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)mj3@ the resistance to freezing )l of )l intertidal invertebrates 
)@l2 by )l @geoffrey @a. clark )l @zoology )l @april 1, 1980
)r
)s
)m@u introduction )r
)l
)p one or the chief factors affecting the distribution of intertidal 
organisms at high latitudes, is temperature. subtidal marine life is 
seldom exposed to temperatures below -1.7 degrees celcius, the 
freezing point of sea water (@kanwisher, 1955). ice formation will not 
occur in the tissues of these animals, as the blood salt concentration 
it wither greater than or equal to that of the surrounding sea water. 
intertidal organisms however, can be exposed to temperatures as low as 
-20 degrees celcius, twice daily, at high latitudes during winter 
(@kanwisher, 1955). kanwisher (1955; 1959), found that in the arctic, 
beds of )u @mytilus )u could be found frozen in ground ice for up to 
8 months. )p in a frozen animal, death is generally caused by 
intracellular ice formation and, subsequent cell damage and rupture. 
there are many ways in which animals can resist intracellular ice 
formation and freezing: supercooling; the addition of cryoprotective 
substances to the blood; or a resistance to extracellular ice formation 
in the tissues. lozina-@lozinskii (1974), states that supercooling, 
while a common cryoprotective mechanism in fishes is not common in 
aquatic invertebrates. the addition of cryoprotective substances such 
as glycerine and glycoproteins prevents the formation and growth of ice 
crystals in the blood. these substances while commonly found in the 
blood of insects are not present in the hemolymph of most marine 
invertebrates (@lozina-@lozinskii, 1974; @roland and @ring, 1977). the 
increase in the extracellular solute concentration upon ice formation 
results in an osmotic imbalance between the intra and extracellular 
fluid spaces. as the osmotic pressure gradient increases, fluid flows 
across the cell membrane into the extracellular space. only animals 
resistant to this severe intracellular dehydration can survive 
extracellular ice formation (@kanwisher 1959; @murphy, 1979). 
)p in this paper, the histological and physiological effects of freezing 
on intertidal invertebrates will be discussed. in addition, the resistance 
to freezing of several gastropods will be related to geographic 
distribution, both intertidally, and latitudinally. lastly, the case of 
an antarctic limpet that utilizes an unusual cryoprotective mechanism 
will be studied.
)s
)p severe histological and physiological changes accompany the formation 
of extracellular ice upon the freezing of an intertidal invertebrate. 
kanwisher (1955; 1959), discovered that many intertidal animals were 
imbedded in ice and partially frozen at low tide during the winter. 
subsequent experiments determined that in )u @mytilus edulis )u , )u @modiolus 
modiolus )u , )u @littorina littorea )u , )u @crassostrea virginicus )u , 
and )u @l.~rudis )u , 60-80% of the body water was frozen, and that ice 
formation took place only extracellularly. kanwisher's (1955) data, cannot 
be verified, as an important standard curve was ommitted, and only a 
minimum number of data points were plotted on the graphs. however, 
@roland and @ring (1977), found that in )u @acmaea digitalis )u, 70-80% 
of the obdy water was frozen upon exposure to sub-zero temperatures. 
hargens (1973), determined that if more than 80% of the body water was 
frozen, intracellular organelles began to clump together, and irreparable 
cell damage occurred. therefore, the 60-80% water frozen survival figure 
is probably accurate. )p wolcott (1973; cited in @roland and @ring, 1977), 
determined that )u @a.~digitalis )u died when 76% of the body water was 
withdrawn upon placement in high salinities (400-500% sea water). roland 
and @ring (1977), withdrew 60-65% of the limpet body water using mannitol 
and had a high survival rate. damage was probably caused by an increase in 
intracellular solute concentration, if water was withdrawn by the same 
mechanism in each case (@roland and @ring, 1977). )p kanwisher (1955), 
compared data on freezing in )u @m.~edulis )u with data obtained from an 
ampoule of frozen sea water. the curve for sea water was displaced higher 
than that for )u @m.~edulis )u indicating that some water was "bound" to 
organic substrates (probably proteins) and was not frozen. similar data 
was obtained by @roland and @ring (1977) on )u @a.~digitalis )u (accuracy 
is questionable due to a lack of data points). )p kanwisher (1959) found 
that extracellular ice formation resulted in mechanical deformation of 
tissue in many intertidal invertebrates. the adductor muscle of )u @c.~
virgincus )u , and the foot muscle of )u @l.~littorea )u showed clumping 
of muscle fibres to make room for intervening ice. eggs in the ovary of 
)u @m.~edulis )u shrank severely during the formation or extracellular ice 
(@kanwisher, 1959). subsequent warming of these tissues returned them to 
their original appearance. no permanent damage was indicated (@kanwisher, 
1959).
