Sympatric ampullariids and their endosymbionts: mutualistic and the generalistic hypotheses

DELLAGNOLA FEDERICO, VEGA ISRAEL A

Tucumán

Congreso; Tercer Reunión Conjunta de Sociedades de Biología; 2015

Sociedades de Biología

In some species of Ampullariidae (Caenogastropoda, Architaenioglossa) two forms (C and K) of an endosymbiont occur within cells of the digestive gland. We explore the possibility that the symbiotic association would have occurred early in the evolution of Neotropical Ampullariidae, since it has been reported in two Pomacea species (P. canaliculata and P. scalaris) which are fairly apart within the genus, and also in two other genera (Asolene and Marisa) which are fairly apart from Pomacea within the family. We choose the Regatas Lake (Bs As, Argentine) where three ampullariid species (P. canaliculata, P. scalaris and Asolene pulchella) are found in sympatry. This ecological condition, the restricted study area, and the phylogenetic distance among the species, allowed to study the symbiotic consortium in two hypothetical scenarios, which could be designed as the ?mutualistic? and the ?generalist? hypotheses. The endosymbiont was studied in the feces and the digestive gland of the hosts, using morphometric, ultrastructural (transmission electron microscopy) and (in situ hybridization) molecular methods. It was found that the symbiont was released in the feces by the three sympatric hosts, and that their morphology was specific for each one of them. We found the 16S rRNA on both the C and K morphs, as well as the same prokaryotic characteristics in the three different hosts, which were already reported for P.canaliculata. On its part, morphometric changes of the endosymbionts in the three host species, appears to be compatible with the first hypothesis (?mutualistic?) according to which the endosymbiont would have co-evolved with the hosts, and that transmission in the host populations would occur vertically.