Sea anemones, like every living thing on the earth, reproduce to propagate their existence. But what makes sea anemones special is that they have a myriad of fascinating ways and methods. The way a sea anemone reproduces will depend on the species. These are vast and varied.
Having one in your reef tank at home is an entertaining and enriching way to learn about these amazing and ancient creatures from the sea. Their methods of reproduction are a microcosm of the wonder and power of nature. How they procreate is an interesting and wild event to behold.
Do sea anemones reproduce asexually or sexually?
Although most species of sea anemones reproduce asexually, there are some that are sexual, and yet other species will use a combination of methods to get the job done. Daisy and beadlet anemones will undertake sexual reproduction whereas bubble tip anemones use an asexual means.
The depth of the ocean in their native habitat is what determines sexual or asexual reproduction. The shallower the depth, the more asexual reproduction occurs. The deeper the water, the more sexual reproduction happens. But, there are a couple of species of anemone that defy this rule. So, this is only an average guide.
Sexual Reproduction
Propagation when sperm attaches to an egg, or sexual reproduction, is not uncommon for sea anemones. There are two ways that sea anemones can perform sexual reproduction: internal or external. Either method of fertilization produces genetically different offspring than that of its parents.
Internal Fertilization
When an anemone is viviparous, like a human, they give birth to a formed young from their mouths by way of internal fertilization. The larvae come from the mouth and move down the column, where it sinks into a small depression at the base of the parent’s foot.
They remain with their parent until around three months old. After which time they float away to find their own space to thrive and reproduce.
External Fertilization
Anemones can also reproduce through external fertilization. They release gametes through their mouths, known as an oral disk. The genetic material from two or more anemones joins in the water via sperm and egg, otherwise known as broadcast spawning.
The larvae float around until they locate a suitable spot to develop into a full anemone. Once grown, they too can begin their reproduction process handed down to them from their ancestors.
Asexual Reproduction
Most anemones will reproduce through budding, where they split or break off from the body. These grow into independent creatures. The process of splitting or breaking off from the main animal has two different methods.
Longitudinal Fission & Basal Laceration
The first is Longitudinal Fission, where the creature stretches itself at its foundation and splits in half down the center. Once division completes, each individual closes up. This allows for the edges to come together to regenerate missing or damaged internal structures.
The second is Basal Laceration where small pieces of tissue break away from the anemone’s base. This creates tiny anemones that develop and grow into full size.
Identical DNA
Asexual reproduction means the offspring is identical to that of the parent and gives the opportunity to create many new individuals far more rapid and with less energy than sexual reproduction. Small mutations occur during mitosis which is what allows for quicker responses to environmental changes.
When do sea anemones reproduce?
Upon reaching a mature size, a sea anemone can reproduce. Environmental stressors also provide the impetus for reproduction. If they feel their survival is under threat, they will reproduce to ensure continuity.
Environment
Their immediate environment, aside from stressors, also cues them in. Things like the full moon cycles and low tide are two such indicators. Anemones do all this through instincts and indicators, not a cognitive function. This is because they don’t have a brain.
Time of Day
They usually start in the morning, with their bodies appearing larger. Their mouth or foot will then elongate and begin breaking apart. The process occurs throughout the day, with the final split occurring sometime during the night.
Throughout the Year
Sea anemones can multiply any time of year, but aquarium hobbyists have found them to be consistent with their schedule in the wild. Most of their reproduction activity occurs between February and August.
How long do sea anemones take to reproduce?
If an anemone reproduces through asexual methods in a reef tank, it can take up to a whole day for it to divide itself. This means it could happen within a matter of hours or a little more than a day. When seeing them do this in the wild, it can take anywhere from three to five days.
When sexual reproduction takes place, it can take several weeks to complete the process. For internal fertilization, the young anemone stays with its parent for up to three months before going off on its own.
How often do sea anemones reproduce?
The size, age, environment, food availability and water depth of the anemone determines the frequency with which it reproduces. On average, though, they reproduce at least once a year. Larger, older anemones will reproduce more frequently than younger, smaller ones.
If there’s a lot of pollution, too many predators or a lack of food, sea anemones will reproduce as a mechanism for survival. They do this completely by instinct and feeling; it’s built into their programming when they come into being.
Final Thoughts
Sea anemones are unique and beautiful creatures that ornament the sea and home aquariums. How do sea anemones reproduce in reef tanks only contributes to their wonder and mystique. Whether they reproduce through asexual or sexual methods will depend on how deep their native habitat is in the ocean.
The frequency with which and when they reproduce is instinctual. Often, environmental factors and signals let them know when it’s time to create offspring. Pollution, the full moon, or any threat to their survival will bring on the drive to procreate.
References:
- How do sea anemones reproduce? http://scienceline.ucsb.edu/getkey.php?key=3299
- Reproduction in the Floating Dock Habitat https://depts.washington.edu/fhl/zoo432/floats/flreproduction/flreprod.html
