Ultrastructure of the male genital tract, spermatogenesis and spermatozoa of hattena cometis domrow (Acari: Gamasida: Ameroseiidae)

Abstract

The ameroseiid mite Hattena cometis has a male genital system that consists of an unpaired, u-shaped testis and paired deferent ducts leading into an unpaired accessory genital gland and ejaculatory duct. The genital opening is located anteriorly immediately in front of the sternal shield. Spermatogenesis is simple, probably due to the haploid nature of the male. Eight stages of spermatogenesis could be roughly distinguished. Mature spermatozoa as found in the deferent duct lumen are peculiar in having a bisected nucleus and numerous peripheral flat chambers, which were formed from indentations of the plasmalemma. In inseminated females, spermatozoa were observed in the syncytial tissue of the sperm access system and in the somatic cells of the ovary. These spermatozoa have achieved a new structure, i.e., an electron-dense plate dividing the cell into two unequal halves. The dense plate has an intricate substructure. Its function is unknown. These sperm cells are considered to represent capacitated spermatozoa. The peripheral chambers are reduced in number inside the female. Similar sperm cells, containing a dense plate, were seen in vacuoles within the epithelium of the deferent duct of one male. These cells are evidently under destruction, but before being completely dissolved had undergone a development leading beyond that of the mature sperm cells found in the deferent duct. Apparently, entering the cell of the deferent duct epithelium or the syncytium tissue triggers the production of the dense plate (or the capacitation process). Our observations are compared with results obtained from other anactinotrichid Acari, mainly Gamasida, and confirm and complete the interpretation of the correlated evolution of components of gamasid reproductive systems.

A revision of the family Ameroseiidae (Acari, Mesostigmata), with some data on Slovak fauna

“…— Seeman 1996: 193; Halliday 1997: 190; Faraji and Cornejo 2006: 291; Palma et al 2013a: 404; Palma et al 2013b: 918; Alberti et al 2013: 1010.…”

Sperm structure in Parasitidae mites (Parasitiformes: Mesostigmata: Gamasina)

“…The same sperm type but modified in details is also present in Dermanyssina (Alberti 1980;Alberti and Hänel 1986;Alberti and Di Palma 2007;Alberti et al 2013), a Parasitinarelated but most recently evolved Gamasida group (Klompen et al 2007). Differences in sperm morphology in both sister taxa could be the result of different modes of insemination in Parasitina (Parasitidae) sperm is packed into a spermatophore-like vesicle and transferred into the only, primary genital orifice (oviporus) of the female by means of modified male chelicerae functioning as gonopods.…”

“…Male chelicerae are more modified than in parasitid mites and show a prominent protrusion (spermatodactyl) of the movable digit, used for sperm insertion into the solenostome (Evans 1992;Alberti and Coons 1999;Di Palma et al 2006;Di Palma et al 2009). Both left and right solenostomes are connected with spermatheca via a complicated tubular inseminatory system (for further details and references concerning parasitid versus dermanyssid reproductive systems see Alberti and Coons 1999;Alberti et al 1999a,b;Di Palma and Alberti 2001;Alberti and Di Palma 2002;Di Palma et al 2012;Alberti et al 2013).…”