74
E. NAYLOR
sapidus Rathbun (Fingerman, 1955) and the green shore crab Carcinus
m a e m (L.) (Powell, 1962), respiratory rhythms in Uca (Brown et al.,
1954) and rhythms of locomotor activity in Uca (Bennett et ul., 1957)
and Carcinus (Naylor, 1958, 1963). Experimental acclimatization to
high temperatures, as measured by altered death temperatures, has
been demonstrated in Homarus americanus H. Milne Edwards (Mcleese,
1956), Ligia (Edney, 1960), clrammarus (Kinne, 1953b,c) and Artenzia
(Grainger, 1958).
Amongst molluscs Mytilus has been shown to have considerable
powers of acclimatization (Rao, 1953a,b). Thus M. californianus
Conrad from higher latitudes in North America exhibits consistently
higher rates of ciliary pumping than low latitude species at low temperatures. Moreover, specimens of this species and those of M. edulis
(L.) collected low down on any one shore have lower pumping rates than
specimens of the same species collected higher up the shore. It seems
therefore that the high tide specimens are adapted to the high average
temperatures prevalent in the upper shore, and, in one case, the difference in pumping rates of specimens collected only 75 cm vertically
apart was equivalent to the difference between specimens collected at
the same tidal level in two localities about 330 miles apart in a northsouth direction. Adaptive changes associated with varying temperatures are also evident in Mytilus from further observations by Rao
(1954) who demonstrated a temperature independent tidal rhythm of
pumping activity. Latitudinal acclimatization has also been demonstrated in a variety of other molluscs, including oysters which spawn
at different critical temperatures according to the latitude a t which they
occur (Stauber, 1950; Loosanoff and Nomejko, 1951). Similar phenomena have been demonstrated too in three species of gastropod
molluscs, Thais emarginata Deshayes, Crepidula nummaria Gould and
Lacuna carinata Gould, in which the growth of larvae within the egg
capsules was shown to be from two to nine times faster in Alaskan
specimens than in Californian specimens of the aame species at any
given temperature between 10-16°C (Dehnel, 1955). Physiological
differences according to tidal level have been demonstrated in the limpet
Acmaea limatula Carpenter in which at a given temperature rates of
he& beat are higher in specimens taken from low levels of the shore
than in those from higherlevels, the higher tide specimens apparently
being adapted to higher average temperatures prevalent in that
habitat (Segd et al., 1953). Transplantation of limpets between levels
suggests that complete acclimatization is possible within a few weeks
(Segal, 1956). I n earlier experiments too, various workers have compared the thermal death points of specimens of the same species or of
E. NAYLOR
sapidus Rathbun (Fingerman, 1955) and the green shore crab Carcinus
m a e m (L.) (Powell, 1962), respiratory rhythms in Uca (Brown et al.,
1954) and rhythms of locomotor activity in Uca (Bennett et ul., 1957)
and Carcinus (Naylor, 1958, 1963). Experimental acclimatization to
high temperatures, as measured by altered death temperatures, has
been demonstrated in Homarus americanus H. Milne Edwards (Mcleese,
1956), Ligia (Edney, 1960), clrammarus (Kinne, 1953b,c) and Artenzia
(Grainger, 1958).
Amongst molluscs Mytilus has been shown to have considerable
powers of acclimatization (Rao, 1953a,b). Thus M. californianus
Conrad from higher latitudes in North America exhibits consistently
higher rates of ciliary pumping than low latitude species at low temperatures. Moreover, specimens of this species and those of M. edulis
(L.) collected low down on any one shore have lower pumping rates than
specimens of the same species collected higher up the shore. It seems
therefore that the high tide specimens are adapted to the high average
temperatures prevalent in the upper shore, and, in one case, the difference in pumping rates of specimens collected only 75 cm vertically
apart was equivalent to the difference between specimens collected at
the same tidal level in two localities about 330 miles apart in a northsouth direction. Adaptive changes associated with varying temperatures are also evident in Mytilus from further observations by Rao
(1954) who demonstrated a temperature independent tidal rhythm of
pumping activity. Latitudinal acclimatization has also been demonstrated in a variety of other molluscs, including oysters which spawn
at different critical temperatures according to the latitude a t which they
occur (Stauber, 1950; Loosanoff and Nomejko, 1951). Similar phenomena have been demonstrated too in three species of gastropod
molluscs, Thais emarginata Deshayes, Crepidula nummaria Gould and
Lacuna carinata Gould, in which the growth of larvae within the egg
capsules was shown to be from two to nine times faster in Alaskan
specimens than in Californian specimens of the aame species at any
given temperature between 10-16°C (Dehnel, 1955). Physiological
differences according to tidal level have been demonstrated in the limpet
Acmaea limatula Carpenter in which at a given temperature rates of
he& beat are higher in specimens taken from low levels of the shore
than in those from higherlevels, the higher tide specimens apparently
being adapted to higher average temperatures prevalent in that
habitat (Segd et al., 1953). Transplantation of limpets between levels
suggests that complete acclimatization is possible within a few weeks
(Segal, 1956). I n earlier experiments too, various workers have compared the thermal death points of specimens of the same species or of