Histochemistry and Ultrastructure of the Crypt Cells in the Digestive Gland of Aplysia Punctata (Cuvier, 1803)

Abstract

The crypt cells lining the Aplysia punctata digestive tubules comprise of three types of cell; calcium, excretory, and thin cells. The calcium cells play a role in osmoregulation, mineral storage, exocrine secretion, iron detoxification, and excretion processes. They possess well-developed microvilli and a basal labyrinth, suggesting a role in absorption. The Golgi apparatus is involved in the production of two main components of calcium spherules; the fibrillar material and mineralized granules. Golgi complex, rough endoplasmic reticulum (RER), ribosomes, and altered mitochondria are involved in the formation of calcium spherules. Secretory activity is indicated by the formation of dense granules containing iron and calcium salts. Lipofuscin pigment has been found in large concretions which may arise from cytoplasmic areas surrounded by endoplasmic reticulum, RER and Golgi tubules. There are three stages of excretory cells, called early, mature, and postexcretory cells. This study traces the development of granulofibrillar vacuoles up to the formation of the lipofuscin concretions and shows that excretory cells are in fact degenerating calcium cells. The fine structure of thin cells suggests that they are young calcium cells.

Morphology and Cyclic Activity of the Digestive Gland ofZidona dufresnei(Caenogastropoda: Volutidae)

“…The tubules of the digestive gland of Z. dufresnei shared some characteristics with the digestive tubules in Aplysia punctata (Cuvier, 1803) (Taïeb & Vicente, 1999;Taïeb, 2001) and Strombus gigas (Linnaeus, 1758) (Gros et al, 2009) in that two different type of digestive tubules with different cell types were present. In Z. dufresnei, tubules of type 1 were formed by an epithelium containing two cell types: digestive and basophilic cells, as in most other gastropods that have been studied (Morton, 1955;Merdsoy & Farley, 1973;Reader, 1976;Wigham, 1976;Nelson & Morton, 1979;Dimitriadis & Andrews, 2000;Baqueiro Cárdenas et al, 2007;Gros et al, 2009;.…”

“…In A. punctata, similar cells containing dense granules of calcium salts, named calcium cells, were found (Taïeb & Vicente, 1999). These cells were not observed in the digestive gland of Z. dufresnei.…”

“…Most studies of the histology of the molluscan digestive gland have been conducted on bivalves (Owen, 1970;Thompson et al, 1 Logan et al, 2008) and herbivorous microphagous gastropods (Merdsoy & Farley, 1973;Boghen & Farley, 1974;Reader, 1976;Wigham, 1976;Nelson & Morton, 1979;Taïeb & Vicente, 1999;Lobo-da-Cunha, 1999, 2000Taïeb, 2001;Baqueiro Cárdenas et al, 2007;Gros et al, 2009;. However, a study by Dimitriadis & Andrews (2000) on the neogastropod Nucella lapillus (Linnaeus, 1758) has provided the only report of the functional morphology of the digestive gland of a carnivorous caenogastropod.…”

Survivorship of juvenile surf clams Donax serra (Bivalvia, Donacidae) exposed to severe hypoxia and hydrogen sulphide

“…Lipofuscin seems to be common in molluscs, as it has been reported in situ in various tissues and organs of several species such as the gastropods Maoricrypta monoxyla (Nelson and Morton, 1979) and Aplysia punctata (Taieb and Vicente, 1999) and the bivalves Mytilus galloprovincialis (Viarengo et al, 1987(Viarengo et al, , 1990Regoli, 1992;Sarasquete et al, 1992), Mytilus edulis (Moore et al, 1980;George et al, 1982;Lowe, 1988;Burbidge et al, 1994;Hole et al, 1995;Krishnakumar et al, 1994) and Perna viridis (Krishnakumar et al, 1990;Mathew and Damodaran, 1997). Only a few findings are reported from clams so far: In the alimentary tract epithelium, in gonadal connective tissue and in the renal epithelium of Mya arenaria and Mercenaria mercenaria (Brown and O'Toole, 1978); in the digestive gland of Ruditapes phillipinarum (Sarasquete et al, 1992) and of Sunetta scripta (Mathew and Damodaran, 1997); and in the kidney of Tridacna gigas (Reid et al, 1984).…”

Intraspecific Variation in Cellular and Biochemical Heat Response Strategies of Mediterranean Xeropicta derbentina [Pulmonata, Hygromiidae]

“…The hepatopancreas is strongly involved in metabolic processes even under normal conditions [9], [10], [51]. Besides other factors, the metabolic rate can increase due to high temperatures [52] and, thereby, increases the need of nutrient supply by the hepatopancreas.…”