Ultrastructural and histochemical study of the salivary glands of Aplysia depilans (Mollusca, Opisthobranchia)

Bessette

et al. 2010

Journal of Morphology

To understand the digestive functions in the giant keyhole limpet, it is important to know the types of cells present in each region of the gut and their roles in the secretion of digestive enzymes and absorption of nutrients. This study describes the morphology of cells lining the entire gut and identifies sites that may be secreting materials to aid digestion. Previous studies involving electron microscopy and enzyme analysis have focused on the salivary and digestive glands of several gastropods. Studies on the rest of the gut tract typically include only histological descriptions of the epithelia and although several types of cells have been described, they appear very similar. The purpose of this study is to determine if electron microscopy can provide better insights into the functions of cells in these poorly studied regions of the gut. Our ultrastructural observations suggest that only two types of cells, mucus secreting cells and apocrine secretory cells make up the epithelium in the esophagus, style sac, and intestine. These regions account for 85% of the length of the entire digestive tract. Apocrine secretory cells contain pigment granules, bear cilia, and/or microvilli at their apices, and release product into the gut lumen via apocrine secretion. This suggests that the secretory processes involved with digestion are occurring in most regions of the gut and that apocrine secretion is the primary mode by which materials are introduced into the gut lumen. The lips, salivary glands, stomach, and digestive gland lack apocrine secretory cells and the epithelial cells are similar to those described in other gastropods. J. Morphol. 271:1134-1151, 2010. (c) 2010 Wiley-Liss, Inc.

Section: Discussionmentioning

confidence: 98%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Morphology of epithelial cells lining the digestive tract of the giant keyhole limpet, Megathura crenulata (Mollusca; Vetigastropoda)

Bessette

et al. 2010

Journal of Morphology

“…The tetrazonium reaction for protein detection, the periodic acid Schiff (PAS) technique for polysaccharides and Alcian blue staining for acid mucopolysaccharides, based on the procedures described by Ganter and Jollès (1970), were applied to 6 µm sections of paraffin‐embedded oesophagus or to 2 µm semithin sections of Epon‐embedded sections (Lobo‐da‐Cunha 2001).…”

Section: Methodsmentioning

confidence: 99%

Light and electron microscopic study of the anterior oesophagus of Bulla striata (Mollusca, Opisthobranchia)

et al. 2010

Self Cite

Lobo-da-Cunha, A., Oliveira, E., Alves, Â ., Coelho, R. and Calado, G. 2010. Light and electron microscopic study of the anterior oesophagus of Bulla striata (Mollusca, Opisthobranchia). -Acta Zoologica (Stockholm) 91: 125-138.The anterior oesophagus of Bulla striata was investigated with light and electron microscopy. In the most anterior region, the ridges of the oesophageal wall are covered by a ciliated columnar epithelium forming large apical blebs which are released into the lumen, an activity that is particularly intense in the oesophageal pouch. In the last two-thirds of the anterior oesophagus, the epithelium is covered with microvilli embedded in a cuticle, but apocrine secretion and cilia are absent. Subepithelial secretory cells are very abundant in the oesophageal wall, except in the roof of the pouch. They have a long neck that crosses the epithelium, whereas the cell body containing the nucleus is embedded in the connective tissue. Large electron-lucent secretory vesicles and many Golgi stacks fill most of their cytoplasm. The histochemical and cytochemical assays show that these cells secrete acid mucopolysaccharides. With the current and future studies we aim to obtain data for the establishment of relationships between morphofunctional features of the digestive system and food types in cephalaspideans. Additionally, the new data about the oesophageal pouch of B. striata may be useful for the establishment of eventual homologies with the oesophageal diverticula of other opisthobranchs.

“…1998; Lobo‐da‐Cunha 1999, 2000; Taïeb and Vicente 1999; Taïeb 2001), but in these molluscs other parts of the digestive system have received much less attention. The salivary glands, oesophagus, crop and stomach of A. depilans were investigated using electron microscopy (Lobo‐da‐Cunha 2001, 2002; Lobo‐da‐Cunha and Batista‐Pinto 2003, 2005), but the intestine was not. Although ultrastructural studies of intestinal cells have been performed in some species of pulmonate gastropods (Boer and Kits 1990; Triebskorn and Künast 1990; Franchini and Ottaviani 1992; Leal‐Zanchet 2002), such studies are scarcer in prosobranchs (Bush 1988; Pfeifer 1992) and non‐existent in opisthobranchs.…”

Section: Introductionmentioning

confidence: 99%

Ultrastructural, histochemical and cytochemical characterization of intestinal epithelial cells in Aplysia depilans (Gastropoda, Opisthobranchia)

Lobo-da-Cunha

Batista‐Pinto²

2007

Acta Zoologica

Self Cite

Lobo-da-Cunha, A. & Batista-Pinto, C. 2007. Ultrastructural, histochemical and cytochemical characterization of intestinal epithelial cells in Aplysia depilans (Gastropoda, Opisthobranchia). -Acta Zoologica (Stockholm) 88 : 211-221To improve the current knowledge about the digestive system in opisthobranchs, light and electron microscopy methods were used to characterize the epithelial cells in the mid-intestine of Aplysia depilans . This epithelium is mainly formed by columnar cells intermingled with two types of secretory cells, named mucous cells and granular cells. Columnar cells bear microvilli on their apical surface and most of them are ciliated. Mitochondria, multivesicular bodies, lysosomes and lipid droplets are the main components of the cytoplasm in the region above the nucleus of these cells. Peroxisomes are mainly found in middle and basal regions, usually close to mitochondria. Mucous cells are filled with large secretory vesicles containing thin electron-dense filaments surrounded by electron-lucent material in which acidic mucopolysaccharides were detected. The basal region includes the nucleus, several Golgi stacks and many dilated rough endoplasmic reticulum cisternae containing tubular structures. The granular cells are characterized by very high amounts of flat rough endoplasmic reticulum cisternae and electron-dense spherical secretory granules containing glycoproteins. Enteroendocrine cells containing small electron-dense granules are occasionally present in the basal region of the epithelium. Intraepithelial nerve fibres are abundant and seem to establish contacts with secretory and enteroendocrine cells.