Vascular system, water relations and nitrogenous excretion

Abstract

The location of the heart and the common aorta was described in Section 2.2.2. The anatomy of the heart of L. maximus has been described by MacKay and Gelperin (1972). Injections into the heart have demonstrated that there is an effective auriculo-ventricular valve preventing back flow of blood from the ventricle into the auricle (Duval and Runham, 1981). Duval and Runham also showed that there were no valves between the aorta and ventricle and between the main veins and the auricle. In most slugs the arteries were transparent although in A. ater they were white and opaque due to the presence of calcareous deposits on the outside of the vessel walls (Runham and Hunter, 1970). Curtis and Cowden (1979) examined the structure of the wall of the aorta of L. maximus. Both the anterior and posterior aortae were similar in structure with a loosely organized endothelial layer surrounded by two layers of innervated smooth muscle. The outer (adventitial) layer of the aorta consisted of large, glycogen filled-cells with characteristic arrays of pores in their plasma membranes. These resemble the Leydig cells, described by Runham and Hunter (1970), which are associated with the walls of the arteries and may store glycogen and calcium. Curtis and Cowden (1979) also described blood cells in the form of amoebocytes containing large glycogen deposits which were occasionally found in the walls of vessels.