Fish to amphibian evolution, new research


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The Evolution of Amphibians

23 January 2016

The first major groups of amphibians developed in the Devonian period, around 370 million years ago, from lobe-finned fish which were similar to the modern coelacanth and lungfish.

These ancient lobe-finned fish had evolved multi-jointed leg-like fins with digits that enabled them to crawl along the sea bottom. Some fish had developed primitive lungs to help them breathe air when the stagnant pools of the Devonian swamps were low in oxygen. They could also use their strong fins to hoist themselves out of the water and onto dry land if circumstances so required.

Eventually, their bony fins would evolve into limbs and they would become the ancestors to all tetrapods, including modern amphibians, reptiles, birds, and mammals. Despite being able to crawl on land, many of these prehistoric tetrapodomorph fish still spent most of their time in the water. They had started to develop lungs, but still breathed predominantly with gills.

From the University of Calgary in Canada:

Fossil holds new insights into how fish evolved onto land

‘It’s like a snake on the outside, but a fish on the inside’

June 21, 2017

The fossil of an early snake-like animal — called Lethiscus stocki — has kept its evolutionary secrets for the last 340 million years.

Now, an international team of researchers, led by the University of Calgary, has revealed new insights into the ancient Scottish fossil that dramatically challenge our understanding of the early evolution of tetrapods, or four-limbed animals with backbones.

Their findings have just been published in the research journal Nature. “It forces a radical rethink of what evolution was capable of among the first tetrapods,” said project lead Jason Anderson, a paleontologist and Professor at the University of Calgary Faculty of Veterinary Medicine (UCVM).

Before this study, ancient tetrapods — the ancestors of humans and other modern-day vertebrates — were thought to have evolved very slowly from fish to animals with limbs.

“We used to think that the fin-to-limb transition was a slow evolution to becoming gradually less fish like,” he said. “But Lethiscus shows immediate, and dramatic, evolutionary experimentation. The lineage shrunk in size, and lost limbs almost immediately after they first evolved. It’s like a snake on the outside but a fish on the inside.”

Lethicus’ secrets revealed with 3D medical imaging

Using micro-computer tomography (CT) scanners and advanced computing software, Anderson and study lead author Jason Pardo, a doctoral student supervised by Anderson, got a close look at the internal anatomy of the fossilized Lethiscus. After reconstructing CT scans its entire skull was revealed, with extraordinary results.

“The anatomy didn’t fit with our expectations,” explains Pardo. “Many body structures didn’t make sense in the context of amphibian or reptile anatomy.” But the anatomy did make sense when it was compared to early fish.

“We could see the entirety of the skull. We could see where the brain was, the inner ear cavities. It was all extremely fish-like,” explains Pardo, outlining anatomy that’s common in fish but unknown in tetrapods except in the very first. The anatomy of the paddlefish, a modern fish with many primitive features, became a model for certain aspects of Lethiscus’ anatomy.

Changing position on the tetrapod ‘family tree’

When they included this new anatomical information into an analysis of its relationship to other animals, Lethiscus moved its position on the ‘family tree’, dropping into the earliest stages of the fin-to-limb transition. “It’s a very satisfying result, having them among other animals that lived at the same time,” says Anderson.

The results match better with the sequence of evolution implied by the geologic record. “Lethiscus also has broad impacts on evolutionary biology and people doing molecular clock reproductions of modern animals,” says Anderson. “They use fossils to calibrate the molecular clock. By removing Lethiscus from the immediate ancestry of modern tetrapods, it changes the calibration date used in those analyses.”

New Zealand introduced trout eat introduced mice


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Huge Trout Eats Mice – Wild New Zealand – BBC Earth

19 June 2017

With little competition and few predators, the Brown Trout in New Zealand has been known to grow to epic proportions. These prize fish sometimes reaching a metre in length and weighing up to 5 kilos have developed monstrous appetites and a bloodthirsty penchant for mice.

How fish eat coral


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Slimy ‘Kiss’ Lets Reef Fish Feed on Stinging Corals

5 June 2017

(Inside Science) — With their sharp, stony skeletons and stinger-laden flesh, corals are well protected against most potential predators. Tubelip wrasses are one of the few fish to overcome these defenses, and now, scientists have discovered how they do it. The secret is in the lips.

Unlike their thin-lipped relatives, tubelip wrasses have big, fleshy lips that protrude in front of their teeth. These lips appear smooth to the naked eye. But in a study published today in Current Biology, scientists examined them for the first time under an electron microscope, and saw they are actually covered in parallel flaps like the gills of a mushroom. The lips produce huge amounts of mucus, and can close to form a sort of straw.

High-speed videos revealed what the strange lips are for.

“[T]ubelip wrasses feed using short sharp ‘kisses’ to suck mucus and occasionally tissue off the coral surface,” the authors write. The kisses make a smacking sound the researchers describe as “tuk.”

According to the researchers, the lip mucus probably serves a double purpose, forming a seal on the coral’s surface while shielding the fish from stinging barbs known as nematocysts. Thus protected, the fish are free to suck out coral’s nutritious goo.

From ScienceDaily:

With specialized lips, these fish dine on razor-sharp, stinging corals

June 5, 2017

Summary: More than 6,000 fish species that live on coral reefs, but only 128 are known to feed on corals. Now, researchers have discovered how at least one species of coral-feeding fish does it. They ‘kiss’ the flesh and mucus off the coral skeleton using protective, self-lubricating lips.

Of all the things an animal could eat, corals are arguably one of the toughest, thanks to their thin, mucus-covered flesh packed with venomous stinging cells spread over a razor-sharp skeleton. Perhaps that explains why of the more than 6,000 fish species that live on the reef, only 128 are known to feed on corals. Now, researchers reporting in Current Biology on June 5 have discovered how at least one species of coral-feeding fish does it. They “kiss” the flesh and mucus off the coral skeleton using protective, self-lubricating lips.

“The lips are like the gills of a mushroom but covered in slime,” says David Bellwood of James Cook University in Australia. “It is like having a running nose but having running lips instead.”

The researchers suggest that the mucus may facilitate suction while offering protection from corals’ stinging nematocysts.

Bellwood and the study’s first author, Víctor Huertas, recognized that the problem when eating corals would come as lips touched the surface. They wanted to find out exactly what was happening in that process. They used a scanning electron microscope to get extremely high-quality images that could capture the specialized lips of tubelip wrasses (Labropsis australis) in unprecedented detail.

Those images revealed remarkable differences between the lips of the tubelip wrasse and another wrasse species that doesn’t feed on corals. Wrasses that don’t eat corals have lips that are thin and smooth, with teeth that protrude slightly. By comparison, tubelip wrasses have lips that are fleshy and stick out, forming a tube when the mouth is closed that covers all the teeth.

The most prominent characteristic of the tubelip wrasse’s lips, they found, are numerous thin membranes arranged outward from the center like the gills of a mushroom. The mouth surface of tubelip wrasses also includes many folds loaded with highly productive mucus-secreting glands. In other words, their lips drip with slime.

High-speed video images of feeding tubelip wrasses showed that they briefly place their lips in contact with the coral prior to delivering a powerful suck. Rather than grabbing onto coral, they appear to seal the mouth over a small area, presumably to increase suction-feeding efficiency, the researchers report. The new evidence suggests the tubelip wrasses and their mucus-laden lips survive by feeding primarily on coral mucus. The findings open up a whole new way of looking at the nature of feeding in fishes, the researchers say.

“One always assumes that fishes feed using their teeth, but, like us, the lips can be an essential tool,” Bellwood says. “Imagine feeding without lips or cheeks; the same applies to fishes.”

On their quest to learn how the wrasses cope with the challenge of reef feeding, the researchers say the next step is to discover the “magic of the mucus.”

See also here.

Night diving video


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2 June 2017

In this exciting episode of Jonathan Bird’s Blue World, Jonathan explains why night diving is so much fun and so popular with scuba divers. Far from being scary, it’s actually an amazing experience to see the kind of nocturnal animals that come out of hiding at night.

Wolffish, wolf eel video


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21 April 2017

They have big, sharp teeth, long eel-like bodies, and they look like they could bite your fingers right off—but Jonathan can pet them. They’re Wolffish, and Jonathan visits both Atlantic and Pacific species. You won’t believe the amazing encounters he has with these friendly but mean-looking fish.

Night heron uses bread for fishing


This video says about itself:

Smart Heron Used Bread To Fish – Super Smart Animals – BBC Earth

26 May 2017

Hungry Hank is one cool feathery customer. Outmuscled by the resort [Black] Swans, this plucky Night Heron has got his eyes on a much bigger prize, but it might involve the waiting game.

This blog has blogged about other heron species, eg, green herons, doing similar things.