Histopathological Changes in the Hepatopancreas of Freshwater Mussel, Lamellidens marginalis in Response to Seasonal Variations

<div> <p><strong><em><span>Abstract</span></em></strong></p> <p><em><span lang="EN-IN">Histological investigations on the digestive tissues of <em><span>Lamellidens marginalis</span></em> reveal dynamic seasonal changes associated with feeding and environmental conditions. The digestive gland serves as the major site of intracellular digestion and is composed of blind-ending tubules connected to the stomach by ciliated ducts. Two main cell types, digestive and secretory (basophile) cells, constitute the tubule lining, while amoebocytes occur within the intertubular connective tissue. The gland exhibits cyclic phases of digestion—normal, absorptive, disintegrating, and reconstituting—corresponding to variations in food availability and environmental factors. During the monsoon, fragmentation of spherules within the digestive tubules indicates active digestion and intracellular breakdown of food. Post-monsoon and winter seasons are characterised by holding and absorption phases that reflect reduced feeding activity. The height and size of digestive cells increase during monsoon to post-monsoon periods (June–October), coinciding with enhanced food intake and preparation for gonadal maturation. Conversely, during summer, holding and absorption phases dominate due to fluctuating environmental conditions and lower food availability. The cyclic pattern of feeding and digestion in <em><span>Lamellidens marginalis</span></em> is closely correlated with freshwater current dynamics, turbidity, and seasonal nutrient fluctuations. These findings support earlier interpretations that digestion and waste elimination in bivalves occur simultaneously through continuous intracellular and extracellular processes within the digestive diverticula.</span></em></p> </div>