同域共存的两种平鳍鳅科鱼类消化系统的形态差异

为了探究同域共存的2种形态相似的平鳍鳅科鱼类的共存机理, 通过形态学、组织学和组织化学等方法对西昌华吸鳅(Sinogastromyzon sichangensis)和峨眉后平鳅(Metahomaloptera omeiensis)的消化系统进行观察比较。形态学结果显示, 它们的消化系统组成基本相同, 符合杂食性鱼类的特征, 但二者消化系统形态有明显差异。西昌华吸鳅肠道盘旋2回, 呈“φ”字形, 肝胰脏覆盖在消化管腹面; 峨眉后平鳅肠道盘旋5—7回, 肝胰脏镶嵌在消化管之间, 西昌华吸鳅在肠道系数、比消化系统重等形态学指数上大于峨眉后平鳅。组织学结果显示, 在消化道内黏膜褶皱高度、肌层厚度等特征上西昌华吸鳅显著大于(P<0.05)峨眉后平鳅, 肝胰脏没有显著差异。AB-PAS染色显示, 2种鱼消化道内黏液细胞种类相似, 多为Ⅱ型和Ⅳ型黏液细胞, 黏液细胞分布类型与大多数硬骨鱼类近似。消化系统形态学、组织学和组织化学特征能在一定程度上反映鱼类的食性和消化能力, 二者在形态学、组织学上的差异可能暗示着西昌华吸鳅和峨眉后平鳅在食性和消化能力上存在差异, 这可能是二者能够稳定共存的原因之一。

THE MORPHOLOGICAL CHARACTERISTICS OF THE DIGESTIVE SYSTEM IN TWO COEXISTING BALITORIDAES

Most Balitoridae fish with similar shapes separately distribute in different rivers or different sections of a river. Providing the morphological similarities, it’s interesting to find why Sinogastromyzon sichangensisandMetahomaloptera omeiensis coexist in the Zaodu River. To address this, the digestive systems of these two fish species were comparatively analyzed by morphological, histological and histochemical methods. The digestive systems of these two fish were nearly the same at morphology, which were consistent with characteristics of omnivorous fishes, however, the morphological difference of the digestive system was obvious. First, the intestine of S. sichangensis was circled into a" φ”shape, with hepatopancrease covered on the ventral part, however, that of M. omeiensis was organized in a complicated ways. Second, the gut index (GI) and digestive system index (DSI) of S. sichangensis were greater than those of M. omeiensis.Besides, the digestive tract of S. sichangensis had a significant higher mucosal fold and thicker muscular layer compared with M.oneiensis, however, there was no significant difference in hepatopancrease. The mucous secreting cells were similar in these two fishes based on AB (Alcian Blue) and PAS (Periodic Acid Schiff) staining, and most of these cells belong to type Ⅱ and Ⅳ mucous cells that were similar to most teleosts. The characteristics of digestive system reflect the feeding habits and digestive ability of fish, in some degree. Thus, the morphological and histological differences in digestive system between S. sichangensis and M. omeiensis may suggest different diet and digestion, which maybe the reasons for the coexistence of these two morphologically similar species.