Size in relation to salinity in fossil and recent euryhaline ostracods

Abstract

(Text-figs. 1-4) FOSSIL OSTRACODSDuring a recent study of the ostracod faunas of the Portland and Purbeck Beds of the Aylesbury district (a full account of which is in preparation) a euryhaline ostracod fauna was reported. The ostracods in question are Pabanella polita Martin and Pabanella ansata (Jones). A study was made of their vertical distribution at three localities: (a) at the Bugle Pit, Hartwell, It was found possible to subdivide the beds at these localities into a number of facies characterized in the main by ostracod faunas. At the base are (i) the massive cream coloured limestones of the Portlandian with marine ostracods and referred to as the Portland facies. Above these are (ii) laminated marls and limestones with a mixture of marine and euryhaline ostracods referred to as the marine Purbeck facies, (iii) laminated marls and limestones with euryhaline ostracods referred to as the brackish Purbeck facies, and (iv), marls and limestones becoming sandy upwards with freshwater-oligohaline ostracods referred to as the freshwater Purbeck facies. These facies demonstrate a gradual change from marine Portland conditions to the more or less freshwater beds of the Purbeck.Pabanella was found in facies (i), (ii), and (iii), and it was noticed that there seemed to be a slight difference in size between specimens in each of the three facies.All the specimens of Pabanella were measured from the bed in each facies with the largest number of specimens; the results for each locality are shown in Figs. 1 and 2. Histograms are drawn for the lengths of the ostracods from the various beds at each locality. Inspection shows that the range oflength of the instars overlap. To calculate the separate statistics for the instars represented, the results were plotted on arithmetic probability paper. A normal distribution plotted on this paper produces a straight line, and if a bimodal or polymodal distribution is made up from a series of normal distributions then a curve will be produced which is the resultant of two or more straight lines. Using a method described by Harding (1949) the position of these

Eucypris fontana(Graf, 1931) (Crustacea, Ostracoda) in permanent environments of Patagonia Argentina: a geometric morphometric approach

“…8 and 9). These results, negative correlation between valve length and solute concentrations, are agree with the relation described to E. virens, Cyprideis torosa (Jones, 1850), Mytilocypris henricae (Chapman, 1966), L. inopinata and some euryhaline ostracods (Barker, 1963;Martens, 1985;Yin et al, 1999;Fernandes Martins et al, 2009;Van der Meeren et al, 2010).…”

Salinity-driven size variability inCyprideis torosa(Ostracoda, Crustacea)

“…Reconstructing past salinity levels (and variability) plays a fundamental role when studying the evolution of marginal-marine and estuarine ecosystems, particularly where isolated water bodies such as lakes and lagoons are subjected to climatically driven salinity change. Barker (1963) discussed the possible relationship between ostracod carapace size and salinity based on a study from the Tamar Estuary in SW England; subsequent analyses of those data suggest that the failure to identify adults and juveniles correctly had largely led to this erroneous conclusion, with the smaller juveniles having been transported post mortem.…”

A minute ostracod (Crustacea: Cytheromatidae) from the Miocene Solimões Formation (western Amazonia, Brazil): evidence for marine incursions?

“…Aquatic displacement by rivers (downstream) and by tidal currents (up- and downstream) appears unlikely for the euhaline, sublittoral Pellucistoma (Barker 1963 ). Conversely, ocean currents are regarded as a prominent means of passive ostracod transport (e.g.…”