Tag

the incredible series Archives | DIVEIndia | Scuba Diving In Havelock Island, Andamans, India| PADI, SSI Dive Centre

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.

The Incredible Wrasse

Posted by | Articles, Blogs, PADI underwater naturalist, The Incredible Showcase | No Comments

Our first showcase in this series is dedicated to a particularly fascinating and versatile group of fish.*Drum roll* – THE WRASSES!

With nearly 500 known species, wrasses form the second largest marine fish family (Labridae) in the world. Wrasses are generally elongated fish that taper at both ends, you could call that being “cigar-shaped”. Found in tropical and temperature waters, wrasses can be as tiny as the thumb-sized minute wrasse (Minilabrus striatus), but also grow to be as big as the 2 meter long Napoleon wrasse (Cheilinus undulatus).

Portrait of a Napoleon wrasse (Cheilinus undulatus)

picture credit: Gunnhild Sørås

Most people know and love to see the Napoleon wrasse on a dive. A large and majestic fish that appears to carefully inspect divers with its googly eyes as it slowly cruises by. Napoleon wrasses have a single fin that runs continuously along its back (like a Mohawk); a characteristic feature of wrasses. Look carefully next time at a bird wrasse (Gomphosus varius) – you will see that same dorsal fin as the Napoleon, albeit on a smaller scale.

Bird wrasse (Gomphosus varius)

Brian Gratwicke (Wikimedia Commons)

Similar to the Napoleons, many wrasses appear as though their heads have been tattooed with Maori art. Intricate patterns radiate from their eyes in stunning colour schemes and patterns. Admire this artwork the next time you swim close to a red-breasted wrasse (Cheilinus fasciatus) or a moon wrasse (Thalassoma lunare).

Face painting on a Red-breasted wrasse (Cheilinus fasciatus) and a moon wrasse (Thalassoma lunare)

Picture credit: Wikimedia Commons

Wrasses are a family found in great abundance across reefs. Perhaps a key to their diversity lies in their versatile diet. Wrasses leave no part of the reef unexplored. There are wrasses that eat fish, some that graze algae, some that crack open crustaceans and molluscs, and others that suck out worms and coral. A few chase after plankton in the blue.

There are also those that follow other fish, almost like a shadow, watching closely to see what hidden treasures are revealed when these hunters are at work. Look out for the small checkerboard wrasse (Halichoeres hortulanus) hungrily tailing either a triggerfish upturning rocks or goatfish that is stirring up the sand in hope of nabbing a quick crab or clam. What would you call this- Clever? Lazy? Freeloading?

A checkerboard wrasse (Halichoeres hortulanus) waiting to see what goodies the yellow-margin triggerfish (Pseudobalistes flavimarginatus) stirs up!

Photo credit: Bernard Dupont (Wikimedia Commons)

By virtue of their choice of cuisine, some wrasses play critical roles in the functioning of coral reefs as an ecosystem. I am talking about the unassuming but industrious blue-streaked cleaner wrasses (Labroides dimidiatus). Cleaner wrasses feed specifically on parasites, dead tissues and mucous, found on bodies of fish that do not want to keep any of it. In the process, cleaner wrasses have set up some of the most phenomenal symbiotic relationships that can be observed while diving. These wrasses work in pairs or in small groups and work extremely hard to look for fish that are looking to be cleaned. A single cleaner wrasse on duty, working 4 continuous hours, cleans up to 2000 ‘client’ fish. Starting up and running a cleaning station successfully is no joke for these finger-sized fish and there is a lot that we can learn from observing them. (Watch out for our upcoming post- Business lessons from a cleaner wrasse partnership.)

A blue-streaked cleaner wrasse (Labroides dimidiatus) working on a Napoleon wrasse with a keen eye.

Picture credit

Of all the wrasses that we might come across commonly, we are likely to underestimate the anchor tuskfish (Choerodon anchorago) the most. The anchor tuskfish is named so, for its tusk-like canines. These sharp teeth when unleashed, transform the otherwise delightful-looking wrasse into a predator that every hard-shelled animal should be afraid of! Tuskfish can spend hours trying to dig out clams, carry them over to specific spots on the reef where they whack them repeatedly against specific rocks until the shells crack open and are ready for the devouring. Tuskfish are the first wild fish to be documented using tools.

I would like to end this showcase with one of my favourite wrasses of them all. It is one that some of us have probably witnessed, doing something so bizarre, in a span of one second, that no one but you and the wrasse will believe that it happened. Ladies and gentlemen, I give you Epibulus insidiator or the slingjaw wrasse!

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 Center of 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.