A molecular analysis of the phylogenetic position of the suborder Cavernicola within the Tricladida (Platyhelminthes), with the description of a new species of stygobiont flatworm from Benin

Abstract

This paper presents a new species of cavernicolan planarian from the African continent, which enabled us to determine the position of the suborder Cavernicola within the order Tricladida on a molecular basis. A recent paper suggested a sister-group relationship between Cavernicola and marine triclads. However, our work is the first molecular study to demonstrate unequivocally that the Cavernicola does not group with either the freshwater planarians or the land planarians, i.e. is not closely related to the suborder Continenticola, and corroborates the suggested sister-group relationship with the marine triclads or Maricola. Two possible scenarios are proposed for the evolution of the Cavernicola from marine ancestors. The new species is assigned to the genus Novomitchellia and is characterized by the absence of eyes. Testicular follicles are numerous and only dorsal, extending from behind the ovaries to the posterior end of the body. The vasa deferentia separately penetrate the penis bulb and the seminal vesicle. The penis papilla is very short and blunt, and the penis bulb musculature is weak. A long and narrow copulatory bursa is situated behind the gonopore. The common oviduct is orientated perpendicularly to the short bursal canal.

Phylogeny and biogeography of the Cavernicola (Platyhelminthes: Tricladida): Relicts of an epigean group sheltering in caves?

“…6). Two of the new species described since Sluys ' (1990) monographic study also possess these three features, reinforcing their value as diagnostic characters for the suborder (Leal-Zanchet et al, 2014;Harrath et al, 2016) . However, Kawakatsua pumila does not possess a penis bulb with gland cells, while Rhodax does neither exhibit the character "gland cells in the penis bulb" (character 1 in Sluys 1990; see also Fig.…”

“…After this, it took a long time before the number of species for the Cavernicola started to increase slowly. Two new species and one new genus were described in recent years, viz., Zanchet et al, 2014;Harrath et al, 2016). In addition, Laumer and Giribet (2014) reported 18S and 28S rRNA sequences for a new, undescribed species of Cavernicola.…”

The stenoendemic cave-dwelling planarians (Platyhelminthes, Tricladida) of the Italian Alps and Apennines: Conservation issues

“…Nearly 200 species of Platyhelminthes, mostly planarians, have been recorded in underground environments (Romero, 2009). Most of these species are blind and unpigmented, thus showing a strong adaptation to subterranean life (Harrath et al, 2012(Harrath et al, , 2016Stocchino et al, 2013Stocchino et al, , 2017a. In subterranean biotopes, planarians hold an intermediate position in the food web: they represent occasional prey for cave fishes, crayfishes and salamanders (Gillespie, 2013;Manenti, 2014;present paper), while in turn they feed on living or dead cave-dwelling animals such as amphipods, isopods and drowned arthropods such as crickets and dipterans (Romero, 2009).…”

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)

“…More recently, Ax (2008) correctly argued that this marginal band with adhesive papillae is a plesiomorphic feature and therefore cannot support the presumed monophyly of the Maricola. Nevertheless, recent phylogenetic studies on the triclads consistently recover the Maricola as a monophyletic taxon (see Charbagi-Barbirou et al 2011, Sluys et al 2014, Harrath et al 2016. The same molecular studies reveal relationships within the Maricola that differ from those hypothesized by Sluys (1989), thus suggesting that eventually major changes in the current taxonomy of the group may be necessary.…”