Volonterio O.*, Ponce de León R. 2026. Gyratrix hermaphroditus Ehrenberg, 1831 (Platyhelminthes: Kalyptorhynchia) in the Strait of Magellan (Chile): Description and biogeographical insights // Invert. Zool. Vol.23. No.1: 51–60 [in English].
Sección Zoología de Invertebrados, Facultad de Ciencias, Universidad de la República, Iguá 4225, piso 8 sur, Montevideo 11400, Uruguay.
* Corresponding author
Odile Volonterio: o.volonterio@outlook.com ORCID https://orcid.org/0000-0003-4939-9721
Rodrigo Ponce de León: invertepolares@outlook.com ORCID https://orcid.org/0000-0003-3730-9805
doi: 10.15298/invertzool.23.1.03
ABSTRACT: Gyratrix hermaphroditus Ehrenberg, 1831 is a free-living aquatic microturbellarian, recognized as a species complex with a cosmopolitan distribution. In South America, G. hermaphroditus has only been reported from freshwater environments in Colombia, southern Brazil and Argentina. This study provides a comprehensive morphological description of marine specimens of G. hermaphroditus collected from the Strait of Magellan in Chile, and evaluates whether their morphology aligns with the morphological traits and well-established phenotypic stasis observed in other localities. Additionally, an updated key to the species of Gyratrix Ehrenberg, 1831 is given. The results indicate that the Chilean specimens are similar to populations found in European seas. This phenotypic similarity, in the context of the history of the Strait of Magellan, suggests potential human-assisted dispersal via maritime shipping routes. The study also highlights an intriguing biogeographic pattern found among certain putative species within G. hermaphroditus, consistent with vicariant processes associated with continental drift. Their distributions support the hypothesis of a long-term morphological stability within the species complex, potentially persisting for approximately 180 million years. This work contributes to the understanding of the distribution and evolutionary history of G. hermaphroditus, underscoring the plausibility of long-term morphological stasis in the species complex. The report herein is a new locality for the species complex, extends considerably the southern limit of the distribution of G. hermaphroditus in South America, and is the first marine record for the continent.
KEY WORDS: Eukalyptorhynchia, Polycystididae, Gyratricinae, phenotypic stability, cosmopolitanism, cryptic species.