Excretion in basommatophora and stylommatophora pulmonata

Abstract

A comparative study on the kidney of Pulmonata living on land (Stylommatophora) and in fresh water (Basommatophora) was made. The sections performed in three different planes allowed us to know the 3-dimensional pattern of its components: renopericardial duct, kidney sac and ureter. Renopericardial duct runs far into the kidney sac. The duct of Basommatophora is longer and bears also longer cilia than that of Stylommatophora. Kidney sac is similar in both groups and is made up of a wall from which a complex lamellar system spreads into the cavity. Lamellae are longer and more numerous at the dorsal wall, being the lumen of the organ eccentric. The cavity is lined by columnar epithelial cells (nefrocytes) with brush border. Characteristic of the nefrocytes is the presence of a large apical vacuole containing an excretion granule. In Lymnaea there are also lamella lined by cubic epithelium without excretion granule. The union between kidney sac and ureter is different from one another in the three species studied. In Lymnaea the kidney sac narrows and forms the ureter; the connexion in Cryptomphalus is achieved through a 200 micrometer window; and in Helicella there is a duct between both parts. The ureter has a columnar epithelium with very deep infoldings of the basal cell membrane, according to its osmotic regulative function. In Stylommatophora there are primary and secondary ureters, while in Basommatophora there is only one type.