Hunting is the way of life for many organisms in the world, both past and present. Once, humans were only hunters and gatherers as we moved around to follow and chase our prey. While that aspect of ourselves is no longer necessary, it is still there. We see many animals in the wild exhibit a wide variety of predation as they employ their own skills and methods to take down a prey. Some slowly watch and creep up on their prey and pounce when the moment is right. Others chase their prey at high speeds until one or the other cannot go further.
There are those that build traps for the unsuspected and when triggered, their fate is decided. There are numerous ways in which predators hunt their preys. Recently, marine scientist have discovered a new method of predation that has never been seen before. They came across this method while they were examining nudibranchs in their natural habitats below the waters.
What Are Nudibranchs?
Nudibranchs, commonly referred to as sea slugs, are a group of over 3,000 marine species that are soft-bodied and shed their shells after their larval stage. They are among the many different gastropod species, which includes things like snails and slugs. While they are called sea slugs, nudibranchs are not all sea slugs and not all sea slugs are nudibranchs. Sea slugs come from many different taxonomic groups. They are found all over the world in many different saltwater areas and are even found in shallow or deep depths.
This is owed to the fact that there is such a large amount of variety in this group and so there are numerous adaptations to these different environments across the species. Nudibranchs are referred to as benthic animals because they crawl along the surface of whatever body of water they are in. There are a few exceptions to this as the Glaucus genus contains species that float upside down on the ocean surface and two other species of a different genus that exists in the water levels rather than the surface.
Nudibranchs vary in size from 4 to 600mm, but generally are small. They are one of the most colorful groups of organisms in the world. Since they lose their shell at an early time in their life, they have had to develop new ways of protecting themselves. Some use their color and texture to mimic or confuse any potential predator while others their colors to blend into the surrounding area. There are some species that release chemicals meant the deter and keep predators away. There are even some that steal the defense of other species and uses it for themselves.
Nudibranchs that feed on hydrozoids takes the stingers from them and it is placed around their body because it cannot harm the nudibranch and harms everything else. This means that nudibranchs are carnivores and eat things like sponges, hydrozoids, and many other similar species. There are even those nudibranchs that eat other sea slugs, their eggs, and somethings engage in cannibalistic behaviors.
There are a few kleptoparasitic behavior in the world that many people are familiar with. They include animals that steal the food that other animals have gotten. Kleptopredation can be seen as somewhat similar to this but it is some sinister. In the tale of Hansel and Gretel, the witch that lives in the gingerbread house captures the kids and begins to feed them their favorite food: candy. As the kids engorge themselves, the witch has the potential to consume a lot more energy.
Once the kids have eaten their fill, the witch takes them and begins to make her meal of them. Now unfortunately for the witch, the kids do escape and she misses out on all that energy that included the kids and candy they ate. This is essentially what kleptopredation is: allowing a prey to consume a meal, which is also something you enjoy eating, and then consuming that prey. You are getting the energy from both the prey and the food they just ate without doing all the extra work to hunt both food source. The witch in the tale is a kleptopredator, although not a good one.
The research that discovered kleptopredation was led by Dr. Trevor Willis, a senior lecturer and course leader at the University of Portsmouth, as they wanted to learn more about the behavior of these nudibranchs. They examined the behavior of Cratena peregrina, which lives among groups of hydroids. Its diet is 50% plankton and 50% hydroids. The researchers found that the diet of C. peregrina was primarily plankton that was consumed by hydroids. The nudibranch generally feeds off of the hydroids at a slow rate because there is not enough energy in the hydroids to sustain them. This all changes once the hydroids feed on plankton because this instance causes a spike in the eating of hydroids by nudibranchs.
The researchers believe that this occurs because the combination of the hydroid and plankton gives the nudibranch enough energy to grow. It also does not have to expend energy to hunt down plankton when it can have the hydroid do all the work. This makes the nudibranchs a kleptopredator, which combines kleptoparasite, taking something another animal has killed, and direct predation, eating the animal.
While this may seem unfair for the hydroids, the researchers believe that this actually also benefits the hydroids. They believe that because the nudibranchs prefer to wait for hydroids to eat plankton before killing them, this prevents many hydroids from being killed. The nudibranchs get their energy need from this combination kill and do not have to reduce the hydroid population any further.
These new insights into nudibranch behavior are important because it informs us about different methods employed by animals to survive. The more we understand about animal behavior, the easier it becomes to find them and uncover new species. We also can potentially use animal behaviors to inform how we create things as humans. Many of the shipbuilding or airplane building techniques are sometimes informed by avian or sea creatures. There are even trains that have been inspired by the beak of birds, which is used to minimize the effects of pressure build up through tunnels and such.