title: Membrane specializations in the spermatozoa of collembolan insects.
abstract: Here we describe the membrane specializations displayed by "dormant" collembolan spermatozoa, during the period when they are temporarily stored in the male genital ducts before being laid in the soil as a spermatophore, which is then picked up by the female. In the male deferent ducts and in the spermatophore, these "dormant" spermatozoa are rolled up into flattened ellipsoids that surround a central extracellular cavity filled with dense material. In this condition, the plasma membranes that surround the central extracellular cavity contain two types of membrane specializations. One consists of parallel rows of intramembrane particles on the E-face of the membrane facing the outside of the spermatozoa. The other consists of small orthogonal plaques of intramembrane particles intermingled with these rows. These plaques associate with the P-face of the membrane, and are therefore likely to represent preferential sites for receiving and transmuting environmental signals, especially whatever signal(s) induce these spermatozoa to transform into filiform and motile cells upon reaching the female spermatheca.
authors.affiliation: Dipartimento di Biologia Evolutiva, Università di Siena, Via Aldo Moro 2, 53100 Siena, Italy. dallai@unisi.it
authors.forename: Romano
authors.initials: R
authors.lastname: Dallai
authors.forename: Pietro Paolo
authors.initials: PP
authors.lastname: Fanciulli
authors.forename: Francesco
authors.initials: F
authors.lastname: Frati
authors.forename: Eugenio
authors.initials: E
authors.lastname: Paccagnini
authors.forename: Pietro
authors.initials: P
authors.lastname: Lupetti
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000648:ultrastructure*; D048429:Cell Size; D003593:Cytoplasm; D005109:Extracellular Matrix; D005260:Female; D005614:Freeze Fracturing; D007313:Insecta; D008297:Male; D008855:Microscopy, Electron, Scanning; D013094:Spermatozoa / Q000166:cytology* / Q000648:ultrastructure