MARINE RECORD Open Access First record of Thysanozoon brocchii (Platyhelminthes: Polycladida) from Indian waters Reshma Pitale * and Deepak Apte Abstract This work reports the occurrence of Thysanozoon brocchii from the rocky intertidal coast of Ratnagiri and Dwarka, the West Coast of India, for the first time. Two morphotypes were found, the first morph has a buff brownish papillate dorsal surface, with few specimens having white spots. The second morph has light coloured papillae which form a distinct cross marking along the dorsal surface. The species possesses double male copulatory apparatus with seminal vesicle, prostatic vesicle and sclerotized stylet. This cosmopolitan species has previously been recorded from Italy and Mediterranean, Japan, South and West Africa, Florida, New Zealand, Brazil, and United Kingdom. Synonymized species and older descriptions have been compared to examine similarities and dissimilarities. Considering the existence of varied colour morphs of this species, a detailed comparative analysis of morphological characters, reproductive histology and molecular framework is recommended. Keywords: Pseudocerotidae, Colour patterns, Intraspecific variations, Reproductive anatomy, Cosmopolitan, Maharashtra, Gujarat Introduction Polyclad flatworms are free living members of the phylum Platyhelminthes. These coral reef and rocky shore inhabitants are more diverse in the tropical envir- onment (Prudhoe, 1985). Cryptic behavior, apparent specificity with food preference, aposematic colouration and mimicry with opisthobranch molluscs and fishes (Ang & Newman 1998; Newman & Canon, 2005) make them potentially significant in intertidal or reef ecology. Members of the family Pseudocerotidae are peculiar for their brilliant colour patterns. However, colour variation is commonly seen forming species complex in their systematics. Perhaps such complexities arising in the taxonomy of these worms can be resolved by careful observations of external as well as reproductive anatom- ical features. Newman and Canon (1995) described three species of the genus Pseudoceros from the Indo-Pacific region showing remarkable similarity within external appearance. 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 con- sidering the papillate dorsal surface, unlike the rest of the Cotylean genera. Type species of the genus was Thysanozoon diesingii, which has later been synony- mized for T. brocchii. This genus includes about 23 species worldwide (Tyler, 2013). Laidlaw (1902) reported Thysanozoon plehni from the Laccadive Island of India. However, this species has been reviewed and assigned to Acanthozoon plehni. After a gap of about a century, Apte and Pitale (2011) mentioned a member of this genus from Kavaratti, Lakshadweep Island, India. Later, Sreeraj and Raghunathan (2013) reported Thysanozoon nigropa- pilosum from South Andaman. The present study reports Thysanozoon brocchii for the first time from the Indian shoreline. Apart from external morphology and reproductive anatomy, the study encompassed the review of characteristic features of some of the synonyms and a few previous descriptions, and their comparisons with the two different morphs presented herein. * Correspondence: rd.pitale@bnhs.org Bombay Natural History Society, Hornbill House, S.B. Singh Road, Mumbai, Maharashtra 400 001, India © The Author(s). 2017 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. Pitale and Apte Marine Biodiversity Records (2017) 10:21 DOI 10.1186/s41200-017-0123-0