High-pressure freezing and freeze-substitution fixation reveal the ultrastructure of immature and mature spermatozoa of the plant-parasitic nematode Trichodorus similis (Nematoda; Triplonchida; Trichodoridae)

Cytonemes with complex geometries and composition extend into invaginations of target cells

“…High pressure frozen filopodia have been visualized in cross section before, but the shape along the length of filopodia was not assessed. (Lak et al, 2015). Chemical fixation during EM processing causes shrinkage of tissues and distortion of cellular and organellar membranes.…”

“…Although filopodia have been examined by EM before, to our knowledge, this is the first study to examine filopodia in HPF tissue by serial EM. HPF filopodia have been visualized in cross-section before, but the shape along the length of filopodia was not assessed ( Lak et al, 2015 ). HPF-preserved membrane protrusions of human mammary epithelial cells imaged via focused ion beam SEM have bulges and uneven thicknesses ( Jorgens et al, 2017 ), although they are more irregular than the varicosities we observed and do not have a repeating pattern.…”

Analysis of major sperm proteins in two nematode species from two classes, Enoplus brevis (Enoplea, Enoplida) and Panagrellus redivivus (Chromadorea, Rhabditida), reveal similar localization, but less homology of protein sequences than expected for Nematoda phylum

“…In the representatives of Dorylaimia amoeboid spermatozoa 97 with pseudopods filled with cytoskeleton fibers have been described in many taxa (Justine 2002;98 Yushin and Malakhov 2014). This specific morphology of motile sperm is confirmed by direct 99 observation of sperm movement in the dorylaimian Gastromermis sp (order Mermithida) (Poinar 100 and Hess- Poinar 1993 The subclass Enoplia includes taxa where characteristic pseudopod bearing spermatozoa 113 also have been described (Justine 2002;Lak et al 2015;. The 114 spermatozoa of nematodes of the genus Enoplus (order Enoplida) are amoeboid cells moving by crawling; as in many other nematodes they are subdivided into posterior main cell body and 116 anterior pseudopod filled with cytoskeleton fibers (Yushin and Malakhov 1994).…”

Analysis of major sperm proteins in two nematode species from two classes, Enoplus brevis (Enoplea, Enoplida) and Panagrellus redivivus (Chromadorea, Rhabditida), reveals similar localization, but less homology of protein sequences than expected for Nematoda phylum

“…The representatives of Enoplida have plesiomorphic features such as nuclear envelope in 105 spermatozoan nucleus, early indeterminate cleavage, late establishment of bilateral symmetry, late 106 separation of the germ line, absence of eutely (cell constancy), capability to limited regeneration, 107 absence of distal tip cell in gonads (Felix 2004;Joshi and Rothman 2005;Malakhov 1994Malakhov , 1998 also by latest molecular phylogenetic analyses of nematode relationships (Bik et The subclass Enoplia includes taxa where characteristic pseudopod bearing spermatozoa 113 also have been described (Justine 2002;Lak et al 2015;. The 114 spermatozoa of nematodes of the genus Enoplus (order Enoplida) are amoeboid cells moving by 115 crawling; as in many other nematodes they are subdivided into posterior main cell body and 116 anterior pseudopod filled with cytoskeleton fibers (Yushin and Malakhov 1994).…”