Among the intriguing organisms of the ocean, fire coral stands out as a captivating yet cautionary presence. These colonial marine cnidarians, known for their vibrant appearance, can deliver a painful sting upon contact.
Despite their name, fire corals belong to the Milleporidae family and are more closely related to the members of classs hydrozoa than true corals. Scientifically classified under the genus Millepora, they fall into the hydrocoral category. This article delves into the fascinating world of fire coral, exploring its habitat, behavior, diet, survival strategies, and how to handle a Millepora sting safely.
Appearance
Millepora closely resembles stony coral; however, as mentioned before, they are more closely related to jellyfish and anemones than hard corals with calcareous skeletons.
Fire coral can be found growing in several forms, adapting as needed to the changing underwater conditions. The most common growth structures are the branching, plate, and encrusting growth patterns.
- Branching: The coral grows a calcium carbonate structure that branches off into round tips. The ends of these branches somewhat represent fingertips or the structure of a tree trunk with branches. Millepora alcicornis, or sea ginger, is a species of colonial fire coral with a calcareous skeleton.
- Plate: When growing in a plate structure, fire coral grows in upright sheets that are grouped. These sheets are what form the colony of the coral. This structure is similar to the plate-like formation of lettuce coral. Millepora platyphylla or blade fire coral is a type of hydrocoral, in the family Milleporidae.
- Encrusting: Fire coral, when not challenged by other taller growth, can spread along the surfaces of hard corals, rocks, and gorgonian corals, somewhat resembling a blanket covering of Millepora.
The reason for the different growth is not entirely clear, but it has been observed to be related to changing weather conditions and competition on the reef.
For example, when other corals compete for height, Millepora will grow tall, in a branching structure, while in constant rough conditions with little competition, the organism may take an encrusting shape.
Fire coral colonies typically grow between 78 – 118 inches (200 – 300 cm) in diameter, with their vertical plates reaching an average of 78 inches (200 cm) tall.
In conjunction with its branching structure, which loosely represents the fingers of fire, Millepora boasts a bright, yellowish-green-brown skeletal structure, which further adds to its firey appearance. The surface of fire coral colonies is covered in an intricate pattern of tiny, cup-shaped structures called calyces. These homes shelter individual polyps, each equipped with a mesmerizing array of venomous tentacles.
There are different types of spores on the surface of the fire coral one type is called dactylopores. The dactylopores have long fine hairs that protrude from the skeleton. The hairs possess clusters of stinging cells (nematocysts). These hairs capture prey, which is then engulfed by gastrozooids, or feeding polyps, situated within the gastropores.
Habitat
This hydrozoan can be found in various marine environments, including coral reefs, rocky shores, and even shipwrecks or underwater caves.
Preferring subtropical and tropical waters, fire corals thrive in shallow reefs and well-lit waters that allow ample sunlight for photosynthesis by their symbiotic zooxanthellae.
Fire coral is most commonly found in the Indian, Pacific, and Atlantic Oceans, as well as abundantly in the Caribbean Sea.
Typically, these corals make their homes in waters below 10 meters; however, their range spans from 1 to 50 meters.
These hydro corals are known to overgrow or encrust other coral species, particularly gorgonians (sea fans). When this happens, the fire coral extends specialized branches toward the sea fan, eventually circling and covering it.
Fire corals are most commonly found in shallow reefs where an optimum level of sunlight is available and a variance exists in the flow of water.
Diet
Millepora are carnivorous organisms, feeding mostly on small plankton and other microorganisms that drift by in the currents.
At night, the hydrocoral extends its polyp tentacles, exposing its stinging nematocysts used to immobilize its prey.
The stinging polyps of hydrozoans come in two sizes, one known as gastropores and the other as dactylopores. Although these cells are almost microscopic, it is these two pores that aid the fire coral in its feeding.
Did you know that millepora means “thousand pores”?
The Dactylopores (nematocysts) have long, fine hairs that extend out of the skeleton, which are used to capture passing prey. The prey is then brought down to the gastro zooids (situated inside the gastropores) where it is ingested.
Apart from its opportunistic hunting, fire coral, like most coral, gets a large part of its energy from its zooxanthellae algae relationship. The algae photosynthesize and provide the hydrocoral with nutrients and oxygen, while the fire coral provides a safe place for the algae to flourish while supporting it with excess carbon dioxide.
This symbiotic relationship is one of the most complex but crucial processes when it comes to the health of ocean ecology.
Reproduction
The reproduction and lifecycle of fire coral is a complex process, particularly when compared to that of other reef-building corals.
These corals can reproduce both asexually, as well as sexually.
When polyps reproduce sexually, they produce jellyfish-like medusae, which are released into the water from the coral’s ampullae. It is these medusae that contain the reproductive organs responsible for reproductive gametes, such as sperm and eggs. When eggs are fertilized, they develop into free-swimming larvae, which are mobile and can freely swim. Eventually, the larvae will settle on a substrate they deem to be suitable, and begin the development of new colonies.
Asexual reproduction occurs through fragmentation, which usually happens during storms or strong currents.
The life cycle of fire coral can be closely related to that of cnidaria, as the organism can be seen as somewhat of a cross between coral and sea anemone.
Threats
Fire coral do not have many natural predators. Along with this and their unique ability to adjust their growing formation, as well as their defensive toxins, these corals are particularly hardy and don’t face many threats.
That said, they are still threatened by many of the same factors that put the rest of the world’s coral reefs at risk.
Habitat destruction due to coastal development, illegal coral trade, and the introduction of pollutants such as agricultural runoff and chemical waste degrades water conditions and limits viable living environments.
One of the major concerns relating to the preservation of fire coral is that of their zooxanthellae. As zooxanthellae are extremely sensitive to water temperature and light availability when conditions change, the fire coral expels these beneficial algae, which results in coral bleaching.
Although Millepora is particularly resistant to bleaching and tends to recover faster than other coral species when exposed to a stressful environment for a long period, it can lead to the death of the hydrocoral.
More Cool Facts About Fire Coral
- They can form extensive reef-like structures, providing habitat for marine life.
- They have tiny, hair-like polyps that deliver a painful sting to deter predators.
- These corals are more closely related to jellyfish than true corals.
- Their vibrant colors come from symbiotic algae living within their tissues.
- Fire corals can rapidly regenerate damaged tissue to quickly recover from physical disturbances in their environment.
- Their skeleton has a hollow structure that encases the living polyps until they are ready to be released.
FAQs
Can fire coral be harmful to humans?
Yes, contact with fire coral can result in a rash with a painful burning sensation, which can last for a few hours and itching up to a couple of days. That said, these stings are not lethal to humans.
What should I do if I get stung by fire coral?
Burns from fire coral are treated in much the same way as a jellyfish or anemone sting. You can neutralize the venom by rinsing the area with vinegar or something slightly acidic. Avoid using freshwater, as it can cause the stinging cells to release more venom.
Can fire coral be found in cold waters?
Fire coral, like most coral, prefers warm waters. It thrives in tropical and subtropical habitats with higher water temperatures that provide nutrients and energy not found in colder environments.
Can fire coral be used for medical purposes?
Some compounds found in their venomous cells have been studied for potential medical uses, such as for pain relief. Some neurological research has also been conducted on these cells. That said, because of its potentially harmful effects, studies are taken with great caution and under strict control.
