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Ultrastructure of the frontal end of the Arctostemma arcticum (Nemertea, Monostilifera)тезисы доклада
- Авторы: Likhacheva G.V., Cherneva I.A.
- Сборник: Беломорская студенческая научная сессия СПбГУ — 2023. Тезисы докладов
- Тезисы
- Год издания: 2023
- Место издания: Свое издательство Санкт-Петербург
- Первая страница: 75
- Аннотация: Nemertea is a phylum of non–segmented worms. The typical features of this diverse group are: an everting proboscis located in a fluid-filled cavity (rhynchocoel); a ring-shaped brain surrounding the proboscis; a circulatory system, which is not homologous to other Trochophorates, but is a modified coelome. Nemerteans’ morphology is poorly studied. Due to the difficulties of taxonomy, characteristics of the one species could be attributed to the different common species. Even nowadays some mistakes can happen. Nemerteans have cephalic glands in the front of the head. They are not studied enough, but for now researches distinguish three types of these glands: frontal gland, submuscular gland and the cephalic glands (Chernyshev, 2005). They can merge, and homology of the glands even in one family is difficult to establish. There is an opinion, that the frontal gland develops from the part of the larval apical organ. Nemerteans which lack frontal organ usually don’t have frontal gland too. The actual cephalic glands are more numerous and more often located diffusely. The submuscular gland initially lies directly under the musculature of the body wall and open outwards through the integument (Chernyshev, 2011). Arctostemma arcticum, hoplonemertean species, lack frontal organ and so frontal gland. Also, submuscular gland is not found in this species. Cephalic glands are located in the frontal side of the head, towards to the brain, near rhynchostomodeum. They are very diffusive. Likewise, there are some structures in the head of the A. arcticum towards the brain, near the eyes. These structures are recognizable on a living nemerteans. They are looking like a light-reflecting wrapping around the cerebral organ and brain. In mature nemerteans this structure becomes visually bigger. We studied hemi-thin and ultrathin histology of the front end of the A. arcticum. We used the transmission electronic microscopy to see, which types of cells form this structure. In the mature specimen the cells have a big vacuole. The vacuole occupies most of the cell. Other organoids we didn’t found on our sections. In the immature nemertean membrane organoids can be observed. The cells are full of the small vacuoles. Moreover, inclusions inside of the threemembraned structures are found. For now, we can say that it looks like in immature nemerteans this structure performs a secretory function, but in mature nemerteans the secretory process decreases. To check this hypothesis, we plan to make a specific staining on the semi-thin sections.
- Добавил в систему: Лихачева Галина Вячеславовна