Some of the strange places fish live… it’s all about location, location, location!

In bottoms: Pearlfish

Inside another animals’ bottom might seem like very worst place to be, but there are big advantages to the pearlfish’s chosen home.

“The key thing for fish living on coral reefs is to find somewhere to hide and not get eaten,” says Prof Martin Attrill, head of the marine institute at Plymouth University.

This “fascinating way of living”, he says, is very specific to this group of fish; they can also live inside clams, starfish, or anything else “with a hole”.

“Sea cucumbers are like bags – they make a good hiding place for pearlfish.

“They are essentially living in a burrow and they come out at night to feed from the colonic cavity. It is moist and safe in there, and quite often they live in there in pairs.”

And there is no appreciable harm to the sea cucumber; pearlfish are commensal, which means they have a non-parasitic relationship with their hosts.

In trees: Mangrove killifish

A fish out of water: the mangrove killifish can survive for 66 days in moist conditions

This “amazing little fish” can survive up to 66 days out of water.

Kryptolebias marmoratus lives in the mangrove forests of the Western Atlantic and has the capacity to survive a long time out of water in trees and logs, “as long as it keeps moist”, says Prof Attrill.

It is able to do this because of its specially adapted gills; it excretes nitrogen waste through its skin while out of the water and has been recorded as being able to survive up to 66 consecutive days through cutaneous respiration.

One fish can also repopulate an area, even if it ends up stranded on its own.

“They are hermaphrodites – they have [both] male and female organs… which is really unusual in vertebrates,” says Prof Attrill.

“It is a great way to maintain a population and allows them to reproduce without a mate, enabling them to live alone in logs.”

In hot water: Desert pupfish

Some fish like it hot – the desert pupfish can survive water heated to 40C

In the summer, temperatures soar in California’s Death Valley.

To survive this extreme environment – in salty pools that are heated up to 40C – the desert pupfish, or Cyprinodon macularius, has adapted over time.

“People think they survived the last ice age, and evolved to survive in a process of quite extreme natural selection,” says Prof Attrill.

“In fact, only the best survive each summer and reproduce the following summer.”

Despite its apparent resilience, the pupfish is endangered. It is threatened by habitat loss and by competition from other fish species.

Males live inside females: Anglerfish

The female anglerfish becomes home to the male after they fuse together

In the deepest, darkest part of the ocean, it is pretty hard find a mate.

So the anglerfish has come up with a straightforward solution. When a male finds a female by following her scent, he latches on with his teeth and doesn’t let go, fusing to the female.

“This fish is an extreme adaptation in terms of a sexually developed female. A parasitic male is carried by the female and eventually merged in to her body as a bump; all he is used for is his sperm,” explains Prof Attrill.

“In the deep sea, it’s dark, and hard to find another anglerfish, so the best way is to carry another fish around.

“This has developed so that the female carries around just a couple of testes to pass on the genes.”

In the depths: Hadal snail fish

Hadal snail fish are the deepest living fish recorded

True creatures of the deep, the Hadal snail fish, Pseudoliparis amblystomopsi, was described as “surprisingly cute” when it was first discovered.

The “deepest ever” fish found alive, a 17-strong shoal were filmed at depths of 7.7km (4.8 miles) in the Japan Trench in the Pacific, and have to develop to cope with the pressure at that depth.

“The Hadal snail fish is flying the flag for an undiscovered area; they are swimming around in a place man has never set foot,” says Prof Attrill.

The fish use vibration receptors on their snouts to navigate the ocean depths and to locate food.

The researchers who found them thought they would be motionless.

“We certainly thought, deep down, fish would be relatively inactive, saving energy as much as possible, and so on,” Prof Monty Priede from the University of Aberdeen’s Oceanlab told BBC News.

“But when you see the video,the fish are rushing around, feeding accurately, snapping at prey coming past.”

In mouths: Jawfish

Many parents aim to protect their young. But “mouthbrooders” take this to a different level – keeping their young in, as the term suggests, their mouths.

Male jawfish protect their young by housing them in their mouths

Jawfish, are some of the very few saltwater fish to have embraced this mostly freshwater fish practice.

The female lays the eggs and the male takes them in his mouth.

“The bigger the mouth the better,” says Prof Attrill. A male can have up to 400 eggs in his mouth at one time.

“The male can’t feed (while he hosts the young), it’s a case of males, get on with it,” Prof Attrill explains.

“It’s a great place to hide, and as the young get older they spend more time out of the mouth.”

In deep sea vents: Hydrothermal vent eelpout fish

Hydrothermal vents can be up to 380C, and are home to one of the most extreme ecosystems on Earth.

Fish that live on hydrothermal vents have developed so they can avoid hot currents

The eelpout fish (Thermarces cerberus) is the one group that lives on the vents, and feeds on crustaceans. So how does it stay out of hot water?

“It is a long, thin eel-like fish, almost a knife shape, which is great for getting in and around the mussel clumps it feeds on,” says Prof Attrill.

“It has the ideal body form to deal with that.

“What is very interesting is how they travel between vents – using whale bones etc on the sea floor to ‘jump’ between vents.”

In shells: Cichlids

Cichlids like to find shells to live in, which they guard fiercely

Different to true shellfish, these tiny fish live in shells in the Great African Lakes.

More than a thousand new species have evolved over the last 12,400 to 100,000 years, and live in shells as they “need to find really good homes to protect themselves”.

Prof Attrill says: “If they don’t have shells, they feel very nervous as they don’t have anywhere to live.”

In the dark: Blobfish

Considered the ugliest fish alive, the blobfish lives in the deep waters off Australia and New Zealand.

In the deep sea, swimming is hard work if you are a heavy protein-filled fish, so their tissue has become water-based.

“They are almost like jellyfish, and feel quite gloopy… and are charismatically ugly,” says Prof Attrill.

But interestingly, blobfish show “nesting” behaviour.

“Pairs lay eggs on the sea floor and look after them together – it’s really the first time we’ve seen parental care in deep sea fish,” says Prof Attrill.

In anemones: Anemonefish

For most small fish, living within the grasp of the tentacles of predatory sea anemones would mean dicing with death on a daily basis.

But the anemonefish, also known as clownfish, or Amphiprion percula, is unaffected by anemones stinging tentacles.

A substance in the mucous that covers their bodies prevents anemones’ stinging cells from firing and killing the fish.

Clownfish parents clean an area of their host before laying eggs so their young are not harmed either.

The male then protects the young until they are ready to leave their parents.

Underground: Brazilian blind characid

Brazilian blind characids have no pigmentation as

Like most creatures that live underground, this incredibly rare fish is blind, and was only recently rediscovered in wells fed by underground springs in Brazil.

Stygichthys typhlops also lacks pigmentation, a common trait in organisms that live underground in the dark.

Biologists cannot be sure, but they suspect the fish may be a living relic that has survived deep under the ground while its relatives above became extinct.

Unknown home: Baby coelacanths and eels

Baby coelacanths have rarely been sighted

Initially thought to be extinct only one coelacanth has been seen since the species was discovered in 1938.

“Coelacanthsare probably hiding in rocky crevices and caves, but it really highlights how little we know,” says Prof Attrill.

“We don’t know where they go, or what they do. It’s really more of a case that we’ve only recently rediscovered them.”

But there is another species we know very little about – eels.

“The whole migratory cycle of eels is a mystery.

“Once they hit the open ocean we don’t know what happens,” says Prof Attrill.

It is thought baby eels may hatch in the Sargasso Sea,

“We only recently found out what basking sharks do – if something the size of a basking shark can elude us then it may be a while before we find out what eels do.”

It is thought eels hatch in the Sargasso Sea, in the middle of the North Atlantic, where they feed on young plankton, and then migrate to Europe and North America, before returning later in life to spawn.

But very few have ever been caught en route.

Original article written by Anna-Louise Taylor and published on http://www.bbc.co.uk/nature/16251726

UK scientists have found prodigious numbers of a new crab species on the Southern Ocean floor that they have dubbed “The Hoff” because of its hairy chest.

The animal was discovered living around volcanic vents off South Georgia.

Great piles of the crabs were seen to come together.

The creature has still to be formally classified, hence the humorous nickname that honours the often bare-chested US actor David Hasselhoff.

It is, however, a type of yeti crab, said Professor Alex Rogers who led the research cruise that found the animal, and it will be given a formal scientific name in due course.

Yeti crabs were first identified in the southern Pacific and are recognised for their hairs, or setae, along their claws and limbs that they use to cultivate the bacteria which they then eat.

Isis has the capability to dive to more than 6km below the ocean surface

But the new species found around the vents that populate the East Scotia Ridge are slightly different in that they exhibit long setae on their ventral surface – on their undersides.

“Their nickname on the cruise ship was the ‘Hasselhoff crab’, which gives you some idea of what they look like,” explained Dr Rogers from Oxford University’s Department of Zoology.

“The crab occurs in staggering densities. It is just incredible to see these animals literally lying in heaps around the diffuse flow of these vents.

“In places, they reached as many as 600 individuals per square metre.”

The crab occurs in staggering densities - up to 600 individuals per square metre

The Hoff crab is just one of a number of species new to science to come out of the cruise, which also included researchers from the University of Southampton, the National Oceanography Centre and the British Antarctic Survey.

The team reports novel types of starfish, barnacles, sea anemones, and even an octopus – all living some 2,500m down.

The cruise employed the UK deep-diving robotic submersible, Isis, to investigate the slowly spreading ridge near Antarctica.

It is dotted with hydrothermal vents – cracks in the volcanic rock where mineral-rich, hot waters gush from below the seabed to sustain an extraordinary array of organisms.

What surprised the team was not so much what they found, but rather what was absent.

An unidentified pale octopus was seen nearly 2,400m down

Vent systems in other parts of the world are dominated by animals such as tubeworms, mussels, other types of crab, and shrimps. These were all missing from the East Scotia Ridge.

This is fascinating because the cruise was originally initiated to investigate the hypothesis that the Southern Ocean acted as a gateway between the other major oceans of the world, allowing for the dispersal of vent organisms over geological timescales.

It was thought the Southern Ocean’s strong currents might help drive species from one ocean basin to another, and finding a very diverse group of animal types also at East Scotia Ridge would have been a powerful statement in support of this dispersal hypothesis.

The team did see some similarities – such as barnacles that were very similar to Pacific crustaceans, and limpets that looked the same as some Atlantic forms – but nothing like what had been expected.

“We think the very harsh conditions of Antarctic waters, particularly in terms of their extreme seasonality, probably act as a barrier to some of the vent fauna,” explained Professor Rogers.

“What we’ve found is a much more complex situation than we were anticipating, and this has pretty much changed our ideas about how vent organisms are distributed at a global scale.”

Original article written by Jonathan Amos Science correspondent, BBC News and published on http://www.bbc.co.uk/news/science-environment-16394430