344
P. 5. MEADOWS AND J. 1. OAMPBELL
t o show any progressive increase in its response to the abnormal host.
I n this sense, then, preimaginal olfactory conditioning is a phenotypic
effect. More recently, Jermy, Hanson and Dethier (1968) have
conducted analogous experiments. Both these examples are of
experiments concerned essentially with biological conditions-an
unusual host or food plant-but one can obtain the same effect using
highly artificial factors such as the odour of peppermint (Thorpe,
1939; Crombie, 1942) and cedarwood oil (Thorpe, 1938), and so, to
paraphrase Thorpe (1939) a new stimulus (odour) need not be related to
any particular act such as feeding, oviposition or settlement, in order to
produce a preference for itself. Research on this and related topics in
aquatic environments would be very welcome, and must surely have
relevance to the artificial culture of fish, molluscs and other commercial species. It might be possible, for instance, to induce plaice
larvae to accept species A as food when they normally eat species B,
so that they could be transplanted to sheltered inshore waters where
environmental factors were propitious for their survival but where
species A but not B were abundant. At a more academic level,
Wecker's (1963) investigations into the role of early experience in
habitat selection by the prairie deer mouse Peromyscus maniculatus
Bairdi suggest another approach. Amphipods or other invertebrates
having no larval stage could be hatched in the laboratory, reared in
isolation from their natural environment, and then offered choices that
field caught animals are known to respond to in a predictable way.
Similar experiments could be undertaken with invertebrates having a
larval phase although there might be practical difCiculties in rearing.
The responses of invertebrates to some environmental stimuli may
alter either in direction or in intensity as a result of changes in other
variables in their immediate environment (Russell, 1927, p. 248-251).
The most labile of these are responses to light, and although we have
already referred to some examples we will recapitulate in order to
present a complete account. Acartia tonsa Dana, Parmalanus parvus
(Claus) and Calanopia americana Dahl, three species of planktonic
marine copepod studied by Lewis (1959), are indifferent to light between
16°C and 32°C-the annual range in their natural habitat-but are
photonegative a t temperatures above 32°C and photopositive at
temperatures below 16 "C. Two species of planktonic marine Crustacea
studied by Lucas (1936) are increasingly photonegative in higher
concentrations of the diatom Nitzchia closterium Ehrenberg-one of
their usual foods. The water scorpion Ranatra fusca (Hemiptera)
(Holmes, 1905) and the semi-terrestrial isopod Ligia italica (Perttunen,
1961) become increasingly photopositive at higher temperatures, while
the reverse is true of Daphnia magna (Clarke, 19321, of the copepod
P. 5. MEADOWS AND J. 1. OAMPBELL
t o show any progressive increase in its response to the abnormal host.
I n this sense, then, preimaginal olfactory conditioning is a phenotypic
effect. More recently, Jermy, Hanson and Dethier (1968) have
conducted analogous experiments. Both these examples are of
experiments concerned essentially with biological conditions-an
unusual host or food plant-but one can obtain the same effect using
highly artificial factors such as the odour of peppermint (Thorpe,
1939; Crombie, 1942) and cedarwood oil (Thorpe, 1938), and so, to
paraphrase Thorpe (1939) a new stimulus (odour) need not be related to
any particular act such as feeding, oviposition or settlement, in order to
produce a preference for itself. Research on this and related topics in
aquatic environments would be very welcome, and must surely have
relevance to the artificial culture of fish, molluscs and other commercial species. It might be possible, for instance, to induce plaice
larvae to accept species A as food when they normally eat species B,
so that they could be transplanted to sheltered inshore waters where
environmental factors were propitious for their survival but where
species A but not B were abundant. At a more academic level,
Wecker's (1963) investigations into the role of early experience in
habitat selection by the prairie deer mouse Peromyscus maniculatus
Bairdi suggest another approach. Amphipods or other invertebrates
having no larval stage could be hatched in the laboratory, reared in
isolation from their natural environment, and then offered choices that
field caught animals are known to respond to in a predictable way.
Similar experiments could be undertaken with invertebrates having a
larval phase although there might be practical difCiculties in rearing.
The responses of invertebrates to some environmental stimuli may
alter either in direction or in intensity as a result of changes in other
variables in their immediate environment (Russell, 1927, p. 248-251).
The most labile of these are responses to light, and although we have
already referred to some examples we will recapitulate in order to
present a complete account. Acartia tonsa Dana, Parmalanus parvus
(Claus) and Calanopia americana Dahl, three species of planktonic
marine copepod studied by Lewis (1959), are indifferent to light between
16°C and 32°C-the annual range in their natural habitat-but are
photonegative a t temperatures above 32°C and photopositive at
temperatures below 16 "C. Two species of planktonic marine Crustacea
studied by Lucas (1936) are increasingly photonegative in higher
concentrations of the diatom Nitzchia closterium Ehrenberg-one of
their usual foods. The water scorpion Ranatra fusca (Hemiptera)
(Holmes, 1905) and the semi-terrestrial isopod Ligia italica (Perttunen,
1961) become increasingly photopositive at higher temperatures, while
the reverse is true of Daphnia magna (Clarke, 19321, of the copepod