Around the time school begins again in North America, thousands of invasive jellyfish-like sea creatures in the Baltic Sea will be eating their children.
A parent who has just spent a holiday in close quarters with their children might comprehend the motivation behind this, but it is beyond mere annoyance that propels the Baltic jellies to their yearly jelly babies buffet.
The prolific comb jelly depends on its offspring not much as a means to grow its next generation but for the next meal, aiding the species to travel through nutrient-poor bodies of water across the Earth.
The success behind these distinctive animals' capacity to expand has been quite a mystery. Blooms of offspring have been witnessed in bodies of water across the globe that seem to lack the nutrients required to aid survival.
According to a paper published in "Communications Biology," in the western Baltic Sea, comb jellies do this practice when food is scarce. This unearthed fact may explain the triumph of this invasive species and may help the design strategies in controlling its prevalence.
Also known as sea walnut, it is native to the western Atlantic's coastal waters, but in recent years, this gelatinous invertebrate has crossed the waters of Eurasia.
Cannibalism is the key to the species' skill to cross new environs.
"We had this species arrive in the Black Sea in the 80s, and it arrived in the Caspian Sea in the 90s," according to Jamileh Javidpour, lead author of the research and a marine biology professor at the University of Southern Denmark.
Comb jellies are in fact not jellyfish but are among a different group of animals, called Ctenophora which swim through small, hair-like projections called cilia.
The warty comb jelly has been the root of chaos in European waters wherein it consumes fish larvae along with the prey of fish. Indeed, the species resulted in a collapse of the Black Sea's fisheries in the late 1980s.
"The Black Sea just became this gelatinous ocean," said an ecologist at Max Planck Institute for the Science of Human History, Dr. Thomas Larsen.
Jamileh Javidpour, a marine ecologist at the University of Southern Denmark in Odense, and her colleagues accumulated adult and larval comb jellies from a cove of the Baltic Sea called Kiel Fjord in August and September 2008, prior and following the jelly population's slump.
The researchers in the lab chemically marked larvae with a rare type, or isotope, of nitrogen, and positioned the young jellies with starving adults. Thirty-six hours passed and those adults had larger amounts of the isotope than adults provided a normal diet. This is a sign that the sea animals consumed the larvae, the team reported May 7 in "Communications Biology."
Cannibalism may contribute to solving the conundrum of why these sea creatures produce numerous larvae in the late summer despite the fact that they would unlikely thrive in the upcoming winter. The research team surmised that consuming huge numbers of larvae at the climax of the Baltic summer supplies adults with approximately 2-3 weeks of nourishment.
