HABITAT SELECTION BY AQUATIU INVERTEBRATES
305
the eEcacy of chemicals on surfaces for inducing settlement. Cypris
larvae of barnacles settled in Iarge numbers on pitted slate panels
previously soaked in an extract of adult barnacles but not on control
untreated surfaces. Using the technique as a bioassay, Cri;sp and
Meadows established that the chemical to which cyprids respond is
probably the cuticular protein, or family of proteins, arthropodin,
while Crisp (1965) in a subsequent paper proved that cyprids
responded to arthropodin even when it was present as a layer of a
few molecules thick. A similar approach has been adopted by Crisp
(1967) to study the chemical basis of gregarious settlement by
Crassostrea virginica (Gmelin) larvae and by Bayne (1969) to investigate
the chemical nature of the substance responsible for the gregarious
behaviour of oyster larvae (Ostrea edulis). The settlement inducing
activity of adult tissue extracts demonstrated by Bayne could be
fractionally precipitated by ammonium sulphate and was destroyed
by the enzyme pronase, thus establishing the protein nature of the
active substance. Wilson (1968) after seven years of detailed
experiments on the settlement behaviour of larvae of the polychaete
Sabellaria alveolata has confirmed in this species also that gregarious
behaviour depends on larvae recognizing a chemical, which in this case
is the cement secreted by adult Sabellaria to stick together the sand
grains of their tubes. A long term biochemical programme will be
needed to identify in more detail the chemicals recognized by larvae of
different species as they settle. It is however fully justified on applied
criteria alone, since with this information a direct attack can be made
on the problems of the fouling of ships’ bottoms and man-made
structures in ports and estuaries.
If larvae settle near adults of their own species in response to
chemicals, and if gregariousness is to have a biological meaning, both
the response and the chemicals producing it are likely to be species
specific, and this proves to be so. Larvae of several species can
recognize adults of their own species from those of closely related
ones. In reciprocal settlement experiments, more Spirorbis borealis
larvae settled on stones bearing 8. borealis than on stones bearing
S. pagenstecheri, while larvae of S. pagenstecheri settled preferentially
on the stones bearing 8. pagenstecheri rather than on the stones bearing
S. borealis (Table 111) (Knight-Jones, 1951). Cypris larvae of Balanus
balanoides, B. crenatus and Elminius modestus recognize their own
species in a similar way (Knight-Jones, 1953b). Species specific
recognition may occur even at a subspecific level (Daniel, 1955), but
sometimes breaks down at an interspecific level (Wilson, 1968, 1970a
and b). Wilson describes the odd case of two closely related Sabellaria
305
the eEcacy of chemicals on surfaces for inducing settlement. Cypris
larvae of barnacles settled in Iarge numbers on pitted slate panels
previously soaked in an extract of adult barnacles but not on control
untreated surfaces. Using the technique as a bioassay, Cri;sp and
Meadows established that the chemical to which cyprids respond is
probably the cuticular protein, or family of proteins, arthropodin,
while Crisp (1965) in a subsequent paper proved that cyprids
responded to arthropodin even when it was present as a layer of a
few molecules thick. A similar approach has been adopted by Crisp
(1967) to study the chemical basis of gregarious settlement by
Crassostrea virginica (Gmelin) larvae and by Bayne (1969) to investigate
the chemical nature of the substance responsible for the gregarious
behaviour of oyster larvae (Ostrea edulis). The settlement inducing
activity of adult tissue extracts demonstrated by Bayne could be
fractionally precipitated by ammonium sulphate and was destroyed
by the enzyme pronase, thus establishing the protein nature of the
active substance. Wilson (1968) after seven years of detailed
experiments on the settlement behaviour of larvae of the polychaete
Sabellaria alveolata has confirmed in this species also that gregarious
behaviour depends on larvae recognizing a chemical, which in this case
is the cement secreted by adult Sabellaria to stick together the sand
grains of their tubes. A long term biochemical programme will be
needed to identify in more detail the chemicals recognized by larvae of
different species as they settle. It is however fully justified on applied
criteria alone, since with this information a direct attack can be made
on the problems of the fouling of ships’ bottoms and man-made
structures in ports and estuaries.
If larvae settle near adults of their own species in response to
chemicals, and if gregariousness is to have a biological meaning, both
the response and the chemicals producing it are likely to be species
specific, and this proves to be so. Larvae of several species can
recognize adults of their own species from those of closely related
ones. In reciprocal settlement experiments, more Spirorbis borealis
larvae settled on stones bearing 8. borealis than on stones bearing
S. pagenstecheri, while larvae of S. pagenstecheri settled preferentially
on the stones bearing 8. pagenstecheri rather than on the stones bearing
S. borealis (Table 111) (Knight-Jones, 1951). Cypris larvae of Balanus
balanoides, B. crenatus and Elminius modestus recognize their own
species in a similar way (Knight-Jones, 1953b). Species specific
recognition may occur even at a subspecific level (Daniel, 1955), but
sometimes breaks down at an interspecific level (Wilson, 1968, 1970a
and b). Wilson describes the odd case of two closely related Sabellaria