Alfredo Castro-Vazquez

Apple snails and their endosymbionts bioconcentrate heavy metals and uranium from contaminated drinking water

PurposeThe differential ability of apple snail tissues, endosymbionts, and eggs to bioaccumulate several metals (Sb, As, Ba, Br, Zn, Cr, Fe, Hg, Se, and U) was investigated.MethodsMetal concentrations were determined by neutron activation analysis in several tissues, endosymbionts, and eggs from mature apple snails cultured in either drinking water or reconstituted water (prepared with American Society for Testing and Materials type I water).ResultsThe highest bioconcentration factors (BCFs) in the midgut gland were found for Ba, Zn, Se, As, U, Br, and Hg (in decreasing order), while the highest in the kidney were for Ba, Br, and Hg. The foot showed the highest BCFs for Ba, Hg, Br, and Se (in decreasing order). Calcified tissues (uterus, shell) and eggs showed low BCFs, except for Ba. Both C corpuscles and gland tissue showed statistically higher BCFs than K corpuscles for Ba, Fe, U, Br, and Sb. The concentration of most of the studied elements was significantly lower in tissues and endosymbionts obtained from snails cultured in reconstituted water instead of drinking water. Snails cultured in reconstituted water and then exposed or not to Hg, As, and U (at the maximum contaminant level allowed by the US Environmental Protection Agency) also resulted in high levels accumulated in midgut gland, endosymbionts and kidney.ConclusionsOur findings suggest that the midgut gland (and the symbionts contained therein), the kidney, and the foot of Pomacea canaliculata may be useful bioindicators of Hg, As and U pollution in freshwater bodies and that the unrestricted use of ampullariid snails as human and animal food must be considered with caution..

Functional anatomy of male copulatory organs of Pomacea canaliculata (Caenogastropoda, Ampullariidae)

This study was aimed to investigate the functional morphology of copulation and sperm transfer in the invasive snail Pomacea canaliculata. Three-dimensional renderings of the male copulatory apparatus were made and showed elaborate systems for innervation and for hemolymph supply and drainage. A key component of the male copulatory apparatus is the penial sheath, which shows three specialized glands; the medial and distal glands may participate in adherence to the mantle cavity wall of the female during copulation. The outer gland has an epithelium composed of columnar cells with branched microvilli, mucous goblet cells and large granular secretory cells containing intragranular crystalloids, which produce an exocrine secretion during copulation. The interaction of male/female copulatory organs was studied in dissections of snap-frozen pairs. Sperm are left in the sperm pit, at the end of the pallial spermiduct. Afterwards, the muscular action of the penial bulb takes the sperm up to the vermiform penis, which slides from the penial pouch into the central groove of the penial sheath, and it later emerges through a T-shaped sulcus of this structure and enters the female vagina. Then, it climbs through the capsule duct, and its tip reaches the proximity of the seminal receptacle. A model of copulation and sperm transfer is presented on the basis of the new findings and on published literature.

Evidence for a prokaryotic origin of intracellular corpuscles in the digestive gland of the queen conch Lobatus gigas (Linnaeus, 1758) (Gastropoda: Strombidae)

Fil: Dell Agnola, Federico Agustin. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Mendoza. Instituto de Histologia y Embriologia de Mendoza Dr. Mario H. Burgos. Universidad Nacional de Cuyo. Facultad de Cienicas Medicas. Instituto de Histologia y Embriologia de Mendoza Dr. Mario H. Burgos; Argentina. Universidad Nacional de Cuyo. Facultad de Ciencias Medicas; Argentina

Tolerance to hypometabolism and arousal induced by hibernation in the apple snail Pomacea canaliculata (Caenogastropoda, Ampullariidae)

Pomacea canaliculata may serve as a model organism for comparative studies of oxidative damage and antioxidant defenses in active, hibernating and arousing snails. Oxidative damage (as TBARS), free radical scavenging capacity (as ABTS+ oxidation), uric acid (UA) and glutathione (GSH) concentrations, activities of superoxide dismutase (SOD) and catalase (CAT), and the protein expression levels of heat shock proteins (Hsp70, Hsc70, Hsp90) were studied in digestive gland, kidney and foot. Tissue TBARS of hibernating snails (45days) was higher than active snails. Hibernation produced an increase of ABTS+ in digestive gland, probably because of the sustained antioxidant defenses (UA and/or GSH and SOD levels). Kidney protection during the activity-hibernation cycle seemed provided by increased UA concentrations. TBARS in the foot remained high 30min after arousal with no changes in ABTS+, but this tissue increased ABTS+ oxidation at 24h to expenses increased UA and decreased GSH levels, and with no changes in SOD and CAT activities. The level of Hsp70 in kidney showed no changes throughout the activity-hibernation cycle but it increased in the foot after hibernation. The tissue levels of Hsp90 in snails hibernating were higher than active snails and returned to baseline 24h after arousal. Results showed that chronic cooling produces a significant oxidative damage in three studied tissues and that these tissue damages are overcome quickly (between 30min to 24h) with fluctuations in different antioxidant defenses (UA, GSH, CAT) and heat shock proteins (Hsp70 and Hsp90).

Assessment of the kidney and lung as immune barriers and hematopoietic sites in the invasive apple snail Pomacea canaliculata

Knowledge on the immune system of Pomacea canaliculata is becoming increasingly important, because of this gastropod’s role as intermediate host and vector of Angiostrongylus cantonensis, the etiologic agent of eosinophilic meningitis in humans and domestic animals. Immune defenses of this gastropod comprise both humoral and cellular components, but they may also involve organs that act as immune barriers to prevent the spread of alien molecules and organisms. Both the kidney and lung are here shown to serve this function, because of (1) their positions in blood circulation, (2) the intricate architecture of their blood spaces, and (3) the proliferative and nodulation reactions of hemocytes to an immune challenge. However, these organs differ in that only the kidney shows permanent hemocyte aggregations. Microcirculation in the kidney was found to flow through an intricate vascular bed containing the permanent aggregations, which occurred either as hemocyte islets anchored by cytoplasmic projections of the renal epithelium or as perivascular accretions. Within 96 h of the injection of yeast cells, hemocyte nodules were formed both in the kidney and lung. Moreover, cell proliferation in renal hemocyte islets was measured by bromodeoxyuridine (BrdU) incorporation. The proportion of BrdU positive nuclei increased 48 h after injection. Signs of nodule regression (apoptotic bodies, lipofuscin-like deposits) and a decrease in the proportion of BrdU positive nuclei were found at 96 h. In addition, the area of renal hemocyte islets was significantly increased 96 h after injection. Nevertheless, the high complexity of the small vascular chambers that constitute the lung’s respiratory lamina would also facilitate hemocyte-antigen contacts, required to elicit cellular aggregation, and hence, nodulation. To our knowledge, this paper includes the first quantitative indication of hemocyte proliferation after an immune challenge among Caenogastropoda.