A new species of Auriculostoma (Digenea: Allocreadiidae) in South America: life cycle and phylogenetic relationships.

Florencia Liquin,Héctor A Cristóbal,Florencia Cremonte,Dora Davies,José Saravia,Carmen Gilardoni

doi:10.1590/0001-3765202220200538

Abstract

Auriculostoma is a genus of digenean (Trematoda) whose adults are parasites of Neotropical freshwater fishes. We describe Auriculostoma ocloya n. sp. using morphological and molecular tools, and we elucidated its life cycle, the first known of a species of this genus. The first intermediate host is the bivalve Pisidium ocloya, the second intermediate host is the amphipod Hyalella sp., and the definite hosts are siluriform fishes. The adult presents a single pair of muscular lobes on either side of the oral sucker with a broad base, stretching from ventrolateral to dorsolateral side, a structure also present in the rest of species of the genus. Nevertheless, the new species differs from all congeners by the combination of several traits, and mainly because on the dorsal side "free" ends of the lobes are absent because they are fused. This is the first study to provide sequence data on larval and adult stages of a species of Auriculostoma. Our phylogenetic analysis demonstrated its basal position among species of the genus. Therefore, integrative morphological, molecular, and life cycle data on other South American species of the genus, would contribute to reveal more patterns in the allocreadiid systematics.

Highlights

Scholz et al (2004) erected the genus Auriculostoma to include a new species, Auriculostoma astyanace, found in Nicaragua (Central America) and transferred three species formerly described in the genus Crepidostomum from South America, C. platense Szidat, 1954, C. macrorchis Szidat, 1954, and C. stenopteri MañéGarzón and Gascón, 1973 to the new genus as new combinations
We found the adult stage of a new species of Auriculostoma in the intestine of Heptapterus qenqo and Corydoras micracanthus; Psalidodon endy was not infected with this trematode
We describe a new species of allocreadiid digenean of the genus Auriculostoma parasitizing fishes from South America

Summary

Introduction

Scholz et al (2004) erected the genus Auriculostoma to include a new species, Auriculostoma astyanace, found in Nicaragua (Central America) and transferred three species formerly described in the genus Crepidostomum from South America, C. platense Szidat, 1954, C. macrorchis Szidat, 1954, and C. stenopteri MañéGarzón and Gascón, 1973 to the new genus as new combinations. The diagnosis of the genus included the presence of two pairs of muscular oral lobes (one ventrolateral and one prominent dorsolateral). Razo-Mendivil et al (2014), after studying the oral sucker through the scanning electron microscope (SEM), amended the diagnosis establishing that all species of the genus have a single pair of lobes in the oral sucker. Four species of Auriculostoma from Central America have been described, using an integrative taxonomy approach (i.e., applying morphological and molecular tools); or well were described morphologically and subsequently the sequences of the fragment of ITS2 and 28S from ribosomal RNA (rRNA) (Table I) were obtained, whereas five South American species were described only based on morphological characters.

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