Types and arrangement of photoreceptor cells in the eye retina of three species of teleost fish differ in their light environment and nutrient natuture | ||
| Tikrit Journal of Pure Science | ||
| Article 1, Volume 17, Issue 1, March 2012, Pages 41-55 | ||
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| Abstract | ||
| The present study include the investigation of photoreceptor cells(cones and rods) at the level of light microscope, in the eye of three species of fresh water teleost fish, Garra lamta, Acanthobrama marmid and Mastacembelus simach which belong to two different families and differ in their environmental light intensity and feeding habits. type of rod was noted in each species of fish, which The results showed that the three species have duplex retina (with rods andcones).One accumulated as groups,but these groups not organized.The rods differ in lengthin each species and it’s outer segments cylindrical in shape except in the M. simach some of them funnel in shape. The rods in both G. lamta and A. marmid appeared as several layers (stratified).Six types of cones appeared in G. lamta which were unequal double,(dominant),long single, short single, thin& thick dwarf and rarely triple cone, these cones consist of spherical ellipsosomes at the tip of ellipsoids, which disappeare in the cones of other two species. In the A. marmid eight types of cones were noted ,which unequal douple, thick& thin long single, thick and thin short single, thick and thin dwarf and rarely triple cones.In the M.simach there were only two types of cones were noted twin and single cones .The cones classified as above types according to their lengths, thickness, and the number of units(cells).The cones showed different organizations in their arrangement in the three species as well as at the various regions of the same retina.In both G. lamta and A. marmid the cones patterns may be organized rows or randomlydistributed,but in A. marmid more arranged.The cones pattern in the M.smich was square organized in the central retina and row organized in the peripheral retina. | ||
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