An integrative taxonomic approach reveals the first marine triclad (Platyhelminthes) trapped in a cave from a semiarid Neotropical environment

Abstract

A new genus and species of the suborder Maricola, representing the first marine triclad living in freshwater within a cave, is described. These flatworms show specialised features, such as a lack of pigmentation and eyes, indicating their troglobitic condition. Until now, cave-dwelling triclads have only been found as representatives of the other two triclad lineages. The phylogenetic trees based on 18S rRNA and 28S rRNA genes showed their sequences to form a clade situated in a rather derived position within the Maricola. Combining maximum likelihood and Bayesian analyses along with morphological studies, we undertake the first integrative description of a marine triclad. The new genus is characterised by a secondary copulatory bursa and ovaries located behind the root of the pharynx. Nevertheless, its assignment to a family of Maricola was a difficult task especially due to the paucity of unique defining morphological features of their families. The new species is found in a semiarid environment that suffered marine transgressions and regressions during the Cretaceous, which may explain the presence of this originally marine species in a freshwater cave. The restricted distribution of the new species and recent environmental conditions detected at its type locality raise major concern for its conservation.

Da luz à escuridão: história evolutiva do sistema fotosensorial em planárias (Platyhelminthes, Tricladida)

“…The report of Sluysia triapertura, a Maricola brackish water cave inhabitant, corroborate with the hypotheses of a marine transgressions and regressions leading to the isolation of this species inside a cave (Souza et al, 2018).…”

“…However, two other species actually display some troglobiont features, i) Geoplana subterranea is the only terrestrial species that is albine and eyeless, and can be found underground feeding on earthworms (Carbayo et al 2013;Ogren and Kawakatsu 1991); ii) The land species Microplana astricta, although it does not live underground, is suggested to present no eyes, it anteriormost tip of the body is unpigmented making hard to visualize eyes in live animal, displaying a level of pigment loss (Mateos et al, 2017). On the other hand, the cave Maricola species Sluysia triapertura was actually found in a brackish water and present no eyes and no pigmentation, suggesting first evidence of true troglobiont features (Souza et al, 2018).…”

New molecular sequences for two genera of marine planarians facilitate determination of their position in the phylogenetic tree, with new records for two species (Platyhelminthes, Tricladida, Maricola)

“…In the molecular phylogenetic trees generated by Souza et al (2018) their new genus and species Sluysiatriapertura Leal-Zanchet & Souza, 2018 is the sister-group of the ectocommensal species Ectoplanalimuli (Ijima & Kaburaki, 1916), albeit that this relationship only has low support in their trees. In our tree (Figure 1) the topology has changed slightly in that P.trigonocephala has become the sister-species of E.limuli , while S.triapertura forms part of a group of five species that constitutes the sister-taxon of E.limuli plus P.trigonocephala .…”

The complete mitochondrial genome of a marine triclad Miroplana shenzhensis (Platyhelminthes, Tricladida, Maricola)

“…Intriguingly, Miroplana exhibits good adaptation to both brackish water and freshwater habitats, which is similar to Sluysia triapertura (Souza et al. 2018 ) and species of the genus Paucumara (Li et al. 2021 , Chen et al.…”