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Fish faces and reef ecology

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In this section you will learn about the anatomy, diet and evolution of fishes and their roles in underpinning ecosystem resilience. Hi, I’m Associate Professor Andrew Rhodes. I’m a specialist in fish ecology at the University of the Sunshine Coast in Australia. So why do fish have such a variety of faces? To answer this question, first we need to learn a bit about fish. Fish come in all shapes and sizes, ranging from Dorf minnows less than one centimetre long to giant whale sharks up to 20 metres long. There are about 35,000 fish species, which is more than all other groups of vertebrates. Okay, so there are lots of fish. But what really is a fish.
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Fish are aquatic vertebrates, which means they have backbones. They have gills, but they have no limbs. There are five main types of fish, the jawless fishes, cartilaginous fishes, and bony fishes which are all alive today, and the spiny sharks and plate skinned fishes which are extinct. Fish have a variety of body forms and they eat all sorts of things. They’re particularly fond of eating each other. Today, I’m going to tell you about the ecology and anatomy of fishers, and we’ll discuss how their diversity of faces is linked to their jobs, which can be essential for the health of ecosystems like coral reefs. The earliest fishes ate animal tissues and fed by sucking and rasping flesh from their prey.
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They didn’t have Jaws, the evolution of Jaws allowed cartilaginous fishes to capture, hold and consume life prey. Further diversification of the jaws, teeth and other mouthparts permitted bony fishes to eat a variety of foods, including plants and detritus, what cause fish to develop complex jaws and variable teeth. The evolution of Jaws occurred in parallel with the radiation of invertebrate species. Jaws evolved from gills support structures, and the development allowed fishers and all subsequent vertebrates to consume a variety of foods. Starting with invertebrates, fish diets progressively branched out to include other types of prey. jaws are cool, but why does this matter?
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The diversification of feeding structures and strategies occurred as more prey types became available, but also as the number and types of fishes expanded, resulting in high competition for each meal. Different species evolved in distinct ways to capitalise on available prey. And this led to changes in their functional traits, which are their morphological, behavioural and physiological features. So fish began to look different from each other. And because different species eight different things, they also developed distinct childen ecosystems, you might have noticed that fish and indeed fish faces are most variable on coral reefs. It’s true that coral reefs support more species than other marine ecosystems, and about 4000 of these are fish.
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But this does not tell us much about the functional traits of fishes. So to understand why fish faces look the way they do, we need to consider the evolutionary history of both reef fishes and reef corals, fish and corals have existed together for about 60 million years. But most species only arose in the last 5 million years. This diversification of both fish and corals led to increases in reef area, coral cover and fish abundance. So it appears that reefs and refreshes have actually evolved together as the diversity of corals and reef micro habitats increased. Reef fishes also diversified, with different species adopting different strategies, and indeed different functional traits to take advantage of new opportunities.
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Some of these new roles were also beneficial to coral, like the consumption of algae that might otherwise smother reefs, and this allowed corals to expand into new areas and diversify alongside fishes. Reef fishes thus develop the diversity of faces to perform different jobs on coral reefs. Many species are carnivores, some have large teeth and feed on fish, others have mouths, they can protrude in front of their faces to suction food from soft sediments, and several species have find forcep life mouthparts they use to target corals. A host of species also like to feed on plants. Some have developed bird like beaks, which are fused jaws that they use to scrape biofilms from corals.
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Others have comb like teeth that are well suited to brushing fleshy algae from their stocks. And then there are the farmers who tend to crop of preferred algae and defended against all trespassers, including people who might swim close by. So there are lots of jobs for fish to do on coral reefs. To do these Well, fish need different tools. And for animals without hands. This typically means a diversity of facial features. But it turns out that some reef jobs are more popular than others. The most popular jobs are performed by 1/3 of all reef fish species, whereas the least popular 1/3 of jobs are performed by only a single species H.
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Fish that perform popular jobs have adapted to share resources. This is called functional complementarity. They complement each other and it occurs when species that eat similar things do so in different ways. Fish do this by adapting different strategies and distinct functional traits, as we have already seen, and this can increase the diversity of fish faces. That’s great, but what the fish faces and job popularity mean for reef health. Popular jobs that are performed by lots of species will be maintained if some of these are lost. This provides reefs with a level of insurance that helps to protect these functions against disturbance.
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unpopular jobs that are performed by one or just a few species are highly vulnerable, and these functions might decline if key species are lost or removed through harvesting pressure. The diversity of fish faces or rather the functional diversity of reef fishes is that’s tightly linked to reef health. A similar relationship between fish face diversity and ecological resilience also exists for other diverse marine ecosystems like sea grasses and seaweeds, which are formed by Foundation species. conserving this functional diversity of fishers is one tool that might help these ecosystems to recover from local disturbances and to resist global pressures like climate change, at least for a little while.

In this video we Dr Andrew Olds will discuss the different roles different species of fish play in maintaining a coral reef, and which ‘jobs’ are more popular than others.

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