The antidigestive and antinutritive effect of the albumen gland of Pomacea canaliculata (Gastropoda: Ampullariidae)

CADIERNO, M.P.; DREON MS,; HERAS, H

La Serena

Conferencia; 5th Physiomar; 2014

CEAZA

Pomacea canaliculata (Lamark, 1822) is an amphibious freshwater South American species that represents a serious crop pest on introduced areas. Besides, as an intermediate host of the parasite Angiostrongylus cantonensis, the spread of this invasive snail is expanding the rat lungworm disease beyond its native range. The female reproductive tract includes an accessory organ, called albumen gland (AG), that provides fertilized oocytes with a perivitellin fluid. AG secretion includes a series of multifunctional proteins. The most abundant ones are PcOvo and PcPV2 (aprox.70% of total protein), which display antinutritive and neurotoxic properties respectively, are presumably involved in embryo defenses against predators. However, it is unknown if these defenses are already biologically active inside the gland. If active, these proteins could help to explain the behaviour of predators that invariably discard the gland when feeding on P. canaliculata females. In this regard, we have recently tested the neurotoxic effect of the AG´s soluble fraction and found it is lethal when intraperitoneally administered to mice (unpublished data). In the present study we tested the antidigestive effect of the soluble fraction of the AG and the antinutritive effect of PcOvo and PcPV2 isolated from this organ. To that aim, a trypsin inhibition assay (TIA) was carried out by measuring the enzymatic activity spectrophotometrycally. Besides, an in vitro simulated gastrointestinal digestion of purified PcOvo and PcPV2 was performed. The TIA showed that AG`s soluble fraction is able to inhibit the trypsin activity (1 mg of total soluble protein inhibits 70.5 ± 0.4 trypsin U). Purified proteins were resistant to in vitro gastroinestinal digestion for at least 120 min, showing no change in electrophoretic movility along the simulated digestion process. These results indicate that the snails store the egg proteins already in a biologically active conformation inside the gland. As a whole, considering the neurotoxicity of the gland, its capacity to inhibit digestive proteases and the fact that their most abundant storage proteins are resistant to gastrointestinal digestion, the apple snail AG could be considered as a toxic, antinutritive and antidigestive organ. This provides a possible biochemical explanation of the gland-rejection behaviour of predators.