Thoughtful question: Can you guess: are these plants or animals?
NF#1: They are animals and live in a colony: Each animal looks like a minature sea anemone with tiny tentacles on a long body. Each animal is joined to others nearby, sometimes by underground tubes. In some, the animals are embedded in a shared tissue so the entire colony looks like a rubber mat.
NF#2: Some may be highly toxic!
The most toxic marine poison, palytoxine, was discovered in a colonial anemone. A tiny amount of palytoxine can paralyse and even kill. So don't touch them! However, some animals can eat colonial anemones. These include the common hairy crab, filefishes and nudibranchs.
Corny joke: Some colonial anemones are colourful probably to warn of their toxic nature. You should avoid touching pretty and colourful marine life. Just like you shouldn't touch pretty girls!
NF#3: Their leathery skin is composed partly of chitin ("kai-tin"), the same substance that makes up the exoskeleton of insects.
Helpful hints for Naked Hermit Crabs ...
Where seen? There is a big patch of colonial anemones in the pool near the Tanjung Rimau beacon. You may also see them where the sandy beach ends and coral rubble begins, growing among the rubble. When they are out of water, they tuck their tentacles into their bodies and look like blobs of jelly or tiny sausages. Please don't step on them!!
Too Much Information!
Colonial anemones are NOT sea anemones: Sea anemones belong to Order Actiniaria, while colonial anemones belong to belong Order Zoanthinaria. Thus colonial anemones are usually called zoanthids.
What are the different kinds of zoanthids?
Palythoa sp. don't have long body columns. Instead, the polyps are embedded in a shared tissue which may be strengthened by incorporating fine sand and other tiny debris. One study suggests these incorporated elements can make up 45% of the total weight of the colony! Some colonies can grow rapidly, nearly half a cm a day. They are quite aggressive and often overgrow surrounding animals.
Protopalythoa sp. have long body columns, have a wide oral disk and relatively short tapered tentacles, usually in two rows. The oral disk has furrows that radiate from the mouth to the edge of the disk. The polyps are not embedded in a thick common tissue but are joined to one another at the base by underground stems (called stolons).
Zoanthus sp. have a long body column with short, rounded (not tapered) tentacles, usually in two rows. Their distinguishing feature is a muscle surrounding the central mouth that makes the oral disk appear to be divided into two halves. The polyps are embedded in a thin common tissue that is usually hidden by sediments, or joined to one another at the bases by underground stems (called stolons). Sometimes, the individual polyps are so tightly packed that the polyp takes on a polygonal shape.
The zoanthids are currently under revision and classification of species may change.What do they eat?
Zoanthids harbour symbiotic single-celled algae (called zooxanthallae) in their tentacles. The algae undergo photosynthesis to produce food from sunlight. The food produced is shared with the zoanthid, which in return provides the algae with shelter and minerals. It is the zooxanthallae often adds colour to the zoanthid.
Human uses for zoanthids
Palytoxin, the poison extracted from a zoanthid, has been used to better understand how our body works and may provide better treatment of hypertension, heart disease and other disorders. Zoanthids are also a popular item in the live aquarium trade, although their toxins make them dangerous to handle.
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