Centro de Maricultura da Calheta, 9370-135, Calheta, Madeira, Portugal; IRTA, Centre d' Aqüicultura, Ctra. Del Poble Nou, 43540, Sant Carles de La Ràpita, Tarragona, Spain.
CSIC, Institut de Ciències Del Mar, 08003, Barcelona, Spain.
Arthropod Struct Dev. 2022 Sep;70:101168. doi: 10.1016/j.asd.2022.101168. Epub 2022 Jul 12.
The midgut tract of decapods is a digestive organ involved in the synthesis of peritrophic membrane, food transport, absorption of nutrients, and osmoregulation. The midgut tract has been described in detail in adult decapods, but little information is available regarding the morphology and ultrastructure of the midgut tract in larval stages. The present study describes the midgut tract and the midgut-hindgut junction of the larvae of the common spider crab Maja brachydactyla Balss, 1922 using techniques that included dissection, light microscopy, and electron microscopy. The study is mainly focused on the stages of zoea I and megalopa. The results obtained in this study show that the larval midgut tract is a short and simple tube positioned anteriorly, between the stomach and the hindgut tract. During larval development, the maximum length of the midgut tract increases significantly, but no differences were found on either the maximum diameter or the morphological traits of the organ. The midgut tract is active at least ca. 12 h after hatching, as suggested by the presence of the peritrophic membrane in the lumen, the presence of abundant electro-dense vesicles in the cell apex, and the release of the vesicle content on the organ lumen. The midgut-hindgut junction forms an abrupt transition between the midgut tract and the hindgut tract in which epithelial cells with mixed features of midgut and hindgut do not occur.
十足目动物的中肠是一个参与合成围食膜、食物运输、营养吸收和渗透调节的消化器官。中肠在成年十足目动物中已有详细描述，但关于幼虫阶段中肠的形态和超微结构的信息却很少。本研究使用解剖、光学显微镜和电子显微镜技术，描述了普通蜘蛛蟹 Maja brachydactyla Balss, 1922 的幼虫中肠和中肠-后肠交界处。本研究主要集中在幼体 I 期和幼虾期。本研究结果表明，幼虫中肠是一个短而简单的管，位于胃和后肠之间的前部。在幼虫发育过程中，中肠管的最大长度显著增加，但器官的最大直径或形态特征没有差异。中肠在孵化后至少 12 小时就开始活跃，这可以通过管腔中的围食膜、细胞顶端丰富的电子致密小泡以及小泡内容物在器官管腔中的释放来证明。中肠-后肠交界处是中肠管和后肠管之间的突然过渡，交界处的上皮细胞没有中肠和后肠的混合特征。
