Apple Snail Perivitellin Precursor Properties Help Explain Predators? Feeding Behavior

CADIERNO, MP; CADIERNO, MP; HERAS, HORACIO; HERAS, HORACIO; DREON, MARCOS S.; DREON, MARCOS S.

PHYSIOLOGICAL AND BIOCHEMICAL ZOOLOGY

UNIV CHICAGO PRESS

Año: 2017 p. 461 - 470

1522-2152

In contrast with vitellogenin maturation, it is unknown whethergastropod perivitellin precursors are subject to large structuralchanges. The gastropod reproductive tract includes an accessoryorgan, the albumen gland (AG), that produces and secretes perivitellinefluid. In the apple snail Pomacea canaliculata, the large,reddish-pink AG provides eggs with perivitellins that are defensiveagainst predators. Although the AG makes a considerable contributionto apple snail biomass, field observations indicate thatit is rejected by avian and mammalian predators, although theunderlying reason remains unknown. By analyzing the structurefunctionproperties of P. canaliculata perivitellin precursors, weprovide insight into perivitellin maturation and its relationshipwith apple snail predator feeding behavior. Structural analysisusing small-angle X-ray scattering, absorption and fluorescencespectroscopy, circular dichroism, electrophoresis, chromatography,and partial proteolysis showed that the size, shape, andstructure of perivitellin precursors resemble those of egg matureforms. Functional analysis indicates that the precursors of thedefensive perivitellins ovorubin (PcOvo) and perivitellin-2 (PcPV2)are highly stable and antinutritive, withstanding proteinase digestionand displaying structural stability of their quaternary structureunder a wide pH range (4.0?10.0). Furthermore, AG extractslimit a predator?s ability to digest nutrients and are toxicto mice (median lethal concentration 96 h after administration:5.9 mg/kg). Treated mice displayed neurologic signs similar tothose produced by egg PcPV2. Results indicate that apple snailsstore active precursors of egg proteins inside the AG, providingevidence that gastropod perivitellin precursors do not experiencethe large structural processing of invertebrate vitellogenin maturation.These defensive proteins provide the apple snail AG withneurotoxic, antinutritive, and antidigestive activity, a likely explanationfor the predators? feeding behavior.