International Journal of Aquaculture, 2016, Vol.6, No.6, 1
-
10
2
(2009-2010-2011) respectively (El Gamal, 2013), it suffering from deficiency in
L.carinata
production and fries
number due to illegal fishing and collection of fries which require a solution to save stock number, by having deep
knowledge of the biological, reproductive cycle and histological features of the target species to help induced spawning
of it, the previous studies tried to study the biological and histological reproductive characters of
L.carinata
in the same
study area (Mahmoud, 1997; El-Ganainy et al., 2014) but the present study caring about the steroids hormones
concentration which represent a complete knowledge of reproductive and hormonal pattern of
L.carinata
help to give a
solid ground for further induced spawning studies of this species.
Study on annual reproductive cycle of plasma sex steroid hormones and gonad maturity of fish is crucial in
understanding spawning pattern in fish (Lee and Yang, 2002; Manosroi et al., 2003). Sex steroids are responsible for
gonad maturation. Influence of sex steroid hormones like testosterone, and 17β - estradiol in gonad maturation need to
more - emphasized (Lubzens et al., 2010; Schulz et al., 2010). Synthesis of vitellogenin and increase in ovarian size
during final oocyte maturation is controlled by 17b - estradiol which is directly related to gonadosomatic index (Tyler et
al., 1991; Sabet et al., 2009; Heidari et al., 2010; Adebiyii et al., 2013).
This study aims to investigate the annual reproductive cycle of females of
Liza carinata
during processes of formation
eggs (oogenesis) and the maturity stages of ovary respectively in addition to the description of the annual reproductive
cycle and GSI in relation to sex hormonal profiles of testosterone and 17β - estradiol during the spawning period
throughout the year.
2. Materials and Methods
2.1 Study area
Suez Bay or (Bahr el Qulzum) extending about 4.5 miles south from its head is entered between Ras - El Adabia and
Ras - Misalla (NGIA, 2007). Suez Bay is shallow extension on Gulf of Suez, roughly elliptic in shape, with its major
axis in northeast and southwest direction and extends from 29 51′ to 30ᵒN. The bay is connected to Suez Gulf through
the south - eastern side and connected to Suez Canal through the north - eastern side. City of Suez occupies the northern
part of the bay.
2.2 Sampling of fish and histological investigation
718 samples of
Liza carinata
collected from Suez Bay and transferred immediately to the laboratory. The gonads were
removed and weighted to the nearest 0.1 g. Gonadosomatic index (GSI) of this fish was expressed a percentage of
gonad weight (GW) to gutted body weight (BW). Thus: GSI = GW. BW
-1
. 100%.
Fish were anaesthetized and blood samples were taken from the caudal vessels by using heparinized disposable syringes.
Sample was centrifuged for 10 min at 3000 rpm and the plasma was stored at -45
o
C
until steroid analysis. Plasma levels
of (E 2) and (T) were measured by radioimmunoassay using the procedure described by (Rinchard et al., 1993). The test
of profile was done in duplicate.
The fresh gonads were fixed immediately in aqueous Bouin solution. Then gonads were transferred to 70% ethyl
alcohol until used. Samples were embedded in paraffin wax at 57
o
C. Transever sections of about 5-7 μm from female
reproductive organs were made using automatic microtome and stained with haematoxylin and eosin. The stained
sections were examined under Leica DM500 Microscope equipped with camera.
2.3 Statistical analysis
The average of data among treatments was analyzed by one way ANOVA followed by Tukey test using SPSS V 13.
Results are presented as means ±standard error of the mean (SEM).
3 Results
3.1 Oogenesis of
Liza Carinata
I – First growth phase
1 Chromatin –Nucleolus stage:
