Sparring aquarium creature turns out to be a new ‘miniature’ species. See the fish

For nearly 20 years, a “rosy” creature has been a regular part of the aquarium trade. And while experts are familiar with the tiny animal, it has never been officially identified — until now.

Scientists examined a “batch of aquarium fishes” collected from a small pool in Myanmar, according to a study published Nov. 23 in the Raffles Bulletin of Zoology. That’s when they realized they were actually studying a new species: Physoschistura mango.

Using DNA from the specimens and pre-existing sequences from aquarium collections, experts said they determined that the new species matched sequences of the previously unidentified “rosy loach.”

The study’s co-authors examined the eight specimens from Myanmar plus four additional specimens from the aquarium trade with an unknown origin to identify the new species.

Rosy loaches are “sexually dichromatic,” so males and females have different color patterns, researchers said. Males are pale yellow to light orange and have a “solid dark brown to black” stripe on the side of their bodies. Females are light creamy brown to white colored and have “a series of small spots or irregular markings.”

Photos show differences between male and female specimens of the new species.

Male specimens have a dark stripe along the sides of their bodies.
Male specimens have a dark stripe along the sides of their bodies.
Female specimens have “irregular” spots and markings on their heads and bodies.
Female specimens have “irregular” spots and markings on their heads and bodies.

Previously, the loaches had been mistaken for another species, Physoschistura brunneana, and another genus, Petruichthys brevis, but researchers said they distinguished the new species by its “smaller overall body size” and “different” coloring and pattern.

The new species qualifies as a “miniature species,” with specimens’ total length — which measures from their snout to the longest tip of their tail-like fin — ranging from approximately 0.9 inches to 1.1 inches, according to scientists.

The small fish are “moderately elongate,” and they have “large” eyes and a “short” snout, the study said. Most of their body is covered by round scales. They have an “arched” mouth, and their lower lip is thicker than their upper lip.

Males have a longer, pointier, more rigid and wider pectoral fin than females, according to scientists. There are also differences between the male and female swimbladder — which is the organ that helps the creatures with buoyancy.

Researchers named the new species after mango trees, known as Mangifera indica, because of the “orange-yellow flesh of its fruit.”

The new species hasn’t been observed in the wild, but scientists said that in aquariums, the fish swim ”in the lower part” of the water between “short periods of rest” on the ground. Adult males have been seen chasing each other and sparring “aggressively” by nipping at each other’s bodies and fins.

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