Tiny light-emitting organs line the plainfin midshipman’s body like the shiny buttons on a naval uniform jacket. Photo: Phil Edgell
“Midshipman” – the term for a naval officer – is a weird name for a fish. But look closer at this fish’s tiny light-emitting organs (photophores) and it starts to make sense. The plainfin midshipman (Porichthys notatus) has up to 700 photophores lining its body, with most of them (550 photophores) on its underside. They glow like the shiny buttons on a midshipman’s uniform jacket.
The ability of this fish to glow (bioluminesce) is just one of the many reasons why Catherine P., content developer at the Vancouver Aquarium Marine Science Centre, nominated it for February’s Staff Pick of the Month. Although she admits that this fish is “boring-looking,” she goes on to say that “some of the most boring-looking fishes have some of the most interesting life stories.”
Back to those glowing “buttons.” A plainfin midshipman uses bioluminescence to protect itself. As Catherine explains, “Scientists think that the rows of photophores on a midshipman’s underside disguises its outline when it lights up in the dark, helping it hide from predators coming from below.” While this might be a good strategy for plainfin midshipman along California’s coast, the ones off British Columbia’s coast don’t actually emit any light because they don’t eat the particular type of prey (called ostracod) that contains the chemical needed to bioluminesce. Catherine says, “Instead, they rely on their ability to blend in or bury to hide from both prey and predators.”
The plainfin midshipman is not always easy to spot in one of the smaller exhibits in the Treasures of the BC Coast gallery, but when Catherine sees one she says, “It makes me smile and think of all its wonderful adaptations that help it make a living.”
Written by Karen Horak, writer-editor, content and digital experience at the Vancouver Aquarium.