A transparent goldfish that reveals its inner organs has been developed by a joint research team of Mie University and Nagoya University in Japan.

The aim of the project was to create a transparent fish that makes it possible for researchers to study blood constituents and organ behaviour without having to dissect the animal. Unlike ordinary goldfish variants, this type has therefore been made really big and can weigh up to 1 kg. Up until now, the transparent fish of choice for researchers have been the see-through zebrafish, but this tiny fish only weigh abut 3 grams and is therefore much more difficult to study than the 1 kg goldfish.

The translucent goldfish was developed in just three years by repeatedly letting selected pale goldfish specimens mate with each other.

“Pale-colored goldfish have little commercial value, but their negative value has turned into a positive,” said Mie University Associate Professor Yutaka Tamaru.

The creation of a transparent goldfish was announced Wednesday last week at the annual meeting of the Molecular Biology Society of Japan.

First of let me say that I am sorry for the lack of post these last weeks. Internet problems. Will hopefully be back to normal soon. Now to the story

Hearing impairment caused by damage to hail cells in the inner ear is by far the most common cause of hearing loss, but research carried out on Zebrafish might be able to show us how these hair cells can be re-grown.

Scientists involved in the experiments say there could be therapeutic trials to prevent hearing loss using drugs within a decade, while finding a cure for hearing loss using hair-cell regeneration is probably at least 20 years away.

Hair cells in the inner ear can be damaged by a long row of factors, such as noise, drugs, disease and ordinary aging. Once a hair cell dies, mammals – including us humans – aren’t able to replace that hair cell with a new one. Until the mid-1980’s, researchers thought that this was true for all warm-blooded vertebrates, but we now know that birds are able to grow new hair cells and that this hair-cell regeneration can result in improved hearing.

Among the so called cold-blooded animals, aquatic creatures like the zebrafish are equipped with clusters of hair cells running along the outside of the body to help the animal sense vibrations in the water. Just like the birds, zebrafish are capable of regenerating these hair cells if there’re damaged and this has attracted the attention of U.S. researchers looking for a cure for hearing loss.

Why some animals can regenerate hair cells while other can’t, and why some animals – even within the same species – are more vulnerable to hair-cell death, remains a mystery.

“I literally walked around for years wondering about this variability,” says Ed Rubel, a professor of hearing sciences who leads part of a University of Washington research effort in Seattle.

The Seattle research teams are currently using zebrafish to gain a better understanding of hair cell generation in hope of figuring out how to protect human hair cells from becoming damaged and how to stimulate the cells to regenerate. The project is focused on understanding the molecules and genetics involved with hair cell regeneration, and how to mimic this process in animals that don’t spontaneously regenerate hair cells.

In collaboration with Dr. David Raible, another University of Washington scientist, Professor Rubel has already identified chemicals that seem to protect hair cells from damage. Those chemicals are now being tested on mice and rats to see if they will have an affect on warm blooded mammals and not just on zebrafish. The goal is to develop a medicine that can be administered to patients receiving drugs known to kill hair cells, e.g. chemotherapeutic agents.

Dr. Rubel’s and Dr. Raible’s teams also are studying the genetics of zebrafish to identify markers that confer hair-cell protection. The teams are also working on a separate group of studies regarding the genes and other molecules that make the regeneration of hair cells possible in zebrafish, birds and mice. In 2008, the teams jointly indentified several genetic mutations and drug-like compounds that seemed to protect hair cells from death, publishing their findings in the journal PLoS Genetics.

In addition to this, Dr. Rubel’s lab is investigating the role of the so called support cells; cells that surround the hair cells and are capable of both turning into hair cells and generate new hair cells. “If we understand the template of genes that are expressed by the cells we would want to divide, then we could tap into that template to mimic regeneration efforts in mammals”, Dr. Rubel explains.

How do hair cells work?

Hair cells are called hair cells since they look like cells with little hairs growing out of them when you look at them through a microscope. Hair cells are found in our inner ears and damage to these cells is a major cause of irreversible hearing loss. The filament hairs, also known as cilia, bend as sound waves enter the ear, prompting the hair cell to send an electrical signal to the auditory nerve from which it continues to the brain.

A study of the molecular phylogenetic interrelationships of south Asian cyprinid genera Danio, Devario and Microrasbora has resulted in a reclassification of the group and the creation of a new genus: Microdevario.

The study, which has been published in a recent issue of the journal Zoologica Scripta, was carried out by Fang Fang and his colleges at the Swedish Museum of Natural History.

The researchers examined the molecular phylogeny of the Danioninae using fragments of the mitochondrial cytochrome b and nuclear rhodopsin genes from 68 species, including 43 danioinine species.

The analysis revealed the species Microrasbora rubescens and the genera Chela, Laubuca, Devario, and Inlecypris to form a natural group, the Devario clade, with the species Microrasbora gatesi, Microrasbora kubotai and Microrasbora nana being in sister group position to the rest.

Zebrafish

These findings, in combination with subsequent analysis of morphological characters, have made the authors propose four taxonomic changes:

· The species Inlecypris auropurpurea is reassigned as Devario auropurpureus.

· Microrasbora gatesi, Microrasbora kubotai and Microrasbora nana are reassigned to a new genus named Microdevario. Fish of this genus are distinguished from other danioinines by a combination of skull and jaw characters.

· Reassignment of the species Celestichthys margaritatus to the genus Danio in previous studies is confirmed.

· The membership of Chela is restricted to Chela cachius. All other species previously placed in this genus are reassigned to the genus Laubuca, except Chela maassi, which is in the genus Malayochela.

For more information about the study and the suggested taxonomic changes, see the paper Fang, F, M Norén, TY Liao, M Källersjö and SO Kullander (2009) Molecular phylogenetic interrelationships of the south Asian cyprinid genera Danio, Devario and Microrasbora (Teleostei, Cyprinidae, Danioninae). Zoologica Scripta 38, pp. 237–256.