Host preference and habitat segregation among Red Sea anemonefish: effects of sea anemone traits and fish life stages

Abstract

Competition drives habitat segregation between adults and juveniles in many types of organisms, but little is known about this process in anemonefish that compete for host sea anemones which differ in habitat quality. We performed field and laboratory experiments to determine causes of habitat segregation in 2-band anemonefish Amphi prion bicinc tus on coral reefs in the northern Red Sea, where juvenile fish mainly occupy leathery sea ane mones Heteractis crispa, and breeding adults almost exclusively inhabit bulb-tentacle sea anemones Entac maea quadricolor. E. quadricolor were usually larger than H. crispa, and expanded more in response to fish presence. Adult fish visually concealed a larger proportion of their body surface area among the relatively thick tentacles of E. quadricolor than among the thinner tentacles of H. crispa, while juveniles were concealed equally well in both hosts. During field experiments, vacated E. quadricolor were colonized rapidly by fish, whereas H. crispa were not. In laboratory choice experiments, fish at all post-settlement life stages preferred E. quadricolor, and large individuals monopolized this host and relegated subordinates to H. crispa. We conclude that competitive exclusion drives habitat segregation among life stages of this anemonefish and that host anemone traits underlie this process. The non-preferred host H. crispa may func tion as a refuge for juvenile fish while they wait for space to become available in the preferred host E. quadricolor, where they are able to attain sexual maturity. The tentacles of the sea anemone Entacmaea quadricolor offer optimal cover for anemonefish Amphiprion bicinctus.

RETRACTED: Reef fishes can recognize bleached habitat during settlement: sea anemone bleaching alters anemonefish host selection

“…By contrast, A. latezonatus, which uses E. quadricolor and H. crispa as habitat [38], showed a strong preference for the latter species, and was the only fish to preferentially select a bleached over an unbleached host. Heteractis crispa has been suggested to serve as important nursery habitat for A. latezonatus in the Solitary Islands Marine Park, Australia (A. Scott and H. Malcolm 2016, personal communication), and similarly for A. bicinctus in the Red Sea [53].…”

Anemonefish oxygenate their anemone hosts at night

“…wedging, switching) when anemonefishes reside among sea anemone tentacles. Wild individuals of both A. bicinctus and E. quadricolor attain much larger maximum sizes than the individuals examined here, and in the Red Sea, each individual of E. quadricolor usually hosts a pair of adult fish plus up to three juveniles (Chadwick and Arvedlund, 2005;Huebner et al, 2012). The ecophysiological effects of anemonefish size, quantity and social structure on anemone hosts in the wild are largely unknown, and further investigation is needed to clarify the nocturnal behaviors of anemonefish in the wild.…”

Host specialist clownfishes are environmental niche generalists

“…Indeed, juveniles of a host generalist clownfish species can occupy different anemone species than adults. For example, in the case of Amphiprion bicinctus, which occurs in the Red Sea, adults prefer a host in which they can fully conceal their body, while juveniles, which are smaller in size, accommodate well in smaller anemones [48]. It is unclear whether this situation occurs in other regions [49] where the species density of clownfish species is higher (A. bicinctus is the only clownfish species occurring in the Red Sea and juveniles thus compete only with adults).…”