90
E. N A Y M R
tions are largely recruited from waters flowing northwards from the
Gulf of Maine. Off British coasts too, several species regularly transported across the Atlantic by the Gulf Stream and North Atlantic Drift
do not appear to have become established. These include the crab
Planes minutus (Bell, 1863), the isopod Idotea metallica Bosc (Naylor,
1967d) and several other species (Hardy, 1966 ; Naylor, 1967a). Many
of these species are, of course, oceanic forms and so not all would be
likely replacement species in heated coastal areas.
Of the warm water species which are already known to have appeared
in heated localities there is as yet little evidence that they have begun to
spread. However, Jones (1963) has reported that Limnoria tripunctata
is spreading at the expense of L. qdripunctata Holthuis in that part of
Southampton Water which is affected by heated discharges, and Ansell
(19634 gives some evidence for the acclimatization of Venus mercenaria
in the same area. In Southampton Water Venus mercenaria breed in
water where temperatures never exceed 22°C and spawn in the laboratory at 1743°C (Ansell, 1963a), whereas in their native habitat in North
America the minimum temperature for spawning for this species is
reported to be 23OC (Loosanoff, 1937) and 20~6°C (Loosanoff and Davis,
1960). Another example which seems to illustrate that speciation may
be taking place in warmed localities is seen in the serpulid polychaete
Hydroides. Monro (1938) first described as Hydroidea incrwtam a form
from the artificially warmed Shoreham Harbour Canal which differed
from native British Hydroidea norvegicu in several important respects.
Gee (1963) showed that though cross-fertilization between the two forms
can take place, which might suggest that H. incrustam is only a warmwater race, nevertheless interfertility waa greatly reduced. Because of
this Gee (1963) concluded that it is best to maintain the separation of
H. incncstana aa a separate species, at least until more is known of the
geographical distribution of the two forms.
IV. UWATXON OF HEATED EFFLTJENTS
In addition to descriptions of the use of heated effluents for domestic
heating (Klein, 1957) there have also been a few reports of their utilization for more strictly biological purposes. Ritchie (1927), Chadwick
et al. (1960) and Fox and Corcoran (1967), for instance, have described
the thermal control of marine fouling at power stations in Sootland and
in Southern California. A t those stations it waa found that periodic
discharge of the hot effluent through alternative intake conduits wm
suilicient to prevent the attachment of various species of mussel which
formed the main source of fouling (see p. 77). Also, pilot experiments on
the growth of edible fish kept in cooling ponds of power stations have
E. N A Y M R
tions are largely recruited from waters flowing northwards from the
Gulf of Maine. Off British coasts too, several species regularly transported across the Atlantic by the Gulf Stream and North Atlantic Drift
do not appear to have become established. These include the crab
Planes minutus (Bell, 1863), the isopod Idotea metallica Bosc (Naylor,
1967d) and several other species (Hardy, 1966 ; Naylor, 1967a). Many
of these species are, of course, oceanic forms and so not all would be
likely replacement species in heated coastal areas.
Of the warm water species which are already known to have appeared
in heated localities there is as yet little evidence that they have begun to
spread. However, Jones (1963) has reported that Limnoria tripunctata
is spreading at the expense of L. qdripunctata Holthuis in that part of
Southampton Water which is affected by heated discharges, and Ansell
(19634 gives some evidence for the acclimatization of Venus mercenaria
in the same area. In Southampton Water Venus mercenaria breed in
water where temperatures never exceed 22°C and spawn in the laboratory at 1743°C (Ansell, 1963a), whereas in their native habitat in North
America the minimum temperature for spawning for this species is
reported to be 23OC (Loosanoff, 1937) and 20~6°C (Loosanoff and Davis,
1960). Another example which seems to illustrate that speciation may
be taking place in warmed localities is seen in the serpulid polychaete
Hydroides. Monro (1938) first described as Hydroidea incrwtam a form
from the artificially warmed Shoreham Harbour Canal which differed
from native British Hydroidea norvegicu in several important respects.
Gee (1963) showed that though cross-fertilization between the two forms
can take place, which might suggest that H. incrustam is only a warmwater race, nevertheless interfertility waa greatly reduced. Because of
this Gee (1963) concluded that it is best to maintain the separation of
H. incncstana aa a separate species, at least until more is known of the
geographical distribution of the two forms.
IV. UWATXON OF HEATED EFFLTJENTS
In addition to descriptions of the use of heated effluents for domestic
heating (Klein, 1957) there have also been a few reports of their utilization for more strictly biological purposes. Ritchie (1927), Chadwick
et al. (1960) and Fox and Corcoran (1967), for instance, have described
the thermal control of marine fouling at power stations in Sootland and
in Southern California. A t those stations it waa found that periodic
discharge of the hot effluent through alternative intake conduits wm
suilicient to prevent the attachment of various species of mussel which
formed the main source of fouling (see p. 77). Also, pilot experiments on
the growth of edible fish kept in cooling ponds of power stations have