Morphology of the digestive gland of the marine panpulmonate limpetSiphonaria lessonii: A cytological, histochemical, and ultrastructural description

Abstract

The molluskan digestive gland has been widely studied and its structural and ultrastructural descriptions have allowed the understanding of its several functions. Despite siphonarids are broadly distributed around the world, morphological studies on their digestive system are poorly represented. The panpulmonate limpet Siphonaria lessonii is the most abundant gastropod and the dominant herbivore in the rocky intertidal coast of Buenos Aires. The aim of this study was to describe the morphology, histology, ultrastructure, and histochemistry of the digestive gland of this gastropod as well as the cycle of activity of digestion. For that, different histochemical techniques along with light microscopy, transmission electron microscopy, and scanning electron microscopy were employed. This study revealed a complex epithelium, composed of a simple layer with five cell types. Digestive cells and vacuolated cells are responsible for intracellular digestion and energy accumulation; basophilic cells, secrete substances that would be involved in extracellular digestion; pigmented cells might have an excretory function and thin cells would correspond to undifferentiated cells. In addition, the tubules present a changing morphology according to the digestive activity that they undergo. As S. lessonii is a grazer that feeds continuously, the cycle of activity of the digestive gland seems to be daily.

Reproductive pattern of Trochita pileolus (d' Orbigny, 1841) (Gastropoda: Calyptraeidae) and different types of intracapsular development in Trochita species of South America

“…Sections were cut at 5 µm with an electronic microtome (Leica® RM 2155) and stained with hematoxylin and eosin for topographic characterization. Then Sudan black B (SBB) and Periodic Acid-Schiff (PAS) histochemical techniques were used to identify neutral lipids and polysaccharides (glycogen) and mucosubstance (glycoprotein, mucins) in each vitellogenic oocyte according to Suvarna et al (2013), modified for resin sections (Landro et al 2019). Sections of positive and negative controls were performed for all the histochemical analyses.…”