Reproductive strategies of gastropods. Biochemical composition of the eggs of the freshwater snail Pomacea diffusa

BROLA, T.R.; CHIUMIENTO, I.R.; HERAS, H; DREON, M.S.

Buenos Aires

Jornada; XX Jornadas de la Sociedad Argentina de Biología (SAB); 2018

Sociedad Argentina de Biologia

The freshwater snails of Pomacea genus lay their egg masses above water level on emergent substrates. This is an unusual reproductive strategy for an aquatic animal, exposing egg to stressful environmental conditions as well as a wide range of terrestrial predators. In spite of this, these eggs have a high hatching rate and have no described predators in their native distribution range. It is remarkable that some species, such as P. canaliculata and P. maculata (canaliculata clade) have become important invasive species out of their native distribution ranges while others such as P. scalaris and P. diffusa (bridgessi clade), do not have this invasiveness. In previous works, our research group has stablished the role of some egg proteins (hereafter perivitellins) in the adaptation to harsh developmental conditions and in the egg defense against predation. We found interesting structural and functional differences between invasive and non-invasive species on their principal perivitellins. Our general objective is to shed light on the comparative aspects and adaptation mechanism among Pomacea species associated with their invasiveness and geographical distribution and on the role perivitellins play on aerial egg adaptations. The aim of this work was to characterize the biochemical composition of the P. diffusa eggs, a non-invasive Pomacea species belonging to the bridgessi clade and compare it with those previously obtained for other species, focusing on their proteins. The egg masses biochemical composition was dominated, as in the previously studied species by polysaccharides (0.12 g/g) and proteins (4.29 mg/g) being lipids less represented (0.28 mg/g). Egg masses electrolyte concentration was dominated by chloride (0.15 mg/g), followed by sodium, potassium, calcium and magnesium with 0.06, 0.025, 0.024 and 0.015 mg/g respectively. Regarding the egg protein composition, it is dominated by a carotenoprotein (>50% of total soluble protein) with a high hydration density (1.26 g/mL) and a molecular mass of ca. 420 KDa, composed by several ⁓30 KDa subunits. This protein composition dominated by a single high MW oligomeric protein was previously observed in the other Pomacea species. As a whole, these results represent the starting point for future studies on the biochemical defenses of P. diffusa eggs aiming to better understand the reproductive biology of the genus and its associated ecological and evolutionary implications.