Hawaiian bobtail squid facts for kids
Quick facts for kids Hawaiian bobtail squid |
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| The Hawaiian bobtail squid, Euprymna scolopes, swimming in the water column off the south shore of Oahu | |
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The Hawaiian bobtail squid (scientific name: Euprymna scolopes) is a small, special type of bobtail squid. It lives in the shallow coastal waters around the Hawaiian Islands and Midway Island in the central Pacific Ocean. This amazing creature is known for its unique partnership with glowing bacteria.
This bobtail squid is quite small. It grows to about 30 millimeters (just over an inch) long. When they hatch, they weigh only about 0.005 grams, which is super tiny! They grow up quickly, becoming adults in about 80 days. Adult squids can weigh up to 2.67 grams.
In the wild, E. scolopes enjoys eating different kinds of shrimp. These include the Halocaridina rubra, Palaemon debilis, and Palaemon pacificus. Scientists have also fed them other animals in the lab. These include tiny shrimp-like creatures called mysids, brine shrimp, and even small fish like mosquitofish.
The Hawaiian monk seal is a natural predator of the Hawaiian bobtail squid. These seals hunt the squids in the waters of the northwestern Hawaiian Islands.
Amazing Partnerships: The Squid and Its Glowing Friends
Euprymna scolopes has a very special relationship with tiny glowing bacteria called Aliivibrio fischeri. This type of partnership is called symbiosis, where two different living things help each other. These bacteria live inside a special "light organ" in the squid's body.
The squid gives the bacteria a sugary and amino acid-rich meal. In return, the bacteria glow! This glow helps the squid hide from predators. When a predator looks up from below, the squid's silhouette would normally be visible against the moonlight or starlight. But the glowing bacteria match the light coming from above. This trick is called counter-illumination, making the squid almost invisible.
Scientists study the relationship between the Hawaiian bobtail squid and A. fischeri a lot. It helps them understand how animals and bacteria can work together.
How the Squid Gets Its Glowing Bacteria
Baby Hawaiian bobtail squids are born without these special glowing bacteria. They have to find them in the ocean after they hatch. The ocean is full of many different tiny living things, so the squid needs a clever way to pick out only the A. fischeri bacteria.
To do this, the squid makes a sticky mucus. This mucus helps to catch many types of bacteria. However, for reasons scientists are still figuring out, A. fischeri bacteria are much better at surviving and growing in this mucus than other bacteria.
Once the A. fischeri bacteria gather in the mucus, they use their tiny tails (called flagella) to swim into the squid's light organ. They go through small openings and into special tubes. The squid also has ways to make sure only A. fischeri can live there. For example, the squid creates a strong current that pushes out bacteria that can't swim well.
The squid also produces harmful chemicals like hydrogen peroxide. But the A. fischeri bacteria have a special defense! They have a substance called catalase that breaks down the hydrogen peroxide before it can harm them. This allows them to survive and swim deeper into the light organ. Once inside, they settle into tiny spaces called crypts.
The bacteria then feed on the sugars and amino acids provided by the squid. They quickly fill up these spaces within 10 to 12 hours after the squid hatches.
Keeping the Glow Going
A young squid breathes about 2.6 milliliters of seawater every second. Only a tiny amount of A. fischeri cells are present in each breath.
The food from the squid helps the A. fischeri bacteria glow brightly. This glowing takes a lot of energy for the bacteria. Within 12 hours of hatching, the squid's light organ is glowing at its brightest. This means the young squid can use its counter-illumination trick less than a day after it's born!
Scientists have found that if A. fischeri bacteria can't glow, they don't do as well inside the squid. This suggests that glowing is very important for the bacteria to live with the squid. Some scientists think that glowing might have first helped bacteria deal with oxygen, which can be harmful to them.
Daily Cleaning: Venting the Bacteria
Even though the squid works hard to get these glowing bacteria, it gets rid of most of them every day! This process is called "venting." Every morning at dawn, the squid releases up to 95% of the A. fischeri bacteria from its light organ.
The bacteria don't seem to benefit from this daily release. But for the squid, it might save energy. During the day, the squid hides and doesn't need to glow. So, getting rid of the bacteria saves the energy it would take to keep them glowing.
Another important reason might be that venting helps make sure the A. fischeri bacteria stay strong and specific to the squid. It also helps keep a healthy population of these glowing bacteria in the ocean. This way, future baby squids will always have a supply of bacteria to find and partner with.
The Amazing Light Organ
The squid's light organ can react to light, almost like an eye. This suggests it helps the squid sense the light from its glowing bacteria. This allows the squid to control how much light the bacteria produce.
The squid also has other special parts, like small sacs near its eyes. These work with its eyes to check the light coming from above and the light from its own glowing organ. As the squid moves to different depths in the water, it can adjust its glow.
The squid can change the brightness of its light by using its ink sac. The ink sac acts like a curtain or diaphragm around the light organ, letting more or less light out. The light organ also has special tissues that act like reflectors and lenses. These help to bounce and focus the light downwards through the squid's mantle.
The light organ of baby squids looks a lot like an eye. It even uses some of the same genes that are involved in eye development in other animals. This suggests that squid eyes and light organs might have developed using similar "toolkits" of genes.
The squid can adjust its glow perfectly, even as the natural light changes throughout the day and night.
See also
In Spanish: Calamar hawaiano para niños
