334
P. 8. MEADOWS AND J. I. OA?dPBELL
ment of sexual maturity were all highest on the preferred seaweed
species Unduria pinnatim Sur. More recently, Carefoot (1967, 1970)
has analysed the relationships between algal food preferences, growth,
and maturity in various species of the nudibranch Aplysia, while
Bovbjerg (1968) has studied a similar problem in the feeding of the
freshwater gastropod Limnaea stugnalis Say. Limnaea eats both animal
and plant material but can live on either. However it grows fastest and
shows its characteristic reproductive behaviour when given a mixture
of the two rather than either separately. Investigation of the feeding
habits and associated growth in other aquatic invertebrates would be
profitable, and a great deal could be learnt from comparisons with the
terrestrial environment. The feeding habits and physiology of aphids
feeding on plants for instance, have been studied in great depth
(Mittler and Dadd, 1966).
It is evident, therefore, that there are many studies in which both
preferences and lethal limits have been investigated but only a few in
which the two types of experiment have been conducted in enough
detail to allow of a direct comparison. It is to be expected that most
preferences will fall well within lethal limits ; however there are instances
where this is not so, and these we have discussed a t some length. We
have also seen that little is known of the physiological changes that
might occur as animals select their habitats and so in this respect the
careful work of Sakai (1962) on the food preferences and growth of
Haliotis discus hannai and of Carefoot (1967, 1970) on Aplysia represent
an important advance and suggest how similar problems might be
approached experimentally.
VI. MECHANISMS OF HABITAT SELECTION
The behavioural mechanisms by which animals select their habitats,
light reactions, gravity responses, gregariousness and so on, have been
covered already. However there are a number of additional topics
which might be considered most conveniently at this point. They
include behaviour in choice experiments, coarse and h e selection,
indirect clues to habitats, noise in choice experiments, hierarchies of
preferences, and the slope of a preference, amongst others.
Fraenkel and Gunn (1940) have categorized the behaviour of
animals in two dimensional environments, and the behaviour of invertebrates on flat surfaces in water and on land can usually be accommodated to their scheme. But many invertebrates in aquatic environments move in three dimensions; planktonic animals are obvious
examples, while some benthic invertebrates move about on the surface
of sediments, burrow into sediments, and swim in the body of the
P. 8. MEADOWS AND J. I. OA?dPBELL
ment of sexual maturity were all highest on the preferred seaweed
species Unduria pinnatim Sur. More recently, Carefoot (1967, 1970)
has analysed the relationships between algal food preferences, growth,
and maturity in various species of the nudibranch Aplysia, while
Bovbjerg (1968) has studied a similar problem in the feeding of the
freshwater gastropod Limnaea stugnalis Say. Limnaea eats both animal
and plant material but can live on either. However it grows fastest and
shows its characteristic reproductive behaviour when given a mixture
of the two rather than either separately. Investigation of the feeding
habits and associated growth in other aquatic invertebrates would be
profitable, and a great deal could be learnt from comparisons with the
terrestrial environment. The feeding habits and physiology of aphids
feeding on plants for instance, have been studied in great depth
(Mittler and Dadd, 1966).
It is evident, therefore, that there are many studies in which both
preferences and lethal limits have been investigated but only a few in
which the two types of experiment have been conducted in enough
detail to allow of a direct comparison. It is to be expected that most
preferences will fall well within lethal limits ; however there are instances
where this is not so, and these we have discussed a t some length. We
have also seen that little is known of the physiological changes that
might occur as animals select their habitats and so in this respect the
careful work of Sakai (1962) on the food preferences and growth of
Haliotis discus hannai and of Carefoot (1967, 1970) on Aplysia represent
an important advance and suggest how similar problems might be
approached experimentally.
VI. MECHANISMS OF HABITAT SELECTION
The behavioural mechanisms by which animals select their habitats,
light reactions, gravity responses, gregariousness and so on, have been
covered already. However there are a number of additional topics
which might be considered most conveniently at this point. They
include behaviour in choice experiments, coarse and h e selection,
indirect clues to habitats, noise in choice experiments, hierarchies of
preferences, and the slope of a preference, amongst others.
Fraenkel and Gunn (1940) have categorized the behaviour of
animals in two dimensional environments, and the behaviour of invertebrates on flat surfaces in water and on land can usually be accommodated to their scheme. But many invertebrates in aquatic environments move in three dimensions; planktonic animals are obvious
examples, while some benthic invertebrates move about on the surface
of sediments, burrow into sediments, and swim in the body of the