Revision of Gangesia (Cestoda: Proteocephalidea) in the Indomalayan Region: Morphology, Molecules and Surface Ultrastructure Anirban Ash 1 , Toma ´s ˇ Scholz 1 *, Alain de Chambrier 2 , Jan Brabec 1 , Mikula ´s ˇ Oros 3 , Pradip Kumar Kar 4 , Shivaji Prabhakar Chavan 5 , Jean Mariaux 2 1 Institute of Parasitology, Biology Centre of the Academy of Sciences of the Czech Republic & Faculty of Science, University of South Bohemia, C ˇ eske ´ Bude ˇjovice, Czech Republic, 2 Department of Invertebrates, Natural History Museum, Geneva, Switzerland, 3 Institute of Parasitology, Slovak Academy of Sciences, Kos ˇice, Slovakia, 4 Jhargram Raj College, Jhargram, Paschim Medinipur, West Bengal, India, 5 School of Life Sciences, Swami Ramanand Teerth Marathwada University, Nanded, Maharashtra, India Abstract Tapeworms of Gangesia Woodland, 1924 (Cestoda: Proteocephalidea) parasitic in freshwater fishes in the Indomalayan Region were critically reviewed. Evaluation of type specimens and newly collected materials from Bangladesh, Cambodia and India, as well as critical examination of extensive literature have shown that only the following four species, instead of 48 nominal species of Gangesia and Silurotaenia Nybelin, 1942 reported from this region (36 new synonymies proposed), are valid: Gangesia bengalensis (Southwell, 1913), type-species of the genus and most common parasite of Wallago attu (Siluridae), G. macrones Woodland, 1924 typical of Sperata seenghala (Bagridae), both species characterized by the possession of two circles of hooks on the rostellum-like organ and several rows of hooklets on the anterior margins of suckers; G. agraensis Verma, 1928 from W. attu (typical host), which has the scolex with only one circle of hooks and 1–3 incomplete rows of tiny hooklets on the suckers; and G. vachai (Gupta and Parmar, 1988) n. comb. from several catfishes, which possesses 4–6 circles of hooks and 5–11 rows of hooklets on the anterior half of suckers. Scolex morphology, including surface ultrastructure (microtriches), of all but one species (G. vachai) is described for the first time using scanning electron microscopy. A phylogenetic analysis based on the partial sequences encoding the large nuclear ribosomal subunit RNA gene has shown that three Indomalayan species, namely G. bengalensis, G. macrones and G. vachai, form a monophyletic group within Gangesia, whereas G. agraensis tends to form a clade with the Palaearctic species of the genus. A table with differential characters of all species from the Indomalayan Region is also provided together with a key to identification of genera of the subfamily Gangesiinae. The present study demonstrates that species of Silurotaenia do not occur in the Indomalayan region. Citation: Ash A, Scholz T, de Chambrier A, Brabec J, Oros M, et al. (2012) Revision of Gangesia (Cestoda: Proteocephalidea) in the Indomalayan Region: Morphology, Molecules and Surface Ultrastructure. PLoS ONE 7(10): e46421. doi:10.1371/journal.pone.0046421 Editor: Martin Heil, Centro de Investigacio ´ n y de Estudios Avanzados, Mexico Received June 25, 2012; Accepted August 29, 2012; Published October 3, 2012 Copyright: ß 2012 Ash et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This study was financially supported by the Institute of Parasitology, C ˇ eske ´ Bude ˇ jovice (institutional support RVO: 60077344), Czech Science Foundation (Projects Nos. 524/08/0885, P505/12/G112 and 206/09/H026), Slovak Research and Development Agency (No. LPP-0171-09 and APVV 0653-11), Grant Agency VEGA (No. 2/0129/12) and National Science Foundation, United States of America (PBI award Nos. 0818696 and 0818823). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: tscholz@paru.cas.cz Introduction Gangesia was proposed by Woodland [1] to accommodate two species that he described from two catfishes in India, namely Gangesia wallago Woodland, 1924 from the silurid Wallago attu (Bloch and Schneider, 1801) and G. macrones Woodland, 1924 from the bagrid Sperata seenghala (Sykes, 1839) (syns. Mystus seenghala and Macrones seenghala). However, G. wallago in fact included two separate species, one conspecific with Ophryocotyle bengalensis Southwell, 1913 ( = Gangesia bengalensis [Southwell, 1913] Verma, 1928; type-species of the genus) and another one, for which Verma [2] proposed the name Gangesia agraensis (synonym Gangesia wallago Woodland, 1924 in part). Since Woodland [1] used the name G. wallago for both taxa, i.e. G. bengalensis and G. agraensis, Verma’s proposal avoided confusion. His taxonomic action was accepted by subsequent authors, including Freze [3] and Rego [4], but Southwell [5] and Schmidt [6] considered G. agraensis to be a synonym of G. bengalensis. Subsequently, a number of species have been described from the same fish hosts, especially from W. attu and S. seenghala (see Tables 1–3). However, descriptions of these species were inadequate and were based on apparently decomposed specimens, often with missing hooks due to post mortem disintegration of tissues, including detachment of the tegument and surface structures (hooks, hooklets and microtriches) (see, e.g., [7]). In addition, type specimens or vouchers of all but one (G. sindensis) taxa are not known to exist and all requests for their loan have remained unanswered, which casts serious doubts upon reliability of these species descriptions. Recently, extensive materials of Gangesia tapeworms were collected from W. attu, S. seenghala and Mystus spp. from Bangladesh, Cambodia and India. This new, well fixed and PLOS ONE | www.plosone.org 1 October 2012 | Volume 7 | Issue 10 | e46421