'Virgin-born' sawfish are a first in the wild

By Jonathan WebbScience reporter, BBC News

1 June 2015 

Seven sawfish in Florida have become the first virgin-born animals ever found in the wild from a sexually reproducing species.

The discovery suggests that such births may be a natural response to dwindling numbers, rather than a freak occurrence largely seen in captivity.

It was made by ecologists studying genetic diversity in a critically endangered species of ray.

They say that births of this kind may be more common than previously thought.

The findings appear in the journal Current Biology.

Surprisingly common?

There are many species, particularly invertebrates, that naturally reproduce alone; some types of whiptail lizard, meanwhile, are bizarrely all-female.

But for an animal that normally reproduces by mating, a virgin birth is an oddity.

And yet a number of captive animals have produced virgin births. This roster of surprise arrivals includes sharks, snakes, Komodo dragons and turkeys - all species that normally use sexual reproduction.

And in 2012 a US research group reported two pregnant pit vipers, caught in the wild, each gestating baby snakes (inside eggs) that appeared to be fatherless.

But the smalltooth sawfish, a strange-looking beast that grows up to four metres long, is the first sexually reproducing species whose virgin-born babies have been found roaming free and healthy in their native habitat.

Continued ...

International plan launched to save the sawfish

Posted by: Leya Musa / 5 days ago

Scientists from the International Union for Conservation of Nature (IUCN) have launched a global strategy to save the most threatened group of fish in the world – the sawfish. While sharks and rays are regularly featured in popular conservation campaign the sawfish are often the forgotten relations of the big fish.

The new plan is being released by the Shark Specialist Group of the IUCN and is being featured at the Sharks International conference in Durban. Two west African range states are also calling for sawfish to be covered by the Convention on Migratory Species at the next meeting of the convention in November.

“The sawfishes, revered for millennia by coastal cultures around the world, now face greater extinction risk than any other family of marine fish,” said strategy co-author, Dr. Nick Dulvy, who serves as IUCN SSG Co-Chair and Canada Research Chair at Simon Fraser University in British Columbia. “With this comprehensive strategy, we aim to reignite sawfish reverence and spark conservation action in time to bring these iconic species back from the brink.”

Dr. Colin Simpfendorfer, IUCN SSG Co-Chair, Professor of Environmental Science at James Cook University in Queensland explained, “Although these species are perilously close to extinction in many regions, there are some fairly simple ways to help populations recover. For example, we know that sawfish can actually survive capture quite well if handled properly, and hence, basic education of commercial, subsistence, and recreational fishers is central to our conservation strategy.”

Continued

Securing a safe future for sawfishes

Shark and ray experts from around the world gathered last week at the Zoological Society of London to address the plight of the most threatened marine fishes in the world – the sawfishes. The group, convened by the IUCN Species Survival Commission (SSC) Shark Specialist Group, is breaking new ground with the development of a focused global action plan to bring these iconic species back from the brink of extinction.

Once found in tropical and subtropical waters throughout the world, all species of sawfish are now listed as Critically Endangered on the IUCN Red List of Threatened Species™. They have been revered by coastal societies throughout the Atlantic and Indo-Pacific Oceans for centuries. Today, ancient art, folklore, and mythology are almost all that is left to remind us of how widespread and abundant they were. Sawfishes are still featured on Thai postage stamps and West African currency, but the chance of seeing a sawfish in either region, or anywhere else other than the USA or Australia, is exceedingly low.

As their name suggests, sawfishes can be easily identified by their long, toothed rostra or “saws”. Long valued for medicinal and cultural purposes, and as curios, this most distinctive feature has been central to their downfall. The rostra are easily entangled in all kinds of fishing nets that are used extensively throughout the shallow coastal waters and river estuaries where sawfishes live.

Read on:  http://www.iucnredlist.org/news/securing-a-safe-future-for-sawfishes

Sawfish snout senses, swipes and stabs

By Richard BlackEnvironment correspondent, BBC News

The spectacular snouts of sawfish are revealed as complete hunting weapons, sensing prey and killing them.

The saws, which can grow more than a metre long in some species, have previously been identified as able to sense prey by their electric fields.

Now, researchers have filmed the fish impaling prey on the teeth of the saws.

They suggest in Current Biology that sawfish are more active hunters than previously thought, which could help in their much-needed conservation.

All seven species are listed as Critically Endangered on the internationally-recognised Red List.

The researchers, mainly based in Australia, suggest sawfish may be unique among their peers in possessing a snout, or rostrum, that works both as a sensory organ and a hunting weapon.

"I like to call it an antenna and a weapon, because that's what it is - it helps them to find the prey, but then also to kill it," said Barbara Wueringer from the University of Queensland, who led the research team.

The research was done using captive sawfish.

Australian regulations on the ethics of animal research meant the team was not allowed to film the sawfish hunting live prey.

Instead, pieces of mullet and tuna flesh were dangled in their tanks, and underwater video cameras deployed to record them.

Weak electric fields were deployed in the water and on the bottom, to mimic the fields produced by live fish, which sawfish sense using the dense arrays of electroreceptors along the rostrum.

Continued:  http://www.bbc.co.uk/news/science-environment-17258808