Identity and location of the central neural ganglia in the apple snail Pomacea canaliculata

GIRAUD BILLOUD, M; CROCCE, CC; CASTRO-VAZQUEZ, A

Mendoza

Congreso; XXXI Reunión Anual de la Sociedad de Biología de Cuyo; 2014

Sociedad de Biología de Cuyo

According to early authors the central nervous system of this snail is formed by rings of interconnected ganglia around the anterior gut. According to them six ganglion pairs can be distinguished, namely: bucal, cerebral, pedal, pleural, intestinal and visceral, whose precise location was not clear in those early studies. Notwithstanding, recent authors have only mentioned a ring formed by two cerebral ganglia and two pedal ganglia. This apparent contradiction was explored using microdissections and 3D-rendering based on serial sections. The five first ganglion pairs were on the sides and floor of the peripharyngeal sinus, while the sixth one was in the visceral hump. The first pair (bucal) was partly embedded in the pharyngeal bulb, while the second (cerebral) was at the base of the tentacles. Both pedal ganglia were located beneath the bulb, and joined the pleural ganglia in posterior direction on both sides. However, the following pair (intestinal) was asymmetrically located: on the right was continuous with the pleural ganglion, while on the left was separate and communicated only with the left pleural ganglion through a rather long connective. The right intestinal ganglion (?subintestinal?) also communicates with the left one (?supraintestinal?) through a commissure passing over the pharyngeal bulb, just behind the salivary glands. The connectives joining the intestinal with the visceral ganglia should leave the peripharyngeal sinus to enter the visceral hump, where the last ganglion pair lies above the posterior esophagus. Clarification of these matters is significant for further studies of neuronal activation in response to environmental changes and immune challenges.