鳜早期味蕾发育的组织学特征

Histological Characteristics of Taste Bud during Early Development of Mandarin Fish Siniperca chuatsi

采用石蜡切片、H.E染色研究了3～28日龄鳜(Siniperca chuatsi)味蕾发育的组织学特征,并通过扫描电镜观察28日龄鳜口咽腔组织味蕾类型与数目。结果表明,未开口期(3日龄),鳜口裂未张开,味蕾尚未分化;开口期(7日龄),鳜口裂张开明显,味蕾呈椭圆形,突起高度平缓,主要分布在上下颌上皮上,舌、咽、鳃弓上皮上有少量分布;稚鱼期(14日龄),味蕾呈圆锥形,突起高度上升,舌和咽上味蕾数目增加;21日龄,味蕾呈近梯形,突起高度不变,下颌、舌、咽上味蕾数增加,鳃弓上味蕾数目显著增加;28日龄,味蕾发育完全,口咽腔味蕾数继续增加。扫描电镜观察表明,鳜味蕾主要有3种类型:Ⅰ型味蕾近球形,含有大量微绒毛,突起高于上皮,味孔向外突起;Ⅱ型味蕾含有少量微绒毛,突起略高于黏膜上皮,味孔向内凹陷;Ⅲ型味蕾微绒毛含量最少,突起几乎与黏膜上皮共面,味孔平坦或凹陷。上下颌、咽、鳃中以Ⅰ型味蕾数量最多,Ⅱ型味蕾最少,舌上主要分布Ⅰ型味蕾,无Ⅲ型味蕾。结果表明,鳜早期味蕾结构发育与其摄食关联,推测其主要通过Ⅰ型味蕾和Ⅱ型味蕾对食物的机械性和化学成分进行识别。

Histological characters of taste bud during early development of Mandarin Fish（Siniperca chuatsi） at 3﹣28 days were observed through the paraffin section and H.E staining, and further observation was made via scanning electron microscopy to analyze the types and density of taste buds at 28 days old. The results showed that the mouth was not open until 3 days old when the taste bud was undifferentiated（Fig. 1 a）; at 7 days old, the mouth was open, and taste bud was in oval shape with gentle projections, which were distributed in the mucosa epidermis of pharynx epithelium, tongue, jaw and gill arch（Fig. 1 b, Fig. 2 a﹣d）; at 14 days old, lower jaw began to develop, and taste bud was conical, meanwhile, the protrusion height was increased, and the number of taste bud in pharynx, gill and tongue began to increase（Fig. 1 c, Fig. 2 e﹣h）; at 21 days old, taste bud was in trapezoidal shape with obvious projections, the number of which has increased in jaw, pharynx and tongue, most notably in gill arch（Fig. 1 d, Fig. 2 i﹣j）; at 28 days old, taste bud developed completely, and the number of taste bud increased in all oropharyngeal cavity（Fig. 2 k）. Three main types of taste buds were observed by scanning electron microscopy（Fig. 3）： type Ⅰ taste bud was in ball-like shape with contained quantities of microvilli, its processes were higher than that in the mucosa epithelium, and taste pores bumped out; type Ⅱ taste bud contained a few microvilli, its processes slightly higher than that in the mucosa epithelial, and taste pore was concave beneath; type Ⅲ taste bud contained a few microvilli, its processes were almost coplanar with the mucosa epithelium and the smooth inner hole. The number of Type Ⅰ taste bud was maximal, and that of type Ⅱ was minimal in the jaw, pharynx, while a large amount of type Ⅰ taste bud was observed in the tongue which contained no type Ⅲ taste bud（Fig. 4, Table 1）. The results showed that taste bud development in early stage played an essential role in feeding, and that type Ⅰand Ⅱ taste buds were properly the main types in mechanical and chemical recognition during food intake.