Subcellular preservation in giant ostracod sperm from an early Miocene cave deposit in Australia

Abstract

Cypridoidean ostracods are one of a number of animal taxa that reproduce with giant sperm, up to 10 000 mm 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 MatzkeKarasz 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.

Nuclei and nucleoli in embryo-like fossils from the Ediacaran Weng’an Biota

“…The identification of nuclei within the Weng'an Biota, along Z. Yin et al Precambrian Research 301 (2017) 145-151 with plausible reports from Phanerozoic deposits (Bomfleur et al, 2012(Bomfleur et al, , 2014Matzke-Karasz et al, 2014;Ozerov et al, 2006), indicates that nuclei can be preserved in the fossil record, contrary to general expectation. Their preservation as external molds, in some instances in association with probable nucleoli, suggests that the nucleus was less susceptible to mineral replication than the surrounding cytoplasm.…”

Mammalian lineages and the biostratigraphy and biochronology of Cenozoic faunas from the Riversleigh World Heritage Area, Australia

“…; Matzke‐Karasz et al . ), taxa from Riversleigh deposits can be identified more reliably. In addition to being already defined in previous work by suites of taxa characterizing each Faunal Zone interval, the Riversleigh biostratigraphy produced in this analysis demonstrates gradual change in the representation of a number of different taxa with overlapping ranges, which arguably would be expected from a series of samples taken throughout a continuous time period, even if that period also contains time horizons corresponding to major faunal turnover events.…”

Structural specialities, curiosities and record-breaking features of crustacean reproduction

“…Ostracods of the suborder Cypridocopina are famed for having some of the longest sperm in the animal kingdom as discussed above. Matzke-Karasz et al (2014) have recently discovered fossil giant sperm by X-ray synchrotron microtomography of 16 million-year-old Heterocypris collaris and Newnhamia mckenziana from Queensland, Australia. Giant sperm bundles were found in the seminal vesicles and vasa deferentia of a male (Fig.…”