Morphological grounds for haematopoiesis in the renopericardial complex of Pomacea canaliculata (Ampullariidae): A 3D reconstruction study

RODRÍGUEZ, CRISTIAN; CASTRO-VAZQUEZ, ALFREDO; VEGA, ISRAEL A

Bahía Blanca

Congreso; 3° Congreso Argentino de Malacología; 2019

Universidad Nacional del Sur

Research on haematopoiesis in gastropods has been practically restricted to six families of Heterobranchia, namely Planorbidae, Bulinidae, Lymnaeidae, Physidae, Bradybaenidae, Strophocheilidae, and Philomycidae. In particular, the haematopoietic tissue of Biomphalaria glabrata, i.e. the ?amoebocyte-producing organ? (APO), occurs in a region lying between the mantle cavity, kidney and pericardium. The APO comprises clusters of blast-like cells and is supplied by blood sinuses that warrant the passage of the newly formed haemocytes to the systemic circulation. Similar, and perhaps homologous structures have been proposed for other heterobranch gastropods. Contrastingly, both in lymnaeids and in the philomycid Meghimatium fruhstorferi (as Incilaria fruhstorferi), haematopoiesis occurs widespread through the connective tissues or into the blood system. There is a paucity of data in other gastropod clades, even in the Caenogastropoda, which encompasses ~60% of gastropod species. Studies in caenogastropods are restricted to two species of Ampullariidae, Marisa cornuarietis and the highly invasive Pomacea canaliculata. However, the site of haematopoiesis in ampullariids is currently a controversial issue because the lung, the kidney and the pericardium have all been proposed as possible sites. The pericardium is indeed a coelomic cavity that directly connects with the renal chamber through a renopericardial canal, but not with the haemocoel (i.e., with urine and not with haemolymph). Therefore, this project was aimed at clarifying the role of the pericardium as a haematopoietic site in P. canaliculata. Specifically, we wanted to test the hypothesis of the existence of a homologue of the APO found in Heterobranchia. Adult individuals of P. canaliculata were obtained from our laboratory (Rosedal) strain and samples from the kidney and pericardium were fixed in 4% paraformaldehyde and processed for paraffin embedding. Pieces of dissection containing (a) the heart, main vessels and the renopericardial canal, and (b) the kidney chamber and the ureter, were serially sectioned, stained with haematoxylin and eosin, photographed and aligned for 3D reconstruction using the software Reconstruct v.1.1.0.0. The 3D reconstruction of the pericardium showed that its walls are formed of a fine network of blood channels and 3D renderings of the renopericardial complex revealed the afferent and efferent connections of the sinuses in the pericardial wall with those of the ?nephridial gland?, the kidney and the ureter. In addition, the exploration of the structures involved (light microscopy of the pericardium and heart) suggested that the presumptive haematopoietic cells occurred into the sinuses of the posterior pericardial wall, at the proximity of the kidney chamber. This study will prove helpful to establish the morphological background of haematopoiesis in the pericardium and surrounding sinuses in this caenogastropod.