三疣梭子蟹卵附着机制及相关形态学特征

Using histological methods and scanning electron microscopy, the structure of cement gland and formation of outer egg-membrane and egg-stalk of the swimming crab Portunus trituberculatus were studied to explain the mechanism of egg-attachment and function of the cement gland. Eggs adhered to the setae of pleopodal basipodite and endopodite for hatching followed by spawning but no egg attached on the setae of exopodite. The setae of pleopodal basipodite and endopodite were smooth for egg attachment while the setae of exopodite were branched and suitable for collecting and protecting eggs. Cement gland distributed along longitudinal axis of the pleopodal basipodite and endopodite under epithelia cells. Cells of the cement gland were elliptical and its size was about 50 times of the epithelium. Some glue secreted to the surface of the pleopod along the seta, while the other glue secreted to the surface of the pleopod by the channel which across the integument of the pleopod. The first spawned egg was transferred to the setae that were far from the pore, not attached to the setae of the pleopodal basipodite and endopodite near the genital pore. And the egg attachment became nearer and nearer to the pore with further spawning. Since the eggs to glide rather than roll, there was almost no glue on the contrary surface of the egg at first: and with further secretion, the whole surface was surrounded by glue. The thick part of glue formed one short bud during the glide of the egg and gradually developed into a full egg-stalk. On the other hand, the else glue developed into an outer egg-membrane, which was “trichromatic egg membrane” originally. Each egg attached to the setae of pleopodal basipodite and endopodite with its own egg-stalk. The egg-stalk was a plane strap at the formation stage and later it rolled into a rope shape, but it could be reverted to the former by outside force. Four types of egg attachment : an egg to a seta, an egg to several setae, several eggs to a seta and several eggs to several setae were discovered. In summary, the cement gland existed in the pleopod of the swimming crab and formed outer egg membrane and egg-stalk during the egg attachment Acta Zoologica Sinica 50 (5) : 873 - 879, 2004].

The mechanisms and correlated morphological character of the egg attachment of the swimming crab Portunus trituberculatus