title: Removal of extracellular coat from giant sperm in female receptacle induces sperm motility in Mytilocypris mytiloides (Cyprididae, Ostracoda, Crustacea).
abstract: Previous studies of cypridoidean ostracods have noted that (1) their giant spermatozoa are immotile inside the male, (2) these spermatozoa are motile in the female seminal receptacle and (3) these receptacles are often filled with empty sperm coats. Such findings have led previous authors to hypothesize that sperm must shed their coats in the female receptacle to become motile. We present light and electron microscopy results and video recordings of mating experiments with virgin specimens of Mytilocypris mytiloides. We show that the empty sperm coats frequently found in the female receptacles are not the result of sperm molting but are the resistant inner coats of exhausted sperm not used for egg fertilization. In contrast, we show that an outer granular coating material is successively removed from the sperm while resident inside the female receptacles before first oviposition occurs. During this period, previously immotile sperm gain motility, showing strong movement shortly before first oviposition takes place. By correlation of these phenomena, we suggest that dissolution of the outer coat material is required for motility to develop.
authors.affiliation: Department of Earth and Environmental Sciences, Palaeontology, Ludwig-Maximilians-Universität München & GeoBio-Center LMU, 80333, Munich, Germany. r.matzke@lrz.uni-muenchen.de.
authors.forename: Renate
authors.initials: R
authors.lastname: Matzke-Karasz
authors.affiliation: Lake Biwa Museum, 1091 Oroshimo, Kusatsu, Shiga, 525-0001, Japan.
authors.forename: Robin J
authors.initials: RJ
authors.lastname: Smith
authors.affiliation: Department of Biology, Ludwig-Maximilians-Universität München & GeoBio-Center LMU, 82152, Munich, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Heß
mesh_terms: D000818:Animals; D003445:Crustacea / Q000166:cytology / Q000502:physiology* / Q000648:ultrastructure; D005260:Female; D007091:Image Processing, Computer-Assisted; D008297:Male; D013081:Sperm Motility; D013094:Spermatozoa / Q000502:physiology* / Q000648:ultrastructure
keywords: Sperm coat; Sperm degradation; Sperm movement; Spiral canal; Zenker organ