HABITAT SELECTION BY AQUATIC INVERTEBRATES
359
have been discussed. It is clear that these preferences and
responses will affect the distribution of animals under natural
conditions. I n no case has the response of a predator species
to its prey, and of a prey species to its predator, been
investigated for the same pair of species.
(i) Some intertidal invertebrates migrate from and return to a
recognizable site on the shore. The basis of these homing
migrations is not fully understood.
(j) There are very few studies on the oviposition preferences of
aquatic invertebrates.
5. Although there is in total a large body of work on the habitat
selection of aquatic invertebrates in relation to their non-biological
and to their biological environment, there are very few comprehensive
studies which present a complete picture of the habitat preferences
of a species, and few investigations in which laboratory experiments
have been correlated both with field distribution and with experiments
conducted under field conditions.
6. Most aquatic invertebrates choose habitats that are well within
their lethal limits. The exceptions, where species appear to prefer
habitats that will eventually kill them, are not easy to explain.
7. Very little is known of any changes in physiology associated
with animals living in favourable as compared to less favourable
habitats. The gastropod mollusc Haliotis discus hunnui, one of the few
speci.es studied in any detail, grows fastest and is more likely to reach
sexual maturity when fed on its preferred species of seaweed food.
8. A number of unexpected factors may play a part in habitat
selection and can be listed as follows: indirect clues, slope of a
preference, lack of preference, lack of suitable habitat, coarse and fine
selection, three dimensional behaviour, qualitative and quantitative
differences between choices, and hierarchies of choice.
9. The habitat that an animal selects may depend on its age, its
physiological state, its learning and previous experience, and its past
and present environment.
10. The behaviour of some species shows a great deaI of individual
variation. This may take the following forms: (a) each individual may
have a characteristic response to a particular stimulus but Werent
individuals may show Werent levels of response; ( b ) one or two
individuals in a population may behave atypically ; (c) individuals may
belong to two or more behavioural types present in the population in
approximately equal proportions. It is not clear whether these variations
have a genetic basis.
359
have been discussed. It is clear that these preferences and
responses will affect the distribution of animals under natural
conditions. I n no case has the response of a predator species
to its prey, and of a prey species to its predator, been
investigated for the same pair of species.
(i) Some intertidal invertebrates migrate from and return to a
recognizable site on the shore. The basis of these homing
migrations is not fully understood.
(j) There are very few studies on the oviposition preferences of
aquatic invertebrates.
5. Although there is in total a large body of work on the habitat
selection of aquatic invertebrates in relation to their non-biological
and to their biological environment, there are very few comprehensive
studies which present a complete picture of the habitat preferences
of a species, and few investigations in which laboratory experiments
have been correlated both with field distribution and with experiments
conducted under field conditions.
6. Most aquatic invertebrates choose habitats that are well within
their lethal limits. The exceptions, where species appear to prefer
habitats that will eventually kill them, are not easy to explain.
7. Very little is known of any changes in physiology associated
with animals living in favourable as compared to less favourable
habitats. The gastropod mollusc Haliotis discus hunnui, one of the few
speci.es studied in any detail, grows fastest and is more likely to reach
sexual maturity when fed on its preferred species of seaweed food.
8. A number of unexpected factors may play a part in habitat
selection and can be listed as follows: indirect clues, slope of a
preference, lack of preference, lack of suitable habitat, coarse and fine
selection, three dimensional behaviour, qualitative and quantitative
differences between choices, and hierarchies of choice.
9. The habitat that an animal selects may depend on its age, its
physiological state, its learning and previous experience, and its past
and present environment.
10. The behaviour of some species shows a great deaI of individual
variation. This may take the following forms: (a) each individual may
have a characteristic response to a particular stimulus but Werent
individuals may show Werent levels of response; ( b ) one or two
individuals in a population may behave atypically ; (c) individuals may
belong to two or more behavioural types present in the population in
approximately equal proportions. It is not clear whether these variations
have a genetic basis.