Effects of citronella oil (Cymbopogon winterianus Jowitt ex Bor) on Spodoptera frugiperda (J. E. Smith) midgut and fat body

The armyworm, Spodoptera frugiperda, is the principal pest of corn in Brazil. Control is achieved primarily by synthetic insecticides, which cause problems for the agro-ecosystem. Alternative methods of control are under investigation and citronella (Cymbopogon winterianus) essential oil appears to be a promising agent. We investigated the effects of citronella oil using histological, histochemical and immunohistochemical methods. The midgut of larvae treated with citronella exhibited altered epithelium including cytoplasmic protrusions, columnar cell extrusion, pyknotic nuclei, and increased periodic acid-Schiff positive granules. Regenerative cells in the epithelium of the midgut increased in number, which facilitated subsequent regeneration of this tissue. After exposure to citronella, trophocytes, the principal cell type of the fat body, possessed enlarged vacuoles and mitotic bodies, and contained reduced amounts of glycogen, lipid, and protein. Citronella oil caused morphological changes of the midgut and reduction of stored resources in the fat body, which may adversely affect insect reproduction and survival.     

蜜蜂脂肪体的形态和功能研究进展

脂肪体是昆虫体内的一种多功能器官,近似于脊椎动物的肝脏,分布于昆虫腹部、胸部甚至头部腔体中,以腹部脂肪体最为发达。蜜蜂脂肪体有外周脂肪体和围脏脂肪体两种类型,由营养细胞、尿酸盐细胞和绛色细胞组成。同其他昆虫中类似,脂肪体在蜜蜂的生命活动中扮演着重要的角色,其形态和功能随发育阶段、季节和劳动分工的变化而变化。脂肪体结构相对简单,但生理功能非常复杂。脂肪体最主要的功能是能量物质的储存和代谢,其不仅是蜜蜂营养物质(即脂质、碳水化合物和蛋白质)的中央储存库,而且是营养代谢的中间站,具有多种能量和物质相互转换的酶系,承担代谢水的供应并合成嘌呤和嘧啶及许多重要的蛋白质。同时,脂肪体是昆虫发育和行为调控过程中各种激素和营养信号的交换中心,脂肪体激素和营养信号参与调控蜜蜂脂肪体发育、营养物质代谢、生殖及劳动分工。脂肪体兼具能量储存和释放、生物合成和分解、营养感知调节、代谢信号整合、内分泌调节、免疫和解毒、磁场感受、提高抗寒能力、保护体腔内器官等多种功能。鉴于脂肪体的重要作用,蜜蜂脂肪体形态和功能的研究成果可以对昆虫营养信号通路的解析、蜂产品高产良种的选育和蜜蜂病害防治的研究提供参考和思路。     

Ultrastructural features of the trophonema and oogenesis in the starlet sea anemone, Nematostella vectensis (Edwardsiidae)

Abstract. The starlet sea anemone, Nematostella vectensis Stephenson 1935, is a burrowing, estuarine species that has become a model organism for fundamental studies of cnidarian and metazoan development. During early oogenesis, oocytes appear in the basal region of the gastrodermis in the reproductive mesenteries and gradually bulge into the adjacent connective tissue space (mesoglea) where the majority of oocyte growth and vitellogenesis occurs. However, oocytes do not physically contact the cellular and amorphous matrix of the mesogleal compartment due to a thin, intervening basal lamina. Oocytes retain limited contact with the basal gastrodermal epithelium via groups of ultrastructurally modified gastrodermal cells called trophocytes. Trophocytes are monociliated accessory cells of somatic origin that collectively form a structure called the trophonema, a unique accessory cell/oocyte association not observed outside the Cnidaria. The trophonema consists of 50–60 trophocytes that maintain contact with <1% of the oocyte surface and forms a circular, bowel‐shaped depression on the luminal surface of the gastrodermis as they sink into the mesoglea with the oocyte. The oocyte remains highly polarized throughout oogenesis with the germinal vesicle positioned near the trophonema and presumably representing the future animal pole of the embryo. Contact between the trophonema and the oocyte is restricted to cell junctions connecting peripheral trophocytes and narrow extensions from the oocyte. Previous studies suggest that the trophonema plays a role in transport of extracellular digestive products from the gastrovascular cavity to the oocyte, and the ultrastructural features described in this study are consistent with that view. Vitellogenesis is described for the first time in a sea anemone. Yolk synthesis involves both autosynthetic and heterosynthetic processes including the biosynthetic activity of the Golgi complex and the uptake of extraoocytic yolk precursors via endocytosis, respectively.     

Smooth muscle contributes to the development and function of a layered intestinal stem cell niche

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Ovary structure and transovarial transmission of endosymbiotic microorganisms in Marchalina hellenica (Insecta,Hemiptera, Coccomorpha: Marchalinidae)

Szklarzewicz, T., Kalandyk‐Kolodziejczyk, M., Kot, M. and Michalik, A. 2011. Ovary structure and transovarial transmission of endosymbiotic microorganisms in Marchalina hellenica (Insecta, Hemiptera, Coccomorpha: Marchalinidae). —Acta Zoologica (Stockholm) 00 :1–9. The paired ovaries of Marchalina hellenica are composed of about 200 ovarioles of telotrophic type. In each ovariole, a trophic chamber, vitellarium and ovariolar stalk can be distinguished. The tropharia comprise trophocytes and early previtellogenic oocytes (termed arrested oocytes) or trophocytes only. The arrested oocytes are not capable of further development. In the vitellaria, single oocytes develop that are connected to the tropharium by means of broad nutritive cords. The number of germ cells (trophocytes and oocytes) constituting ovarioles is not constant and may range between 25 and 32. Numerous endosymbiotic bacteria occur in the cytoplasm of trophocytes. The endosymbionts are transported via nutritive cords to the developing oocyte. The obtained results are discussed in a phylogenetic context.     

Graded BMP signaling within intestinal crypt architecture directs self-organization of the Wnt-secreting stem cell niche

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Distinct Mesenchymal Cell Populations Generate the Essential Intestinal BMP Signaling Gradient

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