Subcellular preservation in giant ostracod sperm from an early Miocene cave deposit in Australia.
Cypridoidean ostracods are one of a number of animal taxa that reproduce with giant sperm, up to 10 000 µm in length, but they are the only group to have aflagellate, filamentous giant sperm. The evolution and function of this highly unusual feature of reproduction with giant sperm are currently unknown. The hypothesis of long-term evolutionary persistence of this kind of reproduction has never been tested. We here report giant sperm discovered by propagation phase contrast X-ray synchrotron micro- and nanotomography, preserved in five Miocene ostracod specimens from Queensland, Australia. The specimens belong to the species Heterocypris collaris Matzke-Karasz et al. 2013 (one male and three females) and Newnhamia mckenziana Matzke-Karasz et al. 2013 (one female). The sperm are not only the oldest petrified gametes on record, but include three-dimensional subcellular preservation. We provide direct evidence that giant sperm have been a feature of this taxon for at least 16 Myr and provide an additional criterion (i.e. longevity) to test hypotheses relating to origin and function of giant sperm in the animal kingdom. We further argue that the highly resistant, most probably chitinous coats of giant ostracod sperm may play a role in delaying decay processes, favouring early mineralization of soft tissue.
Department of Earth and Environmental Sciences, Palaeontology and Geobiology, Ludwig-Maximilian-University and GeoBio-Center, Richard-Wagner-Strasse 10, 80333 Munich, Germany r.matzke@lrz.uni-muenchen.de.
Renate
R
Matzke-Karasz
School of Civil Engineering and Physical Sciences, La Trobe University, PO Box 199, Bendigo, Victoria 3552, Australia.
John V
JV
Neil
Lake Biwa Museum, Oroshimo 1091, Kusatsu, Shiga 525-0001, Japan.
Robin J
RJ
Smith
Department of Zoology, Faculty of Science, Charles University, Viničná 7, 12844 Praha, Czech Republic.
Radka
R
Symonová
Department of Zoology, Faculty of Science, Charles University, Viničná 7, 12844 Praha, Czech Republic.
Libor
L
Mořkovský
School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, New South Wales 2052, Australia.
Michael
M
Archer
School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, New South Wales 2052, Australia.
Suzanne J
SJ
Hand
European Synchrotron Radiation Facility (ESRF), 38043 Grenoble, France.
Peter
P
Cloetens
European Synchrotron Radiation Facility (ESRF), 38043 Grenoble, France.
Paul
P
Tafforeau
D000818:Animals; D001315:Australia; D005075:Biological Evolution; D059552:Caves; D003445:Crustacea / Q000648:ultrastructure*; D005580:Fossils; D008297:Male; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D011793:Queensland; D013094:Spermatozoa / Q000648:ultrastructure; D055114:X-Ray Microtomography
Cypridoidea; bat guano; fossil gametes; soft body preservation; synchrotron radiation tomography