<abstract xmlns="http://www.w3.org/1999/xhtml"><p>Spermatological characteristics of <italic>Calicotyle affinis</italic> Scott, 1911, an endoparasitic monocotylid monogenean from the cloaca of a holocephalan fish <italic>Chimaera monstrosa</italic> L, have been investigated by means of transmission electron microscopy for the first time. Spermiogenesis exhibits features basically similar to those of the congeneric <italic>Calicotyle kroyeri</italic> and <italic>Calicotyle australiensis</italic>, but there are some new findings with respect to the formation and fine structure of the spermatozoon including the remarkable complex end-piece (EP). Morphogenesis of the EP, which is located at the anterior (proximal) region of the late spermatid, includes two stages: (1) the centriolar region is continuous with a cytoplasmic mass of the zone of differentiation, the electron-dense surface of the spermatid undergoes significant changes in the sculpturing and the inner core of developing spermatid is electron-lucent; (2) after central fusion of the arching membranes a definitive structure of the EP is subsequently evolved, finally comprising 3 – 4 electron-dense discs attached to a central common electron-lucent column. The EP is considered as a synapomorphy of the genera <italic>Calicotyle</italic> + <italic>Dictyocotyle</italic>. The mature spermatozoon of <italic>C</italic>. <italic>affinis</italic> comprises the EP, two parallel axonemes of almost equal lengths with the 9 + “1” trepaxonematan pattern, mitochondrion, nucleus, and a reduced number of parallel cortical microtubules (1 – 3). The posterior (distal) extremity of the mature spematozoon contains a single tapering axoneme. Ultrastructural characteristics of the mature spermatozoon of <italic>C. affinis</italic> coincide mostly with those of congeneric <italic>C. australiensis</italic>. Variations of the spermatological characters within the genus <italic>Calicotyle</italic>, between <italic>Calicotyle</italic> and enigmatic <italic>Dictyocotyle</italic> as well as other monocotylid monogeneans are discussed.</p></abstract>

Spermatological characteristics of Calicotyle affinis Scott, 1911, an endoparasitic monocotylid monogenean from the cloaca of a holocephalan fish Chimaera monstrosa L, have been investigated by means of transmission electron microscopy for the first time. Spermiogenesis exhibits features basically similar to those of the congeneric Calicotyle kroyeri and Calicotyle australiensis, but there are some new findings with respect to the formation and fine structure of the spermatozoon including the remarkable complex end-piece (EP). Morphogenesis of the EP, which is located at the anterior (proximal) region of the late spermatid, includes two stages: (1) the centriolar region is continuous with a cytoplasmic mass of the zone of differentiation, the electron-dense surface of the spermatid undergoes significant changes in the sculpturing and the inner core of developing spermatid is electron-lucent; (2) after central fusion of the arching membranes a definitive structure of the EP is subsequently evolved, finally comprising 3 – 4 electron-dense discs attached to a central common electron-lucent column. The EP is considered as a synapomorphy of the genera Calicotyle + Dictyocotyle. The mature spermatozoon of C. affinis comprises the EP, two parallel axonemes of almost equal lengths with the 9 + “1” trepaxonematan pattern, mitochondrion, nucleus, and a reduced number of parallel cortical microtubules (1 – 3). The posterior (distal) extremity of the mature spematozoon contains a single tapering axoneme. Ultrastructural characteristics of the mature spermatozoon of C. affinis coincide mostly with those of congeneric C. australiensis. Variations of the spermatological characters within the genus Calicotyle, between Calicotyle and enigmatic Dictyocotyle as well as other monocotylid monogeneans are discussed.

Spermiogenesis and sperm ultrastructure in <italic>Calicotyle affinis</italic> Scott, 1911 (Platyhelminthes, Monogenea, Monopisthocotylea, Monocotylidae)

I.D. Papanin Institute for Biology of Inland Waters

Helminthologia

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Spermiogenesis and sperm ultrastructure in  Scott, 1911 (Platyhelminthes, Monogenea, Monopisthocotylea, Monocotylidae)

Spermatological characteristics of Calicotyle affinis Scott, 1911, an endoparasitic monocotylid monogenean from the cloaca of a holocephalan fish Chimaera...

Spermiogenesis and sperm ultrastructure in Calicotyle affinis Scott, 1911 (Platyhelminthes, Monogenea, Monopisthocotylea, Monocotylidae)

Published Online: Nov 01, 2017

Page range: 348 - 357

Received: Jun 29, 2017

Accepted: Aug 08, 2017

DOI: https://doi.org/10.1515/helm-2017-0039

Keywords
Monogenea, ultrastructure, spermiogenesis

© 2017 M. Bruňanská et al., published by De Gruyter Open

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Spermiogenesis and sperm ultrastructure in Calicotyle affinis Scott, 1911 (Platyhelminthes, Monogenea, Monopisthocotylea, Monocotylidae)

Published Online: Nov 01, 2017

Page range: 348 - 357

Received: Jun 29, 2017

Accepted: Aug 08, 2017

DOI: https://doi.org/10.1515/helm-2017-0039

KeywordsMonogenea, ultrastructure, spermiogenesis

© 2017 M. Bruňanská et al., published by De Gruyter Open

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Keywords
Monogenea, ultrastructure, spermiogenesis