True Or False: Five Myths About Marine Life

This article takes a look at five of myths in an effort to separate fact from fiction.

It has famously been said that we know more about space than we do about the oceans, and it’s certainly true that the marine environment harbors many secrets and mysteries that we have yet to unravel. This lack of certainty has led to the birth of many myths regarding the ocean’s creatures — some of which are true, and some of which are pure fabrication. This article takes a look at five of those myths in an effort to separate fact from fiction.

Sharks are attracted by human urine

Of the many myths connected to sharks, one of the most enduring is that they are attracted by the smell of human urine. In 2011, National Geographic conducted a series of experiments in an attempt to prove or disprove shark-related myths, including the theory of urine as an attractant. Two divers of similar weight and height and wearing identical wetsuits were filmed in the water surrounded by sharks, one of whom was given a bottle of urine that seeped out slowly for the duration of the experiment. The sharks did not react, ignoring both divers equally. The reason for this is that sharks have an incredibly acute sense of smell, and can easily differentiate between the smell of human urine and the more appetizing smell of fish or marine-mammal blood. Therefore, because sharks do not associate the smell of urine with food, it is does not alter their behavior towards humans in any way.

Verdict: False

An octopus can regrow a severed limb

Octopuses are renowned for their intelligence, and for possessing an impressive range of remarkable abilities, one of which is the ability to regrow a lost limb. This power of regeneration is part of a defense mechanism whereby an octopus can willingly lose a tentacle to escape a predator if necessary. The severed limb then grows back, until eventually it is as good as new. This is unusual in the animal kingdom; while lizards and geckos can shed their tails in a similar defensive move, the replacement tail is never quite as good as the original. Scientists are exploring this regenerative power in the hope that it can one day be synthesized in humans who have lost limbs. It is believed that the protein responsible for this remarkable feat is acetylcholinesterase, or AChE.

Verdict: True

Clownfish Can Change Their Gender

All clownfish are born male, and are capable of exhibiting a phenomenon known as sequential hermaphroditism. A clownfish colony typically consists of a single breeding female, a single breeding male and a group of smaller juvenile males. Clownfish are monogamous, meaning that only the alpha pair will mate. However, if something should happen to the female, the breeding male will change gender to replace her, and the largest of the juvenile clownfish will be promoted into the alpha-male position. This process is called protandry, and refers to the process by which a male turns into a female. The ability to change sex is not unusual in the underwater world, but it is more common for female fish to transform into males, via a process called protogyny. Clownfish take approximately two months to change sex, and can only do so if the sudden removal of the breeding female triggers the process.

Verdict: True 

There is a limit to the number of times a pufferfish can inflate

Pufferfish and porcupinefish are both known for their ability to inflate to several times their normal size when threatened. We are often told that there is a limit to how many times these species can do this, perhaps to discourage irresponsible divers from forcing the phenomenon. This is not true, however: inflation is the main defense mechanism of these charismatic fish, and can be performed as often as required. With that being said, inflation can be dangerous for these species, and should never be encouraged unnecessarily. Firstly, the act of inflation by gulping large quantities of water is metabolically taxing for the pufferfish, which can take up to five hours to fully recover from inflation, during which time the fish is especially vulnerable to predation. Secondly, pufferfish that inflate at the surface may ingest air rather than water. It is then difficult for them to deflate, causing sometimes-fatal stress levels.

Verdict: False

Loggerhead turtles return to the beach where they were born to lay their eggs

The idea that a female loggerhead turtle can navigate across thousands of miles to find the exact beach upon which she was born seems too incredible to be true, and yet it is. For many years, scientists have known that these giant turtles return to their natal beach to lay their own eggs, and yet only recently has research provided an answer as to how they do it. A study completed by graduates of the University of North Carolina shows that turtles are able to detect the angle and the intensity of the earth’s magnetic field, and that they can use this information in much the same way that humans use latitude and longitude to pinpoint a specific location. It is thought that maternal instinct is the driving force behind the turtles’ epic migration. After all, the female turtles know from personal experience that the conditions at their hatching beach are conducive to high survival rates for their own offspring.

Verdict: True