长久以来,镰刀菌足的组织学起源一直未确定,不确定它们是由间充质变形细胞还是息肉中的茎和盘外胚层产生的。由于息肉在硬基材上的沉降,对踏板盘的组织学研究很困难。在这项研究中,我们利用附着在薄聚苯乙烯基材上的息肉,研究了亚洲月亮果冻(Aureliacorulea)在足细胞生长过程中息肉的组织学特征。在组织学处理过程中分解基质后,踏板盘的良好组织学特征成为可能。我们的发现明确表明,足细胞的细胞团起源于踏板盘和茎的外胚层,而中胚层中没有变形细胞的参与。在足病菌形成之前,踏板盘经历由细长的茎外胚层细胞促进的扩大,附着在基板上。随后,踏板盘外胚层产生初级足细胞,在细胞质中积累营养颗粒,并与内陷的踏板盘外胚层共同形成囊肿囊。从外胚层细胞到足细胞的直接转化表明足细胞的形成涉及组织去分化。在整个足病菌生产期间,息肉的胃皮与外胚层被中胚层物理分离,没有组织学变化,中胚层中没有变形细胞。这些组织学特性与其他无性繁殖方式完全不同,融合了息肉的内胚层,表明这些无性繁殖和足孢子虫生产之间的发育和进化差异。
The histological origin of podocysts in scyphozoans has long been undetermined, with uncertainty whether they arise from mesenchymal amoebocytes or stalk and pedal disc
ectoderm in polyps. Histological investigation on the pedal disc was difficult due to the settlement of polyps on hard substrates. In this study, we investigated the histological characteristics of polyps during podocyst production in Asian moon jelly (Aurelia coerulea) with utilizing those attached on thin polystyrene substrates. Fine histological features of the pedal disc became possible after the substrates were decomposed during histological processing. Our findings unequivocally demonstrate that the cell mass of podocysts originates from the
ectoderm of the pedal disc and the stalk without the involvement of amoebocytes in the mesoglea. Preceding the podocyst formation, the pedal disc undergoes enlargement facilitated by the elongated stalk ectodermal cells, which attach to a substrate. Subsequently, the pedal disc
ectoderm give rise to the primary podocyst cells with accumulating nutrient granules in the cytoplasm and forming the cyst capsule cooperatively with the invaginated pedal disc
ectoderm. Direct transformation from the ectodermal cells to podocyst cells suggests that podocyst formation involves tissue dedifferentiation. Throughout the period of podocyst production, the gastrodermis of polyps is physically separated from the
ectoderm by the mesoglea and shows no histological changes, and no amoebocytes appear in the mesoglea. These histological properties are totally different from those in other modes of asexual reproduction, which incorporate the endoderm of polyps, suggesting the developmental and evolutionary differences between these asexual reproductions and podocyst production in Scyphozoa.