Presence of cleaner wrasse increases the recruitment of damselfishes to coral reefs.

Mutualisms affect the biodiversity, distribution and abundance of biological communities. However, ecological processes that drive mutualism-related shifts in population structure are often unclear and must be examined to elucidate how complex, multi-species mutualistic networks are formed and structured. In this study, we investigated how the presence of key marine mutualistic partners can drive the organisation of local communities on coral reefs. The cleaner wrasse, Labroides dimidiatus, removes ectoparasites and reduces stress hormones for multiple reef fish species, and their presence on coral reefs increases fish abundance and diversity. Such changes in population structure could be driven by increased recruitment of larval fish at settlement, or by post-settlement processes such as modified levels of migration or predation. We conducted a controlled field experiment to examine the effect of cleaners on recruitment processes of a common group of reef fishes, and showed that small patch reefs (61-285 m(2)) with cleaner wrasse had higher abundances of damselfish recruits than reefs from which cleaner wrasse had been removed over a 12-year period. However, the presence of cleaner wrasse did not affect species diversity of damselfish recruits. Our study provides evidence of the ecological processes that underpin changes in local population structure in the presence of a key mutualistic partner.

Cephalo-traumatic secretion transfer in a hermaphrodite sea slug.

Mating rituals in the animal kingdom are often quite extraordinary, in particular when mating is traumatic. We here describe the exceptional traumatic mating behaviour of the currently undescribed sea slug, Siphopteron sp. 1. Similar to four congeners, Siphopteron sp. 1 routinely exhibits traumatic secretion transfer through a stylet-like penis appendage. Contrary to previous descriptions, however, prostate secretions are injected centrally into the partner's forehead, representing, to our knowledge, the first-known instance of 'cephalo-traumatic secretion transfer'. We further provide a comparative quantification of within- and between-species variation in injection sites and derive a potential neurophysiological function of prostate secretions that are injected close to, or into, the central nervous system.

Power and temptation cause shifts between exploitation and cooperation in a cleaner wrasse mutualism.

In many instances of cooperation, only one individual has both the potential and the incentive to 'cheat' and exploit its partner. Under these asymmetric conditions, a simple model predicts that variation in the temptation to cheat and in the potential victim's capacity for partner control leads to shifts between exploitation and cooperation. Here, we show that the threat of early termination of an interaction was sufficient to induce cleaner wrasse Labroides dimidiatus to feed selectively against their preference (which corresponds to cooperatively eating client fish ectoparasites), provided that their preference for alternative food was weak. Under opposite conditions, cleaners fed selectively according to their own preference (which corresponds to cheating by eating client mucus). By contrast, a non-cleaning fish species, Halichoeres melanurus, failed to adjust its foraging behaviour under these same conditions. Thus, cleaners appear to have evolved the power to strategically adjust their levels of cooperation according to the circumstances.

No effect of mate novelty on sexual motivation in the freshwater snail Biomphalaria glabrata.

BACKGROUND: When mating effort (e.g. via ejaculates) is high, males are expected to strategically allocate their resources depending on the expected fitness gains from a given mating opportunity. One mechanism to achieve strategic mating is the Coolidge effect, where male sexual motivation declines across repeated encounters with a familiar partner, but resuscitates when encountering a novel female. Experimental tests of male mate choice via mechanisms such as the Coolidge effect, however, remain scarce. Moreover, it is untested to date whether the Coolidge effect occurs in a sex-specific manner in simultaneous hermaphrodites, where the motivation to mate with a familiar partner may vary with previous mating activity in the male or female role. RESULTS: We exposed focal hermaphroditic freshwater snails, Biomphalaria glabrata, repeatedly to either a familiar or a novel partner. None of our proxies of sexual motivation (remating likelihood, mating delay, copulation duration) varied between the novel and familiar partner treatments. Moreover, the mating role taken during the first copulation did not affect the subsequent choice of mating roles in the familiar partner treatment as would be expected if focals preferred to avoid mating twice in the same role with a familiar partner. This indicates the absence of sex-specific effects of partner novelty. CONCLUSION: Our data indicate that mate novelty does affect neither overall sexual motivation nor the choice of mating roles in B. glabrata. Hence, male mate choice via a Coolidge effect appears inexistent in this invertebrate hermaphrodite. We discuss the possible roles of insufficient fitness gains for discriminatory behaviour in populations with frequent mate encounters as well as poor mate discrimination capacities. Our findings lend also no support to the novel prediction that sexual motivation in simultaneous hermaphrodites varies with the mating roles taken during previous copulations, calling for empirical investigation in further hermaphrodite systems.

Female fitness optimum at intermediate mating rates under traumatic mating.

Traumatic mating behaviors often bear signatures of sexual conflict and are then typically considered a male strategy to circumvent female choice mechanisms. In an extravagant mating ritual, the hermaphroditic sea slug Siphopteron quadrispinosum pierces the integument of their mating partners with a syringe-like penile stylet that injects prostate fluids. Traumatic injection is followed by the insertion of a spiny penis into the partner's gonopore to transfer sperm. Despite traumatic mating, field mating rates exceed those required for female fertilization insurance, possibly because costs imposed on females are balanced by direct or indirect benefits of multiple sperm receipt. To test this idea, we exposed animals to a relevant range of mating opportunity regimes and assessed the effects on mating behavior and proxies of female fitness. We find penis intromission duration to decrease with mating rates, and a female fecundity maximum at intermediate mating rates. The latter finding indicates that benefits beyond fertilization insurance can make higher mating rates also beneficial from a female perspective in this traumatically mating species.