Morphological study of members of the genus Echeneibothrium (Cestoda: Rhinebothriidea: Echeneibothriidae) from rajiform skates of the Argentine Sea and analysis of the phylogenetic relationships within the family Echeneibothriidae

A new cestode species of the genus Echeneibothrium van Beneden, 1850 was collected from a rajiform skate in the Argentine Sea: Echeneibothrium cristinae sp. nov. parasitizing Bathyraja cousseauae Diaz de Astarloa & Mabragana, 2004, from coastal waters off Tierra del Fuego Province. This species differs from congeners by a particular combination of the following features: total length, number of proglottids, number of loculi and presence of a medial longitudinal septum on the distal bothridial surface, length of bothridial stalks, size of the cirrus sac, position of the ovarian isthmus and course of the vagina. In addition, two known Echeneibothrium species, originally reported in Dipturus chilensis (Guichenot, 1848) from the Chilean Sea, were collected from a new host in the Argentine Sea: Echeneibothrium multiloculatum Carvajal & Dailey, 1975 and Echeneibothrium williamsi Carvajal & Dailey, 1975, parasitizing the rajiform skate Dipturus brevicaudatus (Marini, 1933) from coastal waters off Buenos Aires Province (E. multiloculatum) and Patagonia (both species). Emendations were made to the descriptions and redescriptions of these species, including the modification of measurement ranges for several characters and the addition of important morphological information omitted in previous studies. Finally, a phylogenetic analysis based on morphological characters was performed to determine the inter-relationships within the family Echeneibothriidae, this study being the first to consider representatives of all known genera belonging to that family.

Automated summary

A new species of cestode belonging to the genus Echeneibothrium was discovered in the Argentine Sea, along with two previously known species. The study also provides emendations to the descriptions and redescriptions of these species and performs a phylogenetic analysis to determine the relationships within the family Echeneibothriidae.