MICROANATOMY OF THE DIGESTIVE SYSTEM OF ENTEROCTOPUS MEGALOCYATHUS (CEPHALOPODA, OCTOPODA) OF THE SOUTHWEST ATLANTIC

Abstract

A detailed description of the microanatomy of the digestive system of Enteroctopus megalocyathus is given, and this revealed some differences between this octopod species and other species of Octopodidae previously described. These differences are mainly related to tissues lining the lumen of digestive organs. Unlike descriptions in some octopods mucosa, in E. megalocyathus a pseudostratified epithelium is found covering the lumen of oesophagus, crop, stomach, intestine and caecum. Another major finding is that in the posterior salivary glands, two cell types are present in the same tubular adenomere; they do not constitute independent glandular tubules with only one type of glandular cells. The tubules of these glands are lined by two distinct epithelial cells, distributed from the distal to the proximal zones: type A, in the proximal zone of the glandular tubule, with cylindrical cells and globular mucous cells; and type B in the distal zone, cylindrical, with a weakly eosinophilic cytoplasm. The secretion of the cells was detected applying PAS and alcian blue at different pH. In the octopuses maintained without food in the aquarium for two days, histological structure of the epithelium of the caecum, intestine and digestive gland showed histological changes specially related with the mucosa. Taken together, the results allow to set the histological structure of the digestive tract of E. megalocyathus in their natural habitat and to provide preliminary evidence that this system responds rapidly (~2 days) to food deprivation, and give baseline data for future studies investigating the impact of environmental changes on the gut.