Terrestrial Amphipoda — Hurley 
123 
may survive as long as 9 days in fresh tap- 
water, but "on the other hand it is much more 
susceptible to dry air in which it succumbs 
very quickly,” a statement which incidentally 
raises questions regarding control of osmotic 
pressure within the body. 
These points further emphasise a very im- 
portant aspect of the ecology of the cryptozoic 
fauna, that "the forest community, by its 
very nature, solves the problem of water con- 
servation for a host of plants and animals, 
making unnecessary for them the specific 
adaptations to economy of water that may be 
essential in other terrestrial environments” 
(Allee, Emerson, et aL^ 1949). 
EXCRETION 
The excretory problems facing animals of 
marine origin which colonise the land are 
well known. Foremost amongst these is the 
retention of water, which requires the de- 
velopment of mechanisms for the resorption 
of water from excreta, and adaptation of the 
excretory end product. In most groups, this 
is expressed by a change in the major nitrog- 
enous end product from the ammonia of 
marine groups to the urea or uric acid of 
terrestrial groups, with accompanying com- 
plexity of excretory organs. 
Dresel and Moyle (1950) describe studies 
on nitrogenous excretion in amphipods and 
isopods, including a supralittoral species of 
Orchestia. They conclude that more than 50 
per cent of the total soluble nonprotein 
nitrogen of the excreta is in the form of 
ammonia. "The level of nitrogen excretion is 
appreciably lower in the terrestrial species 
than in any of the others, indicating that, in 
this group, adaptation to terrestrial condi- 
tions has been attended by a general sup- 
pression of nitrogen metabolism rather than 
a transformation to other, less toxic prod- 
ucts.” Some excretion of uric acid, 5-10 per 
cent of the total soluble nonprotein nitrogen, 
took place in the terrestrial isopods. Associ- 
ated with this excretion, "some retention of 
this insoluble compound usually occurs, and 
it was found that among the terrestrial species 
the amount so stored parallels the degree of 
morphological and physiological adaptation 
to terrestrial conditions. ... It seems more 
plausible, however, to attribute this increased 
uric acid retention in the more xerophilous spe- 
cies to a reduced rate of excretion rather than 
to a fundamental difference in metabolism.” 
Thus, they conclude that "adaptation to 
terrestrial conditions [in the Isopoda and 
Amphipoda] has been attended by a general 
suppression of nitrogen metabolism rather 
than by a transformation of ammonia to 
other, less toxic products.” 
Apart from this work of Dresel and Moyle, 
nothing is known of excretory processes or 
mechanisms in the terrestrial amphipods. 
OXYGEN CONSUMPTION 
The rate of oxygen consumption in Tali- 
trus sylvaticus has been investigated by Clark 
(1955). Apart from a decrease in rate of 
respiration relative to increase of body weight, 
which is normal for Crustacea, he found that 
oxygen consumption was relatively higher in 
winter than in summer, the winter consump- 
tion corresponding to that at a temperature 
2.5°C. higher in summer. "Of the factors in- 
fluencing the rate of oxygen consumption 
. . . first order interactions occurred between 
temperature and body weight, temperature 
and season, and season and body weight. 
There was also a significant second order 
interaction between temperature, body weight 
and season. . . . Adaptation ... to oxygen 
uptake by Talitrus sylvaticus to seasonal dif- 
ferences in temperature was not sufficient to 
enable it to maintain the same rate of output 
of energy in winter as in summer” (Clark, 
1955). 
The occurrence of a seasonal adaptation of 
rate of oxygen uptake has been found only 
infrequently in invertebrates, and the neces- 
sary physiological mechanism is unknown. 
RESPIRATION AND PLEOPOD STRUCTURE 
It is interesting to compare the relationship 
