The gar family, famous for containing the largest fresh water fishes in Mexico, is currently at risk of becoming extinct – something which Mexican researchers are working hard to prevent.

“This fish is native to our country and the United States”, Doctor Eduardo Mendoza Alfaro explains. “Currently, its populations are threatened due to excessive hunting, — for there are no rules that regulate its fishing — urban expansion, pollution, and particularly the dams´ construction, which caused the destruction of their breeding grounds. These factors led this species to reduce to only forty adult specimens in the country — in inventory and considered national patrimony.”

Doctor Eduardo Mendoza Alfaro*, a member of the ‘Eco-physiology Group,’ from the Universidad Autonoma de Nuevo Leon’s (UANL) School of Biological Sciences Ecological Department, is currently researching gar reproduction and diet in order to find ways of efficiently raising gars in captivity. The team also works with several other types of endangered fish, but the gar – which can reach a length of three meter and is highly esteemed by sport fishers – is arguably the most iconic.

Lepisosteus platostomus – Shortnosed gar, Copyright www.jjphoto.dk

One of the hurdles that must be overcome to ease gar raising in captivity is how to distinguish males from females. In a reproductive facility you want to keep an ideal sex ration – with gars this is four males for each female – but this is difficult to accomplish without reliable sexing methods.

“We could not identify females and males, because, morphologically, they are

Identical”, says Dr Alfaro. “Even though most of the fish can be cannulated in order to know their gender and maturation status, for gar is not the same process, that is what represents

the first obstacle for scientifics when they were carrying out the reproduction

studies and establishing fish’s gender. Most of the fish can be cannulated by introducing them a catheter in the oviduct in order to take the oocytes (ovules). However, this process cannot

be carried out with the gar. They are so primitive fish, which date since 189 million years ago and their urinal tract which ends with the oviduct in a kind of sewer that cannot allow the

cannulation.”

To overcome the problem, Dr Alfaro and his team devised a new technique based on a molecule known as vitelogenine. Vitelogenine is present only in females from puberty and onwards, and can be used as a biochemical marker.

First, the team purified the molecule. Then, they created antibodies against the molecule for recognizing and quantifying it.

“Currently, we got an extremely sensitive method which allows us to dose this molecule with only a small sample of fish’s skin mucus, says Dr Alfaro. “So, we not only identified if it is a female or a male, but we can follow up females’ sexual maturation.”

Gar facts

· The gar family evolved during the cretaceous.

· A gar can weigh up to 220 lbs.

· The gar is a predatory fish with an elongated jaw. It is sometimes referred to as alligator fish due to its resemblance to the predatory reptile. It has numerous sharp teeth and a body protected by hard scales.

· Gars spawn in swamps during the wet season and destruction of wetlands poses a problem for them.

· In the wild, several males follow the female wanting to fertilize her eggs as she deposits them.

· Mexico is the world’s leading gar specimen producer.

*Roberto Eduardo Mendoza Alfaro is a professor at the UANL´s School of Biological Sciences Ecology Department in Leon, Mexico.

New research has revealed that the tapetail, bignose and whalefish are in fact all the same fish.

For decades, three different names have been used for three very different looking underwater creatures: the Tapetail, the Bignose and the Whalefish. A team of seven scientists*, including Smithsonian curator Dr Dave Johnson, has now discovered that these three fishes are in fact part of the same family.

After studying the body structures of the tapetails (Mirapinnidae), bignose fish (Megalomycteridae) and whalefish (Cetomimidae) and taking advantage of modern DNA-analysis, the team realized that the three are actually the larvae, male and female, respectively, of a single fish family – Cetomimidae (also known as Flabby whalefish).

“This is an incredibly significant and exciting finding,” says Johnson. “For decades scientists have wondered why all tapetails were sexually immature, all bignose fishes were males and all whalefishes were females and had no known larval stages. The answer to part of that question was right under our noses all along—the specimens of tapetails and bignose fishes that were used to describe their original families included transitional forms—we just needed to study them more carefully.”

If you wish to find out more, the article “Deep-sea mystery solved: astonishing larval transformations and extreme sexual dimorphism unite three fish families” has been published in the journal Biology Letters by the Royal Society, London.

http://publishing.royalsociety.org/

http://journals.royalsociety.org/content/g06648352k5m1562/

* The seven scientists behind the discovery are:

G.David Johnson, Division of Fishes, National Museum of Natural History, Smithsonian Institution, Washington, DC 20560, USA

John R. Paxton, Ichthyology, Australian Museum, Sydney, New South Wales 2010, Australia

Tracey T. Sutton, Virginia Institute of Marine Science, Gloucester Point, VA 23062, USA

Takashi P. Satoh, Marine Bioscience, Ocean Research Institute, University of Tokyo, Nakano-ku, Tokyo 164-8639, Japan

Tetsuya Sado, Zoology, Natural History Museum and Institute, Chuo-ku, Chiba 266-8682, Japan

Mutsumi Nishida, Marine Bioscience, Ocean Research Institute, University of Tokyo, Nakano-ku, Tokyo 164-8639, Japan

Masaki Miya, Zoology, Natural History Museum and Institute, Chuo-ku, Chiba 266-8682, Japan

A newly investigated 290 million year old fossil may be an evolutionary missing link in the amphibian family tree. The fossil was collected in Texas by a palaeontologist with the Smithsonian Institution in the mid-1990s. The fossil eventually ended up at the National Museum of Natural History in Washington, D.C., where it was re-discovered and investigated in 2004.

The new analysis of the fossil has been carried out by Jason Anderson, a comparative biologist at the University of Calgary, Canada. According to Anderson, the fossil has an overall amphibian look but with interesting archaic features. The animal resembles a salamander, but the tail is stubby and the ears are similar to the ears of a frog.

“So it’s kind of a frogamander, if you will,” Anderson sais to National Geographic News.

The fossilized species has been given the name Gerobatrachus hottoni. Until recently, scientists believed that frogs, salamanders and the wormlike caecilians all hailed from a common ancestor. Gerobatrachus hottoni suggests that frogs and salamanders are much more closely related to each other than to the caecilians.

Read more in Anne Casselman’s article for National Geographic News.

http://news.nationalgeographic.com/news/2008/05/080521-frog-fossil.html

The study of the fossil appears in this week’s (May 21^st 2008) issue of the journal Nature.