Coming out in a harsh environment: a new genus and species for a land flatworm (Platyhelminthes: Tricladida) occurring in a ferruginous cave from the Brazilian savanna

Abstract

Faunal inventories in ferruginous caves from an area belonging to the Brazilian savanna (Cerrado phytophysiognomy), on the eastern margin of the Serra do Espinhaço Plateau, in southeastern Brazil, have revealed the occurrence of land flatworms. Herein, a flatworm sampled in such subterranean environment is described as a new genus and species of the Neotropical subfamily Geoplaninae, Difroehlichia elenae gen. nov., sp. nov. The new genus shows rare features within Geoplaninae, namely sub-cylindrical body, poorly developed sub-epidermal musculature and a narrow creeping sole. Some features, such as a small body and a broad sensory margin in the anterior region of the body, as well as the fact that the holotype showed signs of recent copula, may indicate an adaptation to the subterranean environment, probably representing a troglophile. Difroehlichia elenae is characterized by an almost homogeneous dark brown pigmentation over dorsal surface and body margins, a short cylindrical pharynx, and a tubular and unforked intrabulbar prostatic vesicle, among other features. The holotype shows a secondary male copulatory organ located immediately behind the primary one, both communicating with the female atrium and gonopore canal. Since the species seems to have low abundance and restricted distribution and its type-locality is affected by mining activities, major concern arises regarding its conservation.

Increasing the species diversity of the genus Paraba (Platyhelminthes) with the description of two new species from the southern atlantic forest

“…Despite the large number of known species, knowledge about the diversity of Geoplaninae has been constantly expanded, with recent descriptions of new genera and species. The subfamily currently consists of 25 genera, among them Paraba (Carbayo et al, 2013;Leal-Zanchet and Marques, 2018;Negrete et al, 2019).…”

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

“…However, recently studies reported interesting finding, species of terrestrial and Maricola living in cave locations. Between the cave terrestrial species majority of them do not present evidences for troglobitic traits, suggesting the use of caves as shelter or temporary habitat (Amaral et al, 2019;Leal-Zanchet & Marques, 2018a, 2018b. 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).…”

“…The evolutionary mechanisms (e.g., natural selection, indirect selection, neutral selection) underlying cave trait loss are still under discussion, it is reasonable to assume that each event of cave conquest may present unique evolutionary case. Towards the course of evolution probably different Tricladida species end up trapped inside caves, using cave as a shelter, or to find food, or sometimes due to water transgressions and regressions leading these animals to inhabit dark environments (Amaral et al, 2019;Leal-Zanchet & Marques, 2018a, 2018bSouza et al, 2018). Selection pressures acted on these species, leading to changes related to troglobiont features, and the mechanisms involved in the convergent evolution of regressive traits are not fully comprehended (Aspiras et al, 2012;Krishnan & Rohner, 2017;Stemmer et al, 2015).…”