The Company of Biologists

Table 1.

Comparison of the mean rate of CO₂ emission from the mesothoracic spiracles and elytral case in four species of dung beetles

Species	P. femoralis	S. gariepinus	S. striatum	C. bacchus^*
N	5	7	6	6
Mass (g)	5.117±0.62^a	1.716±0.35^b	0.742±0.20^b	7.427±1.86^c
Rate of CO₂ emission (μl h^-1)
Mesothoracic spiracles	35.53±28.7^a	24.88±19.2^a	27.68±19.7^a	258.2±118.2^b
Posterior spiracles	468.39±97.13^a	121.45±75.3^b	28.56±11.0^b	119.5±123.6^b
Ratio of CO₂ emission
Mesothoracic:elytral case	0.083±0.07	0.31±0.3	1.56±2.1	3.47±2.0
	(range 0.019–0.22)	(0.11–1.06)	(0.22–5.9)	(0.42–6.81)
% total CO₂ emitted through mesothoracic spiracles	7.31±6.5	20.07±15.05	46.23±22.9	79.4±4.48
Frequency (mHz)	0.73±0.3^a	0.33±0.2^b	0.42±0.2^b	0.26±0.05^b
DGC cycles per hour	2.6±1.1^a	1.2±0.6^b	1.5±0.8^b	0.94±0.2^b
Total rate of CO₂ emission
(μl h^-1)	503.92±87.5^a	146.03±87.2^b	56.24±11.5^b	377.74±138.7^c
(μl h^-1 g^-1)	98.66±13.2^a	80.53±39.6^a,b	80.19±25.4^a,b	51.52±18.12^b

Species	P. femoralis	S. gariepinus	S. striatum	C. bacchus^*
N	5	7	6	6
Mass (g)	5.117±0.62^a	1.716±0.35^b	0.742±0.20^b	7.427±1.86^c
Rate of CO₂ emission (μl h^-1)
Mesothoracic spiracles	35.53±28.7^a	24.88±19.2^a	27.68±19.7^a	258.2±118.2^b
Posterior spiracles	468.39±97.13^a	121.45±75.3^b	28.56±11.0^b	119.5±123.6^b
Ratio of CO₂ emission
Mesothoracic:elytral case	0.083±0.07	0.31±0.3	1.56±2.1	3.47±2.0
	(range 0.019–0.22)	(0.11–1.06)	(0.22–5.9)	(0.42–6.81)
% total CO₂ emitted through mesothoracic spiracles	7.31±6.5	20.07±15.05	46.23±22.9	79.4±4.48
Frequency (mHz)	0.73±0.3^a	0.33±0.2^b	0.42±0.2^b	0.26±0.05^b
DGC cycles per hour	2.6±1.1^a	1.2±0.6^b	1.5±0.8^b	0.94±0.2^b
Total rate of CO₂ emission
(μl h^-1)	503.92±87.5^a	146.03±87.2^b	56.24±11.5^b	377.74±138.7^c
(μl h^-1 g^-1)	98.66±13.2^a	80.53±39.6^a,b	80.19±25.4^a,b	51.52±18.12^b

Comparison of the mean rate of CO₂ emission from the mesothoracic spiracles and elytral case in four species of dung beetles (mean± s.d.). N, number beetles measured. Means in the same row, followed by the same letter are not significantly different(P<0.05; ANOVA with LSD range test). ^*From Duncan and Byrne (2002).

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