Fgure
6.7 The water relations of terrestrial plants and animals can be summarized body flows to its mouth (ig. 6.8). Onymacris also takes in
water with its food. Some of this water is absorbed within the
tissues of the food. The remaining water is produced when
the beetle metabolizes the carbohydrates, proteins, and fats
ontained in its food. We can see the source of this water if we
look at an equation for oxidation of glucose
CH1206+602-6 CO2+6H2O
As you can see, cellular respiration liberates the water that
combined with carbon dioxide during the process of photo
synthesis(see chapter 5 ) The water released during cellular
respiration is called metabolic water.
Paul Cooper(1982)estimated the water budget for free
ranging Onymacris from the Namib Desert near Gobabeb
estimated the rate of water intake by this beetle at 49.9 mg of
H20 per gram of body weight per day. Of this total, 39.8 mg
came from fog. 1. 7 mg came from moisture contained within
food, and 8.4 mg came from metabolic water. The rate of
that c
water loss by these beetles, 41.3 mg of H20 per gram per
4. y, was slightly less than water intake. Of this total, 2.3 mg
ere lost with feces and urine, and 39 mg by evaporation.
moist
The water budget of the beetle studied by Cooper is shown
In figure 6.9
Sn, While Onymacris gets most of its water from fog, other
lall desert animals get most of their water from their food
surviv
