Comparative Studies On The Morphology And Ultrastructure Of Compound Eyes In Some Crustacean

The morphology and fine structure of compound eyes in four species(Daphnia pulex ,Mysis Latreille, Penaeus monodon,Scylla serrata) were studied by electron microscope. The morphology of the compound eyes in this four spieces was studied by a scanning electron microscope. The result was: The compound eye of Daphnia pulex was globular and without eyestalk. The ommatidia that formed the compound eye were round and with large span. The area of an ommatidium was about 284.58μm2,meanwhile the number of the ommatidia was about 22.The compound eye of Mysis latreille was nearly 3/4 globular. The ommatidia that formed the compound eye were hexagon. But at border of eyestalk there were pentagon and quadrangle.The area of an ommatidium was about 157.16μm2. The development of the zoea's compound eyes was incomplete. The form of ommatidia that composed the compound eyes was circularity with large span. The number of ommatidia that composed the adult compound eyes was about 600. The form changes from circularity at zeoa's stage to typical hexagon at adult stage. The increase of the zeoa's compound eyes mainly results from the increase of the area of the ommatidia, then the increase of the fledged young's compound eyes mainly results from the increase of the number of ommatidia. The sequence of the development of the ommatidia is from distal region to proximal region.The compound eye of Penaeus monodon Fabricius was nearly globular.The eyestalk was thin and long. The ommatidia that formed thecompound eye were square. The area of an ommatidium was about 1139.06μm2. The number of ommatidia that composed one compound eye was about 80000. The ommatidia at the border of eyestalk were regular. The compound eye of Scylla serrata was semi-globular. On the back of the compound eye there was a thumb-shaped area which had no ommatidia. The ommatidia that formed the compound eye were hexagon. The area of an ommatidium was about 25.4μm2,and the number of ommatidia that composed one compound eye was about 930000. The fledged young's compound eyes were mainly square.The fine structure of the compound eyes was studied by transmission electron microscope.An ommatidium of Daphnia pulex was composed of cornea, two comeagenous cells, five cone cells,two supporting cells and five retinular cells.So there were 14 cells in one ommatidium .The rhabdom formed by microvillus was short,thick in distal part and thin in proximal part. The cross section of the rhabdom was irregular.It was divided into parts with large span. So the Compound eye of Daphnia pulex's ultrastructure was original.An ommatidium of Mysis Latreille was composed of cornea, two comeagenous cells, four cone cells and seven retinular cells. The cone cells were unique.Two of them were in distal part. They were more compact than the other two,and the other two cells were located boths sides of the first two cells,and their volume increased when extended to proximal part . The cone cell linked to the rhabdom. Seven retinular cells formed the retina. The diameter of rhabdom in distal part was about 8.4μm. On cross section the area of the rhabdom was bigger than retinular cells. So the interval among rhabdoms of different ommatidia was small.The rhabcom changed gradually to thinness in proximal part,and then disappeared.The retinular cells arranged loosely.An ommatidium of Penaeus monodon was composed of cornea, twocomeagenous cells, four cone cells and seven retinular cells. The diameter of rhabdom which was formed by microvillus was 9.25μm. All the retinular cells contained organelles such as mitochondria, multivesicular body, endoplasmic reticulum and pigment granule. Our results showed that the fine structure of the compound eye in Penaeus monodon showed the typical character of Macrura. There were two kinds of pigment granules in retinular cells(small and big).The perirhabdomal vacuole around the rhabdom was small. We didn't find the proximal pigment cells arround the retinular cells which were seen in Brachyura.There w...