For some blenny fish species, looks can be deceiving

DNA analysis is changing the way we classify fish. A recent Smithsonian study of fish thought to be three species of Starksia blennies were actually ten different species, seven of which were hiding in plain sight.

Some fish aren’t what they appear to be. Scientists from the Smithsonian Institution collected three different species of the fish genus Starksia, commonly known as Starksia blennies, from several locations across the Caribbean. But when they ran DNA analysis on the specimens, they found that some fish thought to be the same species showed different DNA results. So they took a closer look, not just at the DNA results but also the appearance of the fish. The results were surprising: what they thought were three fish species turned out to be ten, with seven of them being species new to science.

Starksia blennies are small, colorful marine fish about two inches long. They’re found in shallow to moderately-deep – about 100 feet – waters, among rock and coral reefs of the western Atlantic and eastern Pacific oceans. There are currently 21 recognized species in the Starksia genus, but that’s probably about to change!

A Smooth-eye Blenny (Starksia atlantica), trying hard to blend into the brown coral next to it. Photo Credit: Peter de Graaf

Traditionally, a species is classified based on its appearance, or morphology. Dr. Carole Baldwin and her team at the Smithsonian Institution had been trying to match larval reef fish with adults of the same species. Since the appearance of young and adult fish can be quite different, they decided to use a technique called DNA barcoding. This method of DNA analysis involves sequencing a short segment of DNA from a standard part of the genome in all animals. Each species should have its own signature.

However, they found different DNA barcodes for some adult fish thought to be of the same species. Could it be that there were several different species masquerading as one?

DNA analysis alone is not enough to taxonomically describe a species; there have to be morphological differences in an animal to support that claim. Tipped off by the unusual DNA results, the team carefully examined specimens of the three Starksia blenny species they had caught at different locations in the Caribbean, looking at features such as color, pigmentation patterns on the scales, and numbers of fin rays.

The result of their investigation, recently published in the journal Zookeys, showed that what they thought were three Starksia blenny species – smooth-eye blenny (Starksia atlantica), blackcheek blenny (Starksia lepicoelia), and chessboard blenny (Starksia sluiteri) – were actually ten different species, with seven of them fitting the criteria for new species. In describing the new proposed species, the Smithsonian team made a detailed inventory of all features on the fish’s body, such as the body shape, unusual features, number of rays on the fins, scale pigment patterns, and so on. Each of the species appeared to have a geographically restricted range, perhaps indicating that they evolved from a common ancestor in isolation at those locations.

Peter de Graaf, a wildlife photographer living in Bonaire, generously shared photos of two blenny species in the Smithsonian study with EarthSky.

A Chessboard Blenny (Starksia sluiteri) seeking refuge in a coral grotto in the reef at Bonaire. Photo Credit: Peter de Graaf

So, let’s take a test! Peter identified the fish he photographed based on their original species name. See if you can figure out the “new” species name for the fish in Peter’s photographs by comparing them with specimen images used by the Smithsonian team.

(1) Compare Peter’s photos of the smooth-eye blenny (Starksia atlantica) with the photos in Dr. Baldwin’s paper. What do you think is its “new” species name?
(a) Starksia atlantica
(b) Starksia sangreyae
(c) Starksia springeri
(d) Starksia sp. (Saba)

A beautiful Smooth-eye Blenny (Starksia atlantica) in the Bonaire coral reefs. Photo Credit: Peter de Graaf

(2) Check out Peter’s photos of the chessboard blenny (Starksia sluiteri) with the specimen images from the Smithsonian team. What is the “new” species name for Peter’s chessboard blenny?
(a) Starksia greenfieldi
(b) Starksia langi
(c) Starksia sluiteri
(d) Starksia fasciata

A Chessboard Blenny (Starksia sluiteri), stretched out to show off its exquisite body patterns. Photo Credit: Peter de Graaf

How well did the species you identified in Peter’s photos from Bonaire match up with the species found by the Smithsonian team at the same vicinity? Take a look at the map in Dr. Baldwin’s paper. Bonaire is located at the bottom of the map, flagged by a red symbol and a green symbol side by side that mark the location of two of the newly-discovered blenny species (see the map legend). Are they the same ones you identified in Peter’s photos? Pretty cool, isn’t it?!

The Smithsonian team believes that the use of DNA barcoding and morphological studies, together, will uncover even more new fish species. Said Dr. Baldwin, in a press release issued by the Smithsonian Institution,

DNA analysis has offered science a great new resource to examine old questions. This discovery is a perfect example of how DNA barcoding is illuminating species that we’ve missed before, particularly small cryptic reef fishes like Starksia blennies. We don’t know where we stand in terms of understanding species diversity, and our work suggests that current concepts may be surprisingly incomplete.

This was certainly a surprising outcome for what started out as routine DNA barcoding studies! Three species of Starksia blennies, collected from several regions in the Caribbean, turned out to be ten species, with seven of them possibly being new. Furthermore, these new species appear to be confined to specific geographical locations in the Caribbean, suggesting that they evolved in isolation from a common ancestor. The innovative technique of using traditional morphological studies of a fish specimen along with DNA barcoding has the potential for uncovering many more new species, broadening the notion of what we call biodiversity.

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