دراسـة الظـاهـرة الخـنثيـة Protandrous لأسماك الشعـم الفضي (الشـانـك)Acanthopagrus latus فــي بـحـيـرة الــرزازة

Rp-Study of the hermaphroditism Protandrous in the yellow fin sea bream Acanthopagrus latus in AL - Razaza lake

The phenomenon of Protandrous hermaphrodite has been studies in Acanthopagrus latus that is currently available in Al Razaza lake which fished by gill nest or cast net . A sample of 161 was chosen for the period of begining of August 2008 up to the end of January 2009 . Through this study , the fish gender and its sexual maturation were limited , and a studying monthly varieties of gonads function values GSI and liver function HIS and studying fish length at the first sex adulthood . The study also included the external and structure descriptive of the fish gonads . It was notices , according to the study , that the sex proportion was 38.51 for males and 44.72 for females and 16.77 for the hermaphrodite . This proportion was counted , when some hermaphrodite fish was considered as female when the ovary forms more than 95% of the gonad size and considered males when the testicle form more than 95% of the gonad size . The statistic analysis results showed that there are no moral differences between the observed and expected sex proportion ( p >0.05 ) . For the male proportion to the female in the total gathering is 1:0.86 ; it was noticed that the proportion tends to for the female with the age progress .this refers to the sex diversion from the male to male Protandrous .   The study showed that the Acanthopagrus  latus  males formed the majority during December and January , while the during August , September , October and November . The hermaphrodite fish was noticed in all months save August , and reached its top in November forming the majority . The monthly changes in gonad function values of males and females showed that the increase in GSI values of both sexes start from September with a continual increase till reach the highest value in January 1.47 for male and 2.30 for female . The monthly change of the liver function showed that the increase in HIS values start from September with a continual increase reaching the top in January to 2.11 for male and 2.26 for female . It was also noticed that the sex maturity was age of two years for male and of three years for female . So the males have the majority at the age of two years forming 62.5 while the females have the majority at the age of six years forming 83.33 . The hermaphrodite fish had the highest proportion 30.35 at the age of two years . It was also noticed that the smallest sex adult male was about 193 mm with an age of two years . The smallest sex adult female was about 200 mm with an age of three years . This study also asserted that the males dominate the small lengths between ( 13-15 ) cm while the female dominate in big lengths between ( 16-30 ) cm. The lengths of the hermaphrodite fish was between 135 to 202 mm . This indicates that the males mature before the females in length and age . The external examination for the Acanthopagrus latus gonads identified three types of gonads : male , female and hermaphroditic . The mature male gonads are white and stripe forming three quarters of abdominal cavity ; the female gonads with a red , rosy , transverse , lobated and veined occupy three quarters of the abdominal cavity . The hermaphrodite gonads appear as one gonad consisted of two parts . The first is external and rosy representing the ovary . The second is abdominal and white representing the testicles . The tissue examination of gonads indicated presence of male and female sex cells with their mature stages . Concerning the hermaphrodite gonads , it was noticed that the gonads contain the male and the female sex cells with various sizes , numbers , and proportion . The study showed that the Acanthopagrus latus is hermaphrodite of Protandrous type , that because the males change in to females through age progress of the different lengths .