257
response at the cellular level; a physiological
response of the whole animal, such as a modifi cation of the circulatory system, or a behavioural
response, such as modifi ed feeding habits.
At the cellular level, the metabolic responses
of animals to anoxia are similar to those of bacteria. However, vertebrates tend to have less ability
to adapt to anaerobic conditions than invertebrates. The vertebrates and many invertebrates
are limited to anaerobic respiration to glycolysis
or to the pentose monophosphate pathway whose
dominant end product is lactate. Further, the
broad range of animal feeding responses closely
refl ects their habitats. Adaptations of feeding
appendages, for example, seem to be more
closely related to feeding habits than to taxonomic relationships.
Further, examples of positive interactions
amongst wetland species point to an extremely
interesting line of research which have hitherto
been given less importance. However, research in
this line may lead to signifi cant new insights into
the complexity of mutualistic adaptations and
energy dynamics in wetland ecosystems.
Summary
1. In many ways, the wetland environment is
physiologically harsh. The major stresses are
anoxia and the wide range of salinity and
water fl uctuations which are characteristic of
an environment which is neither terrestrial nor
aquatic. Adaptations to this environment have
a cost of energy. It is either because an organism’s cells operate less effi ciently (conformer)
or because the organisation expends energy to
protect its cells from the external stress
(regulator).
2. It could be said that all organisms have almost
similar kind of adaptations at the cellular
level. However, unicellular organisms may
display more novelty. Adaptations of these
organisms include the ability to respire
anaerobically, to detoxify end products of
anaerobic metabolism, to use reduced organic
compounds in the sediments as energy sources
and to use mineral elements in the sediment as
alternative electron acceptors when oxygen
is unavailable.
3. On the other hand, a wider range of responses
are available to multicellular plants and animals. It is because of the fl exibility afforded
by the development of organ systems and
division of labour within their body, mobility
and complex life history strategies.
4. It is not surprising that those plants and animals which are regularly found in wetlands
have mostly evolved functional mechanisms
to deal with these stresses. Adaptations could
be broadly classifi ed into two categories,
namely, (a) those which enable the organisms
to tolerate stress and (b) those which enable it
to regulate stress. ‘Tolerators’ have functional
modifi cations which enable it to survive and
often to function effi ciently in the presence of
stress. Conversely, ‘regulators’ actively avoid
stress or modify it to minimise its effects.
Suggested Readings
Grosse W, Frye J, Lattermann S (1992) The effect of pressurized gas transport on nutrient uptake during
hypoxia of alder roots. Bot Acta 105:223–226
Roberts JKM (1988) Cytoplasmic acidosis and fl ooding
in crop plants. In: Hook DD, McKee WH Jr, Smith
HK, Gregory J, Burrell VG, DeVoe MR, Sojka RE,
Gilbert S, Banks R, Stolzy LG, Brooks C, Matthews
TD, Shear TH (eds) The ecology and management of
wetlands, vol 1. Timber Press, London
Smits AJM, Kleukers RMJC, Kok CJ, van der Velde AG
(1990a) Alcohol dehydrogenase isozymes in the roots
of some nymphaeid and isoetid macrophytes: adaptations to hypoxic sediment conditions? Aquat Bot
38:19–27
Smits AJM, Laan P, Their RH, van der Velde AG (1990b)
Root aerenchyma, oxygen leakage patterns and alcohol fermentation ability of the roots of some nymphaeid and isoetid macrophytes in relation to the sediment
type of their habitat. Aquat Bot 38:3–17
Tiner RW (1998) In search of Swampland: a wetland
sourcebook and fi eld guide. Rutgers University Press,
New Brunswick, pp 264
Suggested Readings
response at the cellular level; a physiological
response of the whole animal, such as a modifi cation of the circulatory system, or a behavioural
response, such as modifi ed feeding habits.
At the cellular level, the metabolic responses
of animals to anoxia are similar to those of bacteria. However, vertebrates tend to have less ability
to adapt to anaerobic conditions than invertebrates. The vertebrates and many invertebrates
are limited to anaerobic respiration to glycolysis
or to the pentose monophosphate pathway whose
dominant end product is lactate. Further, the
broad range of animal feeding responses closely
refl ects their habitats. Adaptations of feeding
appendages, for example, seem to be more
closely related to feeding habits than to taxonomic relationships.
Further, examples of positive interactions
amongst wetland species point to an extremely
interesting line of research which have hitherto
been given less importance. However, research in
this line may lead to signifi cant new insights into
the complexity of mutualistic adaptations and
energy dynamics in wetland ecosystems.
Summary
1. In many ways, the wetland environment is
physiologically harsh. The major stresses are
anoxia and the wide range of salinity and
water fl uctuations which are characteristic of
an environment which is neither terrestrial nor
aquatic. Adaptations to this environment have
a cost of energy. It is either because an organism’s cells operate less effi ciently (conformer)
or because the organisation expends energy to
protect its cells from the external stress
(regulator).
2. It could be said that all organisms have almost
similar kind of adaptations at the cellular
level. However, unicellular organisms may
display more novelty. Adaptations of these
organisms include the ability to respire
anaerobically, to detoxify end products of
anaerobic metabolism, to use reduced organic
compounds in the sediments as energy sources
and to use mineral elements in the sediment as
alternative electron acceptors when oxygen
is unavailable.
3. On the other hand, a wider range of responses
are available to multicellular plants and animals. It is because of the fl exibility afforded
by the development of organ systems and
division of labour within their body, mobility
and complex life history strategies.
4. It is not surprising that those plants and animals which are regularly found in wetlands
have mostly evolved functional mechanisms
to deal with these stresses. Adaptations could
be broadly classifi ed into two categories,
namely, (a) those which enable the organisms
to tolerate stress and (b) those which enable it
to regulate stress. ‘Tolerators’ have functional
modifi cations which enable it to survive and
often to function effi ciently in the presence of
stress. Conversely, ‘regulators’ actively avoid
stress or modify it to minimise its effects.
Suggested Readings
Grosse W, Frye J, Lattermann S (1992) The effect of pressurized gas transport on nutrient uptake during
hypoxia of alder roots. Bot Acta 105:223–226
Roberts JKM (1988) Cytoplasmic acidosis and fl ooding
in crop plants. In: Hook DD, McKee WH Jr, Smith
HK, Gregory J, Burrell VG, DeVoe MR, Sojka RE,
Gilbert S, Banks R, Stolzy LG, Brooks C, Matthews
TD, Shear TH (eds) The ecology and management of
wetlands, vol 1. Timber Press, London
Smits AJM, Kleukers RMJC, Kok CJ, van der Velde AG
(1990a) Alcohol dehydrogenase isozymes in the roots
of some nymphaeid and isoetid macrophytes: adaptations to hypoxic sediment conditions? Aquat Bot
38:19–27
Smits AJM, Laan P, Their RH, van der Velde AG (1990b)
Root aerenchyma, oxygen leakage patterns and alcohol fermentation ability of the roots of some nymphaeid and isoetid macrophytes in relation to the sediment
type of their habitat. Aquat Bot 38:3–17
Tiner RW (1998) In search of Swampland: a wetland
sourcebook and fi eld guide. Rutgers University Press,
New Brunswick, pp 264
Suggested Readings