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The pituitary gland of fundulus.

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Tlic pituitary gland of tclcosts has received scant attention.
Sifc~nclcll ( ’14) des(~ri1)osthe relatioiiships and striictnrc of
this organ in scvcral of the bony fishes with special rcfcrciicc
to ilnguillu, E:POS and (:yprinns. tic. Beer ( ’26) gives R hrief
dc script ion of thc I)i tiii t ary of t clcosts in general, emphasi zing the fact tliat little is Iinown of the structure of the gland
in tliis group, and more remn
E’loreiitiii (’34) has giveii a
short account of the pituitary of teleosta. While carrying
out some experiments 071 the sex cyale i n Fiindulus it was
foi11-d necessary to analyze the structure of tho pituitar;v of
this animal. (:lands of 1ij2 animah have so far hc?n PXamiried, of which sc\-eiity-cigIitwere untreated norrrial animals,
iii(1lutling Imth iiialcs and femwlcs, and form the basis for the
followiiig tlcw4l)tion. Thcsc animals were collected at
various times from the l)elaware River. Some were killed
irniiieditttely, others werc kept f o r longer or shorter periods iii
the laboratory and iiidividualx killctl ;It definite intervals. A
few of the animals, t h o s ~killed in July, were froni ’iVoods
IIolc. For microscopic study aerial sections were madc
and stained with amr-cosiri, the stain found to be the most
satisfactory of several that were tried, sections rcinaiaiiig iu
the stain for 01115.- 4 hours.
‘l‘lic pituitary gland of E’uiidulus lies on thc ventral surface
of the brain immetliaiely postel-ior t o the optic chiasma and
betweeii the iiiferior 1ol)es. It is covered velitr~llyby the
n:ir~~sphcnoiclhone although there is no excavation in this
1)orie cornparahlo l o :L s e l h tiiwica. ‘I’li~ gland caii be swn
l.(wtlily Iliroagh the i*oof of the mouth a s iooii a s ilie iriiicoiis
membrane is dissectcd an.ay from thci micl-line a i d mav be reriiovetl froni survival aniirials by this appi*owcli ( 11atthcn -,
’ 3 3 ) . The infiinclihalar stalk is short arid relatively broad,
ruiining ventrally from the clienceplialon l o the inccliaii portion
of the pituitary, IVhcii exarriiiied from the vcliitral view in a
fresh cvxiditioii I h t t gland 1)imeiits three divisions, a larger
ior and a sina1Icr posterior pari of compact millt;r.-~vhi
tissue, t l i ~ s ctwo parts being separated by u riarrow I ~ ~ C ~ U I R T
zoiic of clearor material. Tlie significance of thwe surlacc
marlrings api)ears wlien scxtioiis of the gland are c~xuiniiietl.
1wo iriaiii rogioiis m a y then he ilistinguislied, a pal’s ~ ~ C L ’ V O F B
aiid a pars glanclnlaris, the latter being further siibtliuitlctl
into a so-callcd iransitional rcgioi? and a pars intermedia
(fiz. 1). Tlir?rc is no hj-popliysial c:uvit y. The pars i i e r v o s ~ ,
as i n vcrtcbralcls in p r i e m l , is composed mainly of fibrous
~iiatcrial. Fibers lrom t l i ~infundihulum extend into the
gland from the median rloiml point where ihc: iiifiintlibnlar
stalk joiiis the pituitary arid from this region radiate out in
a11 directions into t hc siihslaiice of the pars glandularis. In
the a i i t P r i o r portion of tlir gl!:lwntl11ies~fibers are sc1)arated
f r o m ihe free snrface by a r ~ l a l i r c l ywide zo1ie of glaiiclidar
cells, but a t one region, sonicwliat iicarcr the posterior end of
tlic pituitary, the fihcrs of ihc pars iicrvosa reach quite mar
r 1
t’ig. 1 Fundillus pituitar?, sagittal section. x 66. PS, pars ncrvosii; 1’1,
pars intermedia, and PT, traiisitiimtl Icgion. the two sul)tiivision.i of t h r par‘
Fig. 2 Acidnphilicz erlls from traiisitional rtgioii of ariirrial killrd 12/17/32.
granultv stain less intcnsc4y tEiaii
(‘amera I i ~ i d outlinr,
x 900. In these c d l s
do those iii the acidophilrs of the pars interm a (fig. 5) and do mot photograp11
Fig. 3 Cllroniophobic cells from transitional rcBgion of ariim:tl killrcl 7/30/33.
Canicm lucida outline, X 900.
Fig. 4 D e ( ~ p t a i n i a gbayophilcs f r o m posterior pole of animal killcd R ’24,’
X 690.
Fig. 5 Par? intrrmrilia killccl 9/54/35. X fi90. A(‘, acidnphile; (’11. chroiiro
phobc ; PS,prowss of pars m r i 088.
Fig. (i Pars interinedia of : m i n d killcil 10/9/35.
X 690. l:, basophilc: (‘TI.
vhroniophohe ; PX, process of pars ncnos:i.
Figures 1 t o 6
the ventral surface. Tt is this zone wliich can be seen in the
fresh coiitlitiori as a narrow irregular band of clcarer t issue
sq)aratiiig the anterior two-thirds of the gland from tho posterior third, N S mentioncd above. Reattcred among thc fibers
of the pars n(?rvosa are a number of neurogliu cells. Large
masses of colloid material may be seen only occasionally, but
considerable amounts of small droplets or graiiules can be
foinnd scattered freely among the fibcrs. This mattlrial is
acidophilie and is most abundant n r w thc pars intermedia
which borders the pars nervosa. Stendell believes tliat these
arc droplets of secretion from the cells of the pars intermedia.
Thc similarity in staining between these granules or clroplcts
and the cptoplasmic inclusions of ilic acidophilic cells of the
I ) N ~ S intermedia immediately adjacent to the pars n e r ~ o ~ a
suggwt s a relationship between the two in Fundulixs idso.
The pars g l i ~ ~ t l u l a r of
i s tclcosts lias been subclivicl(x1 by
Stendell aiitl by dc Rccr inlo thrcv rcgions: il pars aiiterior
forming a small aiitero-dorsal portion ; a pars intcrmectia c o n
sistirig of hasophilic 0011s huiiding the processes of thc pars
nervosa ; arid a iraiisitionul regioti (uebergtingsteil) which
forms the hulk of this part of the gland. In Fimdulus, however, thc cells in the antero-dorsal region are so likc those of
thc rest of this part of the gland that 110 pars anterior comparable t o tliat descrihetl f o r other teleosts can 1)c disuished. The entire region forruing the anterior half of the
pars glandularis and cxtencling posteriorly and laterally
corresponds in position arid struetiire to what Stendell calls
the transitional portion (fig. 1). It is composed chicfly of
acidophilic cells with occasioiial basophi les ailti chromophohes.
The acidophilcs vary in appcitranc~i i i animals killed at tliffercnt periods. T n general they are large cclls with nuclei mhich
arc usiially carescent-shaped or folded, rarely spherical, the
cytoplasm containing h e , uniformly tlistrihinted granules
which arc weakly aciclophiliv. In ariiinals killed in late summer
and fall, howcw?r, tlie granules are iargcr, l t m regular iii their
occiirrenccl and stain more intensely (fig. 2). Tlie relatively
rare haso1)liiles rewmble the acidophiles iii shape and niiclear
Y t r uc t u re .
I n addition to the so-called transitional region, the pars
glandularis-presents a pars intermedia, which is made up of
a zone several cells in thickness bordering the processes of
the pars nervosa (fig. 1). I n the anterior part of the gland
the pars intermedia is separated from the free surface by the
transitional portion. At the posterior end, however, the
transitional region is interrupted so that the posterior pole of
the gland is formed entirely by the pars intermedia. The
cytoplasm of the cells of the pars intermedia is usually basophilic. Chromophobes are found occasionally, however (fig.
6 ) , and in many animals those cells which are immediately
adjacent to the processes of the pars nervosa are strongly
acidophilic, the granules in the cytoplasm staining a deeper
red than do those of the acidophiles in the transitional portion
(fig. 5). These acidophiles are always somewhat larger than
the basophiles or chromophobes. In addition there may usually be found a number of large, sharply outlined cells of
which the cytoplasm stains a pale lavender with azur-eosin.
These cells are particularly noticeable at the posterior pole.
I n general they appear like somewhat faded acidophiles.
Finally, in addition to the ordinary type of basophile found
in this region, in which the granules are small and regularly
distributed throughout the cell, a striking feature of the pars
intermedia of animals killed at certain periods is the appearance of large cells with irregularly distributed masses of very
deep staining, basophilic material. The nucleus of this last
cell type is large, pale with a prominent nucleolus, and is often
eccentric in position (fig. 4).
The pars nervosa and the transitional region of the pars
glandularis are well supplied with blood vessels. The pars
intermedia contains no blood vessels, though its cells are all
near the abundant vascular supply in adjacent processes of
the pars nervosa.
I n the series of animals so f a r examined the cells of the
pars glandularis appear to undergo cyclic changes. In the
transitional portion of animals killed at different periods differences were observed in the relative numbers of chromophobes and acidophiles. I n seventy-one animals killed from
September to Map the cells of this region were almost entirely
acidophilic with only occasional basophiles or chrornophobes
In the early part of this period, from September to December,
the acidophiles were large with prominent, deep-staining granules (fig. Z ) , while in animals killed from January to March,
the acidophiles were somewhat shrunken and stained less intensely. The most striking difference in the appearance of
this region, however, was shown during or at the end of the
breeding season, which extends from Xay until the latter part
of July. I n seven animals killed in late May and July the
transitional region of the pituitary consisted almost entirely
of shrunken, chromophobic cells (fig. 3). From an examination of these animals it would thus appear that the transitional region of the gland is predominantly chromophobic in
the summer months, acidophiles appearing in the fall and
persisting throughout the winter, though staining less intensely in late winter and spring.
In the pars intermedia differences were also observed in
different animals both in the number of acidophilic cells adjacent to the pars nervosa and in ihe presence or absence of
those basophiles with large, deep stzining granules described
above. Acidophiles varied considerably both in numbers and
in staining re8ction.l I n the cells counted the percentage of
acidophiles was found to be consistently high during May,
July, and September, varying fro= 50.3 to 55.8 % with an
average of 53.4. While as a rule these cells were less numerous in the fall and winter months such wide variation existed
Cell counts of this region mere made by the sampling method. A ruled square
mounted in the ocular was focusscd in such a way that as much of one side of
the square as possible rested on the boundary between pars nervosa and pars
intermedia and in a11 cases the enclosed area mas selected 80 that the maximum
iiumber of acidophiles was included. A count way then made of acidophilea against
the total number of cells in the circumscribed area, using every fourth section.
The figures thus represent the percentage of acidophiles in the number of cells
counted and not the percentage present in the pars intermedia as a whole. The
latter figure would be considerably lower in all cases owing to the fact that acidophiles are found only along the border of the pars nervosa, the region chosen
for making the count, while below this region are several layers of basophiles or
that any generalization concerning this period is difficult to
make. Thus in October the acidophiles averaged 34.5 "/. of
the cells counted ; in December 40.7 ; in January ( '35) 34.9 "/.
(weak-staining acidophiles) ; in February 32.4 % ; while in
March and April four animals showed no acidophiles whatever
in this region. On the other hand, in January 1936 the acidophiles averaged 49.2 %, o r nearly as high as during the previous July, and the cells were heavily stained. Before they were
killed these animals must have been subjected to a variety
of conditions with respect t o food supply, temperature of the
water, etc. Individual differences such as those observed in
the animals killed in January 1935 as compared with those
killed in January 1936 may be dependent on differences in the
previous history of the two groups of animals. At any rate
while the number of acidophiles in the pars intermedia varies,
in general being highest in late May, July and September
and lowest in March and April, the variation in individuals
killed in the same month of successive years indicates that
factors other than seasonal changes alone must bc concerned
in this variation.
In addition to these changes in the acidophiles of the pars
intermedia the occurrence in this region of cells containing
large granules of deeply staining Fasophilic material varies
considerably. These cells are particularly numerous, when
they occur at all, at the posterior pole of the gland. Apparently they may be found in individual cases throughout
the year but they are much more common during summer and
fall than in winter. Thus in all animals killed during July
and September these cells were found in large numbers and
in October they occurred in moderate numbers in four out of
the five animals killed during this month. I n December, however, only seven out of twenty-three animals showed these
cells and from January through May they were even rarer,
occurring in only five out of thirty-eight animals killed during
this period.
What relation these various cells of the pars intermediachromophobes, basophiles, acidophiles and cells with large
basophilic granules-bear to one another is difficult even to
estimate from a study of these preparations, and of course
conclusive evidence of any relationship, such as might be obtained if the cells could be observed in the living animal, is impossible in material fixed at different periods from different
individuals. No cells intermediate in type between chromophobes and chromophiles or betwccn basophiles and acidophiles have so far been found. The only evidence suggestive
of relationship lies in the fact that deep-staining acidophiles
present in some animals appear as a single layer of cells
separating the rest of the pars intermedia from the pars
nervosa, yet in the same region of other animals only basophiles or chromophobes can be found (figs. 5, 6). Obviously
the acidophiles must develop from either the chromophobes or
the basophiles but so far no evidence has been obtained as to
which is the case. I n the teleosts which he examined Stendell
believed the basophilic granules were ‘unripe, ’ acidophilic
granules representing ripened secretion. On the other hand
the recent work of Severinghaus (’33) indicates that in the
anterior lobe of the mammalian pituitary gland both acidophilic and basophilic cells originate independently from
chromophobes, the chromophobic antecedents of the two types
being distinguished by differences in their Golgi apparatus.
Such work indicates the caution that must be observed in
drawing conclusions from the staining reaction of granules
in the cell alone.
From this examination of these seventy-eight animals it
seems fair to conclude that the pituitary of Fundulus is not
static but that it undergoes cyclic changes. With what these
changes are associated, however, it is difficult to say, particularly since the functions of the pituitary in teleosts is not well
known. A few reports indicate that it may be concerned in
some way with the sex cycle. Thus Houssay (’30) injected
seven South American teleosts (Cnesterodon) with saline
suspension of the pituitaries of four large shad on September
27th. Three of these expelled eggs on the twenty-eighth
and a fourth on the twenty-ninth, the other three animals
dying. Similar results were obtained with another animal
which expelled eggs on the thirtieth of September, 2 days after
injection. Control injections of muscle extracts were ineffective. This season is apparently near the normal breeding season for this species, however, for he found it necessary
to discontinue the experiments 03 the eighth of October,
since at this time several animals expelled eggs spontaneously,
a fact which makes it somewhat difficult to estimate just how
important the injections were in obtaining expulsion of eggs.
More recently Cardoso ( '34) injected saline suspensions of
the pituitaries of Pimelodus into other individuals of the
same species and obtained striking increases in weight in both
testes and ovaries. These experiments suggest that the
pituitary gland plays some part in control of the sex cycle
in this group of vertebrates. In addition it has been shown
that in some teleosts at least, notably Phoxinus and Ameirus,
the pituitary is concerned in part with the pigmentary effector
system (Giersberg '32; Parker, '34). While in Fundulus it
is not essential for ordinary color changes (Matthews, '33)
the pituitary of this animal does contain a substance capable
of producing dispersion of t.hc melanophore pigment in the
catfish, frog and lizard (Rleinholz, '35). The melanophore
principle is produced by the pars intermedia of other animals
(frog, Allen, '30; rat and mouse, Geiling and Lewis, '35).
Hence it may be significant that the highest percentage of
deep-staining acidophiles occurs in the pars intermedia of
Fundulus from May to September inclusive, since Parker
and Brower ('35) have shown that a nuptial sex character
consisting of a well-developed black spot on the posterior part
of the dorsal fin is present in Fundulus at approximately the
same time, namely from April to November, but not at other
times of the year. While similar nuptial characters in other
teleosts are associated with the gonad ( Courrier, '21 ; Blacher,
'26; Kopec, '27; Bock, '28; Tozawa, '29) the gonad may in
turn be controlled by the pituitary. As far as the differences
observed in the transitional portion of the pituitary at the
end of the breeding season are concerned, the lack of acidophiles and large numbers of chromophobes at this period
may be associated either with sexual exhaustion or with
general metabolic changes that may occur a t this time. During and after the breeding season Fundulus is more susceptible to handling and disease that at any other period. I n
this connection there may be mentioned the following observations. I n a series of animals which were injected with
sheep pituitary extract the concentration employed was obviously toxic due probably to the phenol with which it was
preserved. The animals were sluggish, refused food, and
when they were killed their peritoneal cavities were found
to contain considerable quantities of exudate. Seven of these
cases have been observed and in all of them the transitional
region of the pituitary showed few if any acidophiles, consisting almost entirely of chromophobic cells. I n fifteen controls, however, the same region of the pituitary was strongly
Briefly, then, in a series of seventy-eight normal Fundulus
it has been found that the glandular portion of the pituitary
shows certain cytological differences in animals killed at different periods, differences which are thought to represent a
cycle of changes that occurs in each individual. With what
these changes are associated can be determined accurately
only by appropriate experiments.
ALLEN, B. M. 1930 Source of the pigmentsry hormone of the amphibian hypophysia. Proe. SOL Exp. Biol. and Xed., vol. 27, p 504.
DE BEER,G. R. 1926 The Comparative Anatomy, Histology, and Development
of the Pituitary Body Oliver and Boyd, London.
L. J. 1926 The dependence of secondary sex characters upon tcstieular
hormones in Lebistea reticulatus. Biol. Bull., vol. 50, p. 374.
BOCK,I?. 1928 Kastration und sekundire Geschlechtsmerkmale bei Teleostiorn.
Zeit. f. wissensch. Zod., Ed. 130, 8. 455.
CARDOSO, D. 1934 Relations entre l'hypophyse et les organes sexuels e h a lee
poissons. Compt. Rend. de la Biol., T. 115, p. 1347.
C ~ V R R I F ~R., 1921 8ur le conditionncment des caracthres scxuels secondairos ehez
les poissons. Compt. Rend. de la Soc. de Biol., T. 85, p. 486.
P. 1934 Histophyaiologie compar6e do 1'hypophysoe. L 'excr6tion
de la oolloide hypophysaire chez les t616ost8ons. Ann. de Physiol.,
T. 10, p. 963.
GEILING, E. M. AND M. I(. LEWIS 1935 Further information regarding the
melanophore hormone of the hypophysis cerebri. Am. J. Phys., vol. 113,
p. 534..
GIERSBERG,H. 1932 Der Einfluss der Hypoplryse auf die farbigen Chromatophoren der Elritze. Zeit. f. vergl. Phys., Hd. 18, 8. 309.
B. A. 1930 Accion sexual de la hipofisis en 10s peces y reptiles.
Revista de la Sociedad Argentina de Biol,, vol. 6, p. 686.
L. H. 1935 The melanophore-dispersing principle in the hypophysis
of Fundulus heteroclitus. Biol. Bull., vol. 69, p. 379.
KOPEC,S. 1927 Experiments on the dependence o f the nuptial hue on the
gonads in fish. Biol. Oen., Bd. 3, 9. 259.
MATTHEWS,S. A. 1933 Color changes in F’unciulus after hypophysectomy. Biol.
Bull., vol. 64, p. 315.
G. IF. 1934 Color changes of the catfish Ameiurus in relation to
neurohumors. J. Exp. 2001, vol. 69, p. 199.
C-. H. AXD H. P. B R Q ~ E R
1935 A nuptial secondary sexcharacter h
Funundulus heteroclitus. Biol. Bull., vol. 68, p. 4.
A. E. 1933 A cytological study of the anterior pituitary of the
rat, with special reference to the Golgi apparatus and t o cell relationship. Anat. Rec., vol. 57, p. 149.
W. 1914 Die Hypophysis Cerebri. I n Oppel’s “Lehrbuch der vergl.
mikros. Anat.,” Teil 8.
T. 1929 Experiments on the development of the nuptial coloration and
pearl organs of the Japanese bitterling. Folia Anat. Japon., Bd. 7,
9. 407.
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fundulus, pituitary, gland
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