The royal gramma (Gramma loreto) is a species of fish found in the Grammatidae family. They are a ray-finned fish more commonly known as basslets, and known for their vibrant colours. The royal gramma in particular is sometimes called the fairy basslet.
Appearance and key features
The royal gramma is a small fish, growing up to 8cm in length. You can’t miss them thanks to their incredibly bright two-tone body. The front half is typically a deep purple or violet, with the back half a bright, golden yellow.
If you look closely, you’ll also see a dark line running through each eye and a small black dot at the top of the dorsal fin. Royal grammas have specialised pigment cells in their skin that produce the vivid colours, called chromatophores. They reflect light and help to scatter the light waves to create an iridescent sheen.
While royal grammas display little sexual dimorphism, which means there’s a difference between males and females, there are some slight differences. Adult males are usually larger than their female counterparts and they may show a richer or deeper purple. Adult males might also have a slightly longer pelvic fin.
Habitat and range
The royal gramma lives in the tropical western Atlantic, including the Caribbean and parts of Central and South America. They can be found amongst the coral reefs, typically staying close to rock walls, caves and crevices,. This is because royal gramma fish prefer shelter.
Royal grammas can be solitary and territorial, defending a small area that contains ideal hiding spots. However, they are known for gathering in social groups led by a dominant males with multiple females.
Behaviour
Royal gramma fish will stake out a crevice or rock overhang and rarely stray from it. They can be aggressive towards other cave-dwelling fish or species with similar body shapes, but they will ignore other peaceful species like clownfish and gobies.
Royal grammas are known for swimming or hanging upside down. This is because they like to keep their bellies closest to the nearest solid surface, which could be the ceiling of a cave or rock overhang. This helps them to feel more secure and safe.
It’s thought that royal gramma fish play an important role in their ecosystem, as they pick off ectoparasites off the bodies of larger passing reef fish as well as eating zooplankton.
See royal gramma for yourself at Bristol Aquarium
At Bristol Aquarium we’re home to a vast range of tropical species, including the royal gramma. Our Coral Seas exhibit is the perfect place to see lionfish, moray eels, clownfish and pufferfish, alongside the vibrant royal gramma. Book your tickets online today!