Anemonefish Amphiprion Clarkii Research Articles

Effects of Personality and Behavioral Syndromes on Competition for Social Hierarchical Status in Anemonefish Amphiprion clarkii.

In this study, the behavioral ethogram of Amphiprion clarkii during the growth phase prior to sexual differentiation was summarized based on behavioral observations in three social environments. These behaviors can be classified into four categories: in addition to normal behaviors, the other three categories of behaviors-threatening, agonistic, and appeasing behaviors-represent different intentions in interactions with other individuals. Subsequently, the personalities of each individual were assessed by testing their reactions to intruders. These individuals mainly exhibited two distinct personality types: bold-aggressive and shy-submissive. In pairing experiments, the interactive behaviors of the anemonefish were observed in pairing combinations of different body sizes and personalities. The impact of personality on the establishment of a stable social hierarchy was confirmed by significant differences in the success rates of different pairing combinations, with the frequency of appeasing behaviors being the main factor influencing the success rate. Our results suggested that in natural waters, when juvenile individuals migrate among host anemones, shy-submissive individuals are more likely to be accepted due to their appeasing behaviors towards larger individuals, thus avoiding the risk of being attacked and bitten, and benefiting the survival of the individual. Conversely, bold-aggressive individuals are more likely to be driven away to another host anemone due to their unwillingness to settle for a lower-ranked status, thereby contributing to population dispersal and increasing opportunities for gene exchange between populations.

Scaring Nemo: Contrasting effects of observer presence on two anemonefish species.

Behaviours of Clark's anemonefish Amphiprion clarkii and the dusky anemonefish Amphiprion melanopus were studied in Vanuatu. Six anemones and their resident fish were observed for typical behaviours (hiding, watching, roaming, inter-, and intraspecific behaviour) with and without the presence of a snorkelling observer. Observer presence had significant but contrasting effects on hiding behaviour in A. clarkii and A. melanopus. Bolder anemonefish species may be able to outcompete other species in areas with high human presence.

Notes on the Nesting Success and Fecundity of the Anemonefish Amphiprion clarkii at Miyake-Jima, Japan

Notes on the Nesting Success and Fecundity of the Anemonefish Amphiprion clarkii at Miyake-Jima, Japan

Reproductive Behavior of the Anemonefish Amphiprion clarkii at Miyake-Jima, Japan

Reproductive Behavior of the Anemonefish Amphiprion clarkii at Miyake-Jima, Japan

Immunohistochemical Evidence for 11β-hydroxylase (P45011β) and Androgen Production in the Gonad During Sex Differentiation and in Adults in the Protandrous Anemonefish Amphiprion clarkii

To obtain basic information on the endocrine mechanisms underlying sex change in the protandrous anemonefish Amphiprion clarkii, we examined the immunolocalization of the steroidogenic enzyme cytochrome 11beta-hydroxylase (P45011beta), which is involved in 11-ketotestosterone (11-KT) production, and analyzed the ability of gonads to produce steroid hormones throughout the sex differentiation process and at the breeding stage. Immunopositive reactions against P45011beta appeared in sexually undifferentiated gonads at 30 days post hatching (dph). The number of immunopositive cells continued to increase during ovarian differentiation (from 60 to 180 dph) and throughout the formation of ambisexual gonads with both ovarian and testicular tissue until 270 dph. In the male phase, strongly immunopositive cells were observed in the cellular interstices of both testicular and ovarian tissues. P45011beta was localized only in the theca cells enclosing developed oocytes in the female phase. In-vitro 11-KT production in the gonads gradually increased with testicular differentiation (before, during, and after differentiation). Production of 11-KT in the gonads was higher in the male phase than during testicular differentiation or in the female phase. Our results suggest that androgen is involved in testicular differentiation during sex differentiation and spermatogenesis.

Differentiation of ambisexual gonads and immunohistochemical localization of P450 cholesterol side-chain cleavage enzyme during gonadal sex differentiation in the protandrous anemonefish, Amphiprion clarkii

To clarify the relationship between steroid hormones and sex differentiation of the protandrous anemonefish Amphiprion clarkii, we histologically examined its gonadal differentiation. From hatching to 30 days post hatching (dph), all of the gonads surveyed were sexually undifferentiated. The gonads of all fish first differentiated into ovaries at 60 dph, and the oocytes gradually developed and increased in number as the ovaries grew up until 183 dph. Some cysts of differentiated spermatogenic germ cells appeared in the ovaries at 214 dph, and ambisexual gonads with both ovarian and testicular tissues formed by 273 dph. Using immunohistochemistry, we then investigated the expression of cytochrome P450 cholesterol side-chain cleavage enzyme (P450scc), during gonadal sex differentiation. P450scc-immunopositive reactions first appeared in sexually undifferentiated gonads at 30 dph. Beginning at 60 dph, the number of strongly positive cells increased throughout the differentiation of the ovaries and continued to increase during the testicular differentiation until 210 dph. Immunopositive cells were observed more frequently in ovarian tissue than in testicular tissue in the ambisexual gonads at 270 dph. These results suggest that endogenous steroid hormones are important for the sex differentiation, including the primary sex differentiation and subsequent testicular differentiation, of the anemonefish.

Long-term observation in situ of the anemonefish Amphiprion clarkii (Bennett) in association with a soft coral

Long-term observation in situ of the anemonefish Amphiprion clarkii (Bennett) in association with a soft coral

Social and mating systems of the protandrous anemonefish Amphiprion perideraion under the influence of a larger congener

AbstractThe effect of a larger anemonefish Amphiprion clarkii (Bennett) on the social and mating system of a smaller congener Amphiprion perideraion (Bleeker) was investigated on a coral reef at Okinawa, Japan, where both species use the same host sea anemone Heteractis crispa (Ehrenberg). The population of A. perideraion consisted of adult, subadult and juvenile groups. Adult groups, which consisted of one or two adults and a varying number of subadults and juveniles, usually did not share the host with A. clarkii. In contrast, subadult and juvenile groups, which included no adults, always cohabited with A. clarkii. In the heterospecific groups, subadult A. perideraion were able to mature histologically, and changed to female when they were the largest among conspecific members, although their reproduction was suppressed by A. clarkii. After all members of A. clarkii emigrated or disappeared from a heterospecific group, adult A. perideraion could begin breeding. I suggest that A. perideraion in both heterospecific and conspecific groups adopt a mating strategy that involves waiting for vacated breeding posts because of their low mobility and a low host density.

Do anemonefishes use molecular mimicry to avoid being stung by host anemones?

Anemonefishes are known to have a protective mucous coat that allows them to contact the tentacles of their host anemone without being stung. There are two conflicting hypotheses as to the source and biochemical properties of this mucous coating. One hypothesis proposes that anemonefishes acquire anemone substances from their hosts during the behavioral process of acclimation, that protect the fish from being stung. Anemonefishes are considered to use anemone mucus as “chemical camouflage” or “macromolecular mimicry” to avoid recognition as “not-self” by the anemone, and possible subsequent stinging. Another hypothesis is that anemonefishes produce their own protective mucus coat, which lacks substances that elicit cnida (nematocyst and spirocyst) discharge by their hosts. The present study used immunological techniques to test whether the anemonefish Amphiprion clarkii (Bennett) (which was innately protected from two of the anemones used in the present study) has a mucous coat that resembles the external mucus of anemones. Polyclonal antibodies were prepared to the mucus of four species of anemones [ Heteractis crispa, (Ehrenberg) Stichodactyla haddoni (Saville-Kent), Macrodactyla doreenensis (Quoy and Gaimard), and Condylactis gigantea (Weinland)]. Ouchterlony (double immunodiffusion) tests showed that different antigens were present in the mucus of the four anemone species. Anemone antigens were not detected in the mucous coating of either naive (fish that had never before encountered sea anemones) or associated (those living with sea anemones) anemonefishes in Ouchterlony tests. However, more sensitive ELISA (enzyme-linked immunosorbent assay) tests showed that anemone mucus antigens were present in the mucous coating of associated anemonefish, but not naive fish. This showed that an innately protected A. clarkii does not produce a mucus coat that is biochemically similar to that of anemones, but that the same fish does acquire anemone substances in its mucus coat when it associates with anemones in aquaria. It remains to be shown whether these anemone substances actually provide the initial protection for those anemonefishes that must undergo acclimation behavior in order to keep from being stung by their host sea anemones, or additional protection for innately protected fishes.

Step-fathering in the anemonefish Amphiprion clarkii: a removal study

Males were removed artificially from 33 brooding pairs in a population of the anemonefish Amphiprion clarkii living in the warm temperate waters off Japan. Two-thirds of them were replaced by foreign males before the eggs disappeared or hatched. A total of 17 replacement males cared for the foster eggs with the remaining females, and in five pairs the males assumed nearly full responsibility for caring for the eggs, in the same way as males in natural pairs. The most characteristic interaction between the female and replacement male was butting by the former and substrate-biting by the latter in the close proximity of the nest. It appeared that, by butting, the females were persuading or compelling their new mates to undertake the egg-care duty. It was concluded that step-fathering by the replacement male is payment for pairing with the female.

Longevity of the Anemonefish Amphiprion clarkii at Miyake-Jima, Japan with Notes on Four Other Species

Observations at a single study site over a period of 14 years supplied evidence of long term residence at specific locations by six individuals representing five species. A single anemonefish (Amphiprion clarkii) was observed over a period of 11 years and was estimated to be at least 13 years old when it disappeared. Other individuals disappeared at the following estimated ages: Centropyge tibicen (two individuals) = six years; Lactoria diaphana = eight years; Dendrochirus zebra = five years; Plectorhynchus pictus = seven years. The A. clarkii individual was estimated to have contributed about 160,000 propagules in its lifetime, while outliving three mates as a female after nearly three years as a functional male. Evidence is presented showing that sexually functional males disappear more frequently than females, suggesting an advantage for protandry in a monogamous species.

Growth of the anemonefish Amphiprion clarkii in temperate waters, with special reference to the influence of settling time on the growth of 0-year olds

The temperate population of the tropical anemonefish Amphiprion clarkii has a seasonality of reproduction, larval settlement and growth. There was a considerable difference in size (15–47 mm) among 0-year olds in December, after the season of larval settlement and growth. This difference could be attributed mainly to a difference in the duration of the first growing season spent after settlement and a social inhibition of growth of the subordinate late settlers by frequent attacks by the dominant early settlers. The growth equation which was used to describe the growth of tagged individuals estimated that an anemonefish would get an opportunity to spawn within four of five years after settlement. Breeding adult pairs occupied almost all sea anemones essential to breeding within a 50×50 m study area, and all 17 new adults that matured from non-breeding juveniles to breeding adults between June 1983 and August 1985 were found in the territories from which either or both of the mated adults had disappeared. The new adults were large juveniles who had resided near those vacant territories before. These results suggest that the onset of breeding by an individual is not only determined by his age, but also by his ranking in the dominance hierarchy. Therefore, the difference in size among 0-year olds in December might give rise to the difference in age of the earliest breeding and might be a factor in making a female apply more reproductive effort at the beginning of the season.

The acclimation of anemone fishes to sea anemones: Protection by changes in the fish's mucous coat

The anemone fish Amphiprion clarkii (Bennett) lives unharmed among the tentacles of sea anemones following acclimation. What occurs during this process is unknown; however, two hypotheses have been formulated recently. One suggests that the fish coats itself with anemone mucus to mask its chemical stimulus for cnida discharge. The second suggests that the fish is protected by some alteration in its own mucous coating. In order to test these alternative hypotheses, a surrogate anemone was constructed and an Amphiprion allowed to associate with it prior to being placed with a real anemone. If the subsequent acclimation times to a real anemone are reduced significantly after exposure to the surrogate anemone, one would conclude that the fish does not need to coat itself with anemone mucus to become protected. After association with a surrogate anemone, it was found that the acclimation times of isolated A. clarkii to the sea anemone Macrodactyla doreensis (Quoy & Gaimard) decreased seven-fold. These results support the hypothesis that the fish is responsible for manufacturing its own protection from sea anemones, presumably by independently altering its own mucous coat during acclimation.

Morphological and genetic variation in Japanese populations of the anemonefish Amphiprion clarkii

Geographic populations of the anemonefish Amphiprion clarkii (Bennett) from 6 widely separated locations off the coast of southern Japan are morphologically different, exhibiting (1) latitudinal clinal patterns in color pattern and meristics and (2) degrees of genetic differentiation. Electrophoretic examination of 7 polymorphic loci (95% level) among 6 populations collected between July 1979 and January 1980 revealed an average genetic distance value of 0.008. Significance was demonstrated for 39 out of 105 (37%) tests of heterogeneity. Averaged over the 6 populations, the percentage of polymorphic loci ( $$\bar P$$ 0.95) was 24.6% and the proportion of heterozygous loci per individual ( $$\bar H$$ ) was 0.0613. The results indicate that genetic clines are absent and suggest that the morphological variation may not be genetic. Relative isolation of genetic populations may be maintained by (1) localized larval dispersal resulting from a relatively short larval stage, and (2) current gyres tending to trap larvae, increasing the return of juveniles to their adult coastal habitat. Morphological clines may be due to clines in ecological parameters related to latitude.