The Adaptations of the Foraminifera and Ostracoda to Fresh Water Colonisation

Abstract

In marine environments Ostracoda and Foraminifera have been very successful invaders. During the Phanerozoic they colonised the majority of shallow, marginal to deep water, fully marine habitats. Both groups had developed physiological adaptations which pre-adapted them to the invasion of new marine habitats. They adopted a broad range of feeding strategies and reproduction modes. The production of resting stages and brood care may also have contributed to them being efficient invaders. They are also both highly tolerant to variations in salinity. The first invasions of non-marine habitats by ostracods appear to have taken place at the turn of the Devonian and Carboniferous. It is estimated that there had been between 9 and 12 independent invasions of fresh waters by the ostracods. In contrast Foraminifera are typically marine organisms, and only a few species of agglutinated and organic-walled Foraminifera are to be found in brackish and freshwater environments. Agglutinated species build their test using ambient components but are not commonly regarded as calcifying organisms. An impact of salinity on foraminiferal calcification has been observed in several studies. It seems that Foraminifera are incapable of constructing a fully calcified test in low salinity regimes; they use sea water not only as a source of ions to construct shell, but also as a biomineralisation solution. Thus, the success of ostracods in invading freshwater habitats can be attributed to their development of a more effective mechanism of calcification in low mineralisation waters. The core question of this study is to examine possible causes for the differences in success between the two taxa.

The functional significance of the spinose keel structure of benthic foraminifera: inferences from <i>Miliolina cristata</i> Millett, 1898 (Miliolida) from northeast Romania

“…A number of papers discuss the relationship between foraminiferal distribution within lithological successions and their response to their environmental changes (Atkinson, 1971;Murray, 1973Murray, , 1991Murray, , 2006Boltovskoy, 1963;Boltovskoy et al, 1991;Haynes, 1981;Iglikowska and Pawlowska, 2015). Even then, some foraminiferal assemblage changes as well as some specific morphological changes recorded in the fossil material are very difficult to interpret and are not always thoroughly discussed.…”

“…Murray, 1963Murray, , 1973Brasier, 1982;Corliss and Fois, 1990;Boltovskoy et al, 1991;Yanko et al, 1994Yanko et al, , 1998Polovodova and Schönfeld, 2008;Buosi et al, 2010;Mellis and Covelli, 2013;Iglikowska and Pawlowska, 2015). Recent studies based on molecular data show significant variability within distinct molecular groups of foraminifera (Pawlowski and Holzman, 2002;Pawlowski et al, 2003;Longet and Pawlowski, 2007) and prove that two different morphotypes can correspond to the same species in spite of their morphological differences (Pillet et al, 2012(Pillet et al, , 2013.…”

The foraminiferal record in the Holocene evolution of the Mecklenburg Bay (south-western Baltic Sea)

“…reduced oxygenation of the near-bottom water layer and pore water and/ or reduced salinity, for calcareous forms to exist (e.g. Iglikowska & Pawłowska 2015). Leckie and Olson (2003) found a marked increase in the abundance of calcareous taxa to accompany the transition from brackish marginal habitats to open neritic conditions.…”

A reassessment of the origin and distribution of the subterranean genus Pseudolimnocythere Klie, 1938 (Ostracoda, Loxoconchidae), with description of two new species from Italy

“…It is well documented that stygobionts (i.e., taxa occurring exclusively in groundwater during their entire life cycle) can have a double origin (Coineau and Boutin 1992): limnicoid stygobionts derive from epigean freshwater ancestors, while thalassoid stygobionts derive directly from marine ancestors. In the last case, pre-adapted marine species (Iglikowska and Pawłowska 2015), living in the interstitial or in fissured rocky habitats, could have crossed the salinity boundary via an intermediate mixo-to oligohaline coastal zone, and eventually have migrated in inland groundwaters (Boutin and Coineau 1990;Noteboom 1991). It has been suggested that between 9 and 12 independent invasions of freshwaters by marine ostracods have occurred, the first possibly in the early Carboniferous (Iglikowska 2014;Iglikowska and Pawłowska 2015).…”

“…In the last case, pre-adapted marine species (Iglikowska and Pawłowska 2015), living in the interstitial or in fissured rocky habitats, could have crossed the salinity boundary via an intermediate mixo-to oligohaline coastal zone, and eventually have migrated in inland groundwaters (Boutin and Coineau 1990;Noteboom 1991). It has been suggested that between 9 and 12 independent invasions of freshwaters by marine ostracods have occurred, the first possibly in the early Carboniferous (Iglikowska 2014;Iglikowska and Pawłowska 2015).…”