Science is the poetry of Nature.







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Posts tagged "Fish"

kidsneedscience:

Guest Post by Luke Hauser

Leedsichthys belonged to a group of fish know as Pachycormids, a very large ancient fish reaching sizes up to 53 ft, and like the modern whale shark it was a filter feeder with large gill rakers to extract plankton. It lived during the Jurassic in what is now Europe and South America and scientists know from fossils that it was preyed upon by large Pliosaurs.

The name Leedsichthys (Leeds-ich-thys) which means Leeds fish is not named because it was found near the city of Leeds, England. It actually refers to the discoverer a Mr Alfred Nicholson Leeds who was a farmer in the late 19th and early 20th century. He was an avid fossil collector working mostly on fossil of the Oxford clay. He was so prolific that twice he filled parts of his house with fossils later selling his collection to London’s Natural History Museum. The Ancient Greek word ἰχθύς (ichthys) means fish.

The problematicus (proble-mati-cus) part of the name was given to this fish for a very simple reason. This fish was so large that when one died and sank to the bottom a number of things happened: first such a large amount of meat would attract many predators which would break up the body. The other issue would be that such a large animal could never be covered entirely in sediment (this is vital if an animal is to become a fossil). This all results in the fossil remains of the fish being fragmentary and when trying to work out what the animal looked like or what sort of fish it is can be a…..problem.

So there we are Leedsichthys problematicus an amazingly large fish with a fantastically long name-yet the reasons for its name are really quite straight forward.

Special Guest post by Luke Hauser. Luke is a twenty something palaeontologist hailing from the U.K., he works at the University of Portsmouth as PhD student. Interested in all manner of fossil life but focuses on fish and dinosaurs. He also has his own blog called ancient anglers where he discusses fossil fish.
Links

E-mail: luke.hauser@port.ac.uk
Web page: http://www.port.ac.uk/departments/academic/sees/staff/title,143809,en.html
Blog: http://ancientanglers.wordpress.com/
Twitter: https://twitter.com/Palaeofreak

Image of leedsichthys courtesy seamonster wiki, used with permission under a Creative Commons 3.0 license.

s-c-i-guy:

Teleostei

Teleost Fishes (Teleostei) is one of three infraclasses in class Actinopterygii, the ray-finned fishes. This diverse group, which arose in theTriassic period, includes 26,840 extant species in about 40 orders and 448 families; most living fishes are members of this group. The other two infraclasses, Holostei and Chondrostei, may be paraphyletic.

Some teleost fish have also developed jet propulsion, passing water through the gills to supplement fin-driven motion.

The oldest teleost fossils date back to early Triassic, possibly evolving from fish related to the bowfin in the clade Holostei. During the Mesozoic and Cenozoic they diversified and as a result, 96% of all known fish species are teleosts. Teleosts are here divided into twelve superorders, but this system is unlikely to be entirely correct and is in the process of being studied.

source

thelovelyseas:

Purple magnificent Sea Anemone Heteractis magnifica home to clown fish by James Forte

(via kenobi-wan-obi)

ichthyologist:

Sexual Parasitism in Deep Sea Anglerfish

In response to the perilous and opportunistic conditions of the deep sea, some deep sea anglerfish have evolved a very specialised method of reproduction - sexual parasitism.

Due to the fact that individuals of a species are locally rare, encounters between a male a female are very uncommon. As such, when they eventually meet, the fish employ a unique mating method that will ensure that they never separate again.

The fish display extreme sexual dimorphism, with males being many times smaller than females. The method by which a male finds a female differs across different species, but can involve sight or pheromone cues.

When a male anglerfish encounters a female, he latches onto her body with his mouth. He then releases enzymes that digests the skin of his mouth and her body, which fuses the pair down to the blood vessel level.

The male becomes a parasite, surviving solely on the nourishment provided by the female via their linked circulatory systems. In return, he provides sperm for the female. Eventually, his body atrophies until only the gonads are left.

Sexual parasitism benefits both the males and females. For the females, it ensures that there is an immediate source of sperm as soon as she is ready to spawn. The males, being much smaller and less adapted for survive, are much more likely to sire offspring attached to a female than if they were to live a solitary life.

Image: © Pietsch, TW

paleoillustration:

"The Whorl Tooth Sharks of Idaho" opened on June 22 and runs through the end of the year. 

'The exhibit features a wide array of fossils of the 270-million-year-old shark called Helicoprion, along with original artworks by Alaskan artist Ray Troll, life-sized sculptures of the shark bursting through the museum walls by sculptor Gary Staab, original music, a short documentary and much more. There are children’s activities too, so it promises to be fun for the whole family.  The exhibit is a unique combination of science, art, music and humor.’ 

More information and pictures at Ray Troll’s webpage and Idaho Museum of Natural History

mucholderthen:

Evolutionary history of air-breathing vertebrates. Relative abundance and diversity of each group is roughly proportional to the band width.

The groups indicated in horizontal type & bars on the right side relate to the phylogeny of mudskippers, amphibious fish of the Indian and Pacific oceans, and the Atlantic coast of Africa.

[Nelson (ed), 1994 – Fishes of the World – 3rd edition. John Wiley & Sons] [Redrawn from Graham (1997 (ed) – Air–breathing Fishes. Evolution, Diversity and Adaptation

(source)

(via kenobi-wan-obi)

Fossil Fish Is Oldest Creature With a Face

A newly discovered fish fossil is the earliest known creature with what might be recognized as a face.

Entelognathus primordialis was an ancient fish that lived about 419 million years ago in the Late Silurian seas of China. The finding, detailed today (Sept. 25) in the journal Nature, provides a link between two groups of fishes previously thought to be unrelated, challenging long-held notions of how vertebrate faces evolved.

Nearly all vertebrates belong to the group of jawed vertebrates known as gnathostomes. Sometime in the past, the gnathostome family tree branched into two groups: cartilaginous fish (Chondrichthyes) such as sharks and rays, and bony fish and four-limbed animals, including humans (Osteichthyes).

Why Fish Don’t Need to Be ‘Schooled’ in Swimming

How do fish swim in schools, effortlessly coordinating their every move? The answer appears to be ingrained in their genes.

The genetic basis underlying the complex, social behavior of schooling is revealed in two studies published Sept. 12 in the journal Current Biology. The studies suggest that schooling is not a learned behavior, and instead show it relies on several regions of the fish genome.

The findings may point to the genetic underpinning of why humans also are social, and tend to gather in groups, some experts said, although others debated this.

"Ice Fish" Bleeds Clear Blood:

The deep oceans have yielded many mysteries that have puzzled people for centuries, from the giant squid to huge jellyfish that look like UFOs. To that list add a fish with totally transparent blood.

The Ocellated Ice Fish lives in the freezing waters of the Antarctic Ocean, where it manages to keep its body doing all the things that other fish do, but with blood that is absolutely clear, researchers said.

The reason, say experts at Tokyo Sea Life Park, is that the Ocellated Ice Fish has no hemoglobin, making it unique among vertebrates the world over.

Hemoglobin is the protein found in every other animal with bones. It is what makes blood red and is the agent that carries oxygen around the body.

The fish, which has no scales, is a prize catch for the aquarium, the only place on the planet that has the curious specimen in captivity.

Satoshi Tada, an education specialist at the center, said very little is known about the fish, which was brought back to Japan by krill fishermen.

"Luckily, we have a male and a female, and they spawned in January," he said, adding that having more examples to study might help scientists unlock some of the fish’s secrets.

Researchers believe the fish can live without hemoglobin because it has a large heart and uses blood plasma to circulate oxygen throughout its body.

Its skin is also thought to be able to absorb oxygen from the rich waters of the Antarctic, where it is found at depths of up to a kilometer(3,300 feet).

But the evolutionary mechanism that left this creature with clear blood running through its veins is a mystery.

"Why is it the fish lost hemoglobin? More studies are needed on the question," Tada said.

Original Article

ucresearch:

Is that really red snapper on your plate?

A recent survey done by Oceana says that fish found at the market are not always correctly labeled.  So, scientists are working on a genetic sequence technique called fish barcoding that can positively identify fish species.

Marine biologist Ron Burton of the UCSD’s Scripps Institution of Oceanography says it’s important for the public to make sure they’re getting what they think they’re getting:

“In a market like red snapper, we can be seeing red snapper at many fish markets and that would lead somebody to believe that the fish is very common, when in fact what’s being sold is a diversity of species - some of which are common, some of which aren’t. And so it can lead to a false impression about the abundance of species to the public.”

Read more on Science Today

biologyoffishes:

Presence of certain fins and the morphologies of each are determined by the lifestyle of each fish. I use the largemouth bass to present fin structure because it has most of fin structures of fishes.

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(Picture of a largemouth bass (Micropterus salmoides) from here)

Caudal fin - used for forward propulsion of the fish.

Soft dorsal fin - may be used for forward propulsion and as a rutter to change direction.

Spiny dorsal fin - used as a keel to maintain fish balance. Can be lowered to increase streamlining of fish (increase swimming speed)

Pectoral fin - used for braking and turning while swimming and may be used for forward propulsion. 

Pelvic fin - prevents fish from floating upward when fish brakes (with pectoral fins)

Anal fin - acts as a rudder for turning, may be used for forward propulsion.

image

(Tail of bigeye tuna (Thunnus obesus). Picture from here)

Finlets - increase speed of swimming of fish by reducing drag.

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(Picture of rainbow trout (Oncorhynchus mykiss) from here)

Adipose fin - function unknown. Current though is that it does nothing, but new studies suggest that it may have sensory functions.

madamjellyfish666:

via The Scientist:

Image of the Day: Limber Seahorse
CT scans of a seahorse show its bony plates, which slide past each other as the animal bends, allowing it to be hard and yet flexible.
Jacobs School of Engineering

mad-as-a-marine-biologist:

Landmarks on the Dorsal fin of a shark. 

These features can be used to identify different shark species. The inability to ID shark species via their fins has been an argument used to exemplify that the trade in shark fins can’t be regulated by species. 

Dr. Demian Chapman and the Pew Environment Trust show us that that simply is not an excuse anymore, and have made a guide to prove just that. An just in time for CITES, where three types of shark are up for listing. 

1. Porbeagle

2. Oceanic White Tip

3. Hammerhead Sharks ( I say this because if one of the three species are listed, the other two will be by proxy because their fins look too similar to distinguish)

Fins from 14 large-bodied shark species make up roughly 40% of the global fin trade.  The oceanic whitetip and three hammerheads in this guide are included in this group and were estimated to constituted 7-9% of traded fins in 2000.  Shark fin traders in Asia visually sort fins from these species into specific trade categories using the shape and color of the fin.

[…]

This guide is intended to help enforcement and customs personnel in the provisional identification of the first dorsal fins of these five shark species.  In law enforcement situations, this could provide probable cause to hold questionable fins, so that expert opinion could be sought or genetic testing could be conducted to confirm the field identification.

Check out the online ID guide here.

And Dr. Chapman’s recent talk at Yale Shark Talks about wildlife forensics and the shark fin industry.


These sharks are proposed for listing in CITES Appendix II. This means trade would still be allowed, but under tighter regulation that should ensure the products are coming from a sustainable source. Therefore it is vital to be able to identify their fins. 

Science might not always mean Conservation, but Conservation is built on good science. 

drbucketlist:

Nemo flashes a smile. Snapped in the Philippines, this clownfish living amid the stinging tentacles of a huge sea anemone was photographed by Steve De Neef.

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