340
P. S. MEADOWS AND J. I. CAMPBELL
hierarchical relationship between different choices investigated by
Landenberger (1968) and we have attempted to show how this might
influence the distribution of animals under natural conditions. Finally
we have drawn a distinction between those habitats that differ only
quantitatively and those that differ in qualitative characters.
VII. L E ~ N X N O ,
ENVIRONMENTAL HISTORY, AND
PHYSIOLO~ICAL STATE
Habitat preferences may remain fixed throughout the life span of an
animal, or they may alter depending upon its physiological state, its
age, its previous experience and learning, or its past and present
environment (Lindroth, 1953). The evidence in favour of these
possibilities will now be examined.
There are scattered references to changes in the habitat
preferences of animals as they age (Crozier and Arey, 1918; Arey and
Crozier, 1919), and of course a good example of this is the progressive
change in general behaviour and responses to environmental stimuli of
marine and freshwater larvae as they approach metamorphosis (Thorson
1964; Lehmann, 1972; above, p. 302). Amongst freshwater animals,
newly liberated Asellus communis do not react to water currents (Allee,
1912), the young of Daphniapulex (De Geer) are more strongly photopositive and geonegative than are older individuals (Dice, 1914), and
young Gammarus pulex (L.) are more sensitive to pH changes (Costa,
1967) while ecological studies in the marine environment show a change
from gregarious to solitary behaviour amongst older individuals of the
lobsters Jasus lalandei (H. Milne-Edwards) and Panulirus interruptus
(Randall), and of the king crab Parulithodes camtschtica Tilesius
(Fielder, 1965; Lindberg, 1955; Powell and Nickerson, 1965). Behavioural changes of this sort can often be related to the changing distribution of animals under natural conditions. The young of freshwater
and marine planktonic species, for instance, usually occur higher in
the water column than do older individuals (Welch, 1935, p. 225;
Moore, 1958, p. 238), which can in part be explained by their stronger
photo-positive responses (Dice, 1914; Clarke, 1932; Lucas, 1936).
Changes in habitat selection related to physiological state have
occasionally been recorded and may not be unusual. Allee (1913a, b)
publishing the same data twice, observed a single male Asellus communis change its behaviour to currents as it approached and passed
through a moult : between moults it was usually rheopositive, while
it became less so over the period of the moult. But this is really no
more than one might expect for during the moult muscles must be
released from the old cuticle and become functional only when the new
P. S. MEADOWS AND J. I. CAMPBELL
hierarchical relationship between different choices investigated by
Landenberger (1968) and we have attempted to show how this might
influence the distribution of animals under natural conditions. Finally
we have drawn a distinction between those habitats that differ only
quantitatively and those that differ in qualitative characters.
VII. L E ~ N X N O ,
ENVIRONMENTAL HISTORY, AND
PHYSIOLO~ICAL STATE
Habitat preferences may remain fixed throughout the life span of an
animal, or they may alter depending upon its physiological state, its
age, its previous experience and learning, or its past and present
environment (Lindroth, 1953). The evidence in favour of these
possibilities will now be examined.
There are scattered references to changes in the habitat
preferences of animals as they age (Crozier and Arey, 1918; Arey and
Crozier, 1919), and of course a good example of this is the progressive
change in general behaviour and responses to environmental stimuli of
marine and freshwater larvae as they approach metamorphosis (Thorson
1964; Lehmann, 1972; above, p. 302). Amongst freshwater animals,
newly liberated Asellus communis do not react to water currents (Allee,
1912), the young of Daphniapulex (De Geer) are more strongly photopositive and geonegative than are older individuals (Dice, 1914), and
young Gammarus pulex (L.) are more sensitive to pH changes (Costa,
1967) while ecological studies in the marine environment show a change
from gregarious to solitary behaviour amongst older individuals of the
lobsters Jasus lalandei (H. Milne-Edwards) and Panulirus interruptus
(Randall), and of the king crab Parulithodes camtschtica Tilesius
(Fielder, 1965; Lindberg, 1955; Powell and Nickerson, 1965). Behavioural changes of this sort can often be related to the changing distribution of animals under natural conditions. The young of freshwater
and marine planktonic species, for instance, usually occur higher in
the water column than do older individuals (Welch, 1935, p. 225;
Moore, 1958, p. 238), which can in part be explained by their stronger
photo-positive responses (Dice, 1914; Clarke, 1932; Lucas, 1936).
Changes in habitat selection related to physiological state have
occasionally been recorded and may not be unusual. Allee (1913a, b)
publishing the same data twice, observed a single male Asellus communis change its behaviour to currents as it approached and passed
through a moult : between moults it was usually rheopositive, while
it became less so over the period of the moult. But this is really no
more than one might expect for during the moult muscles must be
released from the old cuticle and become functional only when the new