Abstract

For the first time, molecular sequences of the 18S ribosomal DNA were generated for representatives of the genera Obrimoposthia Sluys & Ball, 1989 and Paucumara Sluys, 1989 of the suborder of the marine triclads, or Maricola, by analyzing the species Obrimoposthiawandeli (Hallez, 1906) and Paucumaratrigonocephala (Ijima & Kaburaki, 1916). On the basis of this molecular data the phylogenetic position of these two genera in the phylogenetic tree of the Maricola was determined and compared with their position in the phylogeny based on the analysis of anatomical features. New records for these two species are documented and their taxonomic status is determined on the basis of histological studies.

Highlights

  • The marine planarians or Maricola Hallez, 1892 form only a small suborder of triclad flatworms, comprising approximately 80 species, they exhibit a rather great anatomical diversity, which at times makes it difficult to recognize homological character states and to analyse their phylogenetic relationships

  • The inferred positions of species belonging to the current families Bdellouridae, Uteriporidae and Cercyridae are supported only by Bayesian Inference (BI), as the bootstrap supports for ML are < 75

  • The species Cercyra hastata Schmidt, 1861, Sabussowia dioica (Claparède, 1863), Pentacoelum kazukolinda (Kawakatsu & Mitchell, 1984), Paucumara trigonocephala and Ectoplana limuli (Ijima & Kaburaki, 1916) form an exception, in that their positions in our tree are supported by both ML and BI

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Summary

Introduction

The marine planarians or Maricola Hallez, 1892 form only a small suborder of triclad flatworms, comprising approximately 80 species, they exhibit a rather great anatomical diversity, which at times makes it difficult to recognize homological character states and to analyse their phylogenetic relationships. The first comprehensive study of the phylogenetic relationships among the marine triclads was undertaken by Sluys (1989) and was based on anatomical and morphological features. As morphological support for a monophyletic Maricola was postulated the autapomorphic presence of adhesive papillae arranged in the ventral annular zone, the latter constituting an autapomorphy for the entire group of triclads (Sluys 1989). Ax (2008) correctly argued that this marginal band with adhesive papillae is a plesiomorphic feature and cannot support the presumed monophyly of the Maricola. 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), suggesting that eventually major changes in the current taxonomy of the group may be necessary

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