Morphological and histochemical characteristics of the foregut, midgut, and hindgut, and their alterations during ovarian development in female freshwater prawn, Macrobrachium rosenbergii.

Abstract

The anatomical, histological, and histochemical characteristics of the foregut (FG), midgut (MG), and hindgut (HG), as well as their alterations during the ovarian cycle in female prawns, Macrobrachium rosenbergii, were investigated. The esophagus (ESO), cardia (CD), and pylorus (PY) are the main components of the FG. An epithelium (Ep) with thick cuticle (Cu) layers lining the ESO, and the ESO is encircled by the ESO glands. The CD has a thick musculature, whereas the Ep of the PY are characterized by numerous villi and columnar Ep cells with a thinner layer of Cu. The inner longitudinal (LM) and the outer circular (CM) muscles were both present in the PY. The MG is lined by Ep cells which are connected to the basement membrane, and it lacks Cu. Microvilli, and subapical vacuoles are visible on the apical surface of Ep cells of the MG. The outermost layer is characterized by a dense strip of elastic fibers and a cluster of collagen fibers. The HG has the Ep cells with a thin Cu layer, and the HG glands form a rosette-like structure. The HG is surrounded by the CM and the LM fibers. The reactivities of Periodic Acid Schiff and Alcian Blue in these digestive organs altered throughout the ovarian cycle, and this was supported by the increased expression of mucin levels as ovarian maturation progressed. Our results offer novel and significant insights into the anatomical and histochemical structures of these digestive organs, and demonstrate a significant correlation between ovarian development and feeding in the female prawn, M. rosenbergii.