36
Y. J. WELLS
ments along the areas of suitable habitat available to them-an
assessment particularly difficult to make for a marine animal. A number
of decapods (including Panulirus, see e.g. Hernnkind and Cummings,
1964) are known to make or suspected of making seasonal migrations
(Bainbridge, 1961) and this greatly increases the complexity of the
problem.
Many crustaceans orient themselves with respect to the sun,
either directly or from the polarization of sunlight in the sky (Waterman,
1961) ; one species, Talitrus saltator (Montagu) is dso known to orient
itself with respect to the moon (Papi, 1960). There is some evidence
that appropriate responses in relation to these orienting stimuli are
learned. Thus Pardi (1960) working with Talitrus, Talorchestia and
Orchestia, showed that populations taken from Merent beaches all
escaped from dishes in the directions of “ their ” seas when threatened
with desiccation. Young animals, reared in the laboratory, showed a
tendency to escape in the direction appropriate to the population
from which they were reared-that is, the general escape direction is
genetically determined for each population (cf. spiders, Papi and
Tongiorgi, 1963). But the orientation of laboratory reared animals was
inaccurate compared with that of “ wild ” controls, which implies that
the response becomes refined by experience.
Schbne (1965) has reported similar experiments with the mangrove
crab Goniopsis, in situations where the appropriate escape direction for
individuals varies within a matter of yards along a highly dissected
swamp coastline. Laboratory studies (Schbne, 1963) show that the
animals can orient themselves with respect to polarized light and
compensate for the time of day. The orientation must be learned,
since Goniopsis has pelagic larvae.
A further laboratory experiment by Daumer et al. (1963) has
shown that the shore crab Ocypode ceratophthulma (Pallas) can learn
the direction of an artificial “ burrow,” and that it does this in relation
to the polarization pattern of the sky. In the circular arena shown in
Fig. 21a, crabs, having once established a “ home ” in one of the tubes,
frequently ventured out to the centre hole, where there was food. The
return home was always direct. In a series of test trials the arena was
rotated 45’ when the crabs were in the middle. The direction of their
subsequent runs for home was recorded ; the results are shown in Fig.
21b. Evidently the three animals had all learned the direction of
‘I home ” and the cue used was the sky, since rotation of the whole of
the rest of the environment did not alter the compass-direction of the
home runs. Further evidence was produced to show that the relevant
cue was polarization and not brightness patterns in the sky.
Y. J. WELLS
ments along the areas of suitable habitat available to them-an
assessment particularly difficult to make for a marine animal. A number
of decapods (including Panulirus, see e.g. Hernnkind and Cummings,
1964) are known to make or suspected of making seasonal migrations
(Bainbridge, 1961) and this greatly increases the complexity of the
problem.
Many crustaceans orient themselves with respect to the sun,
either directly or from the polarization of sunlight in the sky (Waterman,
1961) ; one species, Talitrus saltator (Montagu) is dso known to orient
itself with respect to the moon (Papi, 1960). There is some evidence
that appropriate responses in relation to these orienting stimuli are
learned. Thus Pardi (1960) working with Talitrus, Talorchestia and
Orchestia, showed that populations taken from Merent beaches all
escaped from dishes in the directions of “ their ” seas when threatened
with desiccation. Young animals, reared in the laboratory, showed a
tendency to escape in the direction appropriate to the population
from which they were reared-that is, the general escape direction is
genetically determined for each population (cf. spiders, Papi and
Tongiorgi, 1963). But the orientation of laboratory reared animals was
inaccurate compared with that of “ wild ” controls, which implies that
the response becomes refined by experience.
Schbne (1965) has reported similar experiments with the mangrove
crab Goniopsis, in situations where the appropriate escape direction for
individuals varies within a matter of yards along a highly dissected
swamp coastline. Laboratory studies (Schbne, 1963) show that the
animals can orient themselves with respect to polarized light and
compensate for the time of day. The orientation must be learned,
since Goniopsis has pelagic larvae.
A further laboratory experiment by Daumer et al. (1963) has
shown that the shore crab Ocypode ceratophthulma (Pallas) can learn
the direction of an artificial “ burrow,” and that it does this in relation
to the polarization pattern of the sky. In the circular arena shown in
Fig. 21a, crabs, having once established a “ home ” in one of the tubes,
frequently ventured out to the centre hole, where there was food. The
return home was always direct. In a series of test trials the arena was
rotated 45’ when the crabs were in the middle. The direction of their
subsequent runs for home was recorded ; the results are shown in Fig.
21b. Evidently the three animals had all learned the direction of
‘I home ” and the cue used was the sky, since rotation of the whole of
the rest of the environment did not alter the compass-direction of the
home runs. Further evidence was produced to show that the relevant
cue was polarization and not brightness patterns in the sky.