Goose barnacles, also known as stalked barnacles, are a type of crustacean that attaches itself to hard surfaces like rocks, ship hulls, docks, and other structures. They have a muscular stalk that anchors their shell-like body to a substrate. Goose barnacles are found in oceans around the world and are most common in temperate and tropical waters.
Can goose barnacles survive out of water?
Goose barnacles cannot survive for extended periods of time out of water. They are marine organisms that need to be submerged in seawater to live. However, goose barnacles can survive for brief periods out of water, up to a few days at most, under the right conditions.
When goose barnacles are exposed at low tide or removed from water, they quickly close their shell plates tightly to prevent dehydration. This protects their gills and body tissues from drying out. As long as they remain damp and their gills moist, goose barnacles can withstand being out of water for a while.
How long can goose barnacles survive without water?
Most sources indicate that goose barnacles can only survive out of water for 2-3 days at the absolute maximum. However, the exact time depends on temperature, humidity, and how damp the barnacles remain.
In cool, humid conditions, goose barnacles may survive up to 2-3 days out of water if kept in a refrigerator. At room temperature with some dampness, they may last 1-2 days at most. In warmer, dryer conditions, goose barnacles will quickly dry out and die within hours.
During low tide when ocean water recedes, goose barnacles are naturally exposed to air for up to 6 hours or so. They can handle regular tidal changes just fine through their protective shell closing.
Factors that affect survival time
There are several key factors that affect how long goose barnacles can survive out of water:
- Temperature – Cooler temperatures help goose barnacles survive longer without water. Warmer temperatures increase dehydration.
- Humidity – Higher humidity in the air allows goose barnacles to retain internal moisture better.
- Dampness – Keeping the barnacles damp and moist is crucial for their gills to function.
- Oxygen – Goose barnacles can only survive so long without flowing seawater bringing oxygen to their gills.
- Shell closure – How tightly the barnacle can close its shell plates impacts water retention.
Optimizing these conditions by keeping goose barnacles cool, humid, damp, and with some air exposure allows them to survive the longest when removed from water.
Why can’t goose barnacles survive indefinitely without water?
Goose barnacles are adapted to life attached to surfaces in the ocean. They simply cannot survive very long out of water because:
- They require constant immersion in seawater so ocean currents can deliver fresh oxygen, food particles, and other nutrients to their feathery cirri appendages for capturing food.
- Being out of water causes the barnacle’s gills to dry out, preventing oxygen absorption and respiration.
- Goose barnacles lose moisture very quickly without water, leading to dehydration and tissue damage.
- Waste products can’t be carried away without flowing seawater, causing toxin buildup inside the barnacle.
- Being out of their aquatic habitat exposes goose barnacles to temperature and pollution fluctuations they aren’t adapted to handle.
While goose barnacles can temporarily tolerate low tide or short-term removal from the ocean, extended time out of water is simply not something they can endure. Their biology as marine filter feeders means they depend completely on submersion in seawater to get the oxygen, food, hydration, and waste removal they require to live.
Behavior when out of water
When goose barnacles realize they are no longer submerged in water, they react by tightly closing their shell plates and cirri to prevent dehydration and tissue damage:
- The barnacle’s fleshy stalk and shell are retracted upwards.
- The articulated shell plates shut completely to form an airtight seal.
- The feathery thoracic cirri used to filter food are withdrawn inside the shell.
- The soft mantle tissue surrounding the body is contracted.
- Any openings are closed tightly.
This protective closure reflex happens automatically in response to physical stimuli signaling the barnacle is out of water. How long the goose barnacle can remain shut like this without perishing depends on the conditions as previously discussed.
During exposure at low tide, goose barnacles periodically open slightly to allow for gas exchange before closing up again to retain internal moisture. But after too long out of water, the weakened barnacle will be unable to reopen its shell.
Recovery after reimmersion
If reimmersed in seawater in time, goose barnacles can recover after being out of water. However, full recovery ability depends on how long they were exposed:
- Less than 6 hours – Goose barnacles can make a full recovery almost immediately if reimmersed after being stranded at low tide.
- Up to 2-3 days – If kept humid and cool, recovery is likely but may take time for the barnacle to regain strength.
- Over 3 days – Severe weakness and tissue damage. Many barnacles will be unable to recover after this long without water.
When placed back underwater, the revived goose barnacle will slowly begin to reopen its shell plates and cirri and resume normal filter feeding behavior. It takes time to rehydrate tissues and regain organ function, so a recovered barnacle may appear sluggish at first.
In the wild after reimmersion, goose barnacles also must repair damage from predators and environmental exposure. Even if the internal organism survives, the stalk and shell may be too damaged for the barnacle to thrive again.
Interesting facts about goose barnacles
- Goose barnacles are thought to have inspired medieval myths about barnacle geese growing on trees before falling into the ocean.
- The portugese man o’war jellyfish species is named after the man-of-war ship on which goose barnacles were abundant.
- Charles Darwin studied goose barnacles extensively during his early scientific career.
- Goose barnacles are considered a delicacy in Spain and Portugal where they are called percebes.
- The shell of the goose barnacle grows by adding calcium carbonate layers as the animal inside gets larger.
- Goose barnacles breed by releasing sperm and eggs into the surrounding water for fertilization.
- While they can’t survive long out of water, goose barnacles have been found alive on driftwood and debris washed up after months at sea.
- Goose barnacles are one of the few stalked barnacle species. Most other types have unstalked shells attached directly to surfaces.
- Young goose barnacles go through a larval stage where they swim freely before settling on a home surface for adulthood.
- Predators like sea stars, whelks, and fish will prey on exposed goose barnacles stranded during extreme low tides.
Conclusion
To summarize, goose barnacles are specialized marine crustaceans that cannot survive more than a few days at most outside of seawater. They require constant immersion to access food, oxygen, and waste removal. When stranded out of water, goose barnacles quickly seal themselves in a protective shell to avoid dehydration. But prolonged exposure is ultimately fatal if they are not reimmersed. Understanding the biology and behavior of these intriguing organisms sheds light on their dependence on an aquatic environment.
