Have you found any Star Jelly?

While walking a field in the Roncombe Valley looking for its wildlife potential last week I was puzzled to find lumps of clear jelly around the edge of a recently created pond.

Each lump was about the size of my fist, almost completely clear but with faint grey rounded marks through the mass. I wondered if it was frog spawn that hadn’t been fertilised, but the truth turned out to be more macabre.

Have you ever wondered how a small frog can produce a mass of spawn up to ten times larger than itself? Like all vertebrates, female frogs develop their eggs in ovaries, but they are very small with a thin outer coat. When the eggs are released into a pond this outer layer absorbs water and swells up to form a clear jelly. This jelly is buoyant and lifts the spawn to the surface where it can be warmed by the sun.

Female frogs begin producing their eggs from October and through the winter. This makes them even more nutritious for predators such as grass snakes and herons. The problem for the predator is that a lunch mouthful that is full of eggs will swell to a huge lump when they are exposed to the stomach juices. Such a mass would be a potentially gut bursting problem for a grass snake, and it could make a heron or crow very uncomfortable. Scientists are not sure what triggers the response, possibly the jelly has a nasty taste, but the predator regurgitates the remains of the egg mass usually with the nutritious eggs dissolved.

If it drops in a wet place such as the edge of a pond or dewy grass, it finishes swelling to what is effectively a mass of frog spawn but without the ovules having been fertilised. It soon breaks down and so disappears as mysteriously as it appears.

The sudden magical appearance of these jelly masses obviously puzzled people in the past. There are records dating back to the 14^th century. One folk explanation was that they were the remains of falling stars and they became known as star jelly. Its magical appearance and disappearance suggested healing powers and it was used to treat abscesses.

There have been cases where the jelly is found hanging in trees, regurgitated by a bird sitting higher in the tree or even flying over.

The lumps in Roncombe were an unfortunate sign for the frogs, but the good news is that the area has a frog population that has colonised the new pond, and there are other animals playing their part in the web of nature feeding on the frogs. Another exciting find in the next field was a harvest mouse nest and this has been added to the records of the Devon Mammal Group’s Harvest Mouse Project which is cataloguing the population of this delightful but increasingly rare mammal. Nature is thriving in the Roncombe Valley.