Caperucci Débora, Camargo Mathias Maria Izabel
Instituto de Biociências, Departamento de Biologia, UNESP, Universidade Estadual Paulista, Avenida 24 A no. 1515, Rio Claro, SP, CEP: 13506-900, C.P. 0199, Brazil.
Micron. 2007;38(1):65-73. doi: 10.1016/j.micron.2006.03.013. Epub 2006 Apr 19.
The present study aimed describing the ovaries of the sugarcane spittlebug Mahanarva fimbriolata which are meroistic telotrophic with nurse cells and oocytes located in the tropharium. SEM revealed paired ovaries located dorsolaterally around the intestine, and oocytes exhibiting shapes ranging from round (less developed) to elliptic (more developed), suggesting a simultaneous, although, asynchronous development. Based on histological data we classified the oocytes in stages from I to V. Stage I oocytes exhibit follicular epithelium with cubic and/or prismatic cells, fine cytoplasmic granules. Stage II oocytes present intercellular spaces in the follicular epithelium due to the incorporation of yolk elements from the hemolymph. Small granules are present in the periphery of oocytes while larger granules are observed in the center. Stage III oocytes are larger and intercellular spaces in the follicular epithelium are evident, as well as the interface between follicular epithelium and oocyte. Yolk granules of different sizes are present in the cytoplasm. During this stage, chorion deposition initiates. Stage IV oocytes exhibit squamous follicular cells and larger intercellular spaces when compared to those observed in the previous stage. The oocyte cytoplasm present granular and viscous yolk, the latter is the result of the breakdown of granules. Stage V oocytes exhibit a follicular epithelium almost completely degenerated, smaller quantities of granular yolk and large amounts of viscous yolk. Based on our findings we established the sequence of yolk deposition in M. fimbriolata oocyte as follows: proteins and lipids, which are first produced by endogenous processes in stages I and II oocytes. Exogenous incorporation begins in stage III. In stages I and II oocytes, lipids are also produced by follicular epithelial cells. The third element to be deposited is polysaccharides, mainly found as complexes. Therefore, the yolk present in the oocytes of this species consists of glycolipoproteins. Molecular weights of proteins present in M. fimbriolata oocytes ranged from 10 to 92 KDa, differently from vitellogenin, the most common protein present in insect oocytes, weighing approximately 180 KDa.
本研究旨在描述甘蔗沫蝉Mahanarva fimbriolata的卵巢，其为meroistic telotrophic型，营养细胞和卵母细胞位于滋养区。扫描电子显微镜显示，成对的卵巢位于肠道背外侧，卵母细胞形状从圆形（发育程度较低）到椭圆形（发育程度较高）不等，表明发育是同步的，但不同步。基于组织学数据，我们将卵母细胞分为I至V期。I期卵母细胞的卵泡上皮由立方体细胞和/或棱柱体细胞组成，细胞质中有细小颗粒。II期卵母细胞由于从血淋巴中摄取卵黄成分，卵泡上皮出现细胞间隙。卵母细胞周边有小颗粒，中央有较大颗粒。III期卵母细胞更大，卵泡上皮的细胞间隙明显，卵泡上皮与卵母细胞之间的界面也很明显。细胞质中有不同大小的卵黄颗粒。在此阶段，开始沉积卵壳。IV期卵母细胞的卵泡细胞呈鳞状，与前一阶段相比，细胞间隙更大。卵母细胞细胞质中有颗粒状和粘性卵黄，后者是颗粒分解的结果。V期卵母细胞的卵泡上皮几乎完全退化，颗粒状卵黄数量减少，粘性卵黄大量存在。基于我们的研究结果，我们确定了甘蔗沫蝉卵母细胞中卵黄沉积的顺序如下：蛋白质和脂质，它们首先在I期和II期卵母细胞中由内源性过程产生。外源性摄取始于III期。在I期和II期卵母细胞中，脂质也由卵泡上皮细胞产生。第三个沉积的成分是多糖，主要以复合物形式存在。因此，该物种卵母细胞中的卵黄由糖脂蛋白组成。甘蔗沫蝉卵母细胞中存在的蛋白质分子量范围为10至92 kDa，与昆虫卵母细胞中最常见的蛋白质卵黄原蛋白不同，后者的分子量约为180 kDa。
