Ultrastructure of spermatozoa in the seminal receptacle of the liver fluke Opisthorchis felineus (Rivolta, 1884)

Abstract

The spermatozoon ultrastructure in the seminal receptacle of the liver fluke Opisthorchis felineus (Digenea, Opisthorchiidae), the agent of human opisthorchiasis endemic to Russia and Eastern Europe, was examined. The bean-shaped seminal receptacle of O. felineus has a wall consisting of epithelial and muscle layers. Mature spermatozoa are located in the interior of the seminal receptacle, whereas vacuoles containing degenerating spermatozoa are detectable at the periphery. The mature spermatozoon of O. felineus has two axonemes of a 9 + "1" pattern, a nucleus, two mitochondria, a lamellar body, two bundles of parallel cortical microtubules and an external ornamentation of the plasma membrane in the anterior area of the sperm. The lamellar body is likely to be the third mitochondrion of a small size. The cytoplasm of the spermatozoon is filled with numerous electron-dense granules of storage polysaccharides. Additionally, the ultrastructural characteristics of the seminal receptacle and spermatozoa of O. felineus were compared to available published data on other trematode species. The functional roles of the observed structures of this spermatozoon are discussed.

Neomultitestis aspidogastriformis Bray and Cribb, 2003 (Digenea, Lepocreadiidae): mature spermatozoon and sperm morphologies in the Lepocreadioidea

“…The mature spermatozoon of N. aspidogastriformis presents two mitochondria with a first one in the ornamented area, and a second one more posteriorly located, i.e., in the nuclear region. Similar disposition of mitochondria had been reported in other digeneans such as the opecoelids Poracanthium furcatum, Nicolla testiobliquum, and N. wisniewskii (Levron et al, 2004b;Quilichini et al, 2007b, c), the dicrocoeliid Dicrocoelium hospes (Agostini et al, 2005), the troglotrematid Troglotrema acutum (Miquel et al, 2006), the omphalometrid Rubenstrema exasperatum (Bakhoum et al, 2011), or the opisthorchiid Opisthorchis felineus (Zhukova et al, 2014). Within the Lepocreadioidea, two mitochondria have been described in R. fractum, H. caputvadum, and O. bacillaris Kacem et al, 2012;Ndiaye et al, 2015), whereas in the remaining species only one mitochondrion has been reported Quilichini et al, 2011b).…”

“…The anterior spermatozoon extremity of N. aspidogastriformis forms a sharp point. This is the most frequent morphology described in digenean species (Ndiaye et al, ; Agostini et al, ; Quilichini et al, ; Bakhoum et al, ; Zhukova et al, ). In cross‐section, the anterior extremity of the mature spermatozoon of N. aspidogastriformis exhibits one axoneme associated with antero‐lateral electron‐dense material.…”

“…Aldm, antero-lateral electron-dense material; Arrowheads, attachment zones; Ase, anterior spermatozoon extremity; Ax1, first axoneme; Ce2, centriole of second axoneme; Cm, cortical microtubules; Eo, external ornamentation of the plasma membrane; M1, first mitochondrion; Sb, spine-like body. morphology described in digenean species (Ndiaye et al, 2002;Agostini et al, 2005;Quilichini et al, 2011a;Bakhoum et al, 2013b;Zhukova et al, 2014). In cross-section, the anterior extremity of the mature spermatozoon of N. aspidogastriformis exhibits one axoneme associated with antero-lateral electron-dense material.…”

Ultrastructure of the male gamete of Brachylecithum eliomydis (Digenea, Dicrocoeliidae)—A parasite of Eliomys quercinus (Rodentia, Gliridae)

“…Therefore, these ultrastructural criteria possess great phylogenetic interest in understanding the complexes relationships within Digenea in general and Dicrocoeliidae in particular (Agostini et al, 2005;Bakhoum et al, 2013a;Miquel et al, 2013;Quilichini et al, 2010b;Ternengo et al, 2009;Zhukova et al, 2014). Five ultrastructural characteristics present in the spermatozoon of B. eliomydis, are discussed below.…”

Peer Review #1 of "Spermatozoon ultrastructure in two monorchiid digeneans (v0.1)"

“…In all monorchiid species described so far the posterior spermatozoon extremity contains a nucleus as in O. dinema and P. selaris (Table 1). This morphology of the posterior spermatozoon extremity is frequently reported in digenean (Kacem et al, 2010(Kacem et al, , 2015aZhukova, Mordvinov & Kiseleva, 2014;Quilichini et al, 2015) and corresponds to the fasciolidean type or type 2 according to the diagram of Quilichini et al…”