Crying is often seen as a uniquely human experience tied to our emotions. But is it possible for fish, with their alien underwater lives, to shed tears too? The answer may surprise you.
If you’re short on time, here’s a quick answer to your question: While fish don’t cry in the emotional sense that humans do, some fish produce teardrop-shaped secretions from their eyes for a variety of biological reasons.
What Is Crying in Humans vs Fish?
Crying in Humans
Crying in humans is the shedding of tears from the lacrimal glands located above the eyes. Tears secreted from these glands help lubricate and protect the eyes. Humans typically cry in response to strong emotions such as sadness, joy, anger or frustration.
The act of crying is controlled by parts of the brain like the limbic system and frontal lobes.
When humans experience heightened emotions, signals are sent to the lacrimal glands to produce excess tears that overflow onto the cheeks and eyelids. The tears may come steadily with sobbing or choking expressions of grief.
Scientists believe emotional crying serves biological functions related to managing stress.
According to Psychology Today, adults cry an average of 5.3 times per month while crying spells last around 6 minutes. Women tend to cry more frequently and for longer periods. However, men report more intense crying episodes that are harder to stop once started.
Fish Tears
Fish do not cry in the emotional sense as humans do. They lack advanced limbic systems and frontal lobes to process emotions and trigger crying the way humans instinctively cry when upset, happy or stressed.
However, research shows that fish produce tears that serve to moisten and protect their eyes. For example, a 2006 study found that lacrimal glands and tears were present in Arctic char, a species of fish. Their tears contained proteins similarly found in human tears.
While fish tears serve more rudimentary functions, recent studies indicate fish may have some capacity for distress or pain that leads to observable stress responses, though not emotional crying. A 2022 study showed trout initially produced defensive mucus tears when distressed, followed by long term impairment of their tear production capabilities.
| Fish Tears | Human Tears |
|---|---|
| Moisten eyes | Moisten eyes |
| Protect eyes | Protect eyes |
| Defensive stress reaction | Emotional stress reaction |
So while humans clearly cry in a more complex way related to emotions, fish produce tears essential to ocular health and eye functioning that may also indicate distress or discomfort to some degree.
Do Fish Produce Tears?
Although fish do not cry emotional tears like humans, they do produce a tear-like fluid from their eyes and skin for protective purposes. Let’s take a closer look at the details.
Mucus Coating
Fish produce mucus through special glands in their skin and eyes that mixes with tears to create a protective film or coating over their bodies. This moist coating prevents infection, eases movement through water, and protects the skin and scales from abrasion and irritation.
The Mayo Clinic notes that excess mucus production may be a sign of stress in fish [1].
Stress Tears
Fish can produce extra tears and mucus when distressed, though these are still not driven by emotions like in humans. The added fluids may help the fish better escape or defend against difficult situations. Some key signs of stress tears in fish include:
- Increased mucus secretions from the sides, fins, or gills
- Clamped fins
- Swimming erratically or dashing rapidly against aquarium walls
- Isolating themselves from a schooling group
So while fish do have tear-like secretions, these primarily function as mucus barriers rather than emotional releases like the tears of humans. Reasons for excess secretions include infection, water pollutants, diet issues, physical agitation of the skin, and overall stress levels [2].
Monitoring changes in mucus and tear production can help aquarium hobbyists assess a fish’s health status.
Purpose of Fish Tears
Protection
Fish tears serve an important protective purpose for their eyes while living in aquatic environments. The tear film covering the eye helps remove debris, salt, and excess mucus to prevent damage and infection (Tear film overview).
Tears also contain lysozyme, an enzyme that breaks down cell walls of bacteria as a defense mechanism. When a fish’s eye is irritated by toxins or pathogens, reflex tears will wash the eye, eliminating threats.
So in essence, fish tears help clean, lubricate, and protect the sensitive structures of the eye.
Studies have shown that the tear composition of fish is adapted to their saline, aquatic habitat. Marine fish tears contain more salt to match the ocean environment, while freshwater fish tears have minimal salt.
Their tear quantity also varies – saltwater fish produce fewer tears that are protein-rich, while freshwater species have more dilute tears. So evolution has fine-tuned fish tears for optimal eye health in their specific ecosystems.
Communication
Incredibly, scientists have discovered that fish tears can serve as a means of chemical communication. Pheromones and proteins are transmitted via tears to send signals to other fish. These chemical cues may communicate vital information about the reproductive status, hierarchy status, or alarm warnings to members of the same species (Fish tear communication study).
For example, the mangrove rivulus fish uses tear pheromones to indicate dominance and suppress reproduction in subordinate fish. The African cichlid fish sends chemical messages in tears when alarmed to trigger group escape behaviors.
So shedding tears in the aquatic world can silently speak volumes through this novel channel of tear-mediated communication!
What Kinds of Fish Cry?
Sharks
While sharks may seem like intimidating predators, recent research has shown that some species actually produce tears and vocalizations that may indicate distress or pain. Scientists have identified complex neuroanatomical structures in shark brains similar to those in mammals that control emotional responses.
Additionally, certain shark species’ tear ducts have been found to secrete a sodium chloride solution, suggesting tear production. When caught on fishing lines or restrained, sharks have been observed to emit sounds and release tears from their eyes, potentially reflecting a response analogous to crying in distress.
However, more research is still needed to fully understand these behaviors in sharks.
Carp
As common freshwater fish, carp have been shown to produce tear-like secretions from their eyes when stressed or exposed to irritants. Their lacrimal glands located below the eye socket can release mucus and fluid that moistens the eye area.
While carp tears may help protect their eyes, they may also signal distress. A 2010 study found increased tear production in carp that were harvested for food, reflecting elevated stress. Tear production has also been noted in carp transported live for aquaculture and those exposed to pollutants.
This suggests carp tears could indicate negative environmental conditions or physical handling. However, more evidence is needed to confirm if carp tears are a veritable sign of distress and pain, or solely an involuntary reaction to external stressors.
Goldfish
Goldfish are a popular pet fish known for their orange-gold coloring, but did you know they may also produce tears? Goldfish have specialized cells that secrete a watery fluid to moisten and protect their eyes.
When goldfish are exposed to foreign chemicals, rough handling, or adverse environments, their tear glands may work overtime, releasing excess fluid dubbed ‘crying’. These stress tears help flush out irritants and cleanse their eyes.
Interestingly, gilt-head sea bream, close relatives of goldfish, have been found to secrete more tears when given anesthesia or euthanasia drugs, suggesting crying in response to sensations of pain or distress.
However, the implications of tear production in goldfish require more investigation to better understand their emotional lives.
Conclusion
While fish don’t experience emotion-driven tears like humans, many fish secrete eye mucus or tears for key biological functions. Understanding the evolutionary purpose behind these fish tears provides insight into the aquatic world.
So next time you see a fish with a droplet on its eye, it’s crying for a whole different reason than you and I!
