Intestinal Ultrastructure of Nerita picea (Mollusca: Gastropoda), an Intertidal Marine Snail of Hawaii

Abstract

Pfeiffer, C. J . 1992. Intestinal ultrastructure of Neritapicea (Mollusca: Gastropoda), an intertidal marine snail of Hawaii.-Acta Zoologica (Stockholm) 73: 39-47.The neritid snail Neritapicea is a marine prosobranch mollusc which resides high in the intertidal zone on the Hawaiian Islands. Since other studies have shown considerable variations in molluscan gut histology and the relatively few recent ultrastructural reports have revealed novel cellular structures in the molluscan gastrointestinal tract, this investigation was directed toward ultrastructural clarification of the neritid intestine.Seven principal cell types constituted the intestinal architecture, including absorptive cells, rymogen cells, neural and endocrine cells, myocytes, pigment and gland cells. The intestinal epithelium was composed mainly of tall ciliated (9 plus 2 complement of microtubules) columnar absorptive cells which also possessed microvilli, extensive deposits of non-membrane-bound lipid-like droplets, and large reservoirs of glycogen-like granules. Less frequent, columnar zymogen cells contained numerous large zymogen secretory granules and possessed microvilli but not cilia. Small endocrine-like cells with secretory granules were observed basolaterally between some absorptive cells, resembling mammalian gut endocrine cells. Nerve fibers were prevalent in close association with the epithelial cells. A thin layer of non-striated muscle was present, as well as a serosally located gland composed of storage cells with a granular matrix and large granules.

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

“…This association between deep basal cell membrane infolds and mitochondria also occurs in the intestinal epithelial cells of Lymnaea stagnalis (Boer and Kits 1990) and the digestive gland cells of A. depilans (Lobo‐da‐Cunha 1999), among other cases. Likewise, the abundance of mitochondria in the apical region of A. depilans intestinal columnar cells indicates a strong energy requirement for transport and ciliary motion, as previously suggested for the prosobranch gastropod Nerita picea (Pfeifer 1992).…”

“…Secretory vesicles containing electron‐dense filaments in a clear background, like those of A. depilans mucous cells, were also found in the cells of Lymnaea stagnalis intestine, which also contain secretory cells resembling the granular cells of A. depilans (Boer and Kits 1990). Ultrastructural observations of the intestinal epithelium of the marine snail Nerita picea also revealed secretory cells very similar to the granular cells of A. depilans , but mucous cells were not reported in this prosobranch snail (Pfeifer 1992). In another prosobranch, the limpet Patella vulgata , the intestinal epithelium contains club‐shaped protein‐secreting cells that are rich in rough endoplasmic reticulum cisternae and its secretion coats the faecal rods with a protein layer, preventing them from disintegrating (Bush 1988).…”

“…Ciliated or non‐ciliated columnar cells involved in nutrient uptake, intracellular digestion and storage of lipids and glycogen were also found in the intestinal epithelium of pulmonates (Boer and Kits 1990; Franchini and Ottaviani 1992; Leal‐Zanchet 2002) and prosobranch gastropods (Bush 1988; Pfeifer 1992), closely resembling the columnar cells lining the intestine of A. depilans . Ciliated cells were observed with the light microscope in the intestine epithelium of other opisthobranchs (Fretter 1939; Howells 1942; Rudman 1971, 1972; Wägele 1985; Schrödl and Wägele 2001), but were not studied in detail.…”

“…This part of the digestive tract was investigated with light and electron microscopy methods in some pulmonate (Franchini and Ottaviani 1992; Luchtel et al . 1997; Leal‐Zanchet 1998, 2002) and prosobranch gastropods (Bush 1988; Pfeifer 1992; Voltzow 1994), but only with the light microscope in opisthobranchs (Gosliner 1994; Schrödl and Wägele 2001).…”

“…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. However, the intestinal epithelium of A. californica has been used for physiological research (Gerencser 2000; Gerencser et al .…”