Circling and touching: two new behaviours in the courtship of the Picasso triggerfish Rhinecanthus aculeatus (Linnaeus, 1758)
Résumé
The reproduction of Rhinecanthus aculeatus (Linnaeus,
1758), a tropical Indo-Pacific reef fish, occurs around
the full and new moon (Kuwamura 1997). Spawning
begins 16 to 45 min before the sunrise. The courtships
begin 7 to 27 min before the spawning. A specific behaviour
of the courtships is when the male places its
rostrum against the caudal peduncle of the female
(Kuwamura 1997).
Observations have been recorded in the lagoon of
Tiahura [shallow sandy area (0.5 - 2 m deep) with
algae Hypnea spinella (C.Agardh) Kützing, 1847 -
Moorea, French Polynesia; 17°29′27′ S, 149°53′32″O]
in March and April 2015. Fifteen R. aculeatus (five
males and ten females) lived in this area where the
males have territories, which included the subterritories
of the females. During video-recorded courtships,
in addition to the behaviour described by
Kuwamura (the nuzzling), two new behaviours have
been observed: circling and touching. During the circling,
the male and the female swim to the surface in
progressively larger circles (Fig. 1). The circling behaviour
has been observed in other Balistidae such as
Pseudobalistes flavimarginatus (Rüppell, 1829) and
Balistapus undulatus (Park, 1797) (Lobel and
Johannes 1980). During the touching, the abdomens
of the male and the female’s touch each other without
gametes emission (Fig. 2). The touching has been reported
for Xanthichthys mento (Jordan and Gilbert
1882) (Kawase 2003).
Although Balistidae present different reproductive
strategies, they have common reproduction features,
such as the time and the day of hatching and
spawning (Kawase 2003). Our observations are innovative
because the courtship of R. aculeatus is more
complicated than previously described. This result
suggests, thus, that Balistidae have also some common
courtship behaviour features. These behaviours may
facilitate the release of gametes, as with the nuzzling
(Kuwamura 1997) or can convince the partner to mate.
We do not know if these patterns are phylogenetically
related. But as the egg care strategy of Balistidae (biparental
vs maternal) appears to be related to the distribution
of food and breeding sites, more than by the
phylogeny (Kuwamura 1997), more studies on this
topic will be useful to better understand the establishement of these behaviours.