IT came with the hot weather, but it's not the sort of jelly that goes well with ice-cream.

An invasion of jellyfish has arrived in Scotland's seas and coastal waters thanks to a sudden surge in sea temperature this summer.

Hundreds of thousands of the marine animals have been sighted from Orkney to Ayrshire in swarms which have blanketed beaches wherever they are washed ashore.

The Marine Conservation ­Society (MCS) has received more than 70 reports of thousands of jellyfish from around Scotland in the last two days.

Yesterday, a large group or bloom made landfall on the beach at Saltcoats, North Ayrshire, and people heading to the seaside in the coming days have been warned to be on their guard as some species can sting.

There are two main types of jellyfish in Scottish waters – Moon jellyfish, such as those that appeared at Saltcoats, and the larger Lion's Mane, which have distinctive trailing tentacles capable of inflicting severe pain on contact.

Professor Andrew Brierley, of the Scottish Oceans Institute at the University of St Andrews, said that Lion's Mane should be given a wide berth if spotted among the waves.

He said: "Moon jellyfish are more or less harmless, but Lion's Mane have a nasty sting.

"The problem is that they have very long tentacles, and it's easy to swim inadvertently through tentacles without being aware that the jellyfish is there."

"The abundance changes from year to year. Baby jellyfish hatch in the early spring and grow rapidly in summer to these big adults."

The upsurge in jellyfish is thought to be down to the late cold snap this year, which kept their numbers low by minimising conditions the exotic creatures need to thrive.

The rapid rise in temperatures last month has brought about a plankton boom, the main food source for jellyfish, and populations have exploded to take advantage of the bonanza.

Jellyfish will gather together in huge numbers if food is plentiful and the sea currents are not strong enough to scatter them.

The MCS runs a survey each year to monitor their numbers, and has had reports of significant blooms at Rothesay, Argyll, Lochbroom, near Ullapool, ­Maidenhead Bay and Culzean Bay in Ayrshire and Strathlene Beach near Buckie.

Swarms have also been spotted in Helensburgh, while large numbers of Lion's Mane jellyfish have been observed floating in Carradale Bay, Argyll, and at Aberdeen beach, Ullapool and Portmahomack in the Highlands.

A huge stranding of hundreds of thousands belonging to a species known as By-the-Wind-Sailors occurred at the Bay of Skaill, Orkney, on Monday.

Dr Peter Richardson, MCS Biodiversity Programme Manager and jellyfish expert, said: "The scarcity of jellyfish reports before June was unusual and could well be linked to the exceptionally cold spring. However, as our waters warmed, sightings of jellyfish increased, with moon jellyfish reported in large numbers and blooms of Lion's Mane jellies around Scotland."

While jellyfish stings are ­painful, the effects are not usually serious or long-lasting. Doctors advise prompt treatment, including dousing any stings with vinegar.

Professor George Crooks ­Medical Director at NHS 24 said "If you are unfortunate enough to be stung, the most important thing to remember is not to rinse the wound in fresh water and not to rub it or apply ice – even if the area feels hot.

"You should try to soak the affected are in vinegar for 15 to 30 minutes and if vinegar is not available, use alcohol or sea water."

l Public notices have been displayed around Loch Eck in Argyll and Bute to warn people against swimming or water sports following the discovery of blue-green algae after two dogs died.

It can cause upset stomachs or skin problems and people visiting the loch are being protect themselves and their animals from coming into contact with it.