Table 2 Descriptive statistics (median, first and third quartile) of body traits, breeding coloration variables and testis and sperm traits of young and old males used in the analyses

Body size [cm]

4.90

4.70

5.10

5.20

4.95

5.40

Body mass [g]

1.562

1.372

1.712

1.812

1.617

2.031

Body condition

1.30

1.25

1.36

1.29

1.24

1.35

Red area [%]

14.84

6.22

27.21

13.74

6.29

21.94

Carotenoid chroma (A)

0.450

0.287

0.538

0.392

0.189

0.501

UV chroma (A)

0.271

0.244

0.291

0.245

0.209

0.273

Red/orange hue (A) [nm]

506.0

502.0

509.5

505.0

501.0

508.5

Total brightness (A)

2701.70

2072.17

3719.65

3267.38

2489.20

4939.09

Total brightness (R)

3075.86

2374.82

4326.12

1963.18

1402.66

3114.35

Absolute testis mass [g]

0.0107

0.0084

0.0140

0.0165

0.0135

0.0202

Relative testis mass (GSI)

0.697

0.585

0.862

0.951

0.731

1.103

Testis melanisation (L*_total)

39.00

26.88

47.13

60.50

49.38

67.50

Sperm number

9.3_*10⁶

6.0_*10⁶

12.2_*10⁶

10.7_*10⁶

7.9_*10⁶

14.4_*10⁶

Head length [μm]

1.106

1.067

1.128

0.991

0.958

1.011

Tail length [μm]

18.033

16.946

19.280

17.017

16.036

17.600

Head width [μm]

1.076

1.048

1.104

0.999

0.979

1.018

Mid-piece width [μm]

0.782

0.761

0.813

0.766

0.731

0.792

Mid-piece volume [μm³]

0.284

0.268

0.311

0.256

0.239

0.281

Mid-piece length [μm]

0.587

0.548

0.614

0.583

0.515

0.621

Head to tail length ratio

0.094

0.089

0.099

0.091

0.087

0.098