When names are wrong and colours deceive: unravelling the Pseudoceros bicolor species complex (Turbellaria: Polycladida)

Abstract

The polyclad Pseudoceros bicolor derives its name from a distinctive two-coloured dorsal colouration, which consists of a very dark, almost black central area with acute black lobes extending towards a translucent greyish margin. At least three different colour morphs have been described, ranging from a pale speckled brown through an evenly dark brown form, to a morphotype resembling the original species description. Pseudoceros aureolineatus is easily confused with the light brown colour morph of P. bicolor, and P. rawlinsonae resembles both P. bicolor and P. aureolineatus. Using morphological characters of newly collected specimens and nucleotide sequences of the 28S ribosomal DNA gene, the taxonomic validity of P. rawlinsonae and P. bicolor is confirmed and the descriptions of their colouration are emended. The new subspecies, P. bicolor marcusorum subsp. nov. is erected, the genus Cryptoceros is eliminated, and the new combination Maritigrella aureolineata comb. nov. (Euryleptidae) is established for P. aureolineatus.

Keywords:

• Pseudocerotidae
• Pseudoceros bicolor marcusorum subsp. nov.
• Maritigrella aureolineata comb. nov.
• Caribbean
• colour morphs

Acknowledgements

We thank Dr Kate Rawlinson, Dr Marcin Liana, Anne DuPont, Andrew Allan and Joseph Dunn for help with collecting specimens. Our special thanks go to Vinicius Padula, MSc (Museu Nacional, Universidade Federal do Rio de Janeiro, Brazil) for allowing us to use his photograph of a specimen of P. bicolor with a yellow-greenish marginal line (Figure 4N). We also thank Dr Eric Lazo-Wasem, Senior Collections Manager, for accepting our specimens into the collection at the Yale Peabody Museum of Natural History, New Haven, CT, USA. This work was supported by National Science Foundation grant DEB-0412932 and is Scientific Contribution No. 2403 of the New Hampshire Agricultural Experiment Station.