Humpback whales (Megaptera novaeangliae) generally do not travel alone. In addition to its group, the large cetacean generally hosts dozens of remoras. Also known as sucker fish, these evolutionary marvels of Echeneidae the family hitches rides on whales in order to feed on sea lice and other crustaceans that also inhabit the skin of marine mammals. To accomplish this, the remora has a distinctive oval dorsal fin that functions as an adapted suction cup. The ridges of the fin’s flexible membrane raise and lower as needed to generate adhesive force, allowing it to either stick to the whale or release and swim independently as needed.
Although its physical mechanisms are generally understood, marine biologists know less about the remora’s daily life alongside its patron whale. To gain insight into this symbiotic relationship, marine biologists from Griffith University in Australia decided to tag humpback whales with underwater cameras during their seasonal migration along the country’s east coast. So far, they have learned not only the daily habits of the remora, but also the fish’s usual menu as well as how some whales perceive their tagalongs.
Olaf Meynecke recorded several videos from cameras attached to humpback whales. Credit: Griffith University
“I think one of the biggest surprises when we studied the videos captured from our tags was the ability of the remoras to move freely and continue to return to the body of the whale, even during very rapid ascents to the surface and immediately after breaching and the whale’s return to the water,” marine scientist Olaf Meynecke said in a statement.
This feat even extended to occasions when a whale made a rapid ascent and breached the surface of the ocean. Immediately after the whale returned underwater, remoras were seen readily reattaching to their humpback host.
“It was amazing to see how fast and agile they were on several different whale rides,” he added.
Remoras also appear to have adapted to the difficult hydrodynamics of whale travel. Technically, they don’t create suction. Instead, their dorsal plates generate a vacuum effect allowing them to essentially adhere to the whale’s skin.
Remora species like the whale sucker (Remora australis) are also not picky eaters. When sea lice and other parasites are not present, they often begin to nibble on the whales’ skin. But despite their mutual relationships, whales don’t seem to be the biggest fans.
“Even though they are probably beneficial to the whales because they eat other host organisms such as sea lice, the whales don’t seem to like their presence,” Meynecke said. “We’ve watched whales observe them, perform multiple breaches, and then check again.”
Despite this glimpse into the behind-the-scenes data gleaned from their whale cameras, Meynecke’s team still has much to learn about the remora. For example, they still don’t know whether fish accompany whales as they travel south toward Antarctica. Then there is the question of its overall life cycle. Remora spawn along the East Australian Current, where small larvae develop into miniature sucker fish. These young remoras would need to quickly find a host to survive.
“This could suggest that the timing of reproduction could be linked to the whale migration cycle,” Meynecke said.
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