Ecology Characteristic Mix of Many Red Clownfish (Amphiprion Frenatus) and Blue Damselfish

An anemone city off Japan. We see the Ecology characteristic mix of many red clownfish (Amphiprion frenatus) and blue damselfish. The many sea anemones belong to the species Entacmaea Edited by quadricolor Michael Arvedlund, PhD and Peter Symes

ILLUSTRATIONS BY GUNILD AND PETER SYMES

Clownfish sea anemones usu- Anemone cities are not unusual in some ally live solitary lives. On many places. However, these large assemblages are rare compared to the high coral reefs there will normally abundance of solitary giant sea anemo- be only one individual for each nes you may find snorkeling or diving on 50 to 100 meters, perhaps 10 to most tropical shallow coral reefs. There 20 meters of reef. But occasion- are only two known such assemblages in the bay of Aqaba in the Red Sea. ally groups of up to several hun- One is at Ras Muhammad close to dreds of clownfish sea anemo- the popular dive resort Sharm el Sheikh nes are found together within a where it is but one of the many popular small area in an assemblage we dive sites in the area and well visited by many divers being completely oblivious call anemone cities. to the fact that they are diving on a rather unique and fragile structure. They are also found in some parts of Southern Japan, in the eastern area of the Pacific and certain parts of the Indian Ocean. Perhaps the largest tropical sea anemone assemblage in the 2 world covering about 2 km of sea NAOKO MORIMOTO - RYUKYU UNIVERSITY, SESOKO STATION, OKINAWA, JAPAN bottom lives in central Indonesia. This anemone city was recently described by structure and distribution of these dense simply because the necessary resources, Microhabitat the renowned German underwater pho- sea anemone assemblages and what manpower and funding are still not read- The point is that whatever regulates or tographer Helmut Debelius in his Asian kind of impact the unusually high con- ily available in coral reef research. limits the abundance of a species and underwater guide. centration of host anemones have on This is rather unfortunate as unusually their reproductive success is highly relat- the local ecology—especially the settle- large “super-structures” in nature, such ed to the extent of its microhabitat. In this Super structures ment, reproduction and behavior of the as the anemone city at Ras Mohammed case, the microhabitat for a clownfish is Anemone cities are not well understood, symbiotic fishes and crustaceans. Most at the tip of Sinai peninsula, may provide its host anemone and the few meters of but clearly something very different research studies have, so far, only studied us with a much better understanding coral reef surrounding the sea anemone. goes on here. Little is known about the the biology of solitary host sea anemones of both fish and sea anemone biology. Usually a single anemone. So, when

The Danish scientist Ms lar dive spot in South Thea Marie Brolund Sinai, called “anemone The Mysterious Life and Territories in assisted by Anders city”, a dive site often Tychsen and Michael described and recom- Arvedlund recently con- mended as an excel- ducted the first compre- lent dive experience in hensive scientific exami- most popular Red Sea nation of the popu- dive guides. PETER SYMES Anemone City 85 X-RAY MAG : 7 : 2005 EDITORIAL FEATURES TRAVEL NEWS EQUIPMENT BOOKS SCIENCE & ECOLOGY EDUCATION PROFILES PORTFOLIO CLASSIFIED BONAIRE Image of the Red Sea Closeup of an unusal anemonefish Amphiprion pink variety (H. crispa bicinctus in a solitary is normally grey in host sea anemone color) of the clown- Entacmaea quadricolor. fish sea anemone This type of sea anemo- Heteractis crispa, Hospitality Without Limits nes and the fish is what from a shallow coral most snorkelers and divers reef in the southern are likely to encounter Japan during a visit to the Red Sea. Raz Bob, 10 m. depth, Sharm El Sheikh

and behavioral pat- city assemblage of the �� terns. These char- magnificent sea anem- �� acteristic can be ones (Heteractis mag- �� quite obvious to the nifica) is, for example, �� observant visiting found at the southern- �� diver. most point of the Sinai �� Exactly which Peninsula, northern Red �� patterns, how, Sea. It is situated on a $ when and why this reef approximately 150 599 pp/sext

MICHAEL ARVEDLUND complexity and meters east of the pop- MICHAEL ARVEDLUND �� infrastructure is put ular Shark and Yolanda �� nature comes up with an unusual together is some- Reef. At present, about �� super-structure such as an anem- thing we know practically nothing 20-30 large diveboats �� one city, all the usual dynamics about. This gives cause for great with up to 300 divers and the three spot damsel fish your camera. A total of 190 large �� and relationships between the �� concern as these rare structures and 1500 snorkellers visit this (Dascyllus trimaculatus). The clownfish sea anemones were �� organisms in the microhabitat are at great risk of disappearing magnificent superstructure every former are obligate symbionts in counted here. Some were solitary, are bound to change drastically. in front of our very eyes due to day. Most of these visitors have host sea anemones and the latter and some were clusters of pre- New and more complex interac- �� heavy loads of ignorant visiting absolutely no education in proper are facultative symbionts as juve- sumably clonal morphs (offspring �� tions arise between the surround- scuba divers. behavior on coral reefs. nile in host sea anemones. (See produced from “buds”). �� ings, the fish, the crustaceans and �� And the carrying capacity of explanation in sidebar.) �� the anemone hosts, and we see �� At risk daily visitors to any one anemone Record �� marked changes in physiological The popular Aqaba anemone city may only be only 1/10 of Location The anemones were distributed �� PETER SYMES the present load. Consequently, More precisely, anemone city is from a depth of 3 meters down to �� the risk of this anemone city dis- situated on an underwater pla- about 40 meters, which is a new appearing forever within the teau of approximately 100 x 75 record for the species magnifi- SILVER-SPECIAL! �� next decade or two is very real. meters stretching down to an cent sea anemone. �� Despite these facts, the first scien- approximate 20-meter depth. tific study ever of Sinai’s “anem- It begins at a depth of about one city” did not take place 2 meters beneath a short verti- Symbiosis until the summer of 2002 when a cal coral wall from there it drops Danish research team visited the down to 7-9 meters at an angle of Means “life-together”. It exists in sev- site. This article is the summary of 30-45º. From this depth to approxi- eral forms. In mutualism, both species that study.* mately 20 meters, the plateau are benefitting from their association. In commensalism, one species gains Anemone city at Ras is relatively horizontal, sloping an advantage while the other is nei- Muhammad consists of massive only 5-15º. At approximately 20 ther benefitted nor harmed. In parasit- �� amounts of the clownfish sea meters, it ends in a rather sharply ism, one species gains at the expense �� anemones and consequently defined drop-off which plunges to of the other. �� also the local two-banded anem- a depth of about 800 meters. This �� An obligant symbiont is one who can’t �� onefish (Amphiprion bicinctus) is clearly not the place to drop �� live without its associated species, �� The popular dive sites around whereas a facultative symbiont may �� * THE OPINIONS ABOUT THE BEHAVIOR OF DIVERS IN THE Sinai get visited by dozens of RED SEA AND THE POSSIBLE FUTURE FATE OF ANEMONE benefit from the association but also �� CITY AS EXPRESSED IN THIS ARTICLE ARE, HOWEVER, THE live without. �� dive boats every day SOLE RESPONSIBILITY OF THE EDITOR MICHAEL ARVEDLUND ��

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FREE back issues Did you get the previous ecology issues of X-RAY MAG? Why here? that the growth rate is significantly ham- Perhaps this is because of the very clear pered, if the anemonefish are removed water almost devoid of terrestrial and from the host anemone. freshwater input. Simultaneously, the This result may lead to the specula- location of this anemone assemblage tion that the large shoals of three spot renders it subject to unusual and some- damselfish increase the assemblage in a times strong currents. The major currents mutualistic positive feedback between pass in the surface waters anemone and fish. This could up the Gulf of Suez and Magnificient sea perhaps be based on increased the Gulf of Aqaba (the anemones are amounts of ammonium, nitrate latter primarily via the and phosphate, which are likely CAYMAN ISLANDS, Bloody Strait of Tiran) resulting in found in only two to be found here. This is merely Bay Wall, Freediving World Records, Coral Spawning, Innerspace, Wrecks of Narvik upwelling of nutrition-rich relatively large speculation, however. Norway, Siberian Cave Diving, Tagging waters especially from the Whalesharks, Cabilao. Link: X-RAY #5 deep waters of the Gulf of assemblages in the Feedback Aqaba. southern part What are the ecological feedback mechanisms between Currents matter these fish and anemones? Do These nutrition-rich currents pass right more fish lead to more anemones, which by the anemone assemblage at Ras in turn, lead to more fish? If the above Mohammed. At 22-24 meters of depth, thoughts seem to be true, how are they MICHAEL ARVEDLUND approximately at the edge of the pla- related to the question of clonality in H. A closeup of the Red Sea anemonefish Amphiprion bicinctus in an teau where it dropped to vertical the magnifica and its distribution pattern? anemone city anemone Heteractis magnifica reef was devoid of anemones. Perhaps Do the abundance of anemones and in the vicinity of the host anemone, how- PACIFIC NORTH WEST AMERICA. their absence was caused by the anemonefish result in unusual odour Usually magnificient sea anemones are Vancouver Island, Puget Sound, Neah stronger currents here. In the same man- plumes to the surrounding waters? Since only found above 20 meters of depth. H. ever they do not associate with them, Bay, Alaska, Honduras Sharks, Amous ner, there were few anemones above 9 anemonefish depend on olfactory cues magnifica is distributed from the eastern and are not protected from the anemo- Nachoom, Jon Gross, Apeks, Fish Sense meters depth, where there was heavy to finding their host anemones at settle- Pacific to the western Indian Ocean and ne nematocysts. Link: X-RAY #4 wave-induced surges. However, the soli- ment, might one expect altered settle- the Red Sea. However, it reproduces tary anemone exposed to the surges at 3 ment patterns of anemonefish on reefs asexually only in the rim areas of its distri- “Gangs and territories” meters depth seemed to cope well with with anemone assemblages? bution i.e. the Red Sea and the eastern The total number of recorded two-band- it; it was one of the largest anemones of Pacific Ocean. Incidentally, this distribu- ed anemonefish was 243, of which 91 the entire assembly. What do we know? tion seems also to apply to magnificient were dominant. A fish territory could con- The distribution and abundance of the sea anemones assemblages. Thus, the sist of any combination of solitary and Are the fish the cause or result? species magnificient sea anemone, origin of the large aggregations of mag- clustering host sea anemones. Usually, it Factors contributing to the existence of which is the “anemone city” species in nificient sea anemones is probably the consisted of a cluster and some nearby solitary sea anemones. these superstructures of sea anemones the Gulf of Aqaba, was quite dif- asexual reproduction rather than settling MALAYSIA. Coralreeefs after the Tsunami, may be the relatively large schools ferent from most other giant sea of young sexually reproduced anemone Usually, territories of dominant and Whale beachings, Tragedy in South of the three spot damselfish. anemone species in Aqaba. polyps. sub-dominant two-banded anemonefish Africa, Nemo’s Nose: The Science of Fish covered the same area. The territories of Fashion, Ice Diving in Russia. Todd Recently, Israeli experi- Magnificient sea anemones Essick Link: X-RAY #3 ments have shown that (H. magnifica) are found Lots of fish to see two-banded anemonefish and three spot the giant sea in only two relatively At this particular anemone city, the damselfish were often overlapping as anemone E. large assemblages in researchers counted nearly 2000 individ- the group of three spot damselfish would quadricolor the southern part, ual three spot damselfish hovering above are benefiting Anemone City, and a the sea anemones. That is a lot of fish. Dominance from their mutu- few solitary individuals The largest specimens of three spot alistic symbiosis at Raz Ghazlani a few damselfish were never seen among the Dominant: number one, or a high with the fishes, kilometers north of Ras anemone tentacles, but adult three spot number, in the ever-existing pecking to such a degree Mohamed. damselfish will sometimes stay in groups order among anemonefishes Diving in the Himalayas, Swimming with Orcas in Norway, El Dorado in the Three-spotted damselfish Philippines, Gaansbai in South Africa WWW.WIKIPEDIA.COM Link: X-RAY#2 87 X-RAY MAG : 7 : 2005 EDITORIAL FEATURES TRAVEL NEWS EQUIPMENT BOOKS SCIENCE & ECOLOGY EDUCATION PROFILES PORTFOLIO CLASSIFIED Two banded anemone fish peeks out of a magnificient sea anemone in Sinai’s Anemone city Remaining question: the biggest fish swimming the furthest. Small sub-dominant two- Why do only banded anemonefish were rarely some species form observed more than ½ meters from the host anemones. anemone cities? In Anemone City, these adults intermingled with the groups of juvenile three spot damselfish. The territory borders seemed well- defined though no aggressive displays were observed between From an anemone city in Southern Japan, territories. The fish just did not cross Ryukyus Arhipelago Hizushi Beach. Sea certain borders. aneamones of the species Stichodatyla The territorial behaviour of mertensii and two clownfish of the spe- anemonefish seem to be highly cies Amphiprion sandaracinos. Depth 5.7 plastic; the intra- and interspecific meters. This species of anemones do not territorial behaviour may depend form anemone cities MICHAEL ARVEDLUND more on the local distribution pattern, number and size of the host anemones, than perhaps on the anemonefish species.

The significance MICHAEL ARVEDLUND The unusual large structure and many inhabitants of Sinai’s swim from one two-banded behaved almost alike in hovering Anemone City may be the source anemonefish territory to another. in larger or smaller groups ½-2 for new generations of clownfish The three spot damselfish ter- meters above the anemones, and sea anemones in most of the ritories had less defined borders forming some very large groups Gulf of Aqaba due to its size and than those of two-banded anem- below 10 meters. When disturbed placement in string currents from onefish. In areas with many host the three spot damselfish groups southern Red Sea leading into the anemones close to one another, would perform a synchronized straits of Tiran. the groups of three spot damsel- rapid descent towards the host Therefore, further protection fish could become very large with anemones. of Anemone City is most likely one large shared territory. an urgent matter. Unfortunately, The anemonefish the environment of the Ras Hovering groups The two-banded anemonefish Mohammed National Park is Apart from the smallest speci- usually swam closer to the host under increasing stress from pol- mens, the three spot dam- anemones than the three spot lution largely generated by the selfish all damselfish. local tourist industry. Although Usually, the large sub-domi- impressive, the anemones of the nant two-banded anemonefish assemblage were fewer and the were farthest away; they usually surrounding corals more stressed covered the whole territory with than just a few years back. ■

Two-banded anemonefish

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