Spa treatment for whale sharks
With all the crazy $h!t going on in the world, I opted to have my first post for 2021 to be more on the fun side of science, and what better way to do this than to learn about how whale sharks get spa treatment by cleaner fish.
When I'm snorkeling or diving, one of my favorite things to do is to sit and watch the drama going on at a "cleaning station" where cleaner fishes slither around their "clients" or the two chase each other around. Cleaner fishes usually camp out in certain areas of a habitat like reefs, and they're visited by other creatures ranging from small fish to sharks to get all cleaned up. The cleaner fish remove and feed on parasites, dead/injured tissue and mucus on the surfaces of their clients. They can even go into the mouths of large predatory fish to do some dental cleaning - what trust! It's actually intriguing to think about how this mutually beneficial relationship evolved. These cleaning interactions can play an important role in maintaining healthy communities. In Gonzalo Araujo and colleagues' work*, they report on the first observation of the whale shark Rhincodon typus getting a cleaning by two cleaner fish species - a blue-streak cleaner wrasse (Labroides dimidiatus) and a moon wrasse (Thalassoma lunare) - at Oslob, Cebu. This is also only the second documentation of a whale shark-cleaner interaction in the world. The other record was from the Eastern Tropical Pacific at Malpelo Island, Colombia between a whale shark and the king angelfish Holacanthus passer.
Supplementary video in Araujo et al. 2020. Journal of Fish Biology, 97(4). https://onlinelibrary.wiley.com/doi/abs/10.1111/jfb.14464: "Whale shark getting cleaned by the moon wrasse Thalassoma lunare in Oslob, Philippines. The cleaner fish targeted a scar below the first dorsal fin on the left flank."
They were able to observe a total of 36 whale-shark cleaner fish interactions while they were doing photo-ID surveys of whale sharks between May and September 2019. Fourteen identified and one unidentified individual whale sharks were involved in these interactions, and almost all were with the blue-streak cleaner wrasse (only one with the moon wrasse). It appeared that these were more opportunistic rather than planned since these have not been observed in other sites where both whale sharks and cleaner fishes occur, plus the whale sharks were moving at their typical swimming speed rather than stopping/slowing down during the cleaning event. The authors recommend further investigating this rare whale shark-cleaner fish behavior.
*Araujo, G., Miranda, J.A., Allen, H.L., Labaja, J., Snow, S., Ponzo, A. and Legaspi, C.G., 2020. Whale sharks Rhincodon typus get cleaned by the blue‐streak cleaner wrasse Labroides dimidiatus and the moon wrasse Thalassoma lunare in the Philippines. Journal of Fish Biology, 97(4), pp.1247-1251.