Several years ago, divers exploring the western coast of Norway encountered something mysterious that baffled them, and they could not explain it at the time, a huge bubble more than a meter wide, hovering in place between the sea floor and the surface, and a dark line crossed it from the center, but the rest of the mass was almost transparent and empty. It is quite a feature.

It was simply a lump of viscous liquid, and nearly 100 sightings of similar bubbles have been reported around Norway and the Mediterranean since 1985, but these mysterious gelatinous masses have been difficult to classify scientifically.

Thanks to a citizens' scientific campaign that lasted for a year, and after a new DNA analysis, researchers finally identified these bubbles as egg sacs of a common squid called the Southern Shortfin Squid (Illex coindetii), found in the Mediterranean and on both sides of the North Atlantic Ocean.

A dark line cuts through the center, but the rest of the body was translucent (Scientific Reports - open access)

According to a new study published March 30 in the journal Scientific Reports, each bubble may contain hundreds of thousands of tiny squid eggs coated in a mass of mucus that slowly dissolves.

First time

Although scientists have known the southern shortfin squid for more than 180 years, and have extensively defined and classified species around the Mediterranean and both sides of the Atlantic, this is the first time they have encountered these squid egg sacs.

"We also saw what's inside the ball," said lead author Haldis Ringfold, director of the Norwegian marine zoology organization Sea Snack Norway, in a report by Live Science. "We also saw what's inside the ball, showing squid embryos in 4 different stages." .

"We were able to see how the egg sac actually changes the consistency, from solid and transparent to torn and opaque, as the embryos develop," he added.

Southern Shortfin Squid belongs to a common group of squid containing 3 subspecies, 11 genera and more than 20 species found all over the world, and they are caught on a large scale for use as food.

"During reproduction, females in this group produce large leukocytes - or egg lumps - made from their mucus to keep their embryos afloat and safe from predators. However, viewing these egg clumps is rare, and lumps of some species have not been seen," Ringfold explains. Before.

Scientific campaign for citizens

When viewing Norwegian bubbles made international news several years ago, some researchers suspected that the balls were clumps of eggs, but without analyzing the DNA of the bubble's tissue, there was no way to show the type of squid that originally created them.

So, Ringfold and his colleagues launched a citizen science campaign that encouraged divers to collect small tissue samples from water near Norway.

Nearly 100 observations of similar bubbles have been reported around Norway and the Mediterranean since 1985 (Scientific Reports - open access)

And in 2019, divers brought tissue samples from 4 separate points, and collected them in small plastic bottles as they were stored in household refrigerators (the tissue did not appear to damage egg clumps in any way, according to the study).

The samples included both the viscous body of the bullae, as well as embryos at various stages of development.

The researchers wrote that tissue DNA analysis confirmed that the four samples contained southern shortfin squid.

The researchers were unable to confirm that all of the 100 bubbles observed belonged to the same type of squid, however, given that all samples were very similar in shape and size, it is likely that many of them were made by the same squid, the team concluded.

As for the strange dark line that runs through many bubbles, according to the researchers, this could be ink that was released when the eggs were fertilized.

Southern Shortfin Squid belongs to a common group of squid containing three subspecies, 11 genera and more than 20 species (Wikipedia)

The researchers wrote in their study that "bubbles that contain ink or without ink may be a result of being in different stages of maturity, where balls containing ink are newly produced, but after a while, when the embryos begin to grow, the whole ball, including That line, it will start to unravel. "

The research team noted that the streak could also be a kind of camouflage mechanism, which aims to mimic large fish and scare away potential predators.