05 in all cases) nor differed between sexes (t-test, NS in all cases; Table 1). The
dominant frequency of growling sounds was significantly lower than that of both feeding and courtship clicks (Kruskal–Wallis test: H = 11.9; n = 20, P < 0.01; Dunn's post hoc: P < 0.05). Hippocampus reidi produced two types of sounds: clicks and growling sounds. Although click sound production is commonly known from other members of the family Syngnathidae (e.g. Fish, 1953; Colson et al., 1998; Ripley & Foran, 2007; Anderson, 2009), a ‘tambour’ (=drum) sound was only described by Dufossé Ku0059436 (1874) in H. hippocampus. Similar to other fish, seahorses utter sounds in several behavioural contexts. The best investigated acoustic behaviour in seahorses and pipefishes is the production of clicking sounds selleck chemicals llc during feeding (e.g. Colson et al., 1998; Ripley & Foran, 2007; Anderson, 2009). Moreover, seahorses produce sounds during courtship, in stress situations (Dufossé, 1874; Anderson, 2009; present study), during male–male competition (Colson et al., 1998) and when introduced in a new environment (Fish, 1953). The functional significance of feeding clicks is unknown. Feeding clicks are not related to the success in capturing prey (Anderson, 2009), nor are they restricted
to food intake events because they were also recorded in unsuccessful attempts (T. P. R. Oliveira, pers. obs.). buy MG-132 It is unlikely that they are merely a by-product of prey capture because that may increase predation risk. Anderson (2009) suggested that clicks produced
by H. erectus during feeding signal a food source to a mate or may help in locating potential mates in a population where individuals are sparsely distributed. The duration of the feeding clicks produced by H. reidi was similar to that of H. zosterae (5–20 ms: Colson et al., 1998) and two pipefish species (5–22 ms: Ripley & Foran, 2007), but differed from those produced by the sympatric and morphologically similar H. erectus (110 ms: Anderson, 2009). Interspecific differences in temporal patterns of sounds might be used in species discrimination, especially in sympatric and closely related species (e.g. Myrberg, Spanier & Ha, 1978; Malavasi, Collatuzzo & Torricelli, 2008; Colleye et al., 2011). Sound production during reproductive behaviour is well known in at least 20 fish families, and typically, sounds are produced by males when advertising their territories, while attracting females to their nest sites or during courtship and spawning (for a review, see Myrberg & Lugli, 2006). So far female courtship and spawning sounds are known from the croaking gourami Trichopsis vittata (perciform family Osphronemidae) (Ladich, 2007) and from seahorses. In H. reidi (this study) and H. erectus (Anderson, 2009) both sexes vocalize during courtship, in particular on the last day, before copulation.