The ultrastructure and function of the gut of Patella vulgata

• Main Author: Bush, Maxwell Simon
• Published: Royal Holloway, University of London 1986
• Subjects: 594; Zoology
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.704707

The limpet gut consists of a long coiled tube lined by a ciliated columnar epithelium, into which open the ducts of the salivary and digestive glands. Six sections can be distinguished: the buccalcavity, oesophagus, stomach, style sac, intestine and rectum. The oesophagus can be subdivided into a dorsal food channel and a series of lateral pouches forming the oesophageal gland. The intestine is divisible into sections designated A, B, C, D and E. Ultrastructural and histochemical analyses revealed nine cell types, seven of them glandular. A single type of gland cell lining the tubules of the salivary gland produces a viscous secretion that lubricates the radula and entraps particles rasped from the substratum. Mucous cells occur in the buccal cavity, dorsal food channel and rectum; in the rectum, mucus aids defaecation, but elsewhere it entraps loose particles that are consequently transported to the stomach. The only extracellular enzyme, an amylase derived from the gland cells of the oesophageal gland, is mixed with the food in the dorsal food channel. Ciliated and unciliated columnar cells lining the ducts of the digestive gland, stomach, style sac and anterior intestine, release blebs of cytoplasm into the lumen to consolidate loose particles into a faecal rod that is rotated along the intestine. Clavate gland cells and possibly basal gland cells in the posterior intestine, cover the faecal rod with their secretion to form a durable rod. The vacuolated digestive cells of the digestive gland, digest food intracellularly releasing undigestible residues in spherules of cytoplasm, these are bound into a liver string by the proteinaceoussecretion of the basophilic cells. Both these cell types and the amylase-secreting cells exhibit phases of activity, but only that of the latter is related to the tidal cycle. Tritiated D-glucose was absorbed by the oesophagus, intestine and digestive gland by a mechanism inhibited by 2,4-DNP and phloridzin. The mechanisms operating in the oesophagus and posterior intestine were sodium-dependent. Fluid movements from the intestinal lumen to the blood occurred.