Tiniest reef fish breaks world record [ABC 2004-07-08]
Tiniest reef fish breaks world record
[Photo] The stout infantfish, all 8 millimetres of it (Image: C Bento)
ABC Science Online
Thursday, 8 July 2004
The world's smallest vertebrate is a tiny fish that lives in coral lagoons on Australia's Great Barrier Reef, marine scientists say.
The scientists caught it 25 years ago but it has taken them this long to verify it was in fact a new species and a record breaker, at just 7 to 8 millimetres long.
The Australian Museum researchers worked with US scientists to describe the new fish species, the stout infantfish (Schindleria brevipinguis) in the latest issue of the journal Records of the Australian Museum.
The Australian Museum's Dr Tom Trnski, a larval fish expert, said although the sample was collected in 1979, the team did not get around to examining it until eight years ago.
This was partly because there were so many fish to examine from their research, about half a million in total.
During the process, Trnski's colleague Dr Jeff Leis recognised the six infantfish samples as a new species. U.S. scientists confirmed this.
This means there were now three infantfishes in the genus Schindleria, known collectively as "Schindler's fishes".
The other two species are double the size of the record breaking stout infantfish.
Stout by name, not by nature
Female stout infantfish are a fraction larger than the males, with the largest specimen found so far being an 8.4 millimetre female. This displaces the previous record holder, the dwarf goby.
The stout infantfish is also the lightest vertebrate, weighing just one milligram.
The species is paedomorphic, meaning the adults have characteristics of larvae and lack some adult features such as teeth, scales, pigment and pelvic fins. This allows them to reproduce extremely quickly, as they fast-track the time needed to reach maturity.
The lack of pigment and scales makes the infantfish look like tadpoles, with a lack of visible fins, except the caudal (tail) fin.
Due to this lack of colour, their size and the netting method used to collect them, no-one has actually seen the fish alive in the wild, Trnski said.
"Despite not having seen them in the wild, we know they are very abundant in their habitat.
The team found about seven fish per cubic metre, which doesn't sound like a lot, but Trnski said that for fish, that was very dense.
Stout infantfish have only been found in protected coral reef lagoons around Lizard Island, in the Great Barrier Reef, although Trnski says they could live elsewhere.
But, the species may be in danger from the effects of global warming, he said.
"If global warming has its predicted impact, potentially this species could go."
The protected lagoons that make up the infantfish's habitat provide a controlled environment, relatively free from increases in temperature and wave disturbance.
At the moment, scientists are unsure of how important the fish is in the reef's ecosystem, but Trnski believes that due to the relative abundance of the infantfish, it probably plays a significant role in the food chain.
"We just don't know at the moment, but it would certainly be a part of the food chain, feeding on the smaller animals ... and with bigger fish feeding on it," he said.