Nudibranchia, commonly known as Nudibranch or also as a sea slug, is a type of marine gastropod. The word “Nudibranchia,” which translates to “naked gills,” refers to the delicate gills and spikes that the majority of them have on their backsides. Although Nudibranchs have a radula feeding mechanism, they typically don’t have the shell, gills, or mantle chamber found in other mollusks.
The exquisitely colored body features strange protrusions called cerata that act as nematocyst dischargers for defense. There are around 2,000 species of nudibranch and more are constantly being discovered. Although they are present in all of the oceans of the world, shallower, tropical areas are where they are most common.
Below we will explore Nudibranchia and how it fits into the ocean with regard to diet, habitat, reproduction, and all other aspects that cover this species’ life.
Appearance
Nudibranchs can grow from a few millimetres to certain centimeters long and are typically oblong in appearance, they can also be thick or flattened, either long or short, intricately colored or dull to blend in with their environment. Their asymmetrical beginnings are reflected by the location of the male and female genital apertures, which are on the right side of the body.
To ward against predators, certain species have venomous appendages on their flanks.
Many also have a straightforward stomach and a radulated mouth. They have basic eyes that can only distinguish between darkness and light. The eyes are embedded in the body, have a lens and five photoreceptors, and measure about a quarter of a millimeter in diameter.
A few nudibranch species can voluntarily detach their cerata (the finger-like projections) when threatened. These detached cerata may contain toxins or stinging cells, distracting the predator and allowing the nudibranch to escape.
Did you know…
A significant number of nudibranchs obtain their chemical arsenal directly from their prey. By feeding on sponges, corals, anemones, or other invertebrates that possess toxins, they accumulate these compounds in their tissues. This is a clever way to exploit the defenses of their prey for their protection.
Habitat
They are benthic invertebrates that crawl across the substrate. They can be found in oceans all over the globe, from the Arctic to the Southern Ocean near Antarctica. They can also be found in warm and tropical waters. While a few kinds of Nudibranch have been found to live in salt water at lower salt concentrations, they are virtually totally limited to salt water.
They can be found living almost anywhere, from the intertidal zone to depths of more than 2,300 ft. Their largest variety can be found in warm, shallow reefs, or the seafloor, while one species was found in the deep ocean near 8,000 ft.
Diet
All known species are carnivorous. They have two extremely sensitive tentacles on top of their heads called rhinophores that are used to detect prey. The food that they consume gives them their color, which aids in camouflage. Some Nudibranchs feed on sponges, others on hydroids, others on bryozoans, seaweeds and some eat other sea slugs or their eggs.
On some occasions, Nudibranchs are cannibals and will prey on members of their species. Other groups feed on tunicates, barnacles, and anemones. All in all, the diet can be highly specific depending on the species.
Reproduction
Despite being hermaphrodites, they are unable to procreate by themselves. The wooing phase of mating often lasts a few minutes and features dancing. Normally, they encase their eggs in a viscous helix, which is commonly described as resembling a ribbon.
The eggs develop into planktonic (free-swimming) larvae, which drift on ocean currents until they settle out as adults.
Depending on the species, there may be just one or two eggs or as many as a few million. To ward off predators, the eggs are filled with marine sponge toxins. The young, though lesser, resemble their adult counterparts virtually exactly after spawning. Cerata may also be less common in infants. Depending on the species, Nudibranchs can live anywhere from a few weeks to an entire year.
Threats
They are more vulnerable to predators because they lack a shell. However, throughout a long period of adaptation, they have developed several defenses, including acid secretion, which can be produced by either self-production or by consuming something that carries poisons, and camouflage, which renders them impervious to many predators.
They still face some competition from marine spiders and other Opisthobranchia. The majority of species are not at risk. However, because so many rely on coral reefs for their habitat, they are extremely dependent on their survival.
Nudibranchs are not immune to dangers due to the effects of climate change, such as coral bleaching and human damage to reef habitats worldwide. Certainly, there are species all around the world that are at risk.
7 More Surprising Facts about the Nudibranch
- Glaucus atlanticus, the “blue dragon” nudibranch, floats upside down and preys on venomous jellyfish like the Portuguese man of war.
- They can give up a portion of their bodies to protect their nucleus.
- They carry out photosynthesis by ingesting the algae’s chloroplast.
- They constantly glide along, using their muscular foot (similar to a land snail.)
- They use a toothed structure called a radula to feed.
- Jorunna parva, the “sea bunny,” has fluffy-looking appendages that resemble rabbit ears.
- Hexabranchus sanguineus, the “Spanish dancer,” is a large, vibrantly colored nudibranch that undulates its body like a flamenco dancer when it swims.
FAQs
What happens if you touch a Nudibranch?
Sea slugs are known to carry venom in the form of acid ejections. The best policy is to look and not touch. In the case of contact with a Nudibranch that results in a sting, severe pain can be expected. However, it won’t be fatal.
How do Nudibranchs sting?
Numerous nudibranchs consume anemones, coral, jellyfish, or hydroids, all of which possess stinging nematocysts. When contacted, these particular cells release a poisonous projectile that looks like a spear that carries the venom.
Can Nudibranchs survive out of water?
Nudibranchs typically hang out around their prey, such as sea anemones, sponges, and other creatures that will also perish should they become dried. They are typically protected from being taken out of the water because their food can only thrive in damp places.
How do Nudibranchs communicate?
The Nudibranch can detect its prey or other species with the help of its olfactory sensors in a pair of tentacles on its head called rhinophores. Most of them have the capacity to retract their rhinophores and conceal them in a cavity in their skin if they detect a hazard since the rhinophores protrude out and are a lure for hungry fish.
