Females’ sampling strategyto comparatively evaluate prospective mates in the peacock blenny Salaria pavo

Lisa Locatello, Maria Berica Rasotto

SUPPLEMENTARY MATERIAL AND METHODS

Study species

The peacock blenny, S. pavo, is a medium-size fish (up to 17 cm total length) that inhabits the rocky shores of the Mediterranean Sea and adjacent Atlantic coast (Zander 1986). The mating system is promiscuous: males receive eggs in their nest from different females and care for overlapping clutches (Patzner et al. 1986; Pizzolon 2010; Ros et al. 2010; Pizzolon et al. 2012), and females spawn with several males during the breeding season (Patzner et al. 1986). Nesting males are larger than females and exhibit a pronounced head crest that during the breeding season shows a yellow patch on both sides (Oliveira et al. 1999). Larger males may receive more eggs because they occupy better nests (Oliveira et al. 1999; Pizzolon 2010), but have been found to achieve higher mating success regardless of the size of their nest (Gonçalves et al. 2002a). Male body size is also positively related to the number of sperm produced (Pizzolon et al. 2012). Head crest size is informative of male’s fertility and parenting effort (Pizzolon et al. 2012). Moreover, it seems to convey information on different time scales since its general development reflects genetic and/or condition at the time of formation and growth, whilst the colour intensity of its yellow patch signals current health status (Locatello et al. 2012). Male mating success, in term of eggs received, appears to be influenced by specific male traits (Oliveira et al. 1999; Gonçalves et al. 2002b; Fagundes et al. 2007; Ros et al. 2010) as well as by his general attractiveness (Pizzolon et al. 2012). In choosing prospective males, females assess male body size (Fagundes et al. 2007), head crest size (these latter both positively related to male body size) (Gonçalves et al. 2002b; Gonçalves and Oliveira 2003) and coloured ornamentation (Locatello et al. 2012).

Fish capture and maintenance

Fish were captured by scuba-divers using hand-held nets in the Venetian Lagoon during their breeding season (June-August)and immediately transported to the lab where they were maintained in group of three/four individuals in 70L tanks until the experiment (within few days). All tanks were provided with sandy bottoms and artificial shelters. Water was renewed daily, temperature and light regime followed natural conditions. Fish were fed daily with fresh chopped Mytilus sp.

Measure of male morphological traits

To measure male phenotypic traits (TL, head crest size, area of the yellow patch on the head crest) males were anesthetized in a water solution of MS222 (Tricaine sulphate, Sandoz) and photographed alongside a reference rule. The digital picture were further analysed to get the measures of interest.

To assess the colour intensity of the yellow patch each male was housed for 10 minutes in a transparent glass box and compared to a Pantone colour scale fixed on the box wall. Each male was assigned a value ranging from 0, absence of colour, to 4, maximum colour intensity (1= R 255, G 200, B 000; 2= R 255, G 210 B 047; 3= R 225 G 220 B 91, 4= R 225, G 230, B 139). This comparison was performed on free swimming males to avoid problems of colour fade that typically occurs after anaesthesia.

SUPPLEMETARY RESULTS

Table S1. Detailed results of the principal component analyses (PCA) on male attractiveness traits:

Principal component loadings
PC1 / PC2 / PC3
1 Male total length
2 Head crest area
3 Yellow patch area
Eigenvalues
Total variance (%)
Cumulative variance (%) / 0.817
0.947
0.870
2.321
77.36
77.36 / 0.562
-0.078
-0.443
0.518
17.28
94.64 / 0.129
-0.311
0.218
0.161
5.36
100

Table S2. Attractiveness within each of the 9 sets of males (scores of first component from PCA):

range / mean ± st.dev. / variance
1 / -0.997 – 0.915 / -0.282±0.786 / 0.618
2 / -1.436 – 1.485 / -0.439 ± 0.982 / 0.964
3 / -1.022 – 0.636 / -0.112 ± 0.670 / 0.449
4 / -1.41 – 0.656 / -0.614 ± 0.705 / 0.497
5 / -1.266 – 0.914 / 0.041 ± 0.732 / 0.536
6 / -0.234 – 0.491 / 0.060 ±0.381 / 0.146
7 / -1.350 – 1.446 / 0.390 ± 0.987 / 0.973
8 / -0.726 – 2.132 / 0.333 ± 0.990 / 0.976
9 / -1.065 – 3.183 / 0.658 ± 1.737 / 3.017

Table S3. Mean values of preference (time in seconds):

N / mean± st.dev.
On all females
total preference time
total time with the preferred male / 27
27 / 302 ± 185.2
169.0 ± 114.0
time with each of the other male of the set (=total time spent with other males / number of other males visited) / 27 / 35.8 ± 24.6
On females that visited the preferred male more than once
time with the preferred male during the very first visit / 23 / 53.8 ± 72.9
time with preferred male in each visit (= total time with preferred male / total number of visits to preferred) / 23 / 57.1 ± 52.8
% of time with the preferred male at the first visit (on the total time spent with the preferred male) / 23 / 32.3 ± 30.9

References

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