Maritigrella aureolineata ( Verrill, 1901 ) Litvaitis & Bolaños & Quiroga, 2010

Litvaitis, Marian K., Bolaños, D. Marcela & Quiroga, Sigmer Y., 2010, When names are wrong and colours deceive: unravelling the Pseudoceros bicolor species complex (Turbellaria: Polycladida), Journal of Natural History 44 (13 - 14), pp. 829-845 : 841-843

Maritigrella aureolineata ( Verrill, 1901) comb. nov.

Pseudoceros aureolineata Verrill, 1901

Pseudoceros aureolineatus: Marcus, 1950 (new combination)

Cryptoceros aureolineatus: Faubel, 1984 (new combination) Our examination of the histological sections of the hypotype of P. aureolineatus revealed that the specimen had a muscular, tubular pharynx ( Figure 5 ). Tubular pharynges are characteristic of euryleptids, whereas species of Pseudocerotidae have a ruffled pharynx. It is surprising that neither Hyman (1939) nor Faubel (1984) recognized that the species belongs to Euryleptidae . Hyman (1939) makes mention of the cerebral eyes being arranged in two clusters at the base of the tentacles. Pseudocerotids on the other hand, typically have only one cluster of eyes, often in the shape of a horseshoe ( Newman and Cannon 1994, 2003). Recognizing that P. aureolineatus did not quite fit into Pseudoceros, Faubel (1984) placed the species into his newly erected genus Cryptoceros as C. aureolineatus . However, according to his system, Cryptoceros is still a pseudocerotid ( Faubel 1984). He also included Pseudoceros crozieri Hyman, 1939 in the genus. Since then, Newman et al. (2000) recognized the euryleptid characters of P. crozieri and moved it to the genus Maritigrella . We here propose to move P. aureolineatus ( C. aureolineatus ) to Euryleptidae as Maritigrella aureolineata comb. nov. We recognize that this new combination is based on the assumption that the hypotype is representative of the holotype, an assumption that may be difficult to ascertain considering the state of the holotype. However, indirect evidence to support our supposition comes from Verrill’s original drawing ( Verrill 1901; Figure 1B ), in which the marginal tentacles of his specimen are drawn as being distinct and held erect as in euryleptids, especially when compared to his drawing of the pseudotentacles of P. bicolor ( Figure 1A ).

Removing Pseudoceros (Cryptoceros) aureolineatus from Pseudocerotidae has implications for the genus Cryptoceros . In addition to P. crozieri and P. aureolineatus, Faubel (1984) included P. marmoratus Plehn, 1898 and Yungia sasakii Kaburaki, 1923 in Cryptoceros . However, the description by Kaburaki (1923) of Y. sasakii clearly states the presence of a cylindrical pharynx and cerebral eyes arranged in two imperfectly separated groups (p. 197); definite characters that do not warrant its placement in Pseudocerotidae . Similarly, Plehn’s description of P. marmoratus mentions distinct, pointy marginal tentacles and two clusters of cerebral eyes, albeit not sharply separated ( Plehn 1898). Furthermore, although Plehn (1898) describes a finely folded pharynx, she mentions that it clearly differs from the typical Pseudoceros - type ruffled pharynx. It is possible that the slight folding is the result of contraction at fixation and that the pharynx is actually of the tubular type. Hence, the taxonomic affinity of P. marmoratus with Pseudoceros is tenuous at best. It is therefore highly likely that all four species included in Cryptoceros by Faubel (1984) actually belong to Euryleptidae , hence invalidating the genus.

Pseudoceros rawlinsonae has not been found in Panama. Pseudoceros bicolor marcusorum subsp. nov. is present throughout the Caribbean and occurs sympatrically with P. bicolor at our collecting sites in Belize, Florida and Panama ( Table 1). Although both P. bicolor and P. bicolor marcusorum subsp. nov. are found in Honduras and Jamaica, they do not co-occur at the same sites. However, we only recorded P. bicolor marcusorum subsp. nov. in Curaçao and the US Virgin Islands. Correlating the presence of P. rawlinsonae and P. bicolor with specific habitat types revealed that P. rawlinsonae occurs equally in sea-grass beds, on coral reefs, and in the rocky intertidal zone ( Table 1). Pseudoceros bicolor on the other hand, was absent from sea-grass beds. This contrasts with Rawlinson (2008) who lists P. bicolor as the second most common cotylean found in all habitat types. The reason for the discrepancy is that she did not separate the different colour morphs but instead lumped them all into one large, general “ bicolor ” assemblage, which resulted in a large overestimate for P. bicolor and a gross underestimate of P. rawlinsonae (Rawlinson 2008) . Although in this study we confirm the importance of colour pattern (but not colouration) for species distinctions in Pseudocerotidae , we strongly caution against its sole use and emphasize the necessity of adding morphological and molecular data for accurate species identifications.

Figures

Figure 1. Holotypes of Pseudoceros bicolor and Pseudoceros aureolineatus. Original drawings by Verrill (1901) of P. bicolor (A) and of P. aureolineatus (B). Photographs of P. bicolor (C) and P. aureolineatus (D) holotypes at the Yale Peabody Museum, New Haven, CT, USA. Note shape of pseudotentacles of P. bicolor compared with the more distinct tentacles of P. aureolineatus.

Figure 5. Photomicrograph of histological section of the Pseudoceros aureolineatus hypotype, prepared by Hyman (1939) and deposited at the Yale Peabody Museum, New Haven, CT, USA. The section shows a tubular pharynx (ph), the penis papilla (pp), the prostatic vesicle (pv) and the seminal vesicle (sv). Scale bar, 100 µm.