et al. (2012) observed that species capable of denitrification possess large vacuoles
containing sea water with a high concentration of nitrate. Recent studies revealed
that the gene for nitrate reduction could be localised to the symbiont or to the
allogromiid. Foraminifera produced N 2 from NO 3
− and rapidly consumed intracellular nitrate during both oxic and anoxic incubations, thus denitrifying species
should be regarded as facultative anaerobes (Kuhnt et al. 2013), although it was
observed that presence of oxygen partially inhibited or delayed the onset of nitrate
respiration (Bernhard et al. 2012). In oxygen-depleted environments anaerobic
metabolic pathways are required. In the Proterozoic or Palaeozoic, during oxygen
crises, the ability to denitrify could have imparted a major ecological advantage and
contributed to the success of early foraminiferan lineages.
The rate of colonisation depends in part upon the geochemical characteristics of
the new habitat. Substrates which were previously anoxic have completely different
physical and chemical properties compared to well-oxygenated environment. Alve
(1995) recorded that for opportunistic species of Foraminifera it took more than
1 year to colonise sediment which had experienced 5 years of anoxia, however,
invasion by less efficient species may take several years (Alve 1999). It seems that
in marine environment Foraminifera are able to invade more efficiently than
macrofaunal invertebrates. Kaminski et al. (1988) observed for agglutinated
Foraminifera that 9 months may be sufficient time to recover to background levels
of diversity and abundance after severe disturbance (during which time, the macrofauna did not recover).
All studied physiological adaptations developed by Foraminifera and Ostracoda
are collated and summarized in Table 1.
4 Calcification
Both groups, Ostracoda and Foraminifera, seem to be successful invaders of new
environments. 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. Foraminifera and Ostracoda have the ability to construct saturated with
calcium carbonate exoskeleton. How do organisms with a high demand for calcium
compounds cope with the low availability of this element in freshwater habitat?
The shell of ostracods is important for protection, respiration, metabolism and
osmoregulation (Okada 1982; Keyser 1990; Aladin 1993). Sohn (1958) reported the
following constituents for the shell of Chlamydotheca unispinosa: 82.7 % calcium
carbonate, 12.8 % protein, 2.2 % chitin and 1.9 % trace elements as K, Mg, Na, Si,
Sr, Al and Ba. Sohn (1958) also noticed that the CaCO 3 content is variable
depending on species, and ranges from 80 to 90 %. The cuticle of the shell is
mineralised with low magnesium calcium carbonate in the form of calcite, but never
contains aragonite. The highest content of calcium carbonate is found in the shell of
marine Cytheroidea, whereas in freshwater forms, as Cypria ophtalmica, the
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A. Iglikowska and J. Pawłowska
containing sea water with a high concentration of nitrate. Recent studies revealed
that the gene for nitrate reduction could be localised to the symbiont or to the
allogromiid. Foraminifera produced N 2 from NO 3
− and rapidly consumed intracellular nitrate during both oxic and anoxic incubations, thus denitrifying species
should be regarded as facultative anaerobes (Kuhnt et al. 2013), although it was
observed that presence of oxygen partially inhibited or delayed the onset of nitrate
respiration (Bernhard et al. 2012). In oxygen-depleted environments anaerobic
metabolic pathways are required. In the Proterozoic or Palaeozoic, during oxygen
crises, the ability to denitrify could have imparted a major ecological advantage and
contributed to the success of early foraminiferan lineages.
The rate of colonisation depends in part upon the geochemical characteristics of
the new habitat. Substrates which were previously anoxic have completely different
physical and chemical properties compared to well-oxygenated environment. Alve
(1995) recorded that for opportunistic species of Foraminifera it took more than
1 year to colonise sediment which had experienced 5 years of anoxia, however,
invasion by less efficient species may take several years (Alve 1999). It seems that
in marine environment Foraminifera are able to invade more efficiently than
macrofaunal invertebrates. Kaminski et al. (1988) observed for agglutinated
Foraminifera that 9 months may be sufficient time to recover to background levels
of diversity and abundance after severe disturbance (during which time, the macrofauna did not recover).
All studied physiological adaptations developed by Foraminifera and Ostracoda
are collated and summarized in Table 1.
4 Calcification
Both groups, Ostracoda and Foraminifera, seem to be successful invaders of new
environments. 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. Foraminifera and Ostracoda have the ability to construct saturated with
calcium carbonate exoskeleton. How do organisms with a high demand for calcium
compounds cope with the low availability of this element in freshwater habitat?
The shell of ostracods is important for protection, respiration, metabolism and
osmoregulation (Okada 1982; Keyser 1990; Aladin 1993). Sohn (1958) reported the
following constituents for the shell of Chlamydotheca unispinosa: 82.7 % calcium
carbonate, 12.8 % protein, 2.2 % chitin and 1.9 % trace elements as K, Mg, Na, Si,
Sr, Al and Ba. Sohn (1958) also noticed that the CaCO 3 content is variable
depending on species, and ranges from 80 to 90 %. The cuticle of the shell is
mineralised with low magnesium calcium carbonate in the form of calcite, but never
contains aragonite. The highest content of calcium carbonate is found in the shell of
marine Cytheroidea, whereas in freshwater forms, as Cypria ophtalmica, the
102
A. Iglikowska and J. Pawłowska