First report of Temnocephala rochensis (Platyhelminthes: Temnocephalida) from Pomacea canaliculata (Mollusca: Ampullariidae) outside Uruguay: description update based on specimens from the state of Rio Grande do Sul, Brazil

Abstract

Temnocephala rochensis Ponce de Léon, 1979, was the second of four species of Temnocephala Blanchard, 1849 to be described as ectosymbiont of ampullariid apple snails, Pomacea canaliculata (Lamarck, 1822). There have been no records of this Uruguayan species after its initial description. As part of the present study, 111 specimens of P. canaliculata were collected between 2003 and 2009. Temnocephalans found in the pallial cavity were identified as T. rochensis, occurring in single infestations, or concurrently with Temnocephala haswelli Ponce de Léon, 1989. Specimens of T. rochensis showed a conspicuous red eye pigment which faded after ethanol fixation. Important taxonomic characters of the reproductive system were evidenced by several techniques, and documented photographically for the first time for this species: 1) the typical curved cirrus of the species showing very short and stout spines; 2) the vagina with the proximal portion dilated, forming a "vesicula intermedia"; and 3) the distal portion very muscular, as well as the large and symmetrical vaginal sphincter were documented in detail with Nomarski's DIC microscopy. Eggs were observed in the suture, in the spire, and in the umbilicus of the shell; they had a short peduncle or were sessile, always with short and curved, sometimes straight apical filaments. The rounded shape of the dorsolateral 'excretory' syncytial epidermal plates had central nephridiopores. This is the first record of this species outside of Uruguay and in the State of Rio Grande do Sul, Brazil. Even with extended sampling efforts in the eastern region of Rio Grande do Sul, T. rochensis has not been found, showing a geographical distribution restricted to the southern region, close to its type locality of Laguna Negra, Uruguay.