1. THE PITUITARY GLAND
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The pituitary of Lepisosteus, although of different shape, resembles
the Amia gland in essentials ( Kerr, 1949; Sathyanesan and Chavin, 1967).
Main points of difference are: the pars intermedia is larger, with wider
neural interdigitations and a small infundibular funnel; the rostra1 follicles
are smaller, and intermingle more freely with proximal pars distalis cells.
Lepisosteus displays acidophils 1, 2, and 3, and the mantle of basophils 1
seen in Amiu; however, basophils 2 and 3 are less easily separable, apart
from a much sparser granulation in basophil 2 and its more central
location. The neurohypophysis and infundibular floor are essentially as
in Amia.
In both genera, the mantle plexus in the infundibular floor appears
to be supplied by arteries which enter the infundibular region anteriorly
between the optic nerves and the pituitary, although additional sources
may be present.
IV. THE PITUITARY GLAND IN LUNGFISHES
As surviving, though distant, relatives of the animals ancestral to the
tetrapods, the pituitary in lungfishes (Dipnoi) is of great interest, but
there have been few studies on the gland using modem cytological
techniques. The recent work of Wingstrand (1956), Kerr and van Oordt
( 1966), and van Oordt and Kerr ( 1966) all describes the pituitary in the
African lungfish, Protopterus sp.
The organization of the pituitary resembles that of amphibians
rather than other fishes. The adenohypophysis includes a distinct pars
intermedia, dorsally placed and intimately associated with the neurohypophysis, and a ventral pars distalis, separated from the intermedia by
the hypophysial cleft (Fig. 25H). In the pars distalis, as in amphibians,
the cell types are intermingled and not grouped into zones as in so many
fishes.
Five cell types can be distinguished in the pars distalis (Kerr and van
Oordt, 1966). Although the lack of direct experimentation makes it
impossible to associate each of these firmly with the secretion of a particular hormone, in their staining reactions and distribution these cells
resemble the cells of the amphibian pars distalis for which there is
adequate experimental backing for functional identification. On the basis
of these similarities, and considering the time at which the dipnoan cell
types appear during ontogeny, Kerr and van Oordt (19ss) have made
tentative functional identification of some of these cells.
Two acidophils can be identified. Type 1 acidophil is erythrosinophilic
i
81
The pituitary of Lepisosteus, although of different shape, resembles
the Amia gland in essentials ( Kerr, 1949; Sathyanesan and Chavin, 1967).
Main points of difference are: the pars intermedia is larger, with wider
neural interdigitations and a small infundibular funnel; the rostra1 follicles
are smaller, and intermingle more freely with proximal pars distalis cells.
Lepisosteus displays acidophils 1, 2, and 3, and the mantle of basophils 1
seen in Amiu; however, basophils 2 and 3 are less easily separable, apart
from a much sparser granulation in basophil 2 and its more central
location. The neurohypophysis and infundibular floor are essentially as
in Amia.
In both genera, the mantle plexus in the infundibular floor appears
to be supplied by arteries which enter the infundibular region anteriorly
between the optic nerves and the pituitary, although additional sources
may be present.
IV. THE PITUITARY GLAND IN LUNGFISHES
As surviving, though distant, relatives of the animals ancestral to the
tetrapods, the pituitary in lungfishes (Dipnoi) is of great interest, but
there have been few studies on the gland using modem cytological
techniques. The recent work of Wingstrand (1956), Kerr and van Oordt
( 1966), and van Oordt and Kerr ( 1966) all describes the pituitary in the
African lungfish, Protopterus sp.
The organization of the pituitary resembles that of amphibians
rather than other fishes. The adenohypophysis includes a distinct pars
intermedia, dorsally placed and intimately associated with the neurohypophysis, and a ventral pars distalis, separated from the intermedia by
the hypophysial cleft (Fig. 25H). In the pars distalis, as in amphibians,
the cell types are intermingled and not grouped into zones as in so many
fishes.
Five cell types can be distinguished in the pars distalis (Kerr and van
Oordt, 1966). Although the lack of direct experimentation makes it
impossible to associate each of these firmly with the secretion of a particular hormone, in their staining reactions and distribution these cells
resemble the cells of the amphibian pars distalis for which there is
adequate experimental backing for functional identification. On the basis
of these similarities, and considering the time at which the dipnoan cell
types appear during ontogeny, Kerr and van Oordt (19ss) have made
tentative functional identification of some of these cells.
Two acidophils can be identified. Type 1 acidophil is erythrosinophilic
i