The Dynamics of Water Relations
Tomocerus minor
Transpiration
(X bOdy weIght loss/
r 10mtn)
13.001
".OO!
10.00
9.00
14.00 [
13.001
"'OOf
1o.00f
9.00
14.001
11.00
10.00
9.00
8.00
Orchesella cincta
Transpiration
(X bOdy weight /OSS/
10mtn)
5.00
4.00
3.00
5.00
4.00
3.00
2.00
5.00
4.00
..
21
3.00
2.00
~.<
7.00 -+--'-....... _ ................. '-*--'- 1.00 - *
2
3
4
5
days
, , , *~
2
3
4
5
days
Fig. 2..4- Transpiration during an instar in the collembolans Orchesella cincta and Tomocerus
minor. Arrows indicate cessation of feeding activity ... Ecdysis; a 10 s after ecdysis; b 30 min after
ecdysis; c 60 min after ecdysis (Verhoef 1981)
moisture - haemolymph osmolality decreases, since a major water source is
food. Locomotory activity persists even in progressively desiccating substrates and, after deprivation of nutritional water, the animals consume their own
reserves and finally die. Recovery of the population is ensured by a few individuals surviving in favourable microsites.
Fluctuations in blood osmolality during the development of an ins tar
have been observed by Verhoef (1981; Fig. 2.3). Like blood osmolality, integumentary transpiration also fluctuates within instar development. It is high
at the end of the feeding period, probably due to abrasion resulting in
increasing permeability of the cuticle (Fig. 2.4; Verhoef 1981), and is maximal during ecdysis. Higher transpiration rates recorded during ecdysis
emphasise the significance of epicuticular lipids in the water balance of the
animals.