几种枝角类的卵鞍形态及表面超微结构

MORPHOLOGY AND ULTRASTRUCTURE OF THE EPHIPPIA OF SOME CLADOCERA (CRUSTACEA)

用光镜和扫描电镜对浙东地区八种常见淡水枝角类卵鞍形态和表面结构进行了观察和比较。卵鞍形态多为三角形或豆荚形 ,表面大都具特定的纹饰 ,内储冬卵 1～ 2枚。卵鞍的形态、表面纹饰、冬卵的数量和排列方向具有种的特异性。枝角类的分类地位相距越远 ,卵鞍形态和表面结构相差越大 ,相近种和亚种间的卵鞍在光镜下难以区别 ,亚显微结构却有一定的差异。

The morphology and ultrastructure of the ephippia of eight species in the eastern area of Zhejiang Province were observed under light microscope and scanning electron microscope (LM and SEM). The ephippia were gained by artificial inducing or outdoor collecting, some others being picked out from the samples fixed years before. Most of the ephippia were trilateral and beanpod like in shape, bearing special sculpturing on the surface and containing one or two resting eggs. For a light microscopic overview, the shape and structure of the ephippia and their resting egg number were indistinguishable among certain species, especially among those in the same genus, but the outer surfaces of the ephippia of the studied species were distinctly different from one another under SEM. The results indicate that the morphology and surface ultrastructure of the ephippia as well as the number and position of the resting eggs are species specific and subspecies specific. The farther the taxonomic position between species, the clearer the difference of their ephippial morphology and ultrastructure is. It is further verified that the ephippium can provide a morphological proof for the validity of Cladocera's taxon. Here is the identification key based on ephippia characteristics for 10 dominant species of Cladocerra in East Zhejiang Province: 1(6) The ephippium is white or straw yellow, elongated ovoidMoinidae 2(3) There exists one resting egg in the ephippium Moina weismanni 3(2) There exist two resting eggs in the ephippium 4(5) The resting egg's long axis is parallel to the dorsal margin of the ephippium. There exist many spherical lobes on the surface of ephippium M. irrasa 5(4) The resting egg's long axis is vertical to the dorsal margin of the ephippium. There exist many square depressions on the surface of ephippium M. macrocopa 6(1) The ephippium varies from palm yellow to dark brown, being triangle or beanpod likeDaphniidae 7(16) The ephippium is larger, containing two resting eggs Daphnia 8(13) The ephippium is beanpod like, showing an acute angle between its dorsal margin and the resting egg's long axis Ctenodaphnia 9(10) There exist spherical lobes mainly on the surface of ephippium D. magna 10(9) There exist polygonal sculptures on the surface of ephippium 11(12) There exist polygonal recesses mainly on the surface of ephippium D. carinata carinata 12(11) There exist polygonal scaly structure on the surface of ephippium D.carinata spp. 13(8) The ephippium is triangle, its dorsal margin being vertical to the long axis of the resting egg Daphnia s. Str. 14(15) Round holes are obviously wrinkly on the surface of ephippium D. pulex 15(14) Round or ellipse holes are delicately wrinkly D. obtusa 16(7) The ephippium is smaller, containing one resting egg 17(18) The ephippium is semicircle and there exist many round recesses on its surface Scapholeberis mucronata 18(17) The ephippium is triangle and there exist many starry protuberances on its surface Ceriodaphnia cornuta