Animated cartoons can be a fun way to learn interesting facts about the animal kingdom. Pixar's 2003 classic Finding Nemo introduced many children and adults to marine biology for the first time.
Among other things, it described the symbiotic relationship between clownfish and their hosts, sea anemones or actinia: the anemone's sting protects the fish from predators, and the fish in turn helps the actinia keep clean.
A recent study has expanded the understanding of this partnership. Researchers from Osaka Metropolitan University in Japan have observed that clownfish, also known as amphiprion, actively share food with their hosts, strengthening their mutuallistic relationship.
Mutualism is a widespread form of mutualistic cohabitation where the presence of a partner becomes a prerequisite for the existence of each species.
The scientists' findings, published in the journal Scientific Reports, reveal a previously unrecognized advantage of this unique marine cohabitation.
Symbiotic relationship
Survival in the natural world often depends on cooperation. Many species have evolved close relationships classified as mutuallistic, commensalistic (one benefits while the other remains unaffected), or parasitic (one benefits at the expense of the other). Nutrient exchange is a major factor in
symbiosis and occurs in a wide range of species.
For example,
ant ants protect certain trees from herbivores by feeding on their nectar. Wolves provide carcasses to scavengers such as
crows, which in turn learn to follow wolf howls for food. Another well-documented case of gobies and shrimp demonstrates the complexity of interspecific interactions.
Photo: elementy.ru
The shrimp digs a burrow in the sand to shelter itself and the goby. However, since the shrimp has poor vision, it relies on the goby for protection. When a predator approaches, the goby warns the shrimp with a flick of its tail, prompting it to retreat into the burrow. In addition, the shrimp receives nutrients from the goby's waste products, further strengthening their bond.
Special connection
One of the longest-studied marine symbioses is that between sea anemones and clownfish. Although coral reefs are home to a variety of species, they are nutrient-poor, making symbiotic interactions essential for survival.
Sea anemones provide the clownfish with shelter and a safe place to spawn thanks to their stinging tentacles. In turn, the clownfish remove waste, ingest harmful invertebrates, and deposit nutrient-rich feces that benefit the anemones. Until recently, it was thought that their contribution was limited to this, until researchers noticed that amphiprions were deliberately feeding their hosts.
For the first time, scientists have recorded clownfish taking pieces of mollusks, holding them in their mouths and attaching them to the tentacles of their host anemone. This behavior allowed the researchers to hypothesize that clownfish are actively feeding their hosts and prompted further study of the factors that influence this behavior and its effect on anemones.
Fishing for new discoveries
The research team conducted fieldwork at Morode Beach, Ainan, southern Japan, to study the clark's clown amphiprion (Amphiprion clarkii) and its host, the sea anemone Actinia bubblegum (Entacmaea quadricolor).
Observations have shown that clownfish selectively consume small animal foods such as krill, clams, squid and fish, and green macroalgae, leaving larger pieces of animal food for their actinia hosts.
They avoided eating or offering brown macroalgae and sponges, which appeared to be unsuitable as food for either species. At first the fish ate to satisfy their own hunger and then increased the amount of food to feed their hosts as well.
"We also confirmed that feeding clownfish directly increases the growth rate of sea anemones," graduate student Kobayashi explained in a press release. "It is known that in other clownfish species, the number of eggs laid increases when the hosts become larger. For clownfish that cannot leave their sea anemone, feeding their hosts is extremely important and ultimately benefits themselves."
This study represents a rare example of symbiosis with direct food provisioning. Understanding this behavior not only advances ecological and biological research, but also the development of conservation strategies for endangered species.