Prof. Dr. Rahul Mehrotra, Thailand
Info
Tenellia viei (Mehrotra, Caballer & Chavanich, 2020)
Corals are under pressure to survive in several ways: rising water temperatures, discharge of wastewater into the oceans, explosive reproduction of crown-of-thorns starfish and feeding pressure from very small polyp eaters that are often very difficult to recognize in the sea, for example the genus Phestilla, of which there are - as of 2024 - 11 coral-eating species.
Phestilla chaetopterana appears to have lost this association, and now lives inside the tube of the annelid Chaetopterus sp.
These small nudibranchs often specialize on certain types of stony corals, from Acropora to Pavona species.
As part of his doctoral research, Dr. Rahul Mehrotra discovered and described a new species of coral-feeding nudibranch, Tenellia viei, in Lighthouse Bay, Koh Tao, Thailand, in 2019, which specializes on coral polyps of Pavona explanulata.
Rahul and his co-authors write in their article "A new species of coral-feeding nudibranch (Mollusca: Gastropoda) from the Gulf of Thailand." that the easiest way to find the very small snails is to look for the feeding scars and ice marks on the corals, and then for the individuals that left them behind.
Another amazing feature that makes Phestilla vie hard to observe is the fact that the snail "steals" Symbiodinium (the single-celled symbiotic algae, also called zooxanthellae, that provide the coral with energy) and integrates them into its body instead of digesting them - a process called "kleptosymbiosis".
By ingesting the zooxanthellae, the predatory snail can adapt almost perfectly to the color of the coral host.
The 80-120 eggs per clutch contrast strongly with the dense zooxanthellate coral tissue, ranging from white to extremely pale yellow.
Although Phestilla vie is a coral eater, it does not appear to be a major threat to coral populations as it has never been observed to eat all of the coral and no overpopulations or outbreaks have been documented to date.
The animals rarely consumed more than an estimated 10% of the surface area of a coral colony.
Dr. Spencer Arnold reported from Hong Kong that Phestilla vie also attacks the stony coral Pavona decussata, but it remains to be seen whether other Pavona species may also be affected
Recommendation:
In order to prevent the introduction of this and other Phestilla species, purchased Pavona corals should be briefly soaked in fresh water before use so that possible parasites can be rinsed off the corals.
A short bath in fresh water does not harm Pavona stony corals.
Coloration
The body coloration of the snail is generally translucent white to pale yellow.
This coloration is most noticeable over the pericardium and along the midline of the dorsum, where it repeatedly enlarges and contracts along the length of the animal, each enlargement coinciding with a small hump.
There is pale brown pigmentation on both of these humps, extending laterally along the body wall and between the rows of cerata.
The foot is very translucent with clearly visible internal organs and foot margins white to pale yellow.
Oral veil and oral tentacles are translucent white with brown markings that range from ¼ to ¾ the length of the oral tentacles and submarginal along the anterior margin.
These markings may form a reticulate pattern of lines, or a thick continuous line extending posteriorly on the outside of each rhizophore before joining the brown pigment along the dorsum.
A conspicuous one of the oral veil is pigment-free and usually extends to the rhinophores, which may or may not be brown pigmented at the base surrounding the base. Rhinophores translucent white throughout
The cerata is translucent white with brown pigmentation.
The brown coloration is much more pronounced along the ventral region and the dorsal coloration varies depending on the density of the cells of the dinoflagellate
The apices are colorless but opaque, sometimes with a yellowish tint.
Etymology:
The new species was named after local nudibranch enthusiast and scientist Vie Panyarachun, who is known for his extensive contributions to the recording and maintenance of marine snails from Thai waters.
We would like to thank Dr. Rahul Mehrotra, Reef Biology Research Group, Department of Marine Science, Faculty of Science, Chulalongkorn University, Bangkok, Thailand, who kindly provided us with the photos of Phestilla vie.
Dr. Mehrotra was able to describe four other nudibranchs in addition to Tenellia viei:
Armina occulta Mehrotra, Caballer & Chavanich, 2017
Armina scotti Mehrotra, Caballer & Chavanich, 2017
Unidentia aliciae Korshunova, Mehrotra, Arnold, Lundin, Picton & Martynov, 2019
Phestilla arnoldi More
Literature reference:
Mehrotra R., Arnold S., Chavanich S., Hoeksema B. & Caballer M. , 2020.
A new species of coral-feeding nudibranch (Mollusca: Gastropoda) from the Gulf of Thailand
DOI:10.1007/s12526-020-01050-2.
Marine Biodiversity 50:36
Synonymised names
Phestilla viei Mehrotra, Caballer & Chavanich, 2020 · unaccepted > superseded combination
Corals are under pressure to survive in several ways: rising water temperatures, discharge of wastewater into the oceans, explosive reproduction of crown-of-thorns starfish and feeding pressure from very small polyp eaters that are often very difficult to recognize in the sea, for example the genus Phestilla, of which there are - as of 2024 - 11 coral-eating species.
Phestilla chaetopterana appears to have lost this association, and now lives inside the tube of the annelid Chaetopterus sp.
These small nudibranchs often specialize on certain types of stony corals, from Acropora to Pavona species.
As part of his doctoral research, Dr. Rahul Mehrotra discovered and described a new species of coral-feeding nudibranch, Tenellia viei, in Lighthouse Bay, Koh Tao, Thailand, in 2019, which specializes on coral polyps of Pavona explanulata.
Rahul and his co-authors write in their article "A new species of coral-feeding nudibranch (Mollusca: Gastropoda) from the Gulf of Thailand." that the easiest way to find the very small snails is to look for the feeding scars and ice marks on the corals, and then for the individuals that left them behind.
Another amazing feature that makes Phestilla vie hard to observe is the fact that the snail "steals" Symbiodinium (the single-celled symbiotic algae, also called zooxanthellae, that provide the coral with energy) and integrates them into its body instead of digesting them - a process called "kleptosymbiosis".
By ingesting the zooxanthellae, the predatory snail can adapt almost perfectly to the color of the coral host.
The 80-120 eggs per clutch contrast strongly with the dense zooxanthellate coral tissue, ranging from white to extremely pale yellow.
Although Phestilla vie is a coral eater, it does not appear to be a major threat to coral populations as it has never been observed to eat all of the coral and no overpopulations or outbreaks have been documented to date.
The animals rarely consumed more than an estimated 10% of the surface area of a coral colony.
Dr. Spencer Arnold reported from Hong Kong that Phestilla vie also attacks the stony coral Pavona decussata, but it remains to be seen whether other Pavona species may also be affected
Recommendation:
In order to prevent the introduction of this and other Phestilla species, purchased Pavona corals should be briefly soaked in fresh water before use so that possible parasites can be rinsed off the corals.
A short bath in fresh water does not harm Pavona stony corals.
Coloration
The body coloration of the snail is generally translucent white to pale yellow.
This coloration is most noticeable over the pericardium and along the midline of the dorsum, where it repeatedly enlarges and contracts along the length of the animal, each enlargement coinciding with a small hump.
There is pale brown pigmentation on both of these humps, extending laterally along the body wall and between the rows of cerata.
The foot is very translucent with clearly visible internal organs and foot margins white to pale yellow.
Oral veil and oral tentacles are translucent white with brown markings that range from ¼ to ¾ the length of the oral tentacles and submarginal along the anterior margin.
These markings may form a reticulate pattern of lines, or a thick continuous line extending posteriorly on the outside of each rhizophore before joining the brown pigment along the dorsum.
A conspicuous one of the oral veil is pigment-free and usually extends to the rhinophores, which may or may not be brown pigmented at the base surrounding the base. Rhinophores translucent white throughout
The cerata is translucent white with brown pigmentation.
The brown coloration is much more pronounced along the ventral region and the dorsal coloration varies depending on the density of the cells of the dinoflagellate
The apices are colorless but opaque, sometimes with a yellowish tint.
Etymology:
The new species was named after local nudibranch enthusiast and scientist Vie Panyarachun, who is known for his extensive contributions to the recording and maintenance of marine snails from Thai waters.
We would like to thank Dr. Rahul Mehrotra, Reef Biology Research Group, Department of Marine Science, Faculty of Science, Chulalongkorn University, Bangkok, Thailand, who kindly provided us with the photos of Phestilla vie.
Dr. Mehrotra was able to describe four other nudibranchs in addition to Tenellia viei:
Armina occulta Mehrotra, Caballer & Chavanich, 2017
Armina scotti Mehrotra, Caballer & Chavanich, 2017
Unidentia aliciae Korshunova, Mehrotra, Arnold, Lundin, Picton & Martynov, 2019
Phestilla arnoldi More
Literature reference:
Mehrotra R., Arnold S., Chavanich S., Hoeksema B. & Caballer M. , 2020.
A new species of coral-feeding nudibranch (Mollusca: Gastropoda) from the Gulf of Thailand
DOI:10.1007/s12526-020-01050-2.
Marine Biodiversity 50:36
Synonymised names
Phestilla viei Mehrotra, Caballer & Chavanich, 2020 · unaccepted > superseded combination
