الفهرس 
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Abstract
Liza ramada is a euryhaline fish cultured in fresh water, brackish water and sea water. However,
the culture of this fish is closely dependent on the availability of wild fry. In general,
juveniles are collected from the estuaries and tidal creeks for stocking in the ponds.
Nontheless, several points are worthy of consideration in this concern regarding the local
conditions. Primarily, it is well known that the increasing demand for the fry and fingerlings of
mullet for fish farms in Egypt have serious impacts on the production process. In this respect, the
competition between the fish farmers for the mullet fry and fmgerlings, needed for their farms,
have led to raising of price which in tum increases the cost production (net price). Also,
collection of fry from the natural resources disturbs the fish stock in the natural habitat, and
this most probably affects the fisheries of this species. Besides, the ecological balance in the
fishing area would be most probably interrupted as a result of fry collection. In addition, the fry
and fingerlings-stocked in fish farms-will naturally decrease the total production of fry in the
next seasons.
Taking these drawbacks into consideration and also to ensure continuous supply of young mullet, man
must help nature in such respects, through developing and· creating certain efficient means through
developing and stablishing practical techniques for artificial propagation of mullet in order to
avoid fry collection from the wild stocks.
In an attempt to prolong the breeding season of the grey
mullet and obtain fertile eggs throughout the year, the resources of mature female breeders are
vitally important, particularly when linked to mass propagation of juveniles in the hatcheries.
However, the collection of mature females is not possible from the natural habitat since the
prespawning females would have then migrated to the sea for spawning in the usual manner.
In such cases, continous maintenance of broodstock in captivity and the use of special techniques
to control and regulate gonadal development are, therefore of utmost importance.
Thus, the present work was planned to carry out a detailed study of the reproductive processess of
Liza ramada raised in freshwater fish farms relative to those occuring in the natural habitat
(El-Bardawill lagoon) in order to clarify the role of the ecological factors, particularly salinity
in the process of maturation.
Thus, the following points have been followed up: I - Environmental factors:
II- Histological structure and seasonal variation during gonadal maturation of L.ramada.
i) Testis
ii) Ovary
iii) Histochemistry of the stroidogenic enzymes
III-The immunocytochemistry of the different endocrine cells in the pituitary gland of L.ramada
1- Adrenocorticotropic hormone cells (ACTH) 2- Prolactin cells (ProL.)
3- Somatotropic hormone cells (STH) or growth
hormone cells (G H).
4- Gonadotropic hormone cells (GTH).
5- Somatolactin secreting cells (SL).
IV- The effect of environmental factors on the activity of hypophyseal cell types in
L.ramada.
V- Immunocytochemical cyclic changas in the hypophyseal cell
types of L.ramad.
The results accomplished from this investigation are there after summed up:
The present results indicated that the physicochemical
characteristics of water in natural habitat (saline) and captivity (freshwater fish farms) are
different. The natural habitat exhibited high levels of salinity, Na, K, Ca2+ and Mg2+.
The testes of L.ramada - in general- were found to exhibit remarkable seasonal variations in shape,
size, colour and texture. Both Sertoli and interstitial cells were easily recognized in the testis.
In male L.ramada, 3P-hydroxysteroid dehydrogenase enzyme (3P-HSD) activity was confined to Leydig
cells (interstitial cells) and Sertoli cells.
In L. ramada, inhabiting saline water, five developmental stages were distinguished during
testicular cycle. The testis development was initiated when the daylength and water temperature had
begun decreasing (September), while the gradual decrease in both photopriod and water temperatures
ensure its completion (September-December). However, spawning in L.ramada was noticed to occur when
photoperiod and water temperatures had declined to their minimum values (December).
In freshwater fish, the testis development had followed more or less the same course as that living
in saline water. But nonetheless, the appearance of different stages monthwise was delayed
considerably in fresh water:, with relatively lower gonadosomatic indices (GSis). In addition,
spawning did not occur in the fresh water and the resorption of ripe testis had occurred early
during the period from November to late December. Inaddition, primary oocytes had appeared in the
testis of fish captivated in fresh water.
The ovaries of the fish, in both saline and fresh waters, were noticed to exhibit marked variation
in size, weight and colour accompanying the stage of maturity. During ovarian development, only one
clutch of oocytes was found to mature annually. Also, six stages of oocytc development could be
identified, namely primary oocytes stages, vesicles stage, primary yolk stage, secondary yolk
stage, tertiary yolk stage and spawning (ripe) stage.
Yolk deposition had occurred during four of vitellogenic stage: vesicles stage, primary yolk stage,
secondary yolk stage and tertiary yolk stage.
In female L.ramada, 3P-HSD activity occurred in a cell thecal layer and interstital cells.
In L.ramada, inhabiting saline water, seven stages of ovarian development were recognized during
the ovarian cycle, namely: previtellogenesis, early-vitellogenesis, mid vitellogenesis,
late-vitellogenesis, prespawning, spawning (ripeness) and postspawning (spent). The ovarian
development was initiated as-early - vitellogenesis when the daylength (photoperiod) and water
temperature had began decreasing, whereas the gradual decline of both the photoperiod and water
temperatures had ensured completion of ovary development. However, the ripe stage was not found and
no fish with ovaries in this stage were obtained in the present study, except by experimental
induction using hormonal injection (human chorionic gonadotropin and LHR.Ha). Besides, in saline
water, the spawning season extended from late November to late December during the decline of both
photoperiod and water temperatures to minimum values.
In freshwater females, the ovary development had followed more or less the same course as that
living in saline water. But, nonetheless, the appearance of different stages of ovarian maturity
monthwise was delayed considerably in fresh water, with a relatively lower frequency (% of
appearance). Also, the gonadosomatic indices were lower than those of females obtained from saline
water. In addition, the captive freshwater females did not complete final ovarian maturation, but
the oocytes had proceeded to the vitellogenic stages and then became atretic (follicular atresia).
It was observed that granulosa cells play an active role in the phagocytosis and digestion of yolk
during follicular atresia of L.ramada.
Using antiserum to piscine, ovine, rat and human pituitary hormones, immunocytochemistry was
employed to identify and localize the different cell types in the pituitary gland of L.ramada. A
major portion of the rostral pars distalis (RPD) was composed of acidophilic prolactin cells, which
showed specific and strong immunoreactivity with prolactin (PRL) antiserum of chum and coho salmon.
Antiserum to human adrenocorticotropin (ACTH) bound strongly to the ACTH lead hematoxylin- positive
(PbW) cells. These cells form cords of cells, which bordered the prolactin cells. The anti-human
ACTH had also cross-reacted with the melanotrops (MSH cells), which formed the majority of the pars
intermedia (PI) cells and stained positively with lead hematoxylin (PbW). The second cell type of
the PI is the periodic acid-Schiff -positive (PASl cell, which showed strong and specific
immunoreactivity to anti-chum salmon somatolactin (SL). The acidophilic growth hormone (GH) cells
were observed in the dorsal-posterior part of the proximal pars distalis (PPD), frequently arranged
in cords bordering the neurohypophysis. They were specifically bound by anti-chum salmon GH. The
basophilic gonadotrops occupied the major part of the PPD and was also recognized in the periphery
of the Pl.·The gonadotrops were bound strongly and specifically by antiserum to chum
salmon GTH II and ovine luteinizing hormone (anti - oLH). Antiserum to chum salmon GTH IP and GTH
rrp subunits of both coho salmon and killifish failed to bind the gonadotrops.
The immunocytochemical results obtained in the present study indicated that the environmental
parameters affected on the activity of the hypophyseal cell types of L.ramada. The activity of the
PRL, GH, ACTH and MSH celJs in captivity was higher than that of natural habitat.
The gonadotropic potency of the pituitary gland - in general - had undergone an obvious increase
during gonadal development, reaching a peak at the time of reproductive maturity. During the
gonadal cycle of L.ramada, the GTH cells showed an increase in the immunoreactive staining
intensity, granulation, hypertrophy and hyperplasia during sexual maturation. Degranulation,
vacuolization and weak immunoreactivity of these cells had occurred during spawning. The pituitary
gland of L.ramada, reared in captivity, appeared with low activity, which caused a decline in the
gonadal activity as reflected in the form of low values of GSI and earlier resorption of the
ovaries (atresia) and testes.
The SL-immunoreactive cells in Liza ramada showed an
increase in the secretory and the synthetic activity during sexual
maturation and spawning in natural habitat. SL cells were rather small and moderately
immunoreactive in immature fish. They were enlarged and frequently more granulated during gonadal
development. In addition, in late stages of maturation, comparatively larger and more degranulated
cells were noted, also indicating an active release of SL granules. Degranulation, vacuoliztion and
weak immunoreactivity of SL cells have occurred during spawning. The SL cells of Liza ramada,
reared in captivity, appeared with high activity. This may be due to the low concentration of
calcium in fresh water. The gradual stimulation of SL synthesis and release during sexual
maturation and spawning of L.ramada suggest that SL may be involved in the control of some steps of
reproductive processes, such as steroidogenesis, calcium metabolism and energy mobilization.
In addition, the activity of both ACTH and MSH cells showed increase during sexual maturation and
spawning of L.ramada.
These findings lead to the conclusion that, in spite of attaining L.ramada females to the
prespawning stage in saline water, the obtaining of ripe (spawning) females is not possible, where
the prespawning females had thence migrated to the sea for spawning. On the other hand, the
captive freshwater females
did not complete final maturation, but the completion of maturation and the obtaining of ripe
females, ready for spawning, is possible by hormonal therapies in combination with environmental
factors, particularly salinity.
Besides, the present results have urged and stimulated the need for further studies for optimizing
the induced spawning technique of L.ramada and improving its commercial applicability.