anemones

Geographical and Ecological Distribution

Sea anemones live throughout the world’s oceans, from poles to equator, and from the deepest trenches to the shores, as do fishes. But no one kind of either lives in all places. Of nearly 1000 species of sea anemones, only 10 are host to anemonefishes. They live in the parts of the Indian and Pacific Oceans that lie within the tropics or where warm, tropical waters are carried by currents, such as the east coast of Japan (as far north as the latitude of Tokyo!). Because the 28 species of clownfishes live only with these 10 species of sea anemones, they are found in the same places.
These anemones, and their anemonefishes, exist only in shallow water, no deeper than scuba-diving depths. That is because within the cells of an anemone’s tentacles and oral disc live microscopic, single-celled, golden-brown algae (dinoflagellates) called zooxanthellae. Like all plants, they require sunlight for photosynthesis, a process in which solar energy is used to make sugars from carbon and water. Some of these sugars fuel the algae’s metabolism, but most of them “leak” to the anemone, providing energy to it. Therefore, the anemones that are host to clownfishes must live in sunny places. The amount of light in the sea diminishes rapidly with depth because water filters out sunlight. Turbidity also diminishes light penetration. So these anemones live at depths of no more than about 50 m, generally in clear water. (Reef-forming corals also contain algae, and coral reefs occur only in shallow, mostly clear water for the identical reason.)
Anemonefishes live in habitats other than reefs, but are usually thought of as reef dwellers because that is where most tropical diving occurs. Other habitats may be less colourful and diverse than reefs, but they can be equally fascinating. About as many species of host actinians (= sea anemones) live on sand-flats surrounding coral reefs, or even at some distance from reefs, as live on reefs themselves. Individuals of some species can survive in muddy areas, but they generally lack fish symbionts. Even on reefs, most species of host actinians are inconspicuous, unlike their partner fish. Spotting the fish first, then frightening it so that it takes refuge in its anemone, or (preferably) waiting patiently for its periodic bathe among the tentacles, is often the best way to locate an actinian.

How is this relationship possible?

At the time of Collingwood’s discovery, some species of fishes and anemones involved in this relationship had been known to science for a century already. Why had nobody reported their living arrangement before? We can only speculate. Perhaps poisons had been used to collect the fish, which causes them to float to the surface, so nobody could know where they had come from. Perhaps collectors saw fish living in anemones but did not appreciate its significance. Or quite possibly it was seen and simply not believed, so unlikely is an anemone as home to a fish.
Lovely, accessible — and a most unlikely partnership. Sea anemones are related to corals and more distantly to jellyfishes. Common to all of these animals are nematocysts, the harpoon-like stinging capsules that give jellyfish their sting, fire coral their burn, and the tentacles of some sea anemones their stickiness. The microscopic nematocysts, which are manufactured inside cells (but are not themselves cells), are particularly dense in tentacles and internal structures. Those of the tentacles function in defence and prey capture; internal nematocysts are essential to digestion. Within each capsule is coiled a fine tubule many times the capsule’s length. When the capsule is stimulated to fire (a combination of chemical and mechanical stimuli is necessary to trigger most kinds; there are over 30 in all), the tube shoots out, everting like the sleeve of a coat turned inside out, to penetrate or wrap around the target. Many types of nematocysts, although probably not all, contain toxins, which are delivered to predator and prey by or through the everting tubule.

The existence and function of nematocysts were known before the anemonefish symbiosis was described. And so, when Collingwood first reported “the discovery of some Actiniae of enormous size, and of habits no less novel than striking,” his prime concern was with how the fish managed to survive in an environment that is deadly to most fishes, even some much larger than anemonefishes.
Over the years, many biologists have suggested ways in which it might be possible for the fish to survive in its hostile environment. Among the hypotheses [and reasons for discarding them] were the following.
1) Tentacles of these particular anemones do not contain nematocysts. [Not only are there nematocysts, but those of all 10 species of host actinians are typical in kind and quantity to those occurring in the majority of sea anemones.]
2) The fish do not actually touch the tentacles. [While this is certainly true of some Caribbean fish that seek protection behind and under sea anemones, genuine anemonefishes swim among tentacles, and sleep on the oral disc at night.]
3) The skin of anemonefishes is thicker than normal so nematocysts cannot penetrate it. [It differs little from that of other damselfishes, and may even be slightly thinner. Indeed, an unprotected anemonefish can be killed by its host's sting.]
4) While a fish is present, the anemone will not fire its nematocysts. [Although a sea anemone can exert some control over firing, this cannot be the solution to the riddle, because an actinian can sting and capture prey while harbouring clownfish.]

Anemonefishes are easily kept in aquaria, many of which are as large as the fish’s normal territory. Both fishes and sea anemones survive — apparently quite well — when separated from one another. However, if the separation lasts more than a few days or weeks, depending on the species involved, when the partners are reunited and the fish swims into the host’s tentacles, it withdraws rapidly, appearing (sometimes very obviously, sometimes less so) to have been stung. Thus the protection of the fish is elicited or acquired, and can disappear. A fish that had been living alone will be stung by an anemone in which another clownfish is being harboured, so the fish, rather than the actinian, is responsible for the protection.
But a stung anemonefish returns to its host repeatedly, going through an elaborate, stereotyped swimming dance, gingerly touching tentacles first to its ventral fins only, then to its entire belly. Finally, after a few minutes to several hours of such “acclimation” behaviour, it is able to dive right in.
Some anemonefishes nibble at their host’s tentacles, which it had been speculated might immunize them against the sting. But the fish are not immune to being stung, as is sometimes stated. Immunity is a physiological response that extends throughout an animal’s body. Experiments by Davenport and Norris conclusively proved that the protective agent resides in the mucus coating that anemonefishes, like all fishes, have on their surface. But what is the source of this protective mucus?
One theory is that it comes from the host actinian. Supporters of this theory believe that during its elaborate “acclimation” swimming when contact is initially made with its host, the fish smears mucus from the anemone all over itself. Just as the sea anemone does not sting itself, it does not sting a fish, or any other object, covered in its mucus. The fish is thereby chemically camouflaged: it is, essentially, a fish in anemone’s clothing. The fish’s normal behaviour of returning to its anemone at least once a minute can be interpreted as serving to maintain its protective layer of mucus. According to this theory, what allows clownfishes to live in this peculiar habitat is their unusual behaviour.
Finding anemone mucus on many objects with which the animal regularly comes in contact, such as the rocks and algae around it, other scientists believe that its presence on a fish is the result of the fish’s being protected rather than its cause. The fish’s own mucus has evolved to lack components that stimulate nematocyst discharge, according to this theory, and “acclimation” behaviour may be an artifact of artificially separating animals that normally never are parted. The secret to clownfishes’ peculiar habitat, according to this interpretation, is their unusual biochemistry.
As in so much of science, there is probably truth on both sides. Although all anemonefishes are closely related and share an unusual habitat, they vary in some aspects of their biology, including how far they venture from their home, how many fish occupy a single anemone, and which hosts and how many host species they occupy. Similarly, they may not all adapt to an actinian in the identical manner, as is generally assumed, with behaviour and biochemistry probably both playing roles to varying degrees. We believe that for fish that live with many types of hosts, behaviour is likely to be more important to adaptation, whereas for host-specific fish, biochemistry is probably the more significant factor.

Nutrition

Sea anemones that are host to clownfishes, like many tropical actinians and some temperate ones, harbour unicellular algae within the cells of their tentacles and oral disc. A portion of the sugars produced by these plants through photosynthesis are “leaked” to their host. This may be the anemone’s major source of energy. The widely flared oral disc of many host actinians serves not only to accommodate fish, but its large surface area is well adapted for intercepting sunlight.
However, actinians, like all coelenterates, capture and digest animal prey with their nematocysts. We have found small fish, sea urchins, and a variety of crustaceans (shrimps and crabs) in the coelenteron of host anemones. They also appear to feed on planktonic items conveyed by the currents. Although the energy they derive from photosynthesis may be sufficient to live, the anemones need sulfur, nitrogen, and other elements in order to grow and reproduce. These animals are not voracious predators: their prey probably consists of animals that bump into them (e.g. a fish fleeing a more active predator) or stumble over them (e.g. a sea urchin, which has no eyes). Therefore, the supply is probably small and irregular. A more predictable source of these nutrients may be from wastes of their symbiotic fish. This issue deserves to be studied scientifically. Anemones of some species are capable of absorbing nutrients directly from seawater through their thin tissues, and that may be another source of nutrition for these animals as well.

Survival

It is impossible to determine age of a sea anemone, except for one that has been raised in an aquarium or tracked continuously in the wild from first settlement. A small one is not necessarily young, for coelenterates grow only if well fed and shrink if starved. Individuals of species that harbour anemonefishes have been monitored for several years with no apparent change in size (although that is difficult to measure, due to the absence of a skeleton). However, studies on other species, in field and laboratory, have led to estimated ages on the order of many decades and even several centuries. There are scattered records of temperate anemones surviving many decades in commercial aquaria, and the life-span of a small sea anemone in New Zealand has been calculated, based on actuarial tables, to be over 300 years! From such data, it is likely that most individuals of the “gigantic” sea anemones we have encountered during our field work exceed a century in age. This is also consistent with the generalization that large animals of all kinds typically are long-lived.
Coelenterates are protected quite well by their nematocysts, but some predators have developed means of evading their effect. Small tropical anemones may be eaten by butterflyfishes, but large ones appear to have few enemies, and we do not know what might ultimately kill them.

Reproduction

All coelenterates reproduce sexually. An individual of some species may produce both eggs and sperm; host anemones appear to have separate sexes, with an individual being either male or female its entire life. The typical coelenterate pattern is that of most marine animals, one that is fraught with dangers and uncertainty — release of eggs and sperm into the sea, where fertilisation occurs and a larva (a tiny animal looking nothing like its parent that drifts in the sea) develops for several days or weeks before settling in an appropriate habitat. Many species spawn in response to an environmental cue such as a full moon or low tide so that eggs and sperm are in the same place at the same time. Typically, marine animals produce millions of tiny larvae, but the world is not overrun with them, proving that very few survive — usually just enough to maintain a stable population. The rest of the larvae serve as food for a sea full of potential predators. Finally, the surviving larvae must find an appropriate habitat.
We do not know if host actinians follow this pattern. There is a bit of evidence that in at least some species, the eggs are not released, but are fertilised inside the mother (this is not especially rare in corals and anemones; sperm enter the mother with water that is constantly being pumped in and out, and which carries food and oxygen also), where they grow to be released as tiny sea anemones. What is certain is that we seldom see small individuals of most host actinians in nature. However, it is not unusual to find large ones with ripe eggs and sperm. Therefore, we believe that successful recruitment must be rare. Very few eggs may be fertilised, or few larvae may survive, or larval settlement may be difficult, or young anemones may have high mortality (perhaps especially when they are too small to harbour fish). The apparent rarity of successful reproduction is also biologically consistent with long life.
In addition to sexual reproduction, some coelenterates undergo asexual reproduction. Entacmaea quadricolor is one of these. A polyp can divide longitudinally, resulting in two, somewhat smaller individuals, probably within the space of a few days. Each then grows to an appropriate size, divides, and so on. All descendants of the original anemone (the result of sexual reproduction) form a clone, a group of genetically identical individuals. In this species, each polyp is relatively small, but clonemates remain next to one another so their tentacles are confluent, and the associated anemonefish apparently regard them as a single large anemone.
This is so mainly for shallow-water individuals; those in deeper water grow large, and do not divide. Several other species of actinians also have two different reproductive modes: small animals that clone and large ones that do not. This appears true of Heteractis magnifica, too. In the center of its range (i.e. in eastern Indonesia, on the Great Barrier Reef, in New Guinea), it occurs as single, large individuals. To the east and west (i.e. in western Indonesia and Malaysia, and in Tahiti), several to very many small individuals of identical colouration are typically clustered together, appearing to be a single large (or huge!) anemone. Based on their shared colour and their proximity, we infer that they are clonemates.

Locomotion

Once they settle from the plankton, most anemones seldom move from place to place. Although they are usually damaged when people try to collect them, actinians do have the ability to detach from the substratum, partly or entirely. Small, temperate anemones can do this in response to predators or unfavorable physical factors. Indeed, those of a few species can “swim,” awkwardly launching themselves into the water briefly, a motion that often puts them beyond reach of the predator that provoked the activity. More typically, an individual glides on its pedal disc, covering a few millimeters in a day, or it may detach entirely, and roll or be carried quite a distance. That this is not terribly rare is attested by large animals suddenly appearing in well studied areas.

coelacanths

In 1938, thirty two-year-old Marjorie Courtenay Latimer was the curator of a tiny museum in the port town of East London, northeast of Cape Town, South Africa. She had befriended a local seaman, Captain Hendrick Goosen, of the trawler Nerine, which fished the nearby coastal waters of the Indian Ocean. When he put into port the captain made a frequent practice of having the dockman call Miss Latimer to come look over the Nerine’s catch. She was welcome to take any unusual specimens she might want for her museum.
On December 23rd, 1938, the Nerine entered port after a stint trawling off the mouth of the nearby Chalumna River. The dockman called Marjorie, who was busy mounting a reptile collection, but felt she ought at least go down to the docks to wish the crew of the Nerine a merry Christmas. She took a taxi, delivered her greetings, and was about to leave when, according to her account, she noticed a blue fin protruding beneath a pile of rays and sharks on the deck. Pushing the overlaying fish aside revealed, as she would later write, “the most beautiful fish I had ever seen, five feet long, and a pale mauve blue with iridescent silver markings.” Marjorie had no idea what the fish was, but knew it must go back to the museum at once. At first the taxi driver refused to have the reeking, five-foot fish in his cab, but after a heated discussion, he drove Marjorie and her specimen back to the museum.
Raking through the few reference books on hand, Marjorie found a picture that, she has said, led her to a seemingly impossible conclusion. Her specimen bore similarities to a prehistoric fish, particularly in the structure of the head and the tri-lobed shape of the tail. She made a rather crude sketch of the creature, which she mailed, along with a description, to Professor J.L.B. Smith, a forty one- year-old persnickety chemistry teacher with a locally well known passion for fish, at Rhodes University, Grahamstown, some fifty miles south of East London. Smith, however, was away for Christmas holidays, correcting exams at his seaside getaway. Meanwhile, Courtenay’s museum director in East London was not impressed with the find. He dismissed the fish as a common rock cod – a grouper!

But on January 3, 1939, Miss Latimer heard back from Smith in a now famous cable: “MOST IMPORTANT PRESERVE SKELETON AND GILLS = FISH DESCRIBED.” However, in an attempt to preserve the fish by mounting it, the innards had been discarded. A search for them in the museum and town trash bins proved fruitless. Even photographs taken of the preparation had somehow been spoiled.
Smith, anxiously biding his time, wondering how he could incorporate the possibility of such a discovery into an already overloaded dual career, did not arrive at the East London museum until February 16. The professor, a thin wiry man of about 5′7″, sporting, as was his custom, a close-cropped crew cut, khaki bush shorts and sandals, viewed the mounted specimen, exclaiming, according to one account, “I always knew somewhere or somehow, a primitive fish of this nature would appear.” Smith identified the fish immediately as a coelacanth, that is as a member of what must be a still living coelacanth species. The fish would soon be called the “most important zoological find of the century” (an accolade that might now go to the Martian microfossils if they check out.) A living dinosaur, it was said, would be no more amazing than this incredible discovery.
After a local newspaper reporter was allowed to take a single photograph of the mounted coelacanth, the picture soon appeared around the world. Smith, Courtenay-Latimer, and the coelacanth became overnight celebrities. When a public viewing for one day only was arranged, 20,000 visitors are said to have shown up.
But the story of the coelacanth’s “discovery” does not end there. With no internal organs left from the East London specimen, many questions remained unanswered. Smith was soon obsessed with finding a second intact specimen. Speculating that the fish had drifted down from the north on the Mozambique current, he had a reward notice with a picture of the first specimen posted among the East African coast up as far as Kenya. A decade went by with no response. Smith continued a long-term project of cataloging the fishes of the Indian Ocean, always proselytizing about the coelacanth wherever he went. It was during this period that the myth of the coelacanth as a deep ocean fish took hold in the popular and scientific imagination. Expeditions from Europe scoured the ocean depths in search of coelacanths. But Smith remained convinced that the fish’s physiognomy and blue color made it a lower reef predator and not a true deep-water fish.
Captain Eric Hunt, a dapper thirty eight-year-old Briton who owned and helmed a vessel, the Nduwaro, trading among Zanzibar, Madagascar, and the Comoros, a group of small islands in the Mozambique Channel belonging to France at the time, attended one of Smith’s lectures in Zanzibar. An intelligent, curious fellow, with a penchant for marine aquaria, he quickly became fascinated with the whereabouts of the coelacanth. Hunt offered to post Smith’s reward notices among the Comoro islands, which are midway between Tanzania and Madagascar. Smith obliged and with the help of local authorities, the Comoros were soon plastered with coelacanth reward notices.
On December 21, 1952, fourteen years after the discovery of the first living coelacanth, Captain Hunt, returning to the port of Mutsamudu on the Comorian island of Anjouan, was approached by two Comorans carrying a hefty bundle. One, Ahamadi Abdallah, had caught by hand-line what the locals called a “mame” or “Gombessa”, a heavy grouper-like fish that turned up on their lines from time to time. The fisherman was accompanied by an astute schoolteacher, Affane Mohamed, who had noticed that this was the same fish pictured on the reward notices Hunt had posted. Hunt was ecstatic and arranged for Smith’s award of one hundred British pounds to be paid to them. As there was no better preservative available at Mutsamudu, Hunt and his crew salted the fish, then sailed with it to the harbor at Dzaoudzi, an islet off the Comoran island of Mayotte, where he bought formalin from the director of medical services. Already aware of the scientific importance of the internal organs, Hunt injected the preservative into the specimen, then cabled Smith in South Africa. He awaited Smith’s response.
The French authorities at nearby Pamanzi were not sure that this creature was indeed the fabled coelacanth. Nevertheless, concerned that they might be missing out on something important, cables were dispatched to French scientific authorities in Madagascar. But no message came back. Hearing nothing, the Pamanzi authorities decided to take possession of the fish anyway if Smith did not come for it personally. Hunt sent a frantic second cable to Smith, urging him to fly to the Comoros immediately.For J.L.B. Smith this find, if indeed it were a coelacanth, would consummate a fourteen-year obsession. Worried all the time that Hunt’s specimen might not be what he claimed, Smith negotiated with Prime Minister Malan of South Africa, for a plane to fly him to the Comoros. Malan, out of the capital on yet another Christmas holiday, consented. By now Smith was a nervous wreck, hardly amused when the flight crew of a DC3 “Dakota” put at his disposal for the trip, faked a radio message that French fighters had scrambled to intercept them. Having landed in the Comoros, it was a quick trip from the airstrip down to the harbor at Pamanzi where the Nduwaro was moored. When Smith saw the dead fish he wept. It was indeed a coelacanth. He now had his second specimen, organs intact, and the familiarity of the natives with this creature meant that at least one location of the coelacanth’s habitat had been discovered. The Dakota soon left the Comoros with Smith and “his” fish, returning to another round of worldwide publicity.
In the aftermath, the French felt cheated and closed the coelacanth to non-French researchers until the islands became independent in the 1970’s. Four years after the “discovery” of the second coelacanth, Eric Hunt disappeared at sea after his schooner ran aground on the reefs of the Geyser Bank between the Comoros and Madagascar. He was never found. J.L.B. Smith wrote his account of the coelacanth story in the book “Old Fourlegs,” first published in 1956. His book, Sea Fishes of the Indian Ocean, meticulously illustrated and co-authored by his wife Margaret, remains the standard ichthyological reference for the region. In spite of the controversies that followed, he was content with his role in the fabulous coelacanth episodes. Smith died in 1968. Captain Hendrick Goosen passed away just after the fiftieth anniversary of the “discovery” of the coelacanth in 1988. And Marjorie Courtenay-Latimer was alive and well and still living in East London as of January 2001, the lone survivor of the greatest fish story ever told!

Evolutionary Puzzle

The living coelacanths, Latimeria chalumnae,and Latimeria menadoensis are possibly the sole remaining representatives of a once widespread family of Sarcopterygian (fleshy-finned) coelacanth fishes all but one of which disappeared at the end of the Cretaceous, 65 million years ago. The classification of coelacanths is a murky business with more than one variation in the class category, which will go to far ror here.
The coelacanth appears to be a cousin of Eusthenopteron, the fish credited with growing legs and coming ashore – 360 million years ago – as the ancestor of all tetrapods including ourselves.
But this view is controversial. Debate still rages as to whether the coelacanths, presumed to be close relatives of the Rhipidistia fishes from which tetrapod amphibians supposedly arose, are our closest tetrapod ancestors, or if lung fishes, another very ancient line, are more closely related to tetrapods than the Rhipidistia and thus claim the oldest closest relative title. (There are three living genera of lung fishes.) Good genetic and morphological evidence points in both directions. Another line of thinking, based on physiological and anatomical analysis, identifies coelacanths with sharks and other cartilaginous fishes, but this view seems to have fallen from favor. Today’s coelacanths can reach almost six feet (2 meters) in length and weigh up to 150 or more lbs, but they are usually somewhat smaller, particularly the males. They are oportunistic feeders, scarfing up cuttle fishes, squids, and other fishes found in their deep reef and volcanic slope habitats. Coloration is dark blue with distinctive white flecks that can even be used by researchers to designate individuals. (Indonesian coelacanths may be more brown than blue). Scientists believe individual coelacanths may live as long as 60 years. They are ovoviparous, giving birth to as many as 26 live pups which develop from eggs in the oviduct. The coelacanths date back 410 million years to the beginning of the Devonian epoch. One of the incredible aspects of the living coelacanth, Latimeria, is that it offers a genetic and anatomical snapshot of life in those times. The backbone of this fish is composed of a fluid-filled cartilaginous tube, which provides a firm yet flexible support for muscles. Hollow fin spines, identified in fossils, are what got the fish its name- “coelacanth” which literally means ‘hollow spine’. The sucking maws of jawless predecessors have transformed, through a modification of one of the gill arches, into hinged, rigid structures with teeth on the bottom ridge and upper palate- true jaws. The tiny brain, is encased in a hardened skull, which hinges in the middle to increase the gape of the mouth while feeding. The eyes are well developed, with reflecting cells called tapita to enhance night vision. A chambered heart pumps blood in prototype to our own. Three indentations on either side of the snout lead to a peculiar cavity, a jelly-filled rostral organ, which very likely functions as an electro-receptor to help in the location of prey. Along the sides a pressure sensitive lateral line is well developed to sense the proximity of other fishes and surrounding structures- no doubt useful in the submarine caves where coelacanths pass their days. Two back, or dorsal, fins and one protruding beneath the nape of the tail are complimented by paired lobed pectoral and pelvic fins. These contain in their trunks bones mimicking those of Eusthenopteron which later developed into arms and legs. While coelacanths have not been observed to “walk” on the bottom, their pectoral and pelvic fins can be seen as “pre-adaptations” to land locomotion. Used under water their action maintains stability and balance. But in their cousin Eusthenopteron, the same action became four-legged land walking. Coelacanth scales are thick, and lined with serrated rows of hardened toothpick-pointed denticles. Perhaps most distinctive of all is the trilobated tail with its extra trunk and fin protruding from the middle. It was this feature that made fossil coelacanths so easily recognizable and helped clinch the case for the identification of the first living specimen.

Odd Behavior

When Hans Fricke and his submersible pilot first observed coelacanths at depth in 1987 they saw an odd bit of behavior. From time to time the fishes tilted forward, snouts down, and appeared to stand on their heads. Why? No explanation presented itself. Was this some ancient vestigial behavior? – or, as some speculate, a response to the submersible’s electric field or searchlights? As of early 2000, the Fricke submersible visits offer the only direct observations of essentially unstressed coelacanth behavior, save for a brief view by divers off Sodwana, South Africa. Fin movements and swimming styles have been analyzed. Curiously, the coelacanth was never observed to use its paired pectoral and pelvic fins for bottom walking, a behavior that might have been expected of “Old Fourlegs.” Coelacanths were found to congregate in submarine caves on the steep island drop off during the day, where they hovered without touching each other. Their white scale flecks, set against a cobalt blue body color offer excellent camouflage against the cave surfaces covered with white sponges and oyster shells. Fish which had been tagged with sonic devices were found to leave the caves at the same time late each afternoon to forage along the coastal incline during the night. The drift-feeding coelacanth is an opportunistic predator, scarfing up whatever it can with a suction action of the jaw and hinged cranium. Location of prey fish is possibly aided by a rostral organ (in the snout) which acts as an electric field receptor. The coelacanth’s uncanny sense of timing and coastal navigation skills have yet to be explained. Another mystery is the whereabouts of the juvenile fish which are rarely seen in submersible dives and seldom caught by local fishermen.

Population / Location Debate

By doing a rough count of the number of possible coelacanth caves along the west coast of Grand Comoro island – and the number of fish per cave, plus the birth rate, Hans Fricke and associates came up with an estimate for the total coelacanth population in the low hundreds. However, there is some question if this estimate takes into account the known but unexplored coelacanth population at the nearby island of Anjouan, the unseen juvenile population, and the new number of potential embryos (26 as opposed to the previous 5) discovered in the 1991 Maputo, Mozambique trawled specimen. A total population count is also complicated by another until recently unresolved issue: Is the Comorian population the only one? Certainly the Comoro islands are the only place where regular annual catches of 6-8 coelacanths occur at Grand Comoro and 4-5 at Anjouan. But from time to time coelacanths turn up elsewhere: the one trawled off East London, in 1938; the one trawled off Maputo, Mozambique on August 11, 1991; the two netted off Madagascar in 1995/1997- along with other rumored Madagascar catches. Are these fish strays from the Comoros or are they representatives of satellite colonies? No one knows for sure. Fishing activities differ in the other locales and may not be such as to produce regular coelacanth catches. And finally, what about other islands in the Indian Ocean such as the Aldabras and Reunion – which have volcanic drop offs similar to the Comoros? Do they harbor as yet undiscovered coelacanth colonies? These speculations took a back seat to the 1998 confirmed identification by Dr. Mark Erdmann of at least two specimens from North Sulwesi, Indonesia at 10,000 kilometers from the Comoros with no apparent water current interactions, followed by submersible observation of two more in 1999, and the 2000 discovery of at least three coelacanths off Sodwana, South Africa. The Indonesian population appears to be distinct by DNA analysis, although the specimens at least superficially resemble the Comoran coelacanths. In any event, the coelacanth remains a very rare creature, probably deserving of its endangered Appendix I status in the C.I.T.E.S. listings.

Similan Islands

Whales

Living in the ocean whales are large, magnificent, intelligent, aquatic mammals. They breathe air through blowhole(s) into lungs (unlike fish who breathe using gills). Whales have sleek, streamlined bodies that move easily through the water. They are the only mammals, other than manatees (seacows), that live their entire lives in the water, and the only mammals that have adapted to life in the open oceans.
Like all mammals whales breathe air into lungs, whales have hair (although they have a lot less than land mammals, and have almost none as adults), are warm-blooded (they maintain a high body temperature), have mammary glands with which they nourish their young and whales have a four-chambered heart.Size The biggest whale is the blue whale, which grows to be about 94 feet (29 m) long – the height of a 9-story building. These enormous animals eat about 4 tons of tiny krill each day, obtained by filter feeding through baleen. Adult blue whales have no predators except man.
The smallest whale is the dwarf sperm whale which as an adult is only 8.5 feet (2.6 m) long. The blue whale is the largest animal that has ever existed on Earth. It is larger than any of the dinosaurs were. They are also the loudest animal on Earth. Two Types of Cetaceans Cetaceans include the whales, dolphins and porpoises. There are over 75 species of Cetaceans. Whales belong to the order Cetacea (from the Greek word “ketos” which means whale), which is divided into the following suborders:

Toothed whales (Odontoceti) – predators that use their peg-like teeth to catch fish, squid, and marine mammals, swallowing them whole. They have one blowhole (nostril) and use echolocation to hunt. There are about 66 species of toothed whales – killer whales or orcas , beluga whales , narwhals , sperm whales , the beaked whales, dolphins , and porpoises.
Baleen whales (Mysticeti) – predators that sieve tiny crustaceans, small fish, and other tiny organisms from the water with baleen, which are used to filter tiny organisms, like krill and small fish from the water. They use their tongue to dislodge the food from the baleen and swallow it. Baleen is a comb-like structure that filters the baleen whales’ food from the water. Baleen is made of keratin, the same protein that our hair and nails are made of. Baleen whales are larger than the toothed whales and have 2 blowholes (nostrils). There are 10 species of baleen whales – blue whales ,humpback whales , gray whales , bowhead whales , minke whales, and right whales. These large whales are filter feeders and are among the largest animals on earth. Swimming and other water activities Whales have a streamlined shape and almost no hair as adults (it would cause drag while swimming). Killer whales and Shortfin Pilot whales are the fastest, swimming up to 30 miles per hour (48 kph).
Whales swim by moving their muscular tail (flukes) up and down. Fish swim by moving their tails left and right.

Breaching: Many whales are very acrobatic, even breaching (jumping) high out of the water and then slapping the water as they come back down. Sometimes they twirl around while breaching. Breaching may be purely for play or may be used to loosen skin parasites or have some social meaning.
Spyhopping: This is another cetacean activity in which the whale pokes its head out of the water and turns around, perhaps to take a look around.
Lobtailing: Some whales stick their tail out of the water into the air, swing it around, and then slap it on the water’s surface; this is called lobtailing. It makes a very loud sound. The meaning or purpose of lobtailing is unknown, but may be done as a warning to the rest of the pod of danger.
Logging: Logging is when a whale lies still at the surface of the water, resting, with its tail hanging down. While floating motionless, part of the head, the dorsal fin or parts of the back are exposed at the surface. MigrationMany ceteaceans, especially baleen whales, migrate over very long distances each year. They travel, sometimes in groups (pods), from cold-water feeding grounds to warm-water breeding
grounds.
Gray whales make the longest seasonal migration of any of the whales. They travel about 12,500 miles each year.

Social Behavior

Cetaceans have very strong social ties. The strongest social ties are between mother and calf. A social group of whales is called a pod. Baleen whales travel alone or in small pods. The toothed whales travel in large, sometimes stable pods. The toothed whales
frequently hunt their prey in groups, migrate together, and share care of their young. ReproductionCetaceans give birth to live young which are nourished with milk from their mothers – they don’t lay eggs. Cetaceans breed seasonally, usually in warm tropical waters, and females usually have one calf every 1-3 years. The gestation times range from 9-18 months. Whale calves can swim at or soon after birth. Mother whales care for their young for an extended period of time, usually at least a year, feeding them milk and protecting them.
Young cetaceans are frequently mottled in color, camouflaging them from predators. Newborns have a sparse covering of hair which they lose as adults.Whale SongsComplex whales songs can be heard for miles under the water. The humpback’s song can last for 30 minutes. Baleen whales sing low-frequency songs; toothed whales emit whistles and clicks that they use for echolocation The songs are thought to be used in attracting mates, to keep track of offspring, and for the toothed whales, to locate prey.Endangered WhalesThere are many species of whales that are in danger of going extinct. Most baleen whales (the huge whales targeted by commercial whalers) are listed as endangered or protected species. Most other whale species are doing well and are not endangered.

Similan Islands

Seahorse

Family: Syngnathidae
Scientific Name: Hippocampus zosterae
Close Relatives: Other seahorses, pipefishes, seadragons

Tigertail Seahorse (picture taken on Similand Islands – Thailand)

Overview

A seahorse is a type of fish closely related to pipefishes and belonging to the scientific family Syngnathidae. About 35 species of seahorses occur worldwide. The seahorse’s scientific genus name Hippocampus is a Greek word meaning “bent horse.” Depending on the species, seahorses reach lengths of about 5 to 36 cm (2-14 in.).
Seahorses are found in temperate and tropical waters. The longsnout seahorse (Hippocampus reidi) and the Northern seahorse (Hippocampus erectus) live in the Caribbean region of the Western Atlantic. The common seahorse (Hippocampus guttulatus) lives in the Mediterranean Sea and warm areas of the Atlantic. The yellow seahorse (Hippocampus kuda) lives in the Indo-Pacific. The Pacific seahorse (Hippocampus ingens) is the only seahorse on the eastern Pacific coast (found from California to Peru).

Seahorses are well camouflaged among the eelgrasses and seaweeds in which they make their homes. A seahorse often moors itself in the water by curling its prehensile tail around seagrasses and coral branches. The seahorse’s small mouth, located at the end of its narrow tubelike snout, sucks up tiny plankton and fish larvae. Seahorses have been described as voracious eaters. Seahorses swim upright. Pectoral fins on the sides and a small dorsal fin on the back of a seahorses’s body wave rapidly to move the seahorse through the water.

Predators

Many larger fishes prey on seahorses. The tiny juvenile seahorses are eaten by other fishes and by crustaceans and anemones. Humans collect seahorses for many uses. Seahorses use camouflage as their defense against predators, and some species can change colors to match their surroundings. Seahorses and pipefishes are heavily exploited around the world, for use as traditional medicines, aquarium fishes, and curios. At least 40 nations are now involved in a trade which consumes at least 20 million dried seahorses annually and several hundred thousand more live seahorses. These quirky fishes are now a valuable commodity, providing important income for many subsistence fishers. Demand for seahorses will continue to grow as China’s economy expands, but all evidence indicates that current high levels of extraction are already causing marked decline of fished populations. Project Seahorse is an integrated program of seahorse conservation and management, working to ensure long term persistence of wild seahorse populations while still respecting human needs and aspirations.

Appearance

Pygmy or dwarf seahorses are found in a range of colors from black, green, or dull brown to golden yellow. They are approximately 2 to 4½ centimeters (¾ to 1¾ inches) long. Seahorses are remarkable for their long, tubelike snouts and for their prehensile tails, which they use to hold onto objects

Habitat and Range

Dwarf or pygmy seahorses live in seagrass beds in the Gulf of Mexico, Bermuda and the Bahamas.

Reproduction

The tiny young seahorses are born fully formed. They receive no parental care and are independent from birth. Seahorses reach maturity in approximately six months.

Longevity

The exact length of the brief life span of seahorses is not known. It is estimated to be from one to four years, depending on the species.

Status

The World Conservation Monitoring Centre’s IUCN Red List of Threatened Animals classifies the dwarf or pygmy seahorse as “vulnerable.” That means it faces a high risk of extinction in the wild in the medium-term future. Seahorses can’t produce young quickly enough to replace the huge numbers that are fished from the wild for medicines, as pets and as souvenirs.

Did you know … ?

Unlike most fishes, seahorses and their relatives don’t have scales. They have bony plates under their skin, like a suit of armor. The plates provide protection from predators, but, for some species, they make the body semirigid. Because of this, seahorses and their relatives don’t move their bodies in a wavelike fashion. Instead, they glide gracefully by fanning their delicate fins faster than the eye can see.
Seahorses are monogamous. One male and one female form a pair bond and mate repeatedly and exclusively
during the mating season.

Indina Manatees – dugongs

West Indian manatees are large, gray-brown aquatic mammals with bodies that taper to a flat, paddle- shaped tail. They have two flippers with three to four nails on each, and their head and face are wrinkled with whiskers on the snout. The manatee’s closest relative is the elephant and hyrax (a small furry animal that resembles a rodent).
Manatees are believed to have evolved from a wading, plant-eating animal. The West Indian manatee is related to the West African manatee, the Amazonian manatee, the dugong, and Steller’s sea cow, which was hunted to extinction in 1768. The average adult manatee is about 10 feet long and weighs about 1,000 pounds.

Habitat and Range

Manatees can be found in shallow, slow-moving rivers, estuaries, saltwater bays, canals and coastal areas. Manatees are a migratory species.

Behavior

Manatees are gentle and slow-moving. Most of their time is spent eating, resting, and in travel. Manatees are completely herbivorous. They eat aquatic plants and can consume 10-15% of their body weight daily in vegetation. They graze for food along water bottoms and on the surface. They may rest submerged at the bottom or just below the surface, coming up to breathe on the average of every three to five minutes. When manatees are using a great deal of energy, they may surface to breathe as often as every 30 seconds.

Lifespan, Mortality, Population

West Indian manatees have no natural enemies, and it is believed they can live 60 years or more. Many manatee mortalities are human-related. Most human-related manatee mortalities occur from collisions with watercraft. Other causes of human-related manatee mortalities include being crushed and/or drowned in canal locks and flood control structures; ingestion of fish hooks, litter and monofilament line; entanglement in crab trap lines; and vandalism. Ultimately, however, loss of habitat is the most serious threat facing manatees today.

Breeding and Reproduction

The reproductive rate for manatees is slow. Female manatees are not sexually mature until five years old, and males are mature around nine years of age. It is believed that one calf is born every
two to five years; twins are rare. The gestation period is approximately 13 months. Mothers nurse their young for a long period and a calf may remain dependent on its mother for up to two years.

Similan Islands

Nautilus – Octopus – madness

Octopuses belong to the phylum Mollusca which includes snails, clams and chitons. Their closest relatives are the chambered nautilus, cuttlefish and squids. The largest and smallest octopuses are found off the United States. The largest is the North Pacific Octopus (Octopus dofleini) that may grow to over 30 ft. And weighs more than 100 lbs. The smallest is the Californian (Octopus micropyrsus) which only reaches 3/8″ to 1″ in length.

Octopuses have the most complex brain of the invertebrates (animals with out backbones). They have long term and short-term memories as do vertebrates. Octopuses learn to solve problems by trial-and-error and experience. Once the problem is solved, octopuses remember and are able to solve it and similar problems repeatedly.

Octopuses sense of touch is acute in it’s suckers. The rim of the cups are particularly sensitive. A blindfolded octopus can differentiate between objects of various shapes and sizes as well as a sighted octopus.

Octopuses have highly complex eyes which compare to human visual acuity. Focusing is done by moving the lens in and out rather than by changing its shape as the human eye does.
When threatened, octopuses will often try to escape by releasing a cloud of purple-black ink to confuse the enemy. Its body will change color, release an ink cloud and jet away to safety. Several blotches of ink can be released before the ink sac is empty. The ink is toxic to an octopus in a confined space such as in a cave with little water current or in captivity. If the the octopus can not escape the ink (or water is not changed quickly when held in an aquarium), the octopus will become ill or perhaps die.

Color change in octopuses is initiated by the eyes. If an octopus is disturbed, special pigment cells (chromatophores) in the skin will be activated in an attempt to blend in with the surroundings. The chromatophores consist of three bags containing different colors which are adjusted individually until the back ground is matched. Coloration reflects mood, white for fear, red for anger, brown is the usual color.

Many octopuses produce venomous secretions. This venom is fatal to their favorite prey – crabs and lobsters. The tiny Blue Ringed Octopus in Australia is deadly to humans. Its tiny beak can even penetrate a SCUBA diver’s wet suit!

Octopuses have separate sexes (male and female) and fertilization is internal. In some species, the male can be distinguished by modified sucker discs at the tip of one of its arms. This modified arm is used to remove a packet of sperm from within his mantle cavity and insert it into the mantle cavity of the female. Within two months after mating the female attaches strands of clustered eggs to the ceiling of her lair. The number of eggs laid by a female varies greatly depending on the species laying the eggs. The Common Octopus may lay 200,000 – 400,000 tiny eggs. The Pygmy Octopus lays about 150 large eggs. Once the eggs have been laid, the female octopus will gently caress the eggs with her suckers to keep algae and bacteria from growing on them. She keeps the eggs oxygenates by gently squirting them with streams of water from her syphon. After the developing octopus turns in the egg so the tip of its mantle is at the unattached end of the egg and is ready to hatch, the female’s gentle caresses become more violent to help the baby octopus escape from the egg case. Most females will not eat after laying eggs and die soon after her eggs have hatched. Some baby octopuses, like Octopus vulgaris, are carried about in water currents for about a month before they settle to the bottom. Other baby octopuses, like the large egged Octopus joubini, look like miniature adults and immediately start living their life on the bottom. Only one or two out of 200,000 eggs will survive to become adult.

Cephalopods (for example squids) are found in all of the world’s oceans, from the warm water of the tropics to the near freezing water at the poles. They are found from the wave swept intertidal region to the dark, cold abyss. All species are marine, and with a few exceptions, they do not tolerate brackish water.

Cephalopods are an ancient group that appeared some time in the late Cambrian several million years before the first primitive fish began swimming in the ocean. Scientists believe that the ancestors of modern cephalopods (Subclass Coleoidea: octopus, squid, and cuttlefish) diverged from the primitive externally shelled Nautiloidea (Nautilus) very early – perhaps in the Ordovician, some 438 million years ago. How long ago was this? To put this into perspective, this is before the first mammals appeared, before vertebrates invaded land and even before there were fish in the ocean and upright plants on land! Thus, nautilus is very different from modern cephalopods in terms of morphology and life history.

Similan Islands

Holothuria glaberrima – Sea Cucumber or regenerative genius!

Sea cucumbers may look like the fruit in your garden, but they’re actually animals – related to sea stars, sea urchins, sea lilies and sand dollars. Most sea cucumber bodies are covered with tube feet, but only the ones located on the bottom of their bodies are developed enough for use. (However, the hairy cucumber is covered with slender tube feet.) Sea cucumbers use these feet mainly to attach themselves to the bottom, rather than for motion. The tube feet are controlled by changing the water pressure of the animal. By increasing the amount of water, the feet can be extended; and by lessening the amount of water, the tube feet contract -much like how a sea star moves.

Surrounding its mouth are ten to thirty modified tube feet. These sweep the surrounding water, capturing bits of food, and are then transferred one by one to its mouth to wipe off the food. Other sea cucumbers, such as Leptosynapta, burrow in the sediment, digesting what is edible, and excreting the rest.
Sea cucumbers breathe as water is pumped through two respiratory trees located on each side of their digestive tract. Some sea cucumbers can eject their digestive system and associated organs when disturbed (or due to overcrowding or foul water) and grow a new set within a few weeks.
They are sometimes host to the pearl fish, which slides backwards into the respiratory openings of sea cucumbers, often limiting itself to an entire life spent within a single individual. Together, they form a relationship, with one member as an uninvited guest, causing no harm and gaining a little from the association.

Sea cucumbers use their tentacles to capture tiny animals (zooplankton). Some sea cucumbers, such as the worm-like Leptosynapta, burrow and ingest detritus present in the sediment. In Asia, dried sea cucumber bodies (called trepang) and their sex organs are considered a delicacy by humans.

Sea cucumbers are the champions of organ regrowth because they direct their wound healing abilities towards restoring their organs, according to research published in the online open access journal, BMC Developmental Biology. The discovery that Holothuria glaberrima uses similar cellular mechanisms during wound healing and organ regeneration gives us the opportunity to discover how to repair our own wounds and, perhaps eventually, how to regenerate body parts.

The research was carried out by the investigators José San Miguel-Ruiz and José García-Arrarás, at the University of Puerto Rico. “Sea cucumbers should be viewed as the tissue regeneration equivalent of the squid for our knowledge of nerves and Drosophila for genes and the genome. They can help us learn to fix ourselves,” commented Professor Garcia-Arraras. “Many people, including scientists, regard sea cucumbers and other echinoderms like star fish and brittle stars as bizarre, exceptional outcasts because of their regenerative abilities. But we’ve shown that they use the same ‘ordinary’ mechanisms and processes to both regenerate and heal wounds.”

All animals possess some kind of tissue repair mechanism. The sea cucumber, H. glaberrima, belongs to a group of marine animals that are well known for their ability to regenerate, along with the axolotl salamander, which is also famous for regrowing lost limbs. The scientists made observations over a four-week healing period and found that sea cucumbers healed up rapidly after receiving a 3 to 5 millimeter cut along the body wall. The repair process involved special cells called morula cells moving to the injury site and full repair was achieved after just a couple of weeks. The cellular events observed during the healing of sea cucumber muscular, nervous and dermal tissues that correspond to those observed during intestinal regeneration include extracellular matrix remodeling and the differentiation of muscle cells.

Although all animals have wound repair processes, not all regenerate injured or lost body parts. There must be some unusual properties of the healing processes found in animals capable of organ regeneration. So it remains to be seen at a molecular level what limits healing processes being used for regeneration by all animals in all tissue.

“Many of these regenerative mechanisms are the same as those being used by other animals to heal and repair – this includes us humans, “concluded Professor Garcia-Arraras. “Sea cucumbers will probably provide us with the key to deciphering how to regenerate our tissues, or at least find out what is needed to do this.”

Similan Information