帕米尔漠蟾蜍皮肤、肾和肝的组织结构

Histological Structures of the Skin,Kidney and Liver of Bufotes taxkorensis

为探究帕米尔漠蟾蜍(Bufotes taxkorensis)对高原环境的适应特征,观察了其皮肤、肾和肝的组织结构,并对躯干和胫部的皮肤总厚度、表皮层厚度、真皮层厚度和相对腺体数量,肾的肾小球密度、肾相对总滤过面积、远端小管和近端小管的相对管径在SPSS 25.0中做了独立样本t检验分析。结果显示:(1)帕米尔漠蟾蜍皮肤粗糙,布满皱褶,由表皮和真皮组成。皮肤厚度存在部位和性别差异。雌雄性躯干和胫部的皮肤总厚度及真皮层厚度均背部显著大于腹部。雌雄性躯干的表皮层为背部显著小于腹部。雄性胫背部表皮层厚度显著大于腹部,而雌性胫背腹部表皮层厚度差异不显著。黏液腺分布于体背和体腹的真皮疏松层,颗粒腺主要分布于体背真皮疏松层。色素呈不规则网状分布于疏松层,背部较腹部多,部分黏液腺和颗粒腺被不连续的色素层包绕。真皮层中存在大量毛细血管,并可见部分毛细血管突入表皮。帕米尔漠蟾蜍的皮肤组织结构体现了对干燥、低温、强紫外线辐射和低氧生活环境的适应,与同样生活在高原环境中的多数无尾两栖类相似。(2)肾呈饱满长条状。肾小体主要分布于肾中央,部分肾小体中肾小球较小,鲍曼囊较宽阔。肾远端小管数量多于近端小管。管周毛细血管分布密集。帕米尔漠蟾蜍肾的总相对滤过面积介于陆栖与水栖无尾两栖类之间,且其肾组织结构体现了对干燥和盐碱环境的适应。(3)肝内结缔组织较少,相邻肝小叶之间界限不清。肝细胞中可见明显的空泡或间隙,细胞核大多位于细胞一侧。肝实质中存在大量黑色素团块。帕米尔漠蟾蜍的肝组织结构体现了对低温和低氧环境特征的适应。

[Objectives]Bufotes taxkorensis is endemic to China and mainly distributes in Pamirs Plateau at an altitude of 2900﹣3150 m.This species is one of the few anurans that can inhabit saline environments.To investigate the adaptive features of B.taxkorensis to the extreme environment,we conducted qualitative and quantitative analyses on the histological structures of its skin,kidney and liver.[Methods]Three males and three females of B.taxkorensis were used for study(Table 1).The histological structures of their skins,livers and kidneys were observed using paraffin and hematoxylin-eosin staining.The total thickness,epidermis thickness,dermis thickness and relative gland number of the trunk and tibia’s skin,and the corpuscular density,relative filtration area of renal glomerulus,relative filtration area of kidney,relative diameter of proximal and distal tubules of the kidney were measured.The independent sample t-test was used to compare differences in these measurements utilizing software SPSS 25.0.[Results](1)The skin,comprising of the epidermis and dermis,was rough and wrinkled(Fig.1).Skin thickness varied considerably in different regions of the body(Table 2).Both sexes displayed thicker total thickness and dermis thickness in the dorsal truncal and tibial regions than in the ventral truncal and tibial regions(P<0.05).Both sexes displayed thinner epidermis thickness in the dorsal truncal region than in the ventral truncal regions(P<0.05).The epidermis of the tibial region was significantly thicker dorsally than ventrally in males(P<0.05),while the epidermis thicknesses were not significantly different between the dorsal and ventral tibial region in females(P>0.05).The mucous glands and granular glands distributed in stratum spongiosum,with the former in dorsal-ventral skin and the latter in dorsal skin(Fig.1).Chromatophores were found in the stratum spongiosum and presented in irregular web shape,which were richer dorsally than ventrally.Some skin glands were surrounded by discontinuous pigment layers(Fig.1 e,m).There were rich capillary vessels in the dermis,and some of them protruded into the epidermis(Fig.1 j,m,n).(2)The renal corpuscles mostly distributed centrally in kidney(Fig.2).In some renal corpuscles,the glomeruli were smaller and the Bowman’s capsule was broader(Fig.2 b,e).The number of the distal tubules was more than that of the proximal tubules(Fig.2 b,c,e,f).The peritubular capillaries densely distributed(Fig.2).The relative diameter of proximal segment in male was significantly greater than that in female(P<0.05),other measurements showed no significant differences between two sexes(P>0.05)(Table 3).(3)There were no clear boundaries between adjacent hepatic lobules because of less connective tissues in the liver.The hepatocytes contained prominent vacuoles or spaces,with nuclei mostly on the side.The liver parenchyma contained numerous melanin masses(Fig.3).[Conclusion]Our study indicates that the thicker epidermis,rich pigment cells and capillary vessels of B.taxkorensis make this species adapt to the strong ultraviolet radiation,low temperature and hypoxia of the Pamirs Plateau at high altitude.Its wider Bowman's capsule as well as the relative kidney filtration area between aquatic and terrestrial anurans present adaptations to the dry and saline habitat.Its liver contains plentiful pigment cells,which reflects adaptation to the low temperature of the living environment.