Fig. 8

CT-based 3D visualisation of the circulatory, nervous and excretory systems in Alviniconcha. CT-scanned A. kojimai specimen: a 3D overview of cardio-renal complex, sinuses, vessels and nerves identified and visualised from CT volumes (N.B. pedal sinus not segmented, dorsal-most pallial vessels not shown, see Additional file 1); b Inner (i) and outer (ii) apical views of cardio-renal complex: i) Schematic derived from CT visualisation depicting the arrival of blood to the auricle (Au) via the primary efferent branchial vessel (1° EBV), after which blood exits the ventricle (V) via the larger anterior aorta (AA ~ > various cephalopedal sinuses) from which two smaller posterior vessels branch off, including the posterior aorta (PA ~ > visceral arterial sinus VS). Blood from rectal sinus (RS) later drains into the primary afferent branchial vessel – 1° ABV in a) – via lateral blood vessels (BV). Blood returning from head-foot to nephridium (Ne) arrives via the cephalopedal vein (CpV) and then passes to the afferent renal vein (ARV) visible in (ii) running along the right side of the nephridium, parallel with the start of the rectal sinus. Blood-vessel openings have been drawn by hand and are indicative only. Oxygenated blood represented by red vessels and arrows, deoxygenated blood by purple vessels and arrows. Oxygen content in rectal sinus likely decreases along its length. Green arrow in (i): excretion from the nephridium into the pallial cavity is via the renal pore (RP). Figure is of 3D renderings with exaggerated perspective, thus scales are approximate. Additional abbreviations: CBS Co-marginal blood sinus; CoC Circumoesophageal complex; Ct Ctenidium; HF Head-foot; In Intestine; LPN Left pallial nerve; LTN Left tentacular nerve; NR Oesophageal nerve ring; PBN Pedal blood network; PBV Pallial blood vessel; PNN Pedal neural network; POe Lower posterior oesophagus; PS Pallial skirt; Re Rectum; RPN Right pallial nerve; RTN Right tentacular nerve; RVC Right visceral connective; St Stomach