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STARFISH

Underwater photography: images of starfish taken while scuba diving
Horned starfish | Basket starfish | Brittle star | Biscuit starfish | Pincushion starfish | Crown of thorns starfish
Phylum: Echinodermata Subphylum: Asterozoa Class: Asteroidea

Starfish are members of a diverse clan, the Echinoderms, which translates as spiny skin. This group includes brittle stars, sea stars, sea cucumbers and sea urchins. In fact, 6,500 species lurk on the branches of this unusual family tree.

What links the members of this marine group together is their five-point radial symmetry. Their bodies consist of five equal segments, each containing duplicate sets of internal organs, which radiate from a central body mass. This is fairly obvious in a starfish, less so in their relatives. They have no heart, brain or eyes, but some seem to have light sensitive parts on their arms. Mostly their mouth is situated on their underside and their anus on top.

Starfish motion is slower than the proverbial tortoise. They use a complex hydraulic system to move around or cling to surfaces. On their base a mass of tiny tubes run along a distinctive groove in each arm. At the tip of each is a diminutive suction pad – or foot – which is hydraulically controlled by a remarkable system where water is sucked in through a sieve plate on top of their body, then pulsed through interconnecting canals to the toes.

The most incredible starfish feature is their defence mechanism, which is the capability to regenerate. Should they lose an arm (or is it a leg) to a predator, then no problem! They just grow another. Or if an arm gets misplaced, it can regenerate itself into a whole new creature.

Starfish
image gallery

click any image to enlarge
Int. = intermediate stage
Juv.= juvenile

Starfish are NOT listed as a threatened species on the IUCN Red List
Starfish encounters
LOCATION:
Sangalaki Island
DEPTH:
12 metres
SPECIES:
Acanthaster planci
COMMON NAME:
Crown of Thorns starfish
DIVE LOG:

The best known predator in the starfish group is the much-maligned Crown of Thorns starfish. This bewitching creature is best known for being able to wipe out whole colonies of hard coral. They feed on coral polyps by sliding their stomach out and suffocating a whole colony beneath, leaving just the bleached, dead skeleton.

This image was taken at Sangalaki Island during a period where the Crown of Thorrns had become highly prolific. They were seen on almost every dive and always in multiples of three or four. At the time, the water temperature was consistenty over 30°C or 86°F.

french angelfish in Grenada
SPECIES NAMES | Many fish can be hard to identify as they are so similar. Common names vary and even scientists disagree on what is what. If you can name anything we can't, please get in touch.

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