Mouth Vision: Blind Fish Suctions Water to Navigate

By Laura Poppick, Staff Writer | April 02, 2014 03:43pm ET

The Mexican blind cavefish does not have eyes, but it can "see" obstacles in dark caves by puckering its mouth and producing bursts of suction, according to a new study. The research describes this unique form of navigation for the first time.

Scientists previously thought theeye-less Mexican cavefish navigated by sensing changes in water pressure produced by waves sent off from the fish's own body. But when theresearchers examined the fish, they found some problems with this explanation. For example, larger fish, which would presumably produce larger waves, should be able to identify objects from farther away than smaller fish. In fact, larger fish detected objects at about the same distance as smaller fish did.

Researchers at Tel Aviv University in Israel decided to investigate the sightless navigation further, conducting an experiment in which they counted the number of times the fish opened and closed their mouths when near objects the fish were familiar with. The researchers then moved the objects and observed changes in the fishes' mouth movement in the unfamiliar environment. 

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How Remora Fish Get Their Bizarre Suckers

Megan Gannon, News Editor

Date: 07 June 2013 Time: 03:42 PM ET

Scientists say they've confirmed how remora fish grow a weird sucking disc on their heads.

Remoras, which can be up to 3 feet (1 meter) long, have a slatted disc above their eyes, which sort of looks like the bottom of a sneaker. It acts like a sucker and allows them to attach to manta rays, sharks, and boat hulls in tropical waters. But the fish aren't parasites; rather, they harmlessly hitch rides and feed off of scraps of food from their hosts.

CREDIT: Dave Johnson 

It had long been suspected that the sucker was made out of the rearranged parts of a normal dorsal fin, but their development hadn't been studied. By watching remoras grow up from their earliest larva stages, a group of scientists says they finally confirmed that the sucker does indeed come from fin parts.

"We followed the earliest stages of the disc's development by matching the first vestiges of elements of the sucking disc with the first vestiges of elements of the dorsal fins of another fish, the white perch (Morone americana), which has the typical dorsal fin of most fishes," researcher Dave Johnson, zoologist at the Smithsonian's National Museum ofNatural History, explained in a statement.

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