Extraordinary morphological changes in valve morphology during the ontogeny of several species of the Australian ostracod genus Bennelongia (Crustacea, Ostracoda)

Ostracods belonging to the genus Bennelongia differ much in valve morphology between adults and juveniles. Adult valves are asymmetrical, characterised by a beak-like feature in the anteroventral region of the left valve, and, with some notable exceptions, mostly have smooth or weaklyornamented valves. Juvenile specimens, on the other hand, have valves that are almost symmetrical, with no beak-like feature and are often heavily ornamented. We have examined the last 3 - 4 juvenile stages of 6 Bennelongia species from 5 different lineages, in order to decipher the types of external valve ornamentation and their recurrences during ontogeny and across lineages. It is clear that ornamentation is more prevalent at the early instar stages compared to the last 2 pre-adult stages, and especially when compared to the adult stage itself. We also examined the surprising presence of a calcified inner lamella with a prominent inner list in the pre-adult stages of Bennelongia species, that is usually absent in juveniles of other ostracods, thus questioning if heterochronic processes have provided an intermediate valve morphology between the simple (normal) cypridinid juvenile state and the heavily derived and modifi ed state of adult Bennelongia. We discuss the possible (speculative) functionality of the ornamentation in juveniles

Airborne dust traffic from Australia in modern and Late Quaternary times

A review is provided of first-documented occurrences of dust transport within Australia for the last century, but which later on were considerably improved as a result of access to satellite observations and extensive ground observations. This was followed by the use of the HYSPLIT tracking models that enabled people to determine the major sources of dust in Australia. As a result of several important studies, the Lake Eyre Basin in central Australia is now considered to be the main source of dust entrainment, although other regions do contribute to dust production.Many of the chemical analyses of the Australian dust samples were performed during the tenure of an Australian Research Council Discovery grant DP0772180

Intraspecific variation in recent populations of Globigerinoides ruber from the eastern Indian Ocean: evidence from test morphology and geochemistry

Abstrac

Germanium incorporation into sponge spicules: Development of a proxy for reconstructing inorganic germanium and silicon concentrations in seawater

Measurements of germanium (Ge) in deep-sea sponge skeletons are presented for sponges collected by dredge and for spicules isolated from a range of deep-sea sediment cores. Germanium to silicon (Si) ratios (Ge/Sisp) for sponge silica ranged between 0.07

Cyprideis torosa: a model organism for the Ostracoda?

In 1990 Danielopol et al.described the ostracod genus Cytherissa as 'the Drosophila of paleolimnology' in the sense of a model organism for their purposes at that time. In the intervening years Drosophila is no longer seen by biologists as the perfect test model and, for example, the nematode worm Caenorhabditis elegans is now viewed as preferable because 'the fly is much more complex than the worm and the anatomy of the nervous system has not reached the level of completeness achieved for the worm' (Brenner 2003, p. 278). For some years attention has focused on Cyprideis torosa (Jones, 1850), especially since the pioneering work of Rosenfeld & Vesper (1977) on sieve-pore variability in this species in relation to salinity, because torosa is a particularly widely distributed euryhaline living and fossil ostracod species. Cyprideis torosa is not only biogeographically widespread but occurs in a salinity range from freshwater to hypersaline, tolerates a wide range of temperature, oxygen and substrate conditions, and also has a large, well-calcified and easily preserved carapace. The species first occurs in sedimentary formations of early Pleistocene age but may be older. Therefore, it has the potential to be an ostracod model organism. This set of thematic papers is designed to summarize our current knowledge of one of the most important living ostracod species, its distribution, ecology, morphological response to environmental pressures, and molecular characterization, together with our understanding of its origins and value for palaeoenvironmental interpretation. The ultimate aim is to define potentially rewarding research targets using C. torosa as a model organism

Trace-element and stable-isotope composition of the Cyprideis torosa (Crustacea, Ostracoda) shell

Shells of Cyprideis, a widespread euryhaline ostracod, have commonly been used in geochemical investigations involving determinations of trace elements (especially magnesium and strontium) and isotopes (of oxygen, carbon and strontium). In this paper, we evaluate geochemical signatures in Cyprideis based on new and previously published data. Mg/Ca and Sr/Ca determinations of fossil shells that calcified in marine-type water have potential to reconstruct palaeotemperature and past water composition using empirical relationships derived from living ostracods recovered from in vitro cultures or natural settings. For shells that calcified in non-marine waters of contrasting composition, partitioning of trace metals from water into ostracod shells may differ, meaning that relationships developed for marine waters do not apply. However, variations in Mg/Ca and Sr/Ca in Cyprideis in continental settings may still provide valuable palaeohydrological information. Determinations of oxygen isotopes in Cyprideis shells are consistent with positive offsets from equilibrium, in common with other ostracod taxa: carbon-isotope values reflect the fact that Cyprideis is a detritivore. Oxygen-isotope analyses of Cyprideis shells from continental settings provide important palaeohydrological information. Strontium-isotope analyses of Cyprideis shells provide valuable records of mixing of marine and continental water in marginal-marine settings. Geochemical analyses of different morphotypes of Cyprideis lend support to suggestions that ecophenotypic variations are controlled by factors other than, or additional to, salinity

Combining the Mg/Ca of the ostracod Cyprideis torosa with its ontogenic development for reconstructing a 28 kyr temperature record for Lake Banyoles (NE Spain)

Cyprideis torosa is a ubiquitous ostracod found in fresh to hypersaline waters, and commonly in large numbers across the Mediterranean region. Single valves of 51 adult specimens of C. torosa were separated from carapaces that were collected from Lake Banyoles in NE Spain at a depth of 5 m. The Mg/Ca of the valves was compared with known temperatures necessary for successive instar valve calcification, the latter being based on a four-year ecological study of C. torosa collected at Dievengat in northern Belgium by Carlo Heip in 1968–72. Hence, we were able to link the Mg/Ca of fossil valves of C. torosa recovered for a 28 kyr sequence at La Draga, cored on the fringe of Lake Banyoles, with the ontogenic observations of Heip, and reconstruct mean summer temperatures as well as optimal calcification temperature for C. torosa. Principal findings are: (1) the Holocene registered the highest temperatures with also very broad fluctuations; (2) three cold phases are clearly identified at 26.7–23.2, 21.6–20.3 and 16.2–14.3 ka BP; and (3) a prolonged warm phase that lasted about two millennia commenced at 19.5 ka BP and was followed by a progressive temperature decline well over three millennia. Surprisingly the Last Glacial Maximum was not the coldest phase. We finally compare our results with sea-surface temperature (SST) reconstructions from cores from the western Mediterranean Sea. Our record from La Draga clearly matches events recorded in the Alboran Sea that display SST changes obtained from the UK'37 index. The Heinrich 1 and 2 events around 16 and 28 ka BP coincide with significant low temperature excursions at Banyoles, and palynological records in the marine cores which define semi-arid conditions on land match the low temperature record in our core.The coring and analyses were funded by the European Euromaar Project and the Belgian Services fédéraux des affaires scientifiques, techniques et culturelles (SSTC)

Last Interglacial coral record of enhanced insolation seasonality and seawater O enrichment in the Ryukyu Islands, northwest Pacific

金沢大学大学院自然科学系研究科We present a calibrated, high-resolution and 13C/12C record for a well-preserved Last Interglacial Porites sp. coral (U-Th age of 127 } 6 ka) from the sea-level high-stand terrace of Yonaguni Island, Japan. Seasonal variations in the ƒÂ18O and ƒÂ13C values for the fossil coral are greater than those observed in modern coral records from the same reef setting and appear to be driven by the enhanced insolation seasonality in the northern hemisphere during the Last Interglacial maximum. The 18O enrichment of 1.1ñ in the fossil coral compared to the modern analogue cannot be due entirely to a reduction in sea-surface temperature because corals in this region are already growing at their lower thermal limit. Instead, most of the 18O enrichment must be due to a change in the ƒÂ18O of the surface seawater, probably in response to enhanced evaporation of the ocean or a higher volume flux of the Kuroshio Current