Archive for ‘Ecological’

Christmas Tree Worms

By , 17 December, 2014, No Comment

Davy Jones’ Locker is located in the Gulf of Thailand on a paradise island named Koh Tao were here we are fortunate enough to be able to dive all year around in some of the most beautiful waters in the world.

Koh Tao offers scuba divers (beginners to advanced levels) the opportunity to experience diving with a huge variety of marine life.

In the spirit of Christmas below are some facts on one of the many mesmerizing creatures that live in the underwater world that we love to explore every day: Christmas tree worms…

Christmas tree worms (Spirobranchus giganteus ) are Christmas tree shaped tube-dwelling worms with twin spirals of plumes used for feeding and respiration. They have a tubular, segmented body lined with chaeta, small appendages that aid the worm’s mobility. Because it does not move outside its tube, this worm does not have any specialized appendages for movement or swimming. These worms are sedentary, meaning that once they find a place they like, they don’t move much.

They come in many colors including red, orange, yellow, blue and white and though they are small with an average 3.8 cm in span, they are easily spotted due to their shape, beauty and color always makes an eye-catching display.

Christmas tree worms are found on coral reefs in tropical waters worldwide, in relatively shallow waters less than 30 metres.

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Christmas tree worms are polychaete ciliary feeders that feed using their radioles, the hair-like appendages or “feathers” that circle outward from the central spine, to catch phytoplankton floating by in the water. The food is then passed down a food groove by ciliary tracts — lines of tiny hair-like extensions on the surface of cells that generate water currents to move food or mucus. The food particles are sorted and larger particles are discarded. Sand grains are directed to storage sacs to be used later for tube building.

Plumes are also used for respiration. Though the plumes are visible, most of these worms are anchored in their burrows that they bore into live calcareous coral. Christmas tree worms are very sensitive to disturbances and will rapidly retract into their burrows at the slightest touch or passing shadow. They typically re-emerge a minute later, very slowly, to test the water before fully extending their plumes. So if a worm feels threatened, it can withdraw into the hole to protect itself quite easily. For added safety, the Christmas tree worm can also plug its tube with a small plate called an operculum.

There are male and female Christmas tree worms. They reproduce by sending eggs and sperm into the water. The eggs are fertilized in the water then develop into larvae and become part of the zooplankton to be carried by the currents to then settle on coral heads and then burrow into the coral to form their burrows.

As you can see this is just one of the fascinating creatures that we encounter every day here at Davy Jones’ Locker. Feel free to pop in for a visit and we will be happy to share these unforgettable experiences underwater with you.

 

by Sarah

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Turtles of Koh Tao

By , 21 November, 2014, No Comment

Koh tao means turtle island, and it is the dreams of many divers to see one of these beautiful animals in the flesh. There are two types of turtle common to koh tao: The Green turtle and Hawksbill turtle. The Green and Hawksbill turtles look very similar to each other however they have some differences in appearance.  The Hawksbill can be distinguished from the Green Turtle by its sharp, curving beak with prominent cutting edge, and the saw-like appearance of its shell margins.

The Green Turtle is the most typical sea turtle, possessing a teardrop-shaped carapace and a pair of large, paddle-like flippers. Despite the turtle’s common name, it is lightly-coloured all around while its carapace’s hues range from olive-brown to black in Eastern Pacific green turtles. The turtle is actually named for the greenish coloration of its fat and flesh.

The Hawksbill has a worldwide distribution, with Atlantic and Pacific subspecies and the Green turtle can be found throughout tropical and subtropical seas around the world, with two distinct populations in the Atlantic and Pacific Ocean. Unlike other members of the turtle family, the Green turtle is mostly herbivorous. The adults are commonly found in shallow lagoons, feeding mostly on various species of seagrass.  Sponges are the principal diet of hawksbills once they enter shallow coastal waters and begin feeding on the bottom. Some of the sponges eaten by Hawksbills are known to be highly toxic and lethal when eaten by other organisms.  Hawksbills are also known to feed on other invertebrates, such as comb jellies and jellyfish. This is why you must be careful with things like plastic bags as if they end up in the sea a turtle could eat it thinking it is a jellyfish. The largest Green turtle ever recorded weighed 395 kilograms whilst the Hawksbills are generally smaller with the largest recorded tipping the scales at 127 kilograms. You can see both types of turtles at many dive sites through out koh Tao, including sleeping turtles on night dives. If you do see one, make sure to keep a respectful distance and let them go about their day.

 

Sophie

Tortle

 

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Surprise surprise

By , 20 June, 2014, No Comment

The other day, I was teaching an Advanced Open Water course and we had the pleasure of encountering a massive jellyfish.  We do see them on occasions here on Koh Tao, but they are relatively rare, so it’s always a treat.  Especially when we see the big ones.  It can be a little difficult to identify species of jellyfish, but I think it was a white-spotted jellyfish.

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They’re such strange animals that it made me wonder more about them.  Turns out they are not fish at all.  They don’t have specific organs for respiration, digestion or circulation.  In fact, they don’t even really have a central nervous system.  They just have nerves spread throughout their bodies.

 

Jellyfish bodies consist of about 95% water and their skin is so thin that they don’t really breathe, they just get their oxygen by diffusion.  They eat by stinging whatever they come across and jamming it into their bodies.  Because they are transparent, sometimes we see small crabs in their “stomachs”.

 

Always a pleasure to come across one of these strange beings.

 

Pete

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How to make a tropical beach…

By , 18 May, 2014, No Comment

Whilst sipping away on a Piña Colada, watching yet another glorious tropical sunset, have you ever stopped to think where your tropical beach comes from? Maybe this is far back in your mind, lazing away under a palm tree, but the answer may surprise you…

 

Those fine sandy beaches are not just created from millions of years of erosion as your high school Geography teacher may have you think. In fact, we can attribute entire tropical islands to a species of fish which is the bigger, uglier cousin (the cousin that you haven’t really met but you know served a couple of years in juvie for armed robbery) of Koh Tao’s very own Rainbow Parrotfish – the Green Humphead Parrot fish.

 

Both feast on the algae which grows on rocks and coral, problem is for a beast that can grow up to 1.3m is length is getting at it. The not so elegant solution nature came up with is that the combination of their razor sharp teeth, strong bite and incredible digestion system, mean that a school can devour entire coral reefs when coming to graze. They actually eat the rock and coral, process the algae for energy, and then excrete the unwanted rock in the form of fine sand. A single humphead can produce over two tons of sand a year, meaning that entire beaches and even islands are made up of the sand produced by this species.

 

Check this link out to see for yourselves…

 

http://www.youtube.com/watch?v=8T-gnZevlaY

 

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left: Koh Tao’s rainbow parrotfish; right: green humphead parrotfish

 

It’s Koh Tao cousin may not be big enough to be responsible for the formation of Koh Nang Yuen, but if your diving around Twins or White Rock, you’ll see these green and pink fish nibbling away on the rock, and then producing a cloud of sand when they finish digesting, go for a dive tomorrow and check it out for yourselves.

 

So there you have it. The Beach Creator. The Coral Destroyer. Don’t let this put you off your Piña Colada though… the sand still feels amazing between your toes.

 

By Chris Nuttall

 

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Lionfish the dangerous beauty

By , 15 April, 2014, No Comment

Petrois Volitans also known as the lionfish. The lionfish can live to around 16 years in the wild and lionfish often live longer if looked after well in captivity. There are around 8 different recognised species of lionfish that are found in the Pacific Ocean. The lionfish is natively found in coastal waters around rocky crevices and coral reefs where there are lots of smaller fish for the lionfish to eat and also places for the lionfish to hide.

Here on Koh Tao it is rare to find lionfish but there are a few places where you can see one or two of them such as the dive site junkyard an artificial reef just off the beach at Mae head, at the back of the site there is a table tipped over on its side with 3 benches around it here inside the table stand a baby lion fish stays and is almost always there either sleeping or just resting.

The largest of lionfish can grow to about 15 inches in length, but the average is closer to 1 foot. Lionfish prey on a wide variety of small fish and crustaceans that inhabit the tropical reefs. The lionfish is prey to few predators due to the large size of the lionfish and also the fact that the appearance of the lionfish is very intimating to other animals. The spikes that protrude from the body of the lionfish contain venom that the lionfish uses to defend itself if it is being pursued.

The lionfish although dangerous is a beautiful creature and is not inherently aggressive towards humans, this allows us to view it without much worry and admire just how stunning the lionfish really is. So come to Koh Tao request junkyard for your dive and go see the lionfish in all its glory

Nick Kelly

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