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.

New records of Cotylea (Polycladida, Platyhelminthes) from Lizard Island, Great Barrier Reef, Australia, with remarks on the distribution of the Pseudoceros Lang, 1884 and Pseudobiceros Faubel, 1984 species of the Indo-Pacific Marine Region

“…In the examined specimen, those granules do not appear, and thus, the dorsal colouration is lighter. Such variation in the colour tone, while maintaining the basic pattern, has been already described by other authors (Ang & Newman 1998;Litvaitis et al 2010). Although in the original description the inner marginal band is described as sky blue or mauve, in the attached picture it can be seen that, as happens in our specimen, the band fades to white (Newman & Cannon 1994b.…”

“…Pseudoceros stimpsoni shows the colour pattern comparable with the light brown morphotype of Pseudoceros bicolor Verrill, 1901(Litvaitis et al 2010Bahia et al 2014). However, some differences are noticeable between the examined specimen and the light brown morphotype of P. bicolor: first, the orange marginal band is narrow in P. stimpsoni, but wider and diffuse in P. bicolor; although faint, in P. stimpsoni it appears as a black/grey band at both sides of the orange marginal band, while in P. bicolor a discontinuous black band appears only external to the orange one; lastly, the interruptive white speckles of the orange band are quite small in P. stimpsoni in comparison to those in P. bicolor.…”

“…However, some differences are noticeable between the examined specimen and the light brown morphotype of P. bicolor: first, the orange marginal band is narrow in P. stimpsoni, but wider and diffuse in P. bicolor; although faint, in P. stimpsoni it appears as a black/grey band at both sides of the orange marginal band, while in P. bicolor a discontinuous black band appears only external to the orange one; lastly, the interruptive white speckles of the orange band are quite small in P. stimpsoni in comparison to those in P. bicolor. Furthermore, P. stimpsoni occurs in the Indo-Pacific region, while P. bicolor is only known from West Atlantic (Bermuda (Verrill 1901), Curaçao (Marcus & Marcus 1968;Litvaitis et al 2010), Caribbean coast of Colombia (Quiroga et al 2004b), Belize, Florida, Honduras, Jamaica, Panamá (Litvaitis et al 2010), and Brazil (Bahia et al 2014)). However, future DNA analysis should be conducted in order to confirm or reject the synonymisation of these two species.…”

First record of Thysanozoon brocchii (Platyhelminthes: Polycladida) from Indian waters

“…They, too, emphasized the significance of precise documentation of colour and patterns. Litvaitis, et al (2010) tested the coloration pattern of Pseudoceros bicolor complex against molecular evidence and emerging complexities in the taxonomy of the same. Grube (1840) described the genus Thysanozoon considering the papillate dorsal surface, unlike the rest of the Cotylean genera.…”

Evolution of flatworm central nervous systems: Insights from polyclads

“…In addition, a deep-sea specimen of Anocellidus profundus Quiroga, Bolaños and Litvaitis, 2006, from the North Pacific was also included in the analysis (specimen courtesy of Dr. Janet Voight, Field Museum of Natural History, Chicago, Illinois, USA). For details of collection, fixation, and species identification see Litvaitis et al (2010) .…”