KK-42对蜕皮后期日本沼虾头胸甲超微结构的影响

为了深入探究KK-42对表皮结构的影响,本实验以外表皮形成趋于结束而内表皮开始出现的蜕皮后期幼虾为材料,通过扫描电镜观察石蜡切片法,分析了KK-42处理前后头胸甲外表皮,尤其是内表皮结构的变化。将处于蜕皮间期的健康幼虾体长(3.5±0.1)cm]随机分为2组,分别用1.95×10^-4 mol/L的KK-42溶液和不含KK-42的溶液处理,取蜕皮后1.5、3.0、6.0及12.0 h幼虾头胸甲,观察其超微结构。另取蜕皮后6.0 h头胸甲,用解剖刀轻轻刮去内面组织,通过扫描电镜观察内表皮的表面结构。结果显示,蜕皮后1.5和3.0 h,头胸甲只包含上表皮和外表皮,KK-42处理组外表皮的板层数量显著增加,外表皮厚度分别比相应对照组提高了72.07%和38.67%;蜕皮后6.0~12.0 h,外表皮中疏松的板层趋于致密,其厚度在二组间无统计学差异。蜕皮后6.0 h,只有1层板层的内表皮出现,到蜕皮后12.0 h,板层数增至2层(对照组)和3层(处理组),且板层结构均疏松。此外,内表皮表面分布着大小不等、头尾走向的梭形孔道(pore canals);KK-42处理组内表皮结构未见明显变化。实验表明,KK-42对蜕皮后期日本沼虾幼虾头胸甲的超微结构有显著影响,能加快外表皮及内表皮板层的形成速率。

Effect of KK-42 on the carapace ultrastructure in Macrobrachium nipponense during postmolt

In order to further investigate the effect of KK-42 on cuticle structure, the juvenile prawns (Macrobrachium nipponense) in postmolt stage during which the formation of exocuticle gradually ends but that of endocuticle starts, were employed to study the structures of carapace exocuticle and endocuticle using the observation of paraffin section by scanning electron microscopy (SEM). Healthy intermolt M. nipponense with body length of (3.5±0.1) cm were randomly divided into two groups. The M. nipponense were soaked for 1 min in KK-42 solution at a concentration of 1.95×10^-4 mol/L (treatment group) or 0 mol /L (control group), respectively. The carapaces of M. nipponense at 1.5, 3.0, 6.0 and 12.0 h after molting were obtained to be used for ultrastructural observation. To observe directly the surface structure of endocuticle, the carapace obtained at 6.0 h after molting was scraped gently with an anatomical knife to remove tissues on the inner surface of carapace, and then examined using SEM. The results showed that the carapace was only composed of the epicuticle and exocuticle at 1.5 and 3.0 h after molting. The number of exocuticle lamellae derived from KK-42 treatment group rose significantly at 1.5 and 3.0 h after molting, and the thickness of exocuticle increased by 72.07% and 38.67%, respectively, compared with the corresponding control group. At 6 and 12 h after molting, the loose lamellae in exocuticle tended to be dense, and there was no significant difference in thickness to be found between two groups. The number of endocuticle lamellae with a loose structure, being only one at 6.0 h, separately increased to two in control group and three in treatment group at 12.0 h after molting. In addition, pore canals within the endocuticle presented different sizes and head-tail orientation. No significant structural change was observed in the endocuticle after KK-42 treatment. The results reveal that KK-42 has a significant effect on the carapace ultrastructure of juvenile M. nipponense during postmolt, and accelerate the formation rate of the exocuticle as well as endocuticle.