The Zoo

 

My most memorable visit to this zoo was about 15 years ago. The animals were amazing but equally impressive was the open spaces like the lake and trees where birds used to gather. It had a terraced structure which gave the impression that you were climbing down a hill that added to the adventure. Naturally, it showcased only Vertebrates or animals with a backbone and skeleton. Even with my limited knowledge of these things, I knew that there were strange animals called Invertebrates, some so strange that you could almost believe that they were from another planet. So one day I decided to find out.

All animals fall into 35 different groups or Phyla, although only about 9 of them are well-known. All vertebrates (Mammals, fish, birds, amphibians, and reptiles) actually fall under one phylum called Chordata. But what are the other phyla? In the phylum, Mollusca is the snail, whose most prominent features seem to be a muscular foot, a mantle with a shell, and eyes. Snails like other invertebrates do not have a spinal cord or one single brain. Instead, they have a set of ganglia (groupings of neurons) that distribute the control of the various parts of it. Slugs are closely related to snails and its motto seems to be “Just Hang on”, because it is constantly in danger of drying out in warm weather and being eaten by other animals.

So it comes as a surprise that one of the cleverest animals the octopus, is also a mollusk. I once read a weirdly convincing story by one of the world's most renowned science fiction writers who says that octopuses can build and use tools, however being under the sea and unable to use fire to forge metals, its evolutionary growth is stunted. And who can ignore the elusive, haunting giant squid, something straight out of a nightmare.

In any case, Mollusca is the second most diverse animal phylum, after Arthropoda, with approximately 93 000 species distributed between three major lineages: gastropods (‘stomach footed’ – 70 000 species including snails, land and sea slugs, limpets), bivalves (20 000 species including oysters, mussels, clams), and cephalopods (‘head footed’ − 900 species including octopuses, squids, and nautiluses).

Without ever having seen a starfish I had always felt that starfish are overrated in literature, particularly poetry. But one day I was wading in the shallow crystal clear sea in Trincomalee, when I saw a large orange starfish. As I went to have a closer look, it glided swiftly away, it was amazing,  I’ve never seen anything so magical. Starfish are not fish, but are classified under the phylum Echinodermata. Other animals in this group include the sea urchin, sea cucumber, and sand dollar. All animals in this group are only found in the sea.

Of course not all Invertebrates are as magical as the starfish, some are repulsive some are deadly and some are so simple that they could be mistaken for plants. Take the sponge for example (Phylum Porifera), the simplest animal, its motto seems to be “I ain’t going nowhere” because it is attached to the seabed. Sponges are similar to other animals in that they are multicellular, heterotrophic, lack cell walls, and produce sperm cells. Unlike other animals, they lack true tissues and organs. The shapes of their bodies are adapted for maximal efficiency of water flow through the central cavity, where the water deposits nutrients and then leaves through a hole and that’s about it. But if you think Invertebrates are boring wait till you meet the insects some of whom could potentially kill you. Insects come under the Phylum Arthropoda. Other animals in this phylum apart from insects are the myriapods (including centipedes and millipedes); arachnids (including spiders, mites and scorpions); crustaceans (including slaters, prawn and crabs). Although it’s difficult to think of a crab as being related to an insect if you look closely it kind of looks similar.