HABITAT SELECTION BY AQUATIC INVERTEBRATES
343
does influence an animal’s behaviour, there are many ways in which it
might interact with habitat selection to produce an observed pattern
of distribution in the field. Very little is known of these interactions.
There are, however, some species whose preferences are clearly not
affected by their previous experience. The intertidal snail Littorina
obtwata prefers to eat Bucus spiralis L. and B. vesiculosus rather than
F. serratus L. or Pelvetia canaliculata (L.) Dene et Thur. even when they
are fed for 10 days beforehand on the latter two species of seaweed
(Bakker, 1959). There are other examples. The particle size preferences
of Corophium volutator are not affected by the particle size of the
sediment they have previously lived in (Meadows, 1967), the microbial food preferences of the marine copepod Calanus heligolandicus Claus
and of the larvae of the gastropod Nassarius obsoletus are not influenced
by their previous diet (Mullin, 1963; Paulson and Scheltema, 1968),
and the temperature preference of Podon polyphemoides Leuckart
(Cladocera) does not appear to be influenced by their previous
temperature regime (Ackefors and Rosen, 1970). It is quite reasonable
to suggest that these results might have been different if the time during
which the animals were conditioned before the experiments had been
longer, but putting aside this criticism one may ask whether there are
any factors common to those preferences that are influenced by
previous experience as compared to those that are not. A detailed
reading of the papers so far published has convinced us that there are
no such factors.
There are a number of studies on terrestrial invertebrates in
particular on insects that give an important insight into the way in
which previous experience can influence habitat selection. These w i l l
almost certainly be relevant to future studies on aquatic invertebrates
and so are considered here. Thorpe and Jones (1937) persuaded
females of the endoparasitic hymenopteran Nemeritis canescens
Gravenhorst, whose usual host is the moth Ephestia kuhniella Zeller,
to oviposit in an unnatural host, the moth Meliphora grisella Fabricius.
The resultant larvae developed normally, suffered no great mortality,
and gave rise to adults whose morphology and colour was normal,
and so Thorpe and Jones felt able to test the adults’ host
preferences in a Y tube olfactometer. The preferences of adults reared
in M . grisella were significantly different from normal adults.
Although still preferring the smell of E . kuhniella to the smell of M .
grisella they did so to a less marked degree, and in separate experiments
preferred the smell of M . grisella to clean air-a distinction that normal
adults could not make. The authors went on to rear N . canescens on
the abnormal host M . grisella over a number of generations but failed
343
does influence an animal’s behaviour, there are many ways in which it
might interact with habitat selection to produce an observed pattern
of distribution in the field. Very little is known of these interactions.
There are, however, some species whose preferences are clearly not
affected by their previous experience. The intertidal snail Littorina
obtwata prefers to eat Bucus spiralis L. and B. vesiculosus rather than
F. serratus L. or Pelvetia canaliculata (L.) Dene et Thur. even when they
are fed for 10 days beforehand on the latter two species of seaweed
(Bakker, 1959). There are other examples. The particle size preferences
of Corophium volutator are not affected by the particle size of the
sediment they have previously lived in (Meadows, 1967), the microbial food preferences of the marine copepod Calanus heligolandicus Claus
and of the larvae of the gastropod Nassarius obsoletus are not influenced
by their previous diet (Mullin, 1963; Paulson and Scheltema, 1968),
and the temperature preference of Podon polyphemoides Leuckart
(Cladocera) does not appear to be influenced by their previous
temperature regime (Ackefors and Rosen, 1970). It is quite reasonable
to suggest that these results might have been different if the time during
which the animals were conditioned before the experiments had been
longer, but putting aside this criticism one may ask whether there are
any factors common to those preferences that are influenced by
previous experience as compared to those that are not. A detailed
reading of the papers so far published has convinced us that there are
no such factors.
There are a number of studies on terrestrial invertebrates in
particular on insects that give an important insight into the way in
which previous experience can influence habitat selection. These w i l l
almost certainly be relevant to future studies on aquatic invertebrates
and so are considered here. Thorpe and Jones (1937) persuaded
females of the endoparasitic hymenopteran Nemeritis canescens
Gravenhorst, whose usual host is the moth Ephestia kuhniella Zeller,
to oviposit in an unnatural host, the moth Meliphora grisella Fabricius.
The resultant larvae developed normally, suffered no great mortality,
and gave rise to adults whose morphology and colour was normal,
and so Thorpe and Jones felt able to test the adults’ host
preferences in a Y tube olfactometer. The preferences of adults reared
in M . grisella were significantly different from normal adults.
Although still preferring the smell of E . kuhniella to the smell of M .
grisella they did so to a less marked degree, and in separate experiments
preferred the smell of M . grisella to clean air-a distinction that normal
adults could not make. The authors went on to rear N . canescens on
the abnormal host M . grisella over a number of generations but failed