Exploring the anatomy of Cossura pygodactylata Jones, 1956 (Annelida, Cossuridae) using micro-computed tomography, with special emphasis on gut architecture
The anatomy of Cossura pygodactylata Jones, 1956 (Annelida; Cossuridae) is presented, based on the study of specimens collected during the BIOICE project in Icelandic waters and additional material from the White Sea. General gross external and internal anatomy were investigated by means of micro-computed tomography (micro-CT) and compared with results obtained with light microscopy histological sectioning (LMHS). Micro-CT revealed a highly regionalised gut, posterior to the pharyngeal cavity and oesophagus, divided in an anterior stomach and a posterior intestine with different morphologies. The stomach is in the thoracic region, dorsally positioned and divided in a short and narrow anterior part and a longer posterior one, with an increasing diameter towards its posterior end. Both stomach regions bear a dorsal infolding of tissue, along its inner wall, that resembles to the typhlosole of the Clitellata. The heart is dorsally located and contains a heart body above the hind stomach. The intestine is wider than the stomach, without dorsal infolding inside the lumen and filling most part of the internal body cavity. A transitional cup-shaped gut element connecting the stomach and the intestine could be observed at the level of the last thoracic segment. In general, the resolution of micro-CT images reflects reasonably well the main elements of gross external and internal anatomy of cossurids, and that of gut architecture in particular.
KeywordsNE Atlantic Ocean Micro-CT BIOICE Digestive system Polychaeta 3D anatomical reconstruction
The authors would like to thank Gudmundur Gudmundsson, Director of Collections and Systematics Department (Icelandic Institute of Natural History, Reykjavik), Gudmundur Vidir Helgason (Institute of Biology, University of Iceland, Reykjavik) and the Director of the Sandgerdi Marine Centre until 2013 for their help and advice during JP visits to the SMC, and to Solrun Bragadóttir and the rest of the women of the SMC involved in sorting the specimens from the BIOICE samples. The authors are also grateful to María Candás and Xela Cunha-Veira (EBMG, USC) for their help with the micro-CT images. The authors would also like to thank Nathalie Yonow (Swansea, Wales, UK) for linguistic correction of the manuscript, two anonymous reviewers for their helpful comments that greatly contributed to improve the organisation and clarity of the information provided and Karin Meiβner, Guest Editor of Marine Biodiversity, for her support during the review process and generous effort to improve the presentation of the text.
This work was partially supported by several grants from the European Union’s Training and Mobility of Researchers program and the Universidade da Coruña to the first author to visit the Sandgerdi Marine Centre. The micro-CT study was financially supported by the project Fauna Ibérica XI - Polychaeta VI (CGL2014-53332-C5-3-P). The work of AZ, AT and EV was supported by grants 15-29-02447 and 16-04-00343 from the Russian Foundation for Basic Research. The histological investigations were supported by the Russian Scientific Foundation, grant 14-50-00029.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
All applicable international, national, and/or institutional guidelines for the care and use of animals were followed by the authors.
All necessary permits for sampling and observational field studies have been obtained by the authors from the competent authorities and are mentioned in the acknowledgements, if applicable.
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