Complex sentence: While the lion's mane jellyfish generally use their stinging tentacles to prey, sea anemones can capture their tentacles, which then become tangled, torn apart and consumed.
Split into simpler sentences: While the lion's mane jellyfish generally use their stinging tentacles to prey, there is one dangerous variable that works against them. Sea anemones can capture their tentacles, which then become hopelessly tangled, torn apart and consumed.