Aspects of sound communication in the pearlfishCarapus boraborensis andCarapus homei (Carapidae)

Abstract

Several species of Carapidae are known to have symbiotic relationships with marine invertebrates. The two most common species in Moorea (French Polynesia), Carapus boraborensis and Carapus homei, undergo conspecific and heterospecific encounters in the same holothurian host during which they produce sounds. Another characteristic of these fish lies in their abilities to produce sounds. The objective of this study was dual: (1) to seek if there was a sexual difference in the sounds produced by C. boraborensis; (2) to seek if there was a difference in the sound emissions between heterospecific and conspecific encounters. In each trial, sounds were only recorded when one individual entered the sea cucumber that was already occupied. In encounters, sounds were structured in regular pulse emissions whose pulse lengths and periods allowed to significantly distinguish each species, as well as both sexes in C. boraborensis. In the latter species, results show for the first time that temporal features of the emitted sounds can have a functional importance in sex identification. In heterospecific encounters, sounds were reduced 68% of the time to a single pulse emission and there was a modification in the pulse length of each species: it shortens in C. homei and it lengthens in C. boraborensis. It highlights that both carapids are able to adapt their sounds to the facing species. Because a modification of the sound appears to be done at the first emission, it is supposed that recognition precedes the sound emission.

New insights into sound production in <I>Carapus mourlani</I> (Carapidae)

“…They can be single, in trains, or in groups of two to three pulses in C. homei. They are single or in groups of five to six pulses in E. gracilis (Parmentier et al 2003b, 2008, Lagardère et al 2005. Moreover, carapid sounds can also show some variation.…”

“…Another interesting aspect of this group of fishes is their ability to produce sounds (Parmentier et al 2003a,b, 2008, Kéver et al 2014. In captivity, series of pulsed sounds have been recorded for Carapus boraborensis (Kaup, 1856), Carapus homei (Richardson, 1846), and Encheliophis gracilis (Bleeker, 1856), only after an individual had entered a sea cucumber that was already occupied by a conspecific or a heterospecific organism (Parmentier et al 2003b, Lagardère et al 2005). In the Mediterranean Carapus acus (Brünnich 1768), pulses were recorded when the fish was swimming in the observation tank, whereas Carapus mourlani (Petit, 1934) produced calls when competing for access to the oral aperture of a sea star (Parmentier et al 2006a).…”

“…Sounds would be used, at least, for species-specific identification and, in some cases, for sex identification (Lagardère et al 2005). Because sound attenuation by the sea cucumber tegument is negligible at the frequencies emitted by carapids, they have the potential to call for mates from the safety of their hosts (Lagardère et al 2005).…”

“…Sounds would be used, at least, for species-specific identification and, in some cases, for sex identification (Lagardère et al 2005). Because sound attenuation by the sea cucumber tegument is negligible at the frequencies emitted by carapids, they have the potential to call for mates from the safety of their hosts (Lagardère et al 2005). In the species Onuxodon fowleri (Smith, 1955), known to live inside pearl oysters, the sounds can be amplified by the shell cavity enhancing the communication distance (Kéver et al 2014).…”

“…In C. boraborensis, the sounds are composed of trains of 11-30 pulses of a duration of 25-30 s (Parmentier et al 2003b, Lagardère et al 2005. Carapus homei mainly produces brief sequences (about 10 pulses), lasting for 3-5 s, of a slower regular beat although in some cases trains can be made of double pulses.…”