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(2018). "Spermiogenesis and spermatozoon ultrastructure in basal polyopisthocotylean monogeneans, Hexabothriidae and Chimaericolidae, and their significance for the phylogeny of the Monogenea". Parasite 25: 7. DOI:10.1051/parasite/2018007. ISSN 1776-1042.

Spermiogenesis and spermatozoon ultrastructure in basal polyopisthocotylean monogeneans, Hexabothriidae and Chimaericolidae, and their significance for the phylogeny of the Monogenea 

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Instance of	scholarly article
Main subject	parasitology Monogenea sperm Chimaericola leptogaster spermatozoon phylogenetics Chimaericolidae (Chimaericolidae) Hexabothriidae (Hexabothriidae)
Author	Jean-Lou Justine (1) Larisa G Poddubnaya (2)
Published in	Parasite
Copyright license	Creative Commons Attribution 4.0 International (2018–)
Publication date	13 February 2018
Authority file  Q48804949 DOI: 10.1051/PARASITE/2018007 PubMed publication ID: 29436366 PMC publication ID: 5811217 Reasonator Scholia Wikidocumentaries PetScan statistics WikiMap Locator tool KML file Search depicted

Abstract
Sperm ultrastructure provides morphological characters useful for understanding phylogeny; no study was available for two basal branches of the Polyopisthocotylea, the Chimaericolidea and Diclybothriidea. We describe here spermiogenesis and sperm in Chimaericola leptogaster (Chimaericolidae) and Rajonchocotyle emarginata (Hexabothriidae), and sperm in Callorhynchocotyle callorhynchi (Hexabothriidae). Spermiogenesis in C. leptogaster and R. emarginata shows the usual pattern of most Polyopisthocotylea with typical zones of differentiation and proximo-distal fusion of the flagella. In all three species, the structure of the spermatozoon is biflagellate, with two incorporated trepaxonematan 9 + “1” axonemes and a posterior nucleus. However, unexpected structures were also seen. An alleged synapomorphy of the Polyopisthocotylea is the presence of a continuous row of longitudinal microtubules in the nuclear region. The sperm of C. leptogaster has a posterior part with a single axoneme, and the part with the nucleus is devoid of the continuous row of microtubules. The spermatozoon of R. emarginata has an anterior region with membrane ornamentation, and posterior lateral microtubules are absent. The spermatozoon of C. callorhynchi has transverse sections with only dorsal and ventral microtubules, and its posterior part shows flat sections containing a single axoneme and the nucleus. These findings have important implications for phylogeny and for the definition of synapomorphies in the Neodermata. We point out a series of discrepancies between actual data and interpretation of character states in the matrix of a phylogeny of the Monogenea. Our main conclusion is that the synapomorphy “lateral microtubules in the principal region of the spermatozoon” does not define the Polyopisthocotylea but is restricted to the Mazocraeidea.

Abbreviations for all figures

A-CM: Anterior extremity of cortical microtubules

A-IM: Anterior extremity of internal microtubules

AM: Arching membrane

A-Mit: Anterior extremity of mitochondrion

A-N: Anterior extremity of nucleus

ASE: Anterior spermatozoon extremity

Ax, Ax1, Ax2: Axonemes

AZ: Attachment zone

C, C1, C2: Centrioles

CM: Cortical microtubules

D: Dense zone

FF: Free flagellum

IB: Intercentriolar body

IM: Internal microtubules

M: (in micrographs), Mit (in diagrams) Mitochondrion

MCE: Median cytoplasmic process

MT: microtubules

N: Nucleus

O: Ornamentation on membrane

P-Ax1, P-Ax2: Posterior extremity of axoneme 1, 2

PSE: Posterior spermatozoon extremity

P-CM: Posterior extremity of cortical microtubules

P-IM: Posterior extremity of internal microtubules

P-Mit: Posterior extremity of mitochondrion

P-N: Posterior extremity of nucleus

SR: Striated root