Scientists Identify Stunning New Tropical Reef Fish That Shimmers Like An Opal
A small, strikingly beautiful damselfish that is new to science was identified on a coral reef on Madagascar’s northeastern coast
Christmas arrived early in 2018 for reef enthusiasts and marine fish keepers when it was announced that an unknown fish species had been discovered on northeastern Madagascar. This fish was discovered in relatively shallow waters in a reef near a city, and was mostly white in color — yet had never been seen before. Further, which genus this beautiful fish should be placed into confounded the experts, which added to the buzz of excitement surrounding it.
The species, which is new to science, was described and formally named Corazon’s damsel, Pomacentrus vatosoa, by ichthyologist Benjamin Frable, Collection Manager of Fishes at Scripps Institution of Oceanography, and Yi-Kai Tea, an expert on coral reef fishes and a PhD candidate at the University of Sydney studying systematic ichthyology, which is the science of classifying and naming new species, and understanding how they fit into the broader context of life.
Damselfishes are a diverse group of small- to medium-sized fishes that occur throughout the tropics and subtropics.
The newly-described damselfish has a striking pearlescent-white body color with two prominent black spots — one behind the pectoral fin near the middle of its body, and the second saddled across the upper edge of its tail where its fin connects to its body. It also has a sooty black stripe through its eyes that extends upward to its smokey grey dorsal fin that’s edged with electric royal blue. Although a common marking in butterflyfishes, this eye stripe is an extremely rare marking in damselfishes, according to Blue Ocean S.A.R.L., whose divers collected the fish (more here).
The fish’s conspicuous coloring and markings are what first caught the keen eyes of Brian Maravilla, a commercial diver working for the sustainable, ornamental fish export company based in Nosy Faho, a coral reef off the northeastern coast of Madagascar, in early December 2018.
The overall pattern of this mysterious fish’s markings somewhat resembled those of Stark’s damselfish, Chrysiptera starki, which lives on reefs in the far distant Coral Sea, suggesting it may be a new species of Chrysiptera. But because he’d never seen it before, Mr. Maravilla captured it and asked Mr. Tea to identify it.
“When I first received this fish, I was almost certain it was a new damselfish from the genus Chrysiptera,” Mr. Tea said in email. “This genus of damselfish is well known for harbouring some of the most beautiful species, and often they can be pearlescent such as with this one.”
Mr. Tea consulted with a number of fish experts around the world, and they all agreed that this was definitely something new, probably a new Chrysiptera species.
“I like teasing my fellow ‘fish nerds’ (as we call them) with photos of interesting fishes on my personal social media page, so I shared a photo of one just to get a vibe from the community. Often, great ideas get bounced around in such discussions,” Mr. Tea explained in email. “Everyone seemed to think it was a Chrysiptera, too.”
Having recently collaborated on another project with Dr. Frable, Mr. Tea and Dr. Frable again teamed up to work on identifying this mysterious fish. Mr. Tea used molecular techniques to investigate the fish’s genetic relationships and Dr. Frable examined the fish’s morphology — the detailed structure of its teeth, bones, scales, and its body shape.
This fish’s genus seemed to be a forgone conclusion, only requiring scientific confirmation. But this fish had a little surprise in store for all the experts: after examining its genetics and morphology, Dr. Frable and Mr. Tea concluded that this fish is a new species in the damselfish genus Pomacentrus, not Chrysiptera, as they originally suspected.
“It seemed to match the characteristics of Pomacentrus well, except that Pomacentrus species usually have a notch in the bones below their eye which is weak/absent in this species (which led us astray earlier),” Mr. Tea explained in email. “It was far too dissimilar from that species, based on molecular and morphological details. So we dug a little deeper, and examined it a little closer, and we confirmed its placement in the genus Pomacentrus based on details in morphology.”
“Interestingly, its most closely related ‘sister species’ is also found in Madagascar, on the opposite side of the island,” Dr. Frable said. “Unfortunately we haven’t been able to sample it for comparative genetic data, but that is something we can look forward to in the future.”
Dr. Frable and Mr. Tea named the fish “Corazon’s damsel” in honor of Corazon Sibayan Shutman who provided four specimens for this study.
“Incidentally, Corazon is Spanish for ‘heart’, which is vaguely reminiscent of where that big black spot is situated on the new species (if you use a little bit of imagination),” Mr. Tea pointed out.
In recognition of the fish’s opalescent or pearlescent qualities, they gave it the specific name, “vatosoa”, which means “beautiful stone”, a Malagasy word sometimes used in reference to opals or pearls.
Although this new species was particularly exciting for the fish community, in the past year alone, collection staff have described five new fish species — three of which he worked on, according to Dr. Frable. He added: “There are usually between 300–500 new fish species described worldwide every year.”
“There have been 138 new species described in 2019 thus far; Corazon’s Damsel marks 139.”
Are Dr. Frable and Mr. Tea worried this fish will be over-exploited by the aquarium fish trade?
“The aquarium fish hobby can be a very sustainable trade if proper collection methods are employed, and permits and quotas are adhered to. It becomes unsustainable when bad practices such as cyanide fishing or dynamite fishing are employed,” Mr. Tea replied. “But this is not the case here.”
“Small fisheries that provide income for the local community are not a major threat to coral reefs, unlike anthropogenic causes such as climate change and habitat destruction. It is important that we connect with these communities, as they can often provide us with a wealth of knowledge and experience. Bridging this gap between science and community can really help move us along in understanding our Earth’s biodiversity.”
What impressed the researchers most about this fish?
“I think the most exciting aspect about this description is that Corazon’s Damsel doesn’t look very similar to any previously known fish species,” Dr. Frable went on. “It was also collected near a city and at a relatively accessible depth of 45–60 feet. Most new reef fish discoveries are coming from much deeper — the mesophotic reef — below 200 feet.”
Because this fish is so accessible to divers, and because the waters where it was found had been extensively surveyed in the past, how on earth did this distinctive fish manage to stay undetected for so long?
“Coral reefs are some of the most diverse ecosystems in the world, second only to tropical rainforests. Both are incredibly diverse, and the number of species discovered living within these realms are very underestimated,” Mr. Tea replied in email. “However, unlike terrestrial ecosystems, coral reefs are much harder to explore, and you can begin to imagine why when you consider the nuances like the need for diving, the amount of time allowed underwater, the habitat complexity in which little things hide in. But all things considered, it is quite incredible that a beautiful new species like this would remain undiscovered until now, which gave even us quite a surprise!”
“The fact that a new species with distinctive coloration can go unnoticed is a stark reminder that there’s still much to learn about coral reef diversity and our oceans as a whole.”
Benjamin W. Frable, and Yi-Kai Tea (2019). A New Species of Damselfish (Teleostei: Pomacentridae: Pomacentrus) from Nosy Faho, Madagascar, Copeia, 107(2):323–331 | doi: 10.1643/CI-19–221
Originally published at Forbes on 28 June 2019.