26
J. N. BALL AND BRIDGET I. BAKER
techniques, and one must experiment with dyes, timings, and other
variables for each species.
In Poecilia the q-a tinctorial distinction can be made quite easily with
the Azan (Fig. 2) or Aliz B method, the q cells staining red with azocarmine or erythrosin and the a cells staining orange ( Azan) or clear yellow
( Aliz B) (Fig. 3 ) . A similar distinction can be obtained in the eel (Fig.
4) (Olivereau, 1963a), trout (Baker, 19@3a), salmon (Olivereau and
Ridgeway, 1962), Xiphophorus ( Schreibman, 1964), Fundulus kansae
(Ball, 1967), and F. heteroclitus (Ball, 1967; Emmart et al., 1986). Emmart et al. (1966) emphasized the delicacy of the distinction, showing
that the red-yellow differentiation obtained with PAS-erythrosin-orange
G could be reversed by rinsing the slide initially in 1% boric acid. In
Poecilia and F . heteroclitus, the combination Ox-AB-erythrosin-orange G
usually gives a good a-q distinction, as well as staining the basophils in a
sharply contrasting blue.
In Poecilia the a cells occur in the centro-dorsal region of the proximal
pars distalis, intermingled with the much scarcer TSH cells (Figs. 2 and
5). With the light microscope the cells are generally large and rounded
in form, although frequently elongated and ellipsoid; typically, the cell
is crowded with exceedingly fine orangeophilic granules, h e r than the
q granules and often packed so densely as to appear a homogeneous mass.
The nucleus is ovoid, frequently eccentrically placed at one pole of the
cell, and often seems squashed and distorted by the dense packing of the
granules. In any one fish there may be great variations in the size and
shape of the nucleus, and in the size of the nucleolus; the latter is generally prominent, however, and the cells usually show signs of considerable activity. The Golgi image, in the form of a ring or crescent, is usually very prominent, sharply outlined by the dense granulation.
A tendency to sexual dimorphism is evident in the a cells of Poecilia:
In the adult female, the cells are numerous, often tightly packed together,
densely granulated and very active in appearance, as already described,
whereas the male fish usually presents few a cells, poorly granulated or
even degranulated, with a central nucleus, nucleolus insigni6cant or invisible, and no sign of the Golgi image. The a cells mainly lie in the
dorsally projecting fingers of the proximal pars distalis, hence in close
proximity to the neurohypophysis. In the female, they frequently form a
virtually continuous border between the neurohypophysis and proximal
pars distalis, several cells in depth, forming a shell, dorsally concave,
which is easily visible in the middle of a fresh gland, the a granules being
translucent and appearing a dense white in contrast to the more transparent ventral gonadotrops. Similarly in mammals, acidophil granules
appear opaque in fresh material (Purves, 1966). In contrast, in the male
J. N. BALL AND BRIDGET I. BAKER
techniques, and one must experiment with dyes, timings, and other
variables for each species.
In Poecilia the q-a tinctorial distinction can be made quite easily with
the Azan (Fig. 2) or Aliz B method, the q cells staining red with azocarmine or erythrosin and the a cells staining orange ( Azan) or clear yellow
( Aliz B) (Fig. 3 ) . A similar distinction can be obtained in the eel (Fig.
4) (Olivereau, 1963a), trout (Baker, 19@3a), salmon (Olivereau and
Ridgeway, 1962), Xiphophorus ( Schreibman, 1964), Fundulus kansae
(Ball, 1967), and F. heteroclitus (Ball, 1967; Emmart et al., 1986). Emmart et al. (1966) emphasized the delicacy of the distinction, showing
that the red-yellow differentiation obtained with PAS-erythrosin-orange
G could be reversed by rinsing the slide initially in 1% boric acid. In
Poecilia and F . heteroclitus, the combination Ox-AB-erythrosin-orange G
usually gives a good a-q distinction, as well as staining the basophils in a
sharply contrasting blue.
In Poecilia the a cells occur in the centro-dorsal region of the proximal
pars distalis, intermingled with the much scarcer TSH cells (Figs. 2 and
5). With the light microscope the cells are generally large and rounded
in form, although frequently elongated and ellipsoid; typically, the cell
is crowded with exceedingly fine orangeophilic granules, h e r than the
q granules and often packed so densely as to appear a homogeneous mass.
The nucleus is ovoid, frequently eccentrically placed at one pole of the
cell, and often seems squashed and distorted by the dense packing of the
granules. In any one fish there may be great variations in the size and
shape of the nucleus, and in the size of the nucleolus; the latter is generally prominent, however, and the cells usually show signs of considerable activity. The Golgi image, in the form of a ring or crescent, is usually very prominent, sharply outlined by the dense granulation.
A tendency to sexual dimorphism is evident in the a cells of Poecilia:
In the adult female, the cells are numerous, often tightly packed together,
densely granulated and very active in appearance, as already described,
whereas the male fish usually presents few a cells, poorly granulated or
even degranulated, with a central nucleus, nucleolus insigni6cant or invisible, and no sign of the Golgi image. The a cells mainly lie in the
dorsally projecting fingers of the proximal pars distalis, hence in close
proximity to the neurohypophysis. In the female, they frequently form a
virtually continuous border between the neurohypophysis and proximal
pars distalis, several cells in depth, forming a shell, dorsally concave,
which is easily visible in the middle of a fresh gland, the a granules being
translucent and appearing a dense white in contrast to the more transparent ventral gonadotrops. Similarly in mammals, acidophil granules
appear opaque in fresh material (Purves, 1966). In contrast, in the male