江豚皮肤的超微结构及其与其它豚类的比较

江豚皮肤的超微结构与海洋豚类相同,但在各层表皮细胞中存在大量的膜被颗粒,这很可能与江豚适应从海水进入淡水的生活方式有关。大量成束的张力原纤维的存在,有利于江豚在水中深潜和快速游泳,可适应来自各方面的压力,加强细胞之间的联接。在上下颌皮肤的乳头层基部大量被囊神经末梢和有鞘神经纤维束的分布、与江豚水底觅食方式有关。白鱀豚和条纹原海豚皮肤的超微结构与江豚大致相同,但亦有其各自的特点。

THE ULTRASTRUCTURE OF THE SKIN OF NEOPHOCAENA PHOCAENOIDES AND COMPARISON WITH OTHER CETACEANS

Although the ultrastructure of the skin of Neophocaena is similar to that of marine odontocetes, some features are worthy of notice. Numerous membrane coating granules lie close to plasme membranes of the superficilal cell layers. These granules have good function to protect the hydrotropic substances to discharge from inside of the skin into external environment. Most probably, this structure is advantageous to dolphin moving from sea water to freshwater of Changjiang River. A lot of tonofilaments are present in the strata of the skin. They can strengthen the connexion among the cells which are faced with strong pressure and rub on the skin due to diving and fast swimming. Numerous single and clustered encapsulated nerve endings lie at the bases of the sturdier dermal papillae in the region of the tubercles. Many groups of similar encapsulated nerve endings are present in the dermal ridge of the lower jaw. A lot of bundles of myelinated nerve fibres are present in the dermis and the hypodermis of the jaw and the tubercles. These integumental features can be correlated with some of the behavioural characteristics exhibited by Neophocaena in the river, for instance, carrying their calves on their backs and seeking the food from the bottom of the water.