ve, AB + ve, A F + ve, Aniline blue + ve), but can be separated
by details of shape, distribution, and granulation. Type 3 basophils are
restricted to the anterior tip of the gland and are violet after Aliz By
PAS + ve but AF - ve and AB - ve. The Type 1 basophil appears very
early in development and may be a thyrotrop. The Type 3 basophil
appears later in ontogeny, and strongly resembles the amphibian LH cell
in location and staining properties. The Type 2 basophils are found only
in adult fish, in which they may be very abundant, and are possibly FSH
cells (Kerr and van Oordt, 1966). As far as one can compare the descriptions, Godet (1964) suggested a similar functional identification on the
basis of the tinctorial properties of the cells. He observed that all three
basophils regress during estivation, and correlated this with regression
of the thyroid, cessation of spermatogenesis, and atrophy of sex
accessories.
The pars intermedia and neurohypophysis are closely associated to
form a dorsal neurointermediate lobe, separated from the pars distalis by
the neurohypophysial cleft. Protopterus has a thick intermedia, composed
of hollow tubules interdigitating with the neurohypophysial processes.
The cavities of the intermedia tubules often communicate with the hypophysial cleft, from which they are probably ultimately derived, but in
the adult many are closed. In Neoceratodus the hypophysial cleft also
sends diverticuli into the pars distalis, as in Acipenser (Wingstrand,
1966a), and in Lepidosiren the pars intermedia is just a thin layer of cells
(Kerr, 1933). Two pars intermedia cells occur in Protopterms: one is
weakly PAS + ve and AB + ve but strongly AF + ve, while the other is
strongly PAS + ve but AB - ve (Kerr and van Oordt, 1966). The latter
cell type is more abundant in younger fish. There is some indirect
evidence that MSH is secreted by this region as in other fishes. Total
hypophysectomy leads to melanin concentration, but removal of the pars
distalis alone causes melanin dispersion together with hypertrophy of the
pars intermedia ( Godet, 1961a,b, 1963). This hypertrophy together with
persistent skin darkening suggests an enhanced secretion of MSH, and it
is possible that as in many other vertebrates the pars intermedia is innervated by inhibitory hypothalamic nerve fibers which are damaged
when the pars distalis is removed.
Adaptation to aerial life in the cocoon during estivation is accompanied by melanin dispersion in P. aethiopicus, and by degranulation of
the pars intermedia cells, although no histological details were given