BIOLOGY OF SEAWEEDS OF ECONOMIC IMPORTANCE
183
Subsequently, when spore release is imminent from the " cultured "
filaments, two methods of " seeding " the " hibi " are practised. I n
the first of these the nets are suspended in the culture tanks and the sea
water then agitated. I n the second the shells are suspended in vinyl
bags below the " hibi " in the culture grounds, or are fixed in split
bamboo rods. The information recorded above on the times of maximum
spore release are also of value in determining the best times for spreading the " hibi " during the day. The methods of land-based culture
can be successfully carried out on a relatively small scale by individual
fishermen, and will undoubtedly lead to a more efficient industry than
one solely dependent on spore release in nature. Taneka (1959), for
example, suspended 150 " infected " oyster shells in a linear series on
steel wire and then suspended a number of these wires in the sea.
A copious spore release was obtained from the suspended shells in
early autumn. Useful information has also come from a study of the
polarity of spores released from the Conchocelis-phase (Nakazawa,
1958). A predetermined polarity was demonstrated by means of vital
stains, and the " reductive " region of the spore was found to be the one
which formed the attaching surface. This implies that secretion of an
adhesive substance is only found on one part of the spore surface. It
was also reported that some amoeboid movement was exhibited by the
newly settled spore. This type of information could be relevant to the
type of artificial substratum chosen as the " hibi ".
7. Gelidium
Gelidium and the related genus Pterocladia are the two genera,
principally used as sources of agar. Despite the common occurrence
of species of Gelidium in many parts of the world, and the fact that
several species are utilized as sources of agar, comparatively little is
known about many aspects of its biology. The polymorphic nature of
the genus, showing not only variations in growth form in different
habitats, but also in the same habitat at different seasons, is probably
one reason for the lack of critical data about several of the species.
Stoloff (1962) lists eighteen species of G e l X u m which can be used as
sources of agar, but few of these appear to be exploited on a, large
scale. The species principally used are Gelidium amansii and B.
curtilagineum; and used to a much smaller extent G. arborescens and
G. nudifrons.
Other species which could be used as sources of agar, and which
appear to grow in sufficient quantity, are listed in the survey of potential
resources (Table VIII, p. 126).
The most detailed study of the seasonal life of the species of
183
Subsequently, when spore release is imminent from the " cultured "
filaments, two methods of " seeding " the " hibi " are practised. I n
the first of these the nets are suspended in the culture tanks and the sea
water then agitated. I n the second the shells are suspended in vinyl
bags below the " hibi " in the culture grounds, or are fixed in split
bamboo rods. The information recorded above on the times of maximum
spore release are also of value in determining the best times for spreading the " hibi " during the day. The methods of land-based culture
can be successfully carried out on a relatively small scale by individual
fishermen, and will undoubtedly lead to a more efficient industry than
one solely dependent on spore release in nature. Taneka (1959), for
example, suspended 150 " infected " oyster shells in a linear series on
steel wire and then suspended a number of these wires in the sea.
A copious spore release was obtained from the suspended shells in
early autumn. Useful information has also come from a study of the
polarity of spores released from the Conchocelis-phase (Nakazawa,
1958). A predetermined polarity was demonstrated by means of vital
stains, and the " reductive " region of the spore was found to be the one
which formed the attaching surface. This implies that secretion of an
adhesive substance is only found on one part of the spore surface. It
was also reported that some amoeboid movement was exhibited by the
newly settled spore. This type of information could be relevant to the
type of artificial substratum chosen as the " hibi ".
7. Gelidium
Gelidium and the related genus Pterocladia are the two genera,
principally used as sources of agar. Despite the common occurrence
of species of Gelidium in many parts of the world, and the fact that
several species are utilized as sources of agar, comparatively little is
known about many aspects of its biology. The polymorphic nature of
the genus, showing not only variations in growth form in different
habitats, but also in the same habitat at different seasons, is probably
one reason for the lack of critical data about several of the species.
Stoloff (1962) lists eighteen species of G e l X u m which can be used as
sources of agar, but few of these appear to be exploited on a, large
scale. The species principally used are Gelidium amansii and B.
curtilagineum; and used to a much smaller extent G. arborescens and
G. nudifrons.
Other species which could be used as sources of agar, and which
appear to grow in sufficient quantity, are listed in the survey of potential
resources (Table VIII, p. 126).
The most detailed study of the seasonal life of the species of