HABITAT SELECTION BY AQUATIC INVERTEBRATES
341
one has hardened. It is surprising therefore that similar behaviour has
not been recorded for other Crustacea. Prehaps less expected are the
changes in behaviour shown by starved invertebrates. A number of
terrestrial invertebrates alter their habitat preferences as they are
starved, but the only records of similar behaviour in aquatic
invertebrates are those of Gee (1913) and Herter (1929) on freshwater
leeches, of Hazlett (1966) on the marine hermit crab Calcinus tibicelz,
of Jones and Naylor (1970) on the light responses of the intertidal
isopod Eurydice pulchra Leach, and of Brun (1972) on the feeding of
Luidia ciliaris. Although difficult to interpret ecologically, Crozier and
Libby’s (1925) study on the physiology of feeding and starvation in the
terrestrial slug Limax maximus L. may be relevant to future investigations on aquatic invertebrates. Limax maximus is usually photonegative, but after a meal of cooked potato becomes indifferent to
light. The effect is mimicked by injection of M/10 sucrose into the
body fluids or into the stomach via the mouth. Other foods including
raw potato have no influence. Crozier and Libby inferred that the
injected sugar was acting in the same way as the sugar released from
the digestion of cooked starch.
A number of marine invertebrates show clearly defined learning
abilities which may influence habitat selection (Thorpe, 1956 ; Wells,
1965). The brittle star Ophiothrix fragilis (Abildgaard) can be taught to
turn back on encountering a smooth/rough substrate boundary or a
wavy/smooth glass boundary (Diebschlag, 1938) and the starfish
Pisaster giganteus can learn to associate a light stimulus with food
(Landenberger, 1966). The spiny lobster Panulirus argus (Latreille)
learns with a light stimulus to walk down a ramp to an aquarium
containing sea water (Schtine, 1961) and individuals of a related species
Palinurus vulgaris Latreille learn to eat the hermit crab Eupaguruus
bernhardus (L.)-a food they never usually eat-when other food
is scarce (Wilson, 1949). The recognition and association of certain
types of substrate with, say, predators (Ophiothrix), the searching for
food in shady areas of the bottom where food has previously been
encountered (Pisaster), and the ability to learn new sources of food
(Palinurus), will clearly be advantageous to these species in the sea
and will influence their selection of habitats. Hazlett and Provenzano
(1965) have analysed the role played by learning in the development of
intraspecific aggression and ahell selection by young hermit crabs.
They concluded that although individuals execute the appropriate
movements (or behavioural units) the first time they meet another
individual or attempt to enter a gastropod shell they need a number of
encounters before learning to integrate these units into a coordinated
341
one has hardened. It is surprising therefore that similar behaviour has
not been recorded for other Crustacea. Prehaps less expected are the
changes in behaviour shown by starved invertebrates. A number of
terrestrial invertebrates alter their habitat preferences as they are
starved, but the only records of similar behaviour in aquatic
invertebrates are those of Gee (1913) and Herter (1929) on freshwater
leeches, of Hazlett (1966) on the marine hermit crab Calcinus tibicelz,
of Jones and Naylor (1970) on the light responses of the intertidal
isopod Eurydice pulchra Leach, and of Brun (1972) on the feeding of
Luidia ciliaris. Although difficult to interpret ecologically, Crozier and
Libby’s (1925) study on the physiology of feeding and starvation in the
terrestrial slug Limax maximus L. may be relevant to future investigations on aquatic invertebrates. Limax maximus is usually photonegative, but after a meal of cooked potato becomes indifferent to
light. The effect is mimicked by injection of M/10 sucrose into the
body fluids or into the stomach via the mouth. Other foods including
raw potato have no influence. Crozier and Libby inferred that the
injected sugar was acting in the same way as the sugar released from
the digestion of cooked starch.
A number of marine invertebrates show clearly defined learning
abilities which may influence habitat selection (Thorpe, 1956 ; Wells,
1965). The brittle star Ophiothrix fragilis (Abildgaard) can be taught to
turn back on encountering a smooth/rough substrate boundary or a
wavy/smooth glass boundary (Diebschlag, 1938) and the starfish
Pisaster giganteus can learn to associate a light stimulus with food
(Landenberger, 1966). The spiny lobster Panulirus argus (Latreille)
learns with a light stimulus to walk down a ramp to an aquarium
containing sea water (Schtine, 1961) and individuals of a related species
Palinurus vulgaris Latreille learn to eat the hermit crab Eupaguruus
bernhardus (L.)-a food they never usually eat-when other food
is scarce (Wilson, 1949). The recognition and association of certain
types of substrate with, say, predators (Ophiothrix), the searching for
food in shady areas of the bottom where food has previously been
encountered (Pisaster), and the ability to learn new sources of food
(Palinurus), will clearly be advantageous to these species in the sea
and will influence their selection of habitats. Hazlett and Provenzano
(1965) have analysed the role played by learning in the development of
intraspecific aggression and ahell selection by young hermit crabs.
They concluded that although individuals execute the appropriate
movements (or behavioural units) the first time they meet another
individual or attempt to enter a gastropod shell they need a number of
encounters before learning to integrate these units into a coordinated