You loved to wander when you were a kid, but you stayed still when you grew up. I didn’t expect you to be two completely different people…

Barnacles have very hard shells, usually appear in groups and have strong survival ability. In addition to attaching to reefs, ship bottoms and seawalls, crabs, turtles, whales and other places are also their parasites.

Barnacles are also called "horse teeth" or "oysters", and belong to the order Perithorax, class Crustacea, phylum Arthropoda. Barnacles are special crustaceans that live in a settled state, with hard shell plates on the outside of their bodies and a small opening in the middle that resembles a small mountain. They survive by filtering organic matter from seawater.

1. Growth Stage

At different stages of growth, the character of a barnacle can be described as two completely different "barnacles": when it is young, it loves to wander, but when it grows up, it stays still. Its lifestyle is divided into two stages: floating and swimming period (larvae) and fixed period (adults).

1. The first stage - the nauplius stage:

When they first enter the ocean, the larvae of barnacles have no fixed place to stay. Although they can swim, the few times their "short legs (antennae) paddle can only be called paddling, so they mainly rely on "going with the flow" and have to be careful of predators. During the larval stage, the mortality rate of barnacles is very high.

2. The second stage - the larval stage:

After drifting for a while, the barnacles start looking for a place to settle down and start their second stage. The barnacles are very particular about choosing a place to settle down. They will move back and forth on the surface of objects for a short distance, using their tentacles to sense the "terrain". Rough and uneven places are very popular with barnacles! In addition, the flow rate, lighting, temperature, etc. around the settlement are also factors that the barnacles need to consider.

3. The third stage - fixation period:

After choosing a place, the suction cups on their tentacles begin to secrete barnacle glue, which wraps the tentacles and firmly attaches the small barnacles to the surface of the object. Barnacle glue is mainly composed of a variety of protein components and has strong adhesion, waterproofness and anti-biodegradability.

Engineers at Tufts University in the United States have used this feature to create a glue that can be used underwater or in dry environments. It is stronger, the material composition is non-toxic, and it largely avoids the synthesis or use of volatile solvents. During the growth process, barnacles secrete this barnacle glue every time they shed their skin. When they settle on the surface of the animal's skin, they also use the inner buckles on their calcareous outer wall to fix themselves, while continuing to grow downwards. Over time, they will slowly grow into the skin to avoid being thrown away due to the shedding of dead skin of these animals.

2. Buddhist style of eating

Adult barnacles completely give up the ability to move freely and mainly survive by filtering phytoplankton and organic debris. The shell of an adult barnacle is composed of several shell plates, and the body is usually hidden in the shell. There is a hole on the top of the shell, and there are shell plates on the hole that can be opened and closed by muscles. When eating, just open the shell plate and extend the ciliates.

3. Harm of barnacles

1. Bring burden to the host

Since barnacle larvae do not swim very fast, they prefer to parasitize large and slow-swimming creatures such as whales and sea turtles. Although barnacles are not large when they mature, they are still a considerable weight when they appear in groups. Fish and sea turtles attached to them may lose their balance during their daily swimming and hunting.

2. Humans are also victims

Barnacles can attach to the surface of ships, slowing down their speed and increasing fuel consumption, threatening navigation safety. The accumulation of barnacles can increase the weight of offshore oil platforms and related building structures, reducing their ability to resist risks, and even causing them to tilt or collapse.

The power of tiny barnacles should not be underestimated. Studies have found that the attachment strength of barnacles varies at different growth stages. When the barnacles are about 30 days old, the base diameter reaches 1-6 mm. At this time, the shear strength of the barnacles is in the rapid increase period (base diameter 4.0~6.4 mm), which is the best time to remove them mechanically.

References

[1] Ma Yao. Barnacles: The most difficult parasite to get rid of in the ocean[J]. Science Popularization China.

[2] Zhu Chongkai. Underwater glue inspired by barnacles and mussels[J].

[3] Li Jingjing. The trouble that can’t be shaken off - barnacles[J].

[4] Li Youchi. Study on the growth process and attachment strength of marine fouling organism barnacles[J]. Marine Science. 2023.47(8).