Definitive guide to everything you need to know about tropical fish. Secure server guaranteed by ClickBank.

It is interesting to see tropical fish swimming from one place to another with no apparent plan, but this picturesque entertainment reminds us of what other tropical fish, now lost in the night of time, achieved for us. Fish are counted among the oldest vertebrates in the planet.

In fact, the oldest vertebrate yet discovered, named 'Anatolepis,' was a jawless fish from the Cambrian period; its remains are dated to about 515 million years ago. Not much is known about this fish, how was its shape or its lifestyle; fossil fragments corresponding to this animal are scarce and incomplete.

However, the record improves much regarding posterior periods in the evolution of life; the Ordovician followed the Cambrian period, and fish fossils from this time are far better preserved, as those from the continuing Silurian and Devonian periods. Ordovician fish had a shape that indeed, remind us of fish, but were very different: Almost all of them had an impressive body armour and had a terrifying look for us.

It is supposed that fish evolved from annelid worms that used to roam the seabed during the Cambrian; since at that time the first predators appeared, these worms suddenly became very vulnerable and naturally evolved some sort of protection. At that time, predators like 'Anomalocaris' evolved very strong means to break apart the things they intended to eat, so armour had to be really strong.

This predator - the first one yet found - was like a shark of the Cambrian and ate mostly sea bottom entities like trilobites and of course, worms. Slowly fish evolved scales out of the ringed structure typical of annelids, and by the Silurian they had transformed themselves up to a point in which they would be recognisable to us in their general shape. During this period, the first land plants appeared, setting the stage for further evolution.

Silurian seas were warm, but at the end of this period, important environmental changes began to unfold and sea and water levels become quite variable; so, animals and plants may found themselves cut out of the ocean in ponds and small lakes for extended periods, and they were being exposed to the atmosphere, outside water too. Many indeed would have perished, but others began to adapt.

Algae would develop new ways to reproduce themselves outside water, and animals would have to learn to breath and move in this new environment. The first animals that set foot on land were some sort of scorpions of about one to two and a half metres in length; these could swim in the water and walk in the land; both habitats fith them them well.

As for fish, those that found themselves cut from the sea for variable - probably seasonal - periods, had also to develop ways to survive, and in this way is how the first amphibians came to being; they were the first vertebrates that came out of the water, and from which we also come from.

Not bad for some tropical fish.

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