Abstract
This contribution reviews the ultrastructure of ribbon-type sperm in 14 genera of both subfamilies (7 in Pergamasinae and 7 in Parasitinae) of the Parasitidae family (Parasitiformes: Mesostigmata: Gamasina); in total 27 species were considered, of which sperm ultrastructure was studied for the first time in 17 species and 9 genera. We found a wide range of sperm dimensions and nucleus lengths, but basic external and internal structures were substantially constant across genera. Spermatozoa are rod- or club-shaped cells with an elongated nucleus. The chromatin granules are focused in the middle zone of the nucleus. The cytoplasm around the nucleus and in the adjoining postnuclear region is filled with inclusion bodies with striated content (striated inclusion bodies, sIBs), whereas in the distant postnuclear region they are replaced by larger granular inclusion bodies (gIBs) usually containing a striated core surrounded by granular material. Mitochondria are distributed mostly subplasmalemmally in the nuclear region and between gIBs in the postnuclear region of the sperm cell. The most variable feature of the spermatozoa is the number of compound longitudinal ribbons of plasmalemmal origin alternating with subplasmalemmal cisterns: 9 (Leptogamasus anoxygenellus) to 21 (Pergamasus barbarus) in Pergamasinae and 5 (Parasitus berlesei and Paracarpais loricatus) to 30 (Paracarpais lunulata) in Parasitinae. In general, ribbons are electron-dense in the nuclear region but more lucent in the postnuclear region. The variation in sperm structure was not reflected in the taxonomic arrangement of genera and subfamilies within Parasitidae, but it must be emphasized that the taxonomy of Parasitidae is still awaiting a comprehensive modern revision.
Highlights
Parasitid mites, despite their name, are predominantly free-living and predatory inhabitants of humid litter and decaying matter, feeding on immature stages and eggs of microhexapods, as well as small soil oligochaets and nematodes (Micherdzinski 1969; Tichomirov 1977; Hyatt 1980; Karg 1993; Blackman 1997; Szafranek et al 2013)
We considered sperm structure in 27 species (Table 1) of parasitid mites from both subfamilies, Pergamasinae (16 species from 7 genera) and Parasitinae (11 species from 7 genera)
Similar vacuoles can be observed at the nuclear periphery in Anidogamasus teutonicus which contains many small electron-lucent spots making nuclear material inhomogeneous (Figure 7); such heterogeneity is present in Heteroparasitus tirolensis (Figures 3A-B), Cornigamasus lunaris (Figures 12AC), and Paracarpais kraepelini (Figures 14A-B)
Summary
Despite their name, are predominantly free-living and predatory inhabitants of humid litter and decaying matter, feeding on immature stages and eggs of microhexapods, as well as small soil oligochaets and nematodes (Micherdzinski 1969; Tichomirov 1977; Hyatt 1980; Karg 1993; Blackman 1997; Szafranek et al 2013). The male produces a sac-like spermatophore from the genital opening located at the anterior margin of the sternum and by manipulating the chelicerae it transfers the spermatophore into the female genital opening located in a mid-ventral position. This mode of insemination was termed tocospermy by Athias-Henriot and later specified as neotocospermy by Alberti (Athias-Henriot 1968; Alberti 2002).
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