دراسة الهياة الكروموسومية لنوع من اسماك المياه العذبة العراقية سمكة ابو الزمير العميق Mystus pelusius == Karyotyping Study of one Species of Iraqi Freshwater Fish ( Mystus pelusius )
Author name:
هبة حسين رسن
Supervisor name:
اسماء سامي ابراهيم
General topic:
Biology
Specific topic:
zoology - Genetics
Degree:
Master
University:
University of Baghdad
Language:
Arabic
University location:
Baghdad
First pages:
24T3454 - p.pdf
Abstract:
The fish has a great economic and environmental importance, however the cytogenetic studies on them still few, especially the chromosomal studies of local fish, therefore current study aimed to identify the karyotype (Chromosomal type and number) and the sex determination system to a species of Iraqi freshwater fish, which is Mystus pelusius (Solander in Russell, 1794) fish in Iraq, as (20) fish (10) male and (10) female were hunted from Tigris river in Al - Kraat area of Bagdad city.The current study was done to investigate the karyotype, where the chromosomal preparations has been preparing from kidney cells according to (air - drying technique).The results of the males and females kidney cells metaphase chromosomes study showed that the diploid chromosome number was 2n=32, which represents less chromosomal number recorded so far in the studied Iraqi fish, also the results showed that the males chromosomal types included 2n=(6m+13sm+7st+6t) and fundamental number FN=51, the females chromosomal type was 2n=(6m+12sm+8st+6t) and FN=50, also it observed that the first sub metacentric pair was the largest within the biarmed chromosomes.The results revealed that the male (heterogamety) and the female (homogamety), accordingly it follows the sex determination system (XX/XY), as the (X) chromosome represented by medium sized submetacentric (sm) chromosome and (Y) chromosome by small sized subtelocentric (st) chromosome.The results of Giemsa - banding technique (G - banding) showed that the rich regions with Guanine (G) and Cytosine (C) nitrogen bases called (G - light) bands and the rich regions with adenine (A) and thymine (T) called (G - dark) bands, thus it determined more accurately the sister chromosomes in Mystus pelusius males and females, more over thistechnique described sex chromosomes better, it has been observed that most chromosomes in both sexes have (G - light) bands, as all (uniarmed) (telocentric, subtelocentric) autosomes pairs entirely contain (G - light) bands, while in the (biarmed) (metacentric, submetacentric) autosomes chromosomes the light bands concentrated in their telomeres, while the rest regions of these biarmed chromosomes have dark bands. Results of (G - banding) technique confirmed which was shown by the traditional pigmentation method (Giemsa staining technique) about the sex chromosomes discrimination, where this technique showed more accurately and better that the male was heterogamety through a observation of medium sized submetacentric (X) chromosome with (G - light) bands in telomric position of (short arm), while the subtelocentric (Y) chromosome was the larger within the uniarmed chromosomes and it was marked by being entirely dark and lack of (G - light) bands, while it was observed in females a medium sized submetacentric (sm) pairs with (G - light) bands in the telomeric of long and short arms which represents (XX) sex chromosomes, and according to this the females considered to be homogamety and the males heterogamety, and proved that the sex determination system in Mystus pelusius fish was a simple sex determination system of (XX/XY) type
