217 T.G. Shelton, A.G. Appel Journal of Insect Physiology 47 2001 213–224
Table 1 Percentage of recordings showing a calmdown period in CO
2
release over 0–45 min. Paired t-test results [Difference D and P-values] of 0–45 min activity percentages vs. 45–60 min
Species Colony
Caste N
Calmdown D
a
P R. flavipes
A Workers
13 61.5
2 1.26
0.473 Soldiers
17 76.5
2 0.01
0.997 Nymphs
20 70
0.08 0.673
All 50
70 2
0.35 0.710
B Workers
16 50
2 2.72
0.002 Soldiers
19 78.9
2 2.11
0.036 Nymphs
16 68.8
0.285 0.448
All 51
66.7 2
1.57 0.001
C Workers
17 64.7
0.04 0.945
Soldiers 17
76.5 2
0.72 0.289
All 34
70.6 2
0.29 0.499
D Nymphs
17 64.7
2 0.86
0.178 C. formosanus
1 Workers
18 55.6
2 0.49
0.561 Soldiers
15 100
0.06 0.890
Nymphs 19
68.4 2.22
0.101 All
52 73.1
0.59 0.277
2 Workers
19 89.5
2 2.27
0.020 Soldiers
19 89.5
0.26 0.754
Nymphs 9
77.8 3.16
0.042 All
47 87.2
2 0.31
0.618 3
Workers 19
84.2 2
0.29 0.646
Soldiers 16
87.5 0.69
0.271 Nymphs
18 66.7
2.15 0.060
All 53
79.2 0.86
0.085
a
D =
x¯ activity score
− 45
2 x¯ activity score
45 −
60
also examined with analysis of covariance ANCOVA; SAS Institute, 1985 to determine the significance of
species on the combined regression. To compare with Lighton and Fielden’s 1995 mass scaling of metabolic
rates of the arthropods as a whole, we converted V˙
CO
2
ml CO
2
h
2 1
to metabolic rate µ
W using their assump- tions: Q
10
of 2.5 and RQ of 0.72 Lighton and Fielden, 1995; Lighton, 1991a. Data were analyzed with
ANCOVA to estimate the relationship between log
10
µ W
and log
10
mass for C. formosanus and R. flavipes, and to compare this relationship with the same relationship
for other arthropods Lighton and Fielden, 1995.
3. Results
3.1. CO
2
release patterns There was no evidence of the DGC as a specialized
class of cyclic CO
2
release in any of the 344 recordings examined, regardless of caste, colony or species. An
illustration of a typical recording is shown in Fig. 2. The 20 traces using 60-fold greater resolution likewise did
not show evidence of DGC events Fig. 3. CO
2
release never dropped to near base-line levels in any of the
traces, and showed no evidence of DGC periods B, F, or C. CO
2
release patterns of both workers and soldiers
Fig. 3. Increased resolution CO
2
release sample trace recorded from an R. flavipes worker mass
= 0.00330 g. Chamber volume is 0.5 ml
and flow rate is 100 ml min
2 1
.
of both species at 15 °
C, and in 3 h recordings at ambient temperatures, showed no indication of DGC phases.
3.2. Direct observations of movement Termites recorded on videotape moved at constant
rates [C. formosanus workers: 16.4 ±
1.57 range 12–20 cm min
2 1
; soldiers: 17.5 ±
1.12 range 15–20 cm min
2 1
;
218 T.G. Shelton, A.G. Appel Journal of Insect Physiology 47 2001 213–224
R. flavipes workers: 9.2
± 0.65 range 7.5–12 cm min
2 1
; soldiers: 7.0
± 0.57 range 5.45–8.6 cm min
2 1
] over the course of the recordings. Both workers and soldiers of
C. formosanus moved at a faster rate than R. flavipes
workers: W
= 21.5,
P =
0.0094; soldiers:
W =
21.0, P
= 0.0043. Termites did pause briefly range 0:05–5:49
min duration, moving only antennae, but resumed movement in all cases. Thus intensity of movement dur-
ing these video recordings was constant. No abdominal pumping was observed in either caste of either species.
3.3. Effects of movement on CO
2
release There was no relationship between V˙
CO
2
and activity for either species when residuals of the mass scaling
relationship were regressed on activity score C. formos- anus
: df =
1,143; F =
1.46; r
2
= 0.01; P
= 0.229; R. flavipes:
df =
1,141; F =
1.48, r
2
= 0.01, P
= 0.226. Percentages of
recordings showing a significantly negative interaction between time and V˙
CO
2
over the first 45-min interval ranged from 50 R. flavipes colony B workers to 100
C. formosanus colony 1 soldiers; Table 1. Durations of movement during the 0–45-min and 45–60-min per-
iods were not significantly different for all but one col- ony, in which the activity duration was greater during
the 45–60-min interval Table 1.
3.4. Caste, colony, and species effects on CO
2
release Nested ANOVA of the V˙
CO
2
data resulted in only one significant main effect. Colony and caste main effects
were not significant, but species df =
1, 4.60; F =
13.76; P
= 0.0161 were significantly different. Coptotermes for-
mosanus all castes combined V˙
CO
2
0.310 ±
0.011 ml CO
2
g
2 1
h
2 1
was significantly lower than R. flavipes 0.507
± 0.014 ml CO
2
g
2 1
h
2 1
. Interactions were not significant. V˙
CO
2
ranged from 0.229 ±
0.008 ml CO
2
g
2 1
h
2 1
for C. formosanus soldiers to 0.549 ±
0.022 ml CO
2
g
2 1
h
2 1
for R. flavipes soldiers Table 2. Contrast com- parisons of caste by species revealed that C. formosanus
soldiers released CO
2
at a significantly lower rate than C. formosanus
workers and nymphs Table 2. R. flavipes
Table 2 Mean
± S.E. of V˙
CO 2
ml CO
2
g
2 1
h
2 1
and mass in mg of all castes by species of R. flavipes and C. formosanus Species
Caste n
× ¯
± S.E. V˙
CO 2
a
× ¯
± S.E. Mass range
R. flavipes Workers
52 0.544
± 0.033a
2.97 ±
0.052 2.04–4.12 Soldiers
53 0.549
± 0.022a
4.06 ±
0.073 2.75–5.29 Nymphs
52 0.430
± 0.011b
5.36 ±
0.181 3.17–7.82 All
157 0.507
± 0.014
4.14 ±
0.103 2.04–7.82 C. formosanus
Workers 59
0.373 ±
0.018a 2.95
± 0.120 1.32–4.90
Soldiers 59
0.229 ±
0.008b 3.22
± 0.076 1.91–4.58
Nymphs 47
0.332 ±
0.025a 6.27
± 0.206 2.71–8.58
All 165
0.310 ±
0.011 3.99
± 0.136 1.32–8.58
a
Means followed by the same letter within species are not significantly different at the a =
0.05 level, as determined by contrasts.
nymphs released CO
2
at a significantly lower rate than R. flavipes
workers and soldiers Table 2. 3.5. Mass loss and termite condition after
respirometry Because they are soft bodied, termites are one of the
few insects for which dehydration is readily observable. Dehydrated animals have a sunken, flattened abdomen.
Termites removed from the respirometer were not noticeably dehydrated. Mean mass lost for each species
during the trials, which is assumed to be water loss, was 6.55
± 0.40 for C. formosanus and 9.56
± 0.66 for R.
flavipes .
3.6. Mass scaling of V ˙
CO
2
in C. formosanus and R. flavipes
Regressions of log
10
V ˙
CO
2
on log
10
mass for each caste within species resulted in four significant P,0.008
mass scaling effect models, workers [21.64 ±
0.345 M
0.537 ±
0.135
df =
1, 58; F =
15.82; r
2
= 0.22; P
= 0.0002],
and soldiers
of C.
formosanus [21.29
± 0.412
M
0.738 ±
0.165
df =
1, 55; F =
20.07; r
2
= 0.27; P
= 0.0001],
soldiers [20.643
± 0.735
M
0.848 ±
0.307
df =
1, 52;
F =
7.64; r
2
= 0.13;
P =
0.0079] and
nymphs [21.17
± 0.220
M
0.650 ±
0.096
df =
1, 51;
F =
45.63; r
2
= 0.48; P
= 0.0001] of R. flavipes M is body mass in
g. For individual caste models, no mass range was more than 5.87 mg Table 3. Regressions using each species
with combined castes resulted in significant models P
= 0.0001 for both species, with mass ranges of 7.26
and 5.78 mg for C. formosanus and R. flavipes, respect- ively Table 3. The overall model for combined species
was also significant P =
0.0001, resulting in a mass sca- ling coefficient of 0.832
± 0.069 Table 3. The
regression of log
10
V ˙
CO
2
on log
10
mass combining castes for each species resulted in mass scaling coefficients of
0.759 ±
0.070 and 0.715 ±
0.098 for C. formosanus and R. flavipes
, respectively, and is illustrated in Fig. 4. Species did not significantly affect the relationship of
log
10
V ˙
CO
2
on log
10
mass in the combined species model
219 T.G.
Shelton, A.G.
Appel Journal
of Insect
Physiology 47
2001 213–224
Table 3 Results of log
10
V ˙
CO 2
ml CO
2
h
2 1
; from steady-state section only regression on log
10
mass for each species castes combined, caste within species, and both species combined Mass mg
Species Caste
n ×
¯ ±
S.E. Range Slope
± S.E.
Intercept ±
S.E. P
a
r
2
R. flavipes Worker
47 2.98
± 0.05 2.04–4.12
0.486 ±
0.580 2
1.61 ±
1.47 0.4065
0.0150 Soldier
52 4.06
± 0.07 2.75–5.29
0.848 ±
0.307 2
0.643 ±
0.735 0.0079
0.1303 Nymph
51 5.37
± 0.18 3.17–7.82
0.650 ±
0.0962 2
1.17 ±
0.220 0.0001
0.4771 All
150 4.16
± 0.10 2.04–7.82
0.715 ±
0.098 2
1.00 ±
0.235 0.0001
0.2615 C. formosanus
Worker 58
2.95 ±
0.12 1.32–4.90 0.537
± 0.135
2 1.64
± 0.345
0.0002 0.2173
Soldier 55
3.24 ±
0.08 1.91–4.58 0.738
± 0.165
2 1.29
± 0.412
0.0001 0.2710
Nymph 45
6.22 ±
0.21 2.71–8.58 2
0.186 ±
0.154 2
3.14 ±
0.343 0.2347
0.0319 All
158 3.99
± 0.14 1.32–8.58
0.759 ±
0.0703 2
1.13 ±
0.172 0.0001
0.4230 Both species
All 308
4.07 ±
0.09 1.32–8.58 0.832
± 0.0686
2 0.837
± 0.166
0.0001 0.3207
a
P -values are reported for ANOVA test of H
: slope =
0 vs. H
a
: slopeÞ0.
220 T.G. Shelton, A.G. Appel Journal of Insect Physiology 47 2001 213–224
Fig. 4. Plot of V˙
CO 2
data from steady state trace sections only for all castes of R. flavipes and C. formosanus combining castes. Individ-
ual regression models are drawn for each species as well as both spec- ies combined.
df =
1; F,0.13; P =
0.7236. ANCOVA comparison of our data to those of Lighton and Fielden 1995 demon-
strated no
significant difference
df =
1; F
= 0.19;
P =
0.6616 between metabolic rate and termite body mass model and that of the arthropods as a whole.
MR53.15760.192M
0.861 ±
0.079
1 Eq. 1 models the relationship between the metabolic
rate MR of R. flavipes and C. formosanus and body mass M, where MR is metabolic rate in
µ W at 25
° C
Q
10
= 2.5 assuming an RQ of 0.72 Lighton and Fielden,
1995, and M is mass in grams.
4. Discussion
