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Anemonefish can distinguish between anemone species

In a new study led by the Okinawa Institute of Science and Technology (OIST) and Academia Sinica in Taiwan, researchers have illuminated the intricate and selective relationships between anemonefish and their sea anemone hosts in the Mediterranean. 

Specific habitat choices

The findings revealed that some anemonefish species, such as the yellow-tail anemonefish (Amphiprion clarkii), are adaptable generalists inhabiting various sea anemones. 

Other anemonefish, like the tomato clownfish (Amphiprion frenatus), are specialists that coexist exclusively with the bubble-tip sea anemone (Entacmaea quadricolor). 

This specificity in habitat choice has puzzled scientists, partly due to the sparse knowledge on the genetic diversity of giant sea anemones.

Bubble-tip giant sea anemone

The study aimed to shed light on the genetic diversity within the bubble-tip giant sea anemone (Entacmaea quadricolor) population in Japan.

The experts discovered that anemonefish possess a sophisticated ability to distinguish between different populations of giant sea anemones – a task that proves challenging for humans without genetic analysis. 

Genetically distinct lineages 

The research unveiled a significant genetic variety within the bubble-tip sea anemone specimens, identifying four distinct genetic lineages. 

“Within the bubble-tip giant sea anemone species (Entacmaea) our phylogenetic tree reveals the presence of two main groups with a common ancestor in Okinawa,” explained lead author Rio Kashimoto, a PhD student in marine genomics at OIST.

“The first group consists of three categories of descendants, A, B, and C, which are associated with the yellow-tail anemonefish as the host species. The second group, category D, is associated with the tomato anemonefish as the host species.” 

Anemonefish recognize sea anemone lineages

To test if anemonefish could differentiate between the two groups in a controlled environment, the researchers conducted experiments using a large tank at the OIST Marine Science Station. 

“In lab experiments we observed that in most cases each anemonefish species can recognize the sea anemone lineage it is associated with in the wild, despite the fact the clades look the same,” said Vincent Laudet, the leader of the the Marine Eco-Evo-Devo Unit at OIST.

“We also observed that these lineages do not express the same genes, especially genes for toxicity and color – sea anemones use venom for prey capture, digestion and defense, and they probably do not have the same odor, which may be a key part in how anemonefish recognize different lineages.”

Cryptic sea anemone species 

The study not only challenges our previous understanding of the symbiotic relationships between anemonefish and sea anemones but also suggests the existence of two cryptic species within what was thought to be a single species of the bubble-tip sea anemone. 

“Therefore, anemonefish are able to identify distinct lineages of sea anemones that we humans can’t distinguish,” said Laudet.

“We believe that these two main groups represent two cryptic species – species that we cannot identify by looking at them, but they are genetically distinct.”

The findings underscore the marine biodiversity present in Okinawa and Japan and highlight the complex ecological interactions that have yet to be fully understood.

The study is published in the journal Current Biology.


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