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Who Are You Calling an Invertebrate?

Posted by | Articles, The Incredible Showcase, Underwater Naturaliast Course | No Comments

Ernst Haeckel (1834-1919) juggled many professional hats during his life – he was a professor, biologist, philosopher, physician, and in the middle all that, he found the time to be a phenomenal artist as well. He is known for his enormous contribution to science, through the several new species he discovered, scientific concepts he theorized and biological terms he coined. He is also admired across various disciplines for his exquisite and influential collection of illustrations known as the ‘Kunstformen der Natur’ or ‘Artforms in Nature’ (sketched and painted between 1899 -1904).

If you are looking at any of these plates and admiring them for their abstract beauty or commending Ernst Haeckel for his marvellous attempt at science-fiction, take a look again. These are all real marine animals. They actually exist in these very shapes, patterns and forms. Ernst Haeckel observed and appreciated that in these underwater beauties; several decades before the advent of recreational SCUBA diving.

What do all these animals have in common? On careful observation you will notice that, yes they are all stunningly beautiful, there is inherent symmetry, but also, they are all types of ‘invertebrates’. They are all animals that lack a vertebral column or a backbone/spine inside their bodies.

Speaking of invertebrates, I never did understand the figurative use of this term in our society. To call someone a ‘spineless’, ‘invertebrate’ is to describe them as weak, cowardly, inadequate or ineffective. How did this association come to be?

Over 97% of animals on this planet are spineless, especially in the ocean. Some of the most venomous (box jellyfish), strongest (mantis shrimp), smartest (octopus), fastest reflexes (mantis shrimp again!), largest (giant squid), cutest (alright, this one is heavily subjectiveJ) are some form of marine invertebrate or the other.

A barrel sponge (Xestospongia testudinaria) can dwarf you despite your tank and fins
Vandit Kalia @vanditkalia

When reading about evolution and biology today we learn that, more and more, science doesn’t consider evolution to be progressive. Meaning to say that through the course of geological time, being older or having appeared first is no longer considered ‘primitive’ and being more newly evolved doesn’t make you necessarily ‘advanced’. Scientists now prefer to use terms such as ‘ancestral’ and ‘recent’ instead, with much less value judgement. Take sponges for example. Sponges consist of hollow cavities held together by protein fibres and they have numerous different types of cells, to filter food from water that is brought in and sent out. Sponges constitute some of the oldest animals to have ever lived (fossils as old as 640 million years old), and they still exist, all of 9,000 species of them.

A wise old coral colony
Gunnhild Sørås  
@gunnigullet    Vikas Nairi  @vikasnairi

Backbone-free animals are everywhere, and some of them literally shape our world. During the journey of a single dive in a shallow reef, we are immersing ourselves into a world whose multi-dimensional foundation, was built over millions of years, by the remarkably and astonishingly, spineless coral. Stony coral get a majority of their energy from their in-house photosynthetic symbionts and use it to put down calcium carbonate skeletons, layer by layer, that are strong enough to last years, centuries, and millennia. Corals live and lay the foundation of coral reefs, and then everyone else, from feather-duster worms to fish, start to step in to look for ways to build their own lives. An ecosystem is formed.

A closing sea anemone
Chetana Babburjung
 @chutney_babburjung

Through the course of your dive, you will surely find yourself smiling at clownfish in their anemones. Unlike a majority of their coral cousins which live as colonies of polyps, sea anemones are typically singular polyps lined by a whorl of stinging tentacles. Hidden in the centre of the anemone, if clownfish will allow you to see it, is an opening that is its singular window to the outside world- mouth and anus. It happens rarely and very difficult to catch with the naked eye, but sea anemones can move.

A peacock tail anemone shrimp busy on its host anemone
Gunnhild Sørås 
@gunnigullet

Anemones are cheerful hosts that collaborate not just with clownfish, but a variety of crustaceans, especially anemone shrimps and crabs that promise to help the anemone stay clean in return for a home.

Nudibranchs, a cryptic treasure.
Gunnhild Sørås 
@gunnigullet

Some of the more cryptic treasures to look out for on a reef are sea slugs, who are now coming out of the shadow of their celebrity cousins-the octopus. Among the mind-blowing diversity of sea slugs, nudibranchs are unique in that they breathe through gills placed outside their body (hence the name). While they have a versatile diet, some of them love eating fern-like hydroids. Hydroids just like their relatives -coral, anemones and jellies- are laced with stingers. No matter, Aeolid nudibranchs eat them anyway, carefully pocketing the stingers for later use as self-defence. Similarly sap-sucking slugs feed on algae but extract the algal pigments and keep them alive in their bodies for their own personal photosynthetic use. Is that ingenious, or is that ingenious?

Ernst Haeckel was particularly taken by the symmetry he saw in nature. A classic example for us would be- Echinoderms. A group found exclusively in the ocean, echinoderms are the sea stars, feather stars, brittle stars, urchins, cucumbers and several other unbelievable but underappreciated marine invertebrates (and therefore warrant a separate feature altogether).

A mollusc larva dancing in the blue
Vikas Nairi 
@vikasnairi

A typical shallow dive might last forty-five minutes to an hour and we may still not be ready to ascend to the surface, even though the gases in our tanks and bodies might dictate otherwise. But wait, the dive isn’t over yet.  Safety stops are the best time to connect with bizarre but brilliant drifting creatures, as we hover in an endless soup of plankton.

At the end of the day, if Boris Johnson were to ever call me a “supine invertebrate jelly”, I think I might just say, thank you.

Watch this space for our next  showcase on the underwater lives of the Incredibles.

The author, Chetana is a PADI divemaster and resident biologist at DIVEIndia in the Andaman Islands. She is an alumnus of the Masters program at the Wildlife Conservation Society -India program and National Centre for Biological Sciences in Bengaluru. She has been diving and exploring the Andaman Islands since 2013. She is also deeply excited about forests, birds, reptiles and amphibians.

Best time for scuba diving in the Andamans

Best time for scuba diving in the Andamans

Posted by | Andaman scuba diving course, Articles, Scuba Diving Andamans, Scuba diving Courses | No Comments

BEST TIME FOR SCUBA DIVING IN THE ANDAMANS

Best time for scuba diving in the Andamans

Let’s start by clarifying something – rain doesnt matter so much for diving. Yes, it can affect visibility at shallow depths, but this only happens when there is extended rainfall here (which doesnt happen often, even in the monsoons – we usually get short showers). Furthermore, most of our dive sites are off shore and once you descend to the dive depths, conditions arent affected so much. Tides play a much bigger role in affecting underwater visibility and that changes from week to week – so the range of visibility remains more or less the same all year long, whether it is raining or sunny.
What matters more is wind. When it is too windy, the seas are rough and we cannot go out to the open sea (or sometimes, we can go out but decide not to, in order to be safe:  our standard isnt “can we dive in this”, but “if something were to go wrong, can we manage the situation safely for everyone in this”). However, even when it does get rough, we have a bunch of sites that are accessible all year long as they are sheltered from prevailing winds – what we cannot do is visit our remote, highlight sites like Johnny’s Gorge, Dixon’s Pinnacle and Jackson’s Bar. This doesnt affect beginners so much, but does affect certified divers.
Traditionally, this is what the weather holds over the course of the year:

 

January-May period is when the seas are the calmest (especially March-May, when the sea is sometimes to calm that it resembles a mirror) and surface conditions are best for diving.

 

June – August is the rainy season. This is different from the mainland monsoons, and consists of wet periods (when it is cloudy all day and there are frequent, brief showers) and dry periods (when it is sunny and calm for several days or even weeks). During some of this time, we are able to visit all our highlight sites and at other times, we are restricted to the nearby, sheltered sites.   While the diving is usually fantastic due to fish spawning in the warmer water, odds are higher that we will be limited to our nearer sites. However, the weather is usually very pleasant at this time, the package tourists are away and the island reverts back to a sleepy, idyllic paradise.

 

September-November is what we call the “new season” – during this time, the south-westerly winds are starting to die down, but there are still regular showers and occasionally, the winds do pick up. At this time, the diving is absolutely fantastic (a lot of fish spawn in the rainy season, so there is a lot of bio-mass on the reefs) and the sites are at their absolute best. The flip side, of course, is the slightly higher risk that winds may play spoilsport and limit us to nearer sites.  Also, currents can be stronger at this time.

 

December is a bit of a transition time – the terrestrial weather is lovely, sometimes there are showers and the winds can be moderately strong.
Of course, with weather patterns changing over the past 5-6 years, things are a little more blurry now. Over the past 3-4 years, we’ve had very calm conditions in June, with low wind and limited rain. We’ve also had rough conditions in Jan/Feb. At this point,

 

What does this mean?

 

FOR BEGINNERS: It doesnt matter when you come. We have sites that are accessible all year long, even in a storm, and the conditions of these sites usually do not vary that much whether it is on or off-season. In season, things are sunny and the islands are busier – in the off-season, it is quieter, things are more relaxed and the weather is actually very pleasant. And because the rain takes the form of brief showers, you can actually explore the islands without any issues).

 

FOR EXPERIENCED DIVERS: Based on the recent weather trends over the past 5-6 years, we’ll say that March/April/May offer the best chances of calm conditions,  followed by January/February, followed by September-December.     Conditions in June, July and August can vary – if you are lucky, you’ll get superb diving with just 2-3 people on the boat, and if you are unlucky, you’ll be limited to our nearer sites (which are very nice, but probably a step or so behind our highlight, open-sea sites).
Of course, the weather being what it is, there are no guarantees but hopefully, this will help provide some information in helping you plan your trip to the Andamans.

An old “friend” returns?

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Posted by Dive India |

Back in 2002, I was teaching a class at Minerva Ledge with 3 Open Water students.
Back then, there used to be a lot more sharks on this reef and the question wasnt whether we’d see any sharks, but how many and which species. As with most beginners, my students had some concerns about being in the water with sharks, and I gave them my usual spiel: sharks arent dangerous, we are not normal prey, we are too big for most sharks, etc. etc.
We get in the water, and sure enough, we see a white tip cruise by. And then a black tip some time later. By now, my students are converted – they are very excited about the sharks and no longer scared. Towards the end of the dive, yet another white tip goes by – and a few seconds later, one of my students points to the right into the blue and signals “shark.”
I look, expecting to see a white tip and sure enough, there is one swimming towards us. I nod and return to scanning the front, as I am hoping to get a manta today.
Then a small voice pipes in my head, saying “wait a minute – wrong proportions…” I look again, and the shark is coming toward us. Directly towards us. Fins down. Which is an aggressive territorial display.
“Wait a minute,” I remember thinking, “where does a white tip get off being aggressive to three divers”?
Then the initial voice in my head pipes up again “hey… WRONG proportions. Hellooo!”
Right – when looked more closely, this shark just seemed to be a lot bulkier. And not only that, it was a lot bigger. And at that moment, it turned and showed us its size – it was a 4m+ bullshark! Yes, I know bullsharks don’t get bigger than 3m or so – but this was 4m+ and I will stake my diving reputation on it (heck, most people who’ve seen it put it at 5m+, but that is a bit exaggerated). And my divers and I had just been told off in no uncertain terms by Big Guy that we were in his territory. Rather than upset him, we turned around and head back in towards the reef, and that was all we saw of him on this dive.
Over the next few years, Bob the Bullshark would make a reappearance a couple of times each season. Each time, it was at the same site and the same deal: comes straight in, fins down, in a territorial display, turning away a good 10m or so away. We always appreciated the polite warning and would make sure we didn’t hang around for a second pass (and certainly not the third pass, which might involve a “smile”).
And each sighting was absolutely, gloriously epic – there are few things in this world as graceful as an enormous, powerful shark with rippling muscles and gliding by faster than anyone can swim with the merest flick of its tail. It was humbling and it was moving – we were witnessing one of nature’s 2 perfect creations in its element (the other being the crocodile) – and I mean “perfect creation” literally: the shark has not changed or evolved over 350 million years. It is perfect and cannot be improved upon.
The last 3+ seasons, Bob has been AWOL. We put it down to him falling a victim to the local shark fishermen (thanks to the demand for turning this amazingly beautiful animal into soup).
However, a couple of days ago, two of our divers and one of our DMs saw a big shark at a site that is about 250m away from Bob’s old stomping grounds. Initially, we were not sure whether it was a grey reef shark (which has been sighted here occasionally) or a bullshark (which has never been sighted here). Speaking to the divers and comparing notes on size, shape, etc., I am pretty confident it was a big bullshark.
Could Bob be back? I for one certainly hope so – if there ever was a Christmas present that would thrill me beyond belief, this would be it. And at the risk of anthropomorphizing too much, I do wonder if somewhere in that predator mind of his, Bob remembers us?
Welcome back, Bob – we missed you!