» Putrefaction & Colonization
of vascular plants,
including freshwater macrophytes, generally proceeds in three biological
stages: initial rapid loss of the matter due to leaching, microorganism
decomposition and macroinvertebrate processing, plus mechanical fragmentation of
the litter from the outset (for review, see Webster & Benfield, 1986). Smock
& Stoneburner (1980) offer an useful scheme to use visual cues to estimate
four stages of leave decomposition: furled, green (without external signs of
decomposition), partially decomposed yellowing leaves and decomposed brown ones.
context, the most important parameter is decomposition rates of freshwater
freshwater Hydrocharitaceae (Elodea, Hydrocharis and Valisneria),
Nymphaeacea (Nuphar lutea, other
pond-lilies) and Najadaceae (Najas flexis,
numerous Potamogeton spp.) belong to the
group with the highest decomposition rates. Decomposition rates for these
species can 2-3 times (Webster
& Benfield, 1986) exceed the corresponding values for tree leaves (for
example, k = 0,035 day−1 for conditioned leaves of alder, Alnus glutinosa, in Germany: Hieber
& Gessner, 2002). In Podostemaceae (such as Podostenum ceratophyllum) and Typhaceae (Typha latifolia, other cattails), decomposition rates are less
achieving the minimum (less than 0,002 day−1) in Juncaceae (such as Juncus effusus).
rates of freshwater macrophytes is strongly dependent on site, water
temparature and other factors (e.g., Brock et al., 1982; Rodgers & Breen,
particular, Hill & Webster (1992) have studied decomposition rates of hornleaf
riverweed Podostemum ceratophyllum, Canadian
waterweed Elodea canadensis, curly
pondweed Potamogeton crispus, American water-willow
Justicia americana (Acanthaceae) and broadleaf cattail Typha
latifolia in the New River, Appalachia. Decomposition
rates for these species are 0,037; 0,026; 0,021; 0,016 and 0,007 day−1,
respectively. For comparison, litter decay of submerged common rush, Juncus effusus, mentioned above is extremely slow (0.001 day−1), with only the
23% weight loss after 268 days of natural decomposition (Kuehn at al., 2000;
freshwater wetlands in Alabama).
litter processing by microinvertebrates in freshwater ecosystems is considered
in numerous papers (fer review, see Anderson & Sedell, 1979; Cummins &
example, Smock & Stoneburner (1980) have studied the response of
macroinvertebrates to the progressive decomposition of American lotus, Nelumbo lutea, using four stages of
leave decomposition described above. It is shown that macroinvertebrate
densities increase significantly with the onset and progressive senescence of leaves,
as reflected by decreasing chlorophyll concentrations. In total, macroinvertebrates
of 17 families are observed with the maximum density 12093 individuals m-2
leaves surface, in the fourth stage of leave degradation. The chironomid Polypedilum nymphaeorum and three
species of Naididae (Oligochaeta) (such
as Pristina leidyi and other) exhibit
positive responses to presumably increasing levels of food as leave decomposition
is progressed. According to Smock & Stoneburner (1980), P. nymphaeorum larvae probably switch
from feeding on periphyton to utilization of decomposing plant tissue and
associated microbial decomposers once Nelumbo
leaves began to decompose.
al. (1983) have studied in an olfactometer the behavioural responses of the freshwater
pulmonate snail, Biomphalaria glabrata, to homogenates of various aquatic
macrophytes. Among the eleven species studied, three are indifferent, two
contain weak arrestants and three induce strong repellent effects. Only two
species, European marshwort, Apium nodiflorum
(Apiaceae), and lesser duckweed, Lemna paucicostata, induce
significant attractant and arrestant effects comparable to those obtained with the
terrestrial lettuce, Lactuca sativa, as controls. To the point, among
species of the same family ivy leaved duckweed, L. trisulca, is less attractive for snails than L. paucicostata.
It is shown also that homogenate of decaying L. paucicostata (beginning from the 15 % of
decomposition) is much more strong attractant and arrestant than homogenate
made of fresh plant. Sterry et al. (1983) believe that the attractiveness of
decaying duckweed for B. glabrata is mainly determined by short chain
carboxylic acids, in combination with some other compounds.
categories of carboxylic and amino acids have been found to act as attractants
and arrestants to B. glabrata (Thomas et al., 1983). B.
glabrata respond more strongly and consistently to short chain
unsubstituted monocarboxylic acids, propanoate and butan
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Generally, Gammarus pulex and other amphipods are
rather omnivorous than strictly detritivorous freshwater crustaceans (for
rivew, see MacNeil et al., 1977).
particular, G. pulex is most attracted to the aufwuchs on the conditioned discs
made of poplar (Populus canadensis)
leaves and less to the leaves themselves (De Lange et al., 2005). According to data obtained by these authors, fungi
and bacteria within the conditioned leaves are more important than green algae Scenedesmus obliquus.
isopod Asellus aquaticus trigger active feeding behaviour in G. pulex as potential predators (Bengtsson, 1982). It is shown that
15 individuals of A. aquaticus placed
in the 1000 ml bottle actively release in the water amino acid exudates. Within
the first 2 hours of incubation, arginine (8022 ng per liter), lysine,
tryptophan and histidine are most abundant. Wisenden
et al. (1999) have also shown that G.
minus display feeding responses to odor of squashed sympatric isopod Lirceus fontinalis.
Wudkevich et al. (1997) have exposed Gammarus lacustris to chemical stimuli from injured conspecifics and
to chemical stimuli from two types of natural predators: dragonfly larvae, Aeshna eremita, and pike, Esox lucius. An exposure to these three
stimuli causes G. lacustris to reduce
significantly the level of their activity suggesting the presence of an alarm pheromone in the body tissues of G. lacustris. Similarly, chemical
stimuli from sculpin, Cottus gobio, and brown trout, Salmo trutta,
induce short decreasing locomotory activity of G. pulex, whereas
an odor of freshwater signal crayfish, Pacifastacus leniusculus, is
indifferent (Åbjörnsson et al., 2000). There are no significant differences
in activity of G. pulex exposed to water scented by sculpin or
trout, these responses are also independent of the previous diets (G. pulex
or isopod A. aquaticus)
of predatory fish.
et al. (2008) have examined the tendency to aggregate in G. pulex in the absence and presence of predatory fish
odor. In conditioned with
sticklebacks Gasterosteus aculeatus water, amphipods significantly prefer to stay close to conspecifics.
K., Dahl J., Nyström P., Brönmark C. 2000. Influence of predator and dietary chemical cues
on the behaviour and shredding efficiency of Gammarus pulex. Aquatic Ecology 34, 379-387
G. 1982. Energetic costs of amino acid exudation in the interaction between the
predator Gammarus pulex L. and the prey Asellus aquaticus L. Journal
of Chemical Ecology 8, 1271-1281
De Lange H.J.,
Lürling M., Van Den Borne B., Peeters E.T.H.M. 2005. Attraction of the amphipod Gammarus pulex to water-borne cues of food. Hydrobiologia 544, 19-25
H., Thűnken T., Baldauf S.A.,
Bakker T.C.M., Frommen J.G. 2008. Fish odour triggers conspecific attraction behaviour in an aquatic invertebrate. Biology Letters 4,
MacNeil C., Dick J.T., Elwood R.W. 1977. The trophic ecology
of freshwater Gammarus spp.
(Crustacea: Amphipoda): problems and perspectives concerning the functional
feeding group concept. Biological Reviews of the Cambridge Philosophical Society 72, 349-364
B.D., Cline A., Sparkes T.C. 1999. Survival benefit to antipredator behavior in the
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