HABITAT SELECTION BY AQUATIC INVERTEBRATES
279
It is clear that few animals would choose this sort of environment unless
they made some attempt to ameliorate it. Many animals that live in
anaerobic mud bring oxygenated water down to them from the surface
-bivalves use their siphons for instance and others such as Arenicola
marina and Corophium volutator ventilate their burrows with water.
These examples can hardly be regarded as habitat selection, for the
animals are locally modifying their environment to suit their needs.
There appears to be only one instance of a species actually preferring
a deoxygenated habitat under experimental conditions. Corophiurn
votutator prefers both deoxygenated sediments (Meadows, 1964a) and
deoxygenated water (Gamble, 1971), and its respiratory physiology
would clearly be of interest. In other species, animals always prefer the
more oxygenated habitat offered (Corophium arenarium Crawford
(Meadows, 1964a ; Gamble, 1971) ; Gammarus oceanicus Segerstrsle
(Cook and Boyd, 1965); D q h n i a magna, (Ganning and Wulff, 1966) ;
Gammarus pulex (Costa, 1967)). Cook and Boyd’s experiments, however,
should be treated with some caution because they were conducted with
only five male animals, and also because under natural conditions on
the shore the species is found in the anaerobic conditions that it avoids
in the laboratory.
Many intertidal animals must have behaviour patterns that can be
classified as thigmotactic but we know little of them (Russell-Hunter,
1949), and the same is true of responses to the micro-topography of
rock surfaces, mud surfaces and so on, except that the latter are
important to homing limpets (see section on homing, p. 329).
An animal is almost certainly assessing information from a number
of environmental variables as it selects a suitable habitat on the shore,
and occasionally workers have taken account of this (Evans, 1951;
Crisp, 1969). Perhaps the most complete picture for any species com es
from studies on the intertidal amphipod Corophium volutator by Gamble,
McLusky, Meadow8 and Morgan. Corophium lives in U-shaped tubes
on intertidal mud flats often in or at the mouths of estuaries. It is
found in salinities above 2%,, breeds at above 7 ~ 5 % ~
(McLusky, 1968)
and will survive in the laboratory at above 2%, (McLusky, 1967). In
preference experiments it chooses 10-30%, sea water (McLusky, 1970).
McLusky (1968) suggests that where the salinity is above about 6%,,
abundance and distribution are controlled by the nature of the substrate,
and his suggestion is confirmed by the results of laboratory experiments.
C. volutator prefers fine to coarse grained sands and lives slightly longer
in them (Meadows, 1964c; Meadows, 1967); it avoids very shallow
sediments (Meadows, 1964b), is influenced by the nature of the microbial
fauna in the sediment (Meadows, 1964a), prefers deoxygenated sediments and sea water (Meadows, 1964c; Gamble, 1971) and is photo-
279
It is clear that few animals would choose this sort of environment unless
they made some attempt to ameliorate it. Many animals that live in
anaerobic mud bring oxygenated water down to them from the surface
-bivalves use their siphons for instance and others such as Arenicola
marina and Corophium volutator ventilate their burrows with water.
These examples can hardly be regarded as habitat selection, for the
animals are locally modifying their environment to suit their needs.
There appears to be only one instance of a species actually preferring
a deoxygenated habitat under experimental conditions. Corophiurn
votutator prefers both deoxygenated sediments (Meadows, 1964a) and
deoxygenated water (Gamble, 1971), and its respiratory physiology
would clearly be of interest. In other species, animals always prefer the
more oxygenated habitat offered (Corophium arenarium Crawford
(Meadows, 1964a ; Gamble, 1971) ; Gammarus oceanicus Segerstrsle
(Cook and Boyd, 1965); D q h n i a magna, (Ganning and Wulff, 1966) ;
Gammarus pulex (Costa, 1967)). Cook and Boyd’s experiments, however,
should be treated with some caution because they were conducted with
only five male animals, and also because under natural conditions on
the shore the species is found in the anaerobic conditions that it avoids
in the laboratory.
Many intertidal animals must have behaviour patterns that can be
classified as thigmotactic but we know little of them (Russell-Hunter,
1949), and the same is true of responses to the micro-topography of
rock surfaces, mud surfaces and so on, except that the latter are
important to homing limpets (see section on homing, p. 329).
An animal is almost certainly assessing information from a number
of environmental variables as it selects a suitable habitat on the shore,
and occasionally workers have taken account of this (Evans, 1951;
Crisp, 1969). Perhaps the most complete picture for any species com es
from studies on the intertidal amphipod Corophium volutator by Gamble,
McLusky, Meadow8 and Morgan. Corophium lives in U-shaped tubes
on intertidal mud flats often in or at the mouths of estuaries. It is
found in salinities above 2%,, breeds at above 7 ~ 5 % ~
(McLusky, 1968)
and will survive in the laboratory at above 2%, (McLusky, 1967). In
preference experiments it chooses 10-30%, sea water (McLusky, 1970).
McLusky (1968) suggests that where the salinity is above about 6%,,
abundance and distribution are controlled by the nature of the substrate,
and his suggestion is confirmed by the results of laboratory experiments.
C. volutator prefers fine to coarse grained sands and lives slightly longer
in them (Meadows, 1964c; Meadows, 1967); it avoids very shallow
sediments (Meadows, 1964b), is influenced by the nature of the microbial
fauna in the sediment (Meadows, 1964a), prefers deoxygenated sediments and sea water (Meadows, 1964c; Gamble, 1971) and is photo-