云南盘鮈口吸盘发育、表面亚显微结构及功能

DEVELOPMENT, SURFACE ULTRASTRUCTURE OF THE SUCKING DISC OF DISCOGOBIO YUNNANENSIS (REGAN) AND IT'S FUNCTION

云南盘鮈口吸盘发育可划分为5个时期,这一过程在盘鮈属中具有一定代表性。吸盘发育过程或多或少暗示了盘鮈的起源和演化,为进一步探索它们的起源提供了一点线索。吸盘的一些细微结构不失为好的分类性状,有助于系统分类和进化研究。在野外观察和室内饲养观察相结合、宏观和微观形态比较相结合的基础上,阐述口吸盘的功能和适应意义。口吸盘是抵御急流冲击的吸附器官和运动辅助器官,在取食活动中的作用更不可忽视。

The development course of sucking disc of Discogobio yunnanensis(Regan) can be divided into five phasses, i. e. primary phase, horse-shoe-swollen phase, pre-rudiment phase, rudiment phase and shaping phase (fig. 1), which is similar to the course observed by the authors in the development of sucking disc in D. macrophysallidos Huang. This result implies that the genus Discvgo-bio was derived from the fish who does not have sucking disc and develops gradually from the disc shape incomplete to complete. Surface ultrastructures of sucking disc, rostral fold, jaws and barbels are observed by using scanning electron microscopy (pl. Ⅰ). Among these ultrastructures, some of them are good characters for classification. These characters are helpful in the aspects of identification of species or genera, study of systematics and functional analysis of the sucking disc. According to the observation in wild and aquarium, authors consider that adhesive function of the disc is mainly caused by vacuum attraction that is made by reciprocation of the sucking disc central pad. However,papillae of disc and tentacles distributed at the top of papillae can strengthen the action of vacuum attraction. Fishes of D. yunnanensis (Regan) often move along the surface of rock or stone when the disc is sucking on those surfaces. The sucking disc never loses contact with the surfaces of rock or stone in river when the fish moves. The force that pushes the fish forward is mainly produced by tail. It is inferred that wriggles of the papillae and tentacles may assist swinging in the forward movement of the fish. When they move along the surfaces of rock or stone in river, their jaws covered with horny sheath can scrape algae living on surface of rock or stone. Most of their foods are collected in this way. According to the investigation, authors incline that the role of sucking disc is an adhesive organ for keeping body from being swept away by torrent water, a subsidiary organ for movement and a secondary tool for taking food.