Acoustic comparison among soniferous sand gobies
The sounds of seven soniferous sand gobies, Knipowitschia
panizzae Verga, 1841, Ninnigobius canestrinii (Ninni
1883), Orsinigobius punctatissimus (Canestrini 1864),Pomatoschistus marmoratus (Risso 1810), P. pictus (Malm,
1865), P. microps (Krøyer, 1838) and P. minutus(Pallas 1770), were previously recorded and characterised (Lugli et al.,
1995; Lugli & Torricelli, 1999; Malavasi et al., 2008; Amorim et al.,
2013, 2018; Bolgan et al., 2013; Pedroso et al., 2013). However, these
acoustic data were never combined into a single phylogenetic dataset and
analysed interspecifically. Therefore, we studied their interspecific
acoustic variability (P. marmoratus was separated geographically
into two populations, Italian and Portuguese). Briefly, the species were
sampled either from brackish habitats in north Adriatic Sea (K.
panizzae , P. marmoratus and N. canestrinii ), from
freshwaters of north-west part of Reggio Emilia Romagna, Italy (O.
punctatissimus ) (Lugli et al., 1995, 1997; Lugli & Torricelli, 1999;
Lindström & Lugli, 2000), from Portuguese marine/brackish waters
(Amorim et al., 2013, 2018; Bolgan et al., 2013) or the west coast of
Sweden (Pedroso et al., 2013). Sound recordings gathered from the
previously conducted laboratory experiments were re-analysed to allow
for interspecific comparison with a minimal measurement experimental
error. All investigated sand gobies produced pulsatile sounds, thus
enabling acoustic interspecific comparisons. The dataset was composed of
36 individuals of eight soniferous sand gobies including O.
croaticus (min – max: 3 – 5 individuals, except for a single
individual of P. microps ), with at least three sounds recorded
per individual. In total we calculated the means for five acoustic
variables (temporal: DUR in ms, NP, PRR in Hz; spectral: PF and FM, both
in Hz) for each individual. Since gobies included in the current study
were recorded at different water temperatures (range: 15.8 – 22.6°C)
and it is well known that the ambient water temperature affects fish
acoustic signals (Vicente et al., 2015; Ladich, 2018), we conducted two
separate multivariate analyses: the first involving the complete dataset
(all five acoustic features for each species), and the second excluding
the temporal features (DUR and PRR) known to be influenced by water
temperature (Lugli et al., 1996; Vicente et al., 2015).