304
P. 5. MEADOWS AND J. I. CAMPBELL
should be made to Williams’ papers and to more recent ones by
Hubschman (1970) and Straughan (1972).
B. Gregariousness
Many animals appear to recognize other individuals of their own
species by moving towards or staying near them.
Gregarious
behaviour, as here defined, will lead t o aggregations of a species both
in uniform and non-uniform local environments but will be more
obvious in the former. A great deal is known of the gregarious
behaviour of marine invertebrates, and we will summarize this fist
before considering freshwater animals. Field and laboratory experiments show that the larvae of a wide range of sedentary marine species
settle preferentially near adults of their own species. Data are available
for the following species : (a) Coelenterates, Tubularia larynx Ellis and
Solander (Pyefinch and Downing, 1949). (b) Polyzoa, Watersipora
cucullata (Busk) (Wisely, 1958b). (c) Polychaetes, Mercierella enigmatica
Fauvel (Straughan, 1972), Polydora ligni Webster (Blake, 1969))
Subellaria alveolata (L.) (Wilson, 1968), 8. spinulosa Leuckart (Wilson,
1970b), Spirorbis borealis Daudin, S. pagenstecheri Quatrefages (KnightJones, 1951,1953a). (d) Gastropodmolluscs, Rissoa splendida Eichwald,
Bittium reticulatum (da Costa) (Kiseleva, 1967a). (e) Bivalve molluscs,
Ostrea edulis L. (Cole and Knight-Jones, 1949; Knight-Jones 1949;
Bayne, 1969). (f) Cirripedes, Balanw amphitrite Darwin (Daniel,
1955), B. balanoides (L.), B. crenutus BrugiAre (Knight-Jones, 1953b),
Elminius modestus Darwin (Knight-Jones, 1953b; Knight-Jones and
Stephenson, 1950).
Although there may be the occasional exception (Straughan, 1972),
a large body of evidence makes it clear that most larvae settle gregariously in response to chemicals present in, or perhaps in some cases
released by, larvae or metamorphosed adults. The larvae of the
ascidian Styela partita Stimpson, for example, metamorphose sooner
in water that has been occupied by other larvae; the larvae metamorphose sooner the more larvae originally present in the water, to
the point at which they do not metamorphose at all, but die (Grave,
1944). Because of this last observation, the results should be treated
with a little caution. On the other hand the larval life of other
ascidians is shortened in a similar way by larval or adult tissue extracts
(Grave, 1936, 1941 ; Grave and Nicoll, 1940). Grave’s experiments are
the only ones suggesting that larvae produce an external metabolite
which induces something akin to a gregarious response.
The chemical basis of the gregarious behaviour of barnacle cyprids
has been studied in some detail by Crisp and Meadows (1962, 1963).
They developed a technique used by Crisp and Williams (1960) to test
P. 5. MEADOWS AND J. I. CAMPBELL
should be made to Williams’ papers and to more recent ones by
Hubschman (1970) and Straughan (1972).
B. Gregariousness
Many animals appear to recognize other individuals of their own
species by moving towards or staying near them.
Gregarious
behaviour, as here defined, will lead t o aggregations of a species both
in uniform and non-uniform local environments but will be more
obvious in the former. A great deal is known of the gregarious
behaviour of marine invertebrates, and we will summarize this fist
before considering freshwater animals. Field and laboratory experiments show that the larvae of a wide range of sedentary marine species
settle preferentially near adults of their own species. Data are available
for the following species : (a) Coelenterates, Tubularia larynx Ellis and
Solander (Pyefinch and Downing, 1949). (b) Polyzoa, Watersipora
cucullata (Busk) (Wisely, 1958b). (c) Polychaetes, Mercierella enigmatica
Fauvel (Straughan, 1972), Polydora ligni Webster (Blake, 1969))
Subellaria alveolata (L.) (Wilson, 1968), 8. spinulosa Leuckart (Wilson,
1970b), Spirorbis borealis Daudin, S. pagenstecheri Quatrefages (KnightJones, 1951,1953a). (d) Gastropodmolluscs, Rissoa splendida Eichwald,
Bittium reticulatum (da Costa) (Kiseleva, 1967a). (e) Bivalve molluscs,
Ostrea edulis L. (Cole and Knight-Jones, 1949; Knight-Jones 1949;
Bayne, 1969). (f) Cirripedes, Balanw amphitrite Darwin (Daniel,
1955), B. balanoides (L.), B. crenutus BrugiAre (Knight-Jones, 1953b),
Elminius modestus Darwin (Knight-Jones, 1953b; Knight-Jones and
Stephenson, 1950).
Although there may be the occasional exception (Straughan, 1972),
a large body of evidence makes it clear that most larvae settle gregariously in response to chemicals present in, or perhaps in some cases
released by, larvae or metamorphosed adults. The larvae of the
ascidian Styela partita Stimpson, for example, metamorphose sooner
in water that has been occupied by other larvae; the larvae metamorphose sooner the more larvae originally present in the water, to
the point at which they do not metamorphose at all, but die (Grave,
1944). Because of this last observation, the results should be treated
with a little caution. On the other hand the larval life of other
ascidians is shortened in a similar way by larval or adult tissue extracts
(Grave, 1936, 1941 ; Grave and Nicoll, 1940). Grave’s experiments are
the only ones suggesting that larvae produce an external metabolite
which induces something akin to a gregarious response.
The chemical basis of the gregarious behaviour of barnacle cyprids
has been studied in some detail by Crisp and Meadows (1962, 1963).
They developed a technique used by Crisp and Williams (1960) to test