江豚眼的解剖学和组织学研究

统计结果表明:与黄海沿岸种群江豚相比,长江种群江豚眼中央至吻端的平均距离显著较小,与长江弱光环境相适应。长江种群平均眼裂高比较小,眼球平均相对水半径比较短,而前后径比较长。眼球较趋近于圆球型。视觉较近视。在显徽与亚显微结构方面未发现两种群之间有差异。江豚无典型的视锥,而具有细胞核和内节呈视锥状、外节呈视杆状的一种中间型视细胞。

ANATOMICAL AND HISTOLOGICAL STUDIES OF THE EYES OF THE FINLESS PROPOISE, NEOPHOCAENA PHOCAENOIDES

Some differences are found between the measurements of the eye of Yangtze population and Yellow Sea coastal population of Neophocaena phoeaenoides. The mean distance from the center of eye to the tip of snout in Yangtze population is very significantly shorter than that in Yellow sea coastal population (p<0.001), and the mean height of the eye slits is significantly smaller (p<0.05) in the former. The mean relative length of horizontal diameter of the eye ball is significently shorter (p<0.05) and the mean relative axial length of the eye ball is very significantly longer (p<0.01) when compared with those of the coastal form, so that the eye ball in the Yangtze population seems more like a round ball. It is explained as a result of adaptation to dim light in the Yangtze River. The ratio of horizontal to vertical diameter of eye ball in Yellow Sea population is close to that of some other marine whales, and such a ratio in Yangtze population is close to that of Lipotes. No differences are found in other aspects or in micro- and submicroscopic structure of the eye between the two populations.No ciliary muscle fibre is found in the ciliary body and no ellipsoid is found in the inner segment of the visual cell. Both the nuclei in the outer nuclear layer and the inner segments near limiting membrane of the visual cell could be divided into two types according to their electron densities and their diameters. But the outer segments of vi-sual cell are all rod-like, their discs belong to closed type. So the retina of Neophocaena may have no typical cones. The cone may have converted to the "intermediate visual cell" with come-like nucleus, cone-like inner segment and rod-like outer segmenit. Laminated encapsulated receptors are found beneath the epithelium at the temporal margin of cornea, in the neighbouring sclera and in the ciliary body.