The Cryptic Life of Ghost Pipefishes (Full Article)Author: Francesco Ricciardi
Even marine scientists still very poorly know the biology of the ghost pipefishes. Juveniles are planktonic and almost transparent; they move with the oceanic currents and if they survive long enough to find a proper reef, they settle in the proximity of crinoids, gorgonians, or other favorable areas. After that they find a partner, reproduce, and vanish again. Most likely they die after the release of the larvae. Unlike as in their relatives, the seahorses and pipefishes, the female of the ghost pipefishes, carrying the eggs in a brood sac formed by two fused pelvic fins until the hatching and the release of the small embryos in the open sea, is bigger than the male..
The coloring of ghost pipefshes can vary between individuals; the ornate ghost pipefish, for example, is able to change its coloration depending on the area it occupies. It’s not a sudden change like the change we can observe in octopuses and cuttlefishes; the change may take some hours. When found in pairs, ornate ghost pipefish males and females always have the same color. It appears that they make an extra effort to assume the same color as the partner; the advantage of this behavior is not yet very clear to us. In other species, as in the robust ghost pipefish, on the contrary, it is quite common to find a pair with different body colors.
Ghost pipefishes use their capacity for camouflage as both a defensive measure (to avoid being spotted by predators) and as a way to easily approach their prey. Their ability to catch their food (normally tiny crustaceans, like small shrimps or other invertebrates) is based on the anatomy of the mouth, which is tube-shaped as in seahorses and pipefish, with some muscles that can increase the diameter of the tube very quickly, creating a depression that basically “sucks” the prey directly inside the mouth of the fish.
Juvenile ghost pipefishes also have revealed an unusual “sexual plasticity.” Male individuals placed into an aquarium with other males have demonstrated the ability to change sex. It is possible that juvenile ghost pipefishes can change not only sex but also color, depending on the surrounding environment and the presence of potential partners. We don’t know yet whether this kind of hermaphroditism is common in nature or happens only in aquaria.
Called “ghosts” for their ability to appear and disappear, these fishes are not very common, but they appear for short periods of time and become relatively easy to spot if you know how to look for them. Like every other proper ghost, they don’t like to show up for everyone.
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