Parasitology Research

, Volume 115, Issue 6, pp 2285–2297 | Cite as

Ultrastructural observations of the attachment organs of the monogenean Rajonchocotyle emarginata (Olsson, 1876) (Polyopisthocotylea: Hexabothriidae), a gill parasite of rays

  • Larisa G. Poddubnaya
  • Willy Hemmingsen
  • David I. Gibson
Original Paper


The present study uses scanning and transmission electron microscopical observations to examine the haptoral features of the hexabothriid polyopisthocotylean monogenean Rajonchocotyle emarginata from the gills of the elasmobranch Amblyraja radiata. The haptor possesses six equal, pedunculate suckers, each armed with a large, curved, hooked sclerite, and an appendix bearing two small, terminal suckers and a pair of minute hamuli. The outer side of the distal region of the hooked sclerite forms a large bulge along the antero-lateral side of each sucker and the proximal region forms a small bulge on the opposite postero-lateral side; part of the large bulge, which covers the small sclerite hook, surmounts the sucker rim. The sucker sclerite is situated outside the main sucker muscle complex of the sucker wall and is surrounded by its own muscular envelope; close to the sclerite itself, long, tightly packed lamella-like processes of sarcoplasm are present. A muscular sphincter surrounds the distal region of the sclerite shaft. The sclerite consists of three heterogeneous layers, but its hook region is distinguished from the shaft by the presence of an additional homogeneous layer. Hamuli within the appendix consist of three distinct layers loosely surrounded by sarcoplasmic lamellae. The luminal surface of the appendicular suckers is covered with unusual, long, thin, interconnected surface protrusions. In all other regions of the haptor, the tegumental surface is smooth, with numerous shallow pores penetrating the “terminal web” of the syncytial cytoplasm. Unicellular gland cells are localized close to the base of the appendix, with their ducts, containing non-homogenous secretory bodies, opening onto the anterior haptoral surface. Two types of sense receptors are visible on the haptoral surface. The ultrastructural features of the haptor are discussed in relation to our understanding of their function and the evolutionary relationships of the basal polyopisthocotylean monogenean groups Hexabothriidae and Chimaericolidae.


Ultrastructure Monogenea Hexabothriidae Haptor Attachment 



The authors would like to thank the staff of the RV ‘Johan Ruud’, belonging to Tromsø University, for their invaluable help with the fishing. We are also grateful to the staff of the Centre of Electron Microscopy of the I.D. Papanin Institute of the Biology for Inland Waters, RAS, for technical assistance. The present study was supported by the Russian Foundation for Fundamental Research project no. 15-04-02890a (to LGP).


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Copyright information

© Springer-Verlag Berlin Heidelberg 2016

Authors and Affiliations

  • Larisa G. Poddubnaya
    • 1
  • Willy Hemmingsen
    • 2
  • David I. Gibson
    • 3
  1. 1.I. D. Papanin Institute for Biology of Inland WatersRussian Academy of SciencesYaroslavlRussia
  2. 2.Faculty of Biosciences, Department of Arctic and Marine Biology, Fisheries and EconomicsUniversity of TromsøTromsøNorway
  3. 3.Department of Life SciencesNatural History MuseumLondonUK

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