Open the clams and mussels in a pan over the heat, remove them from their shells, leaving just a few in the shells.
Sauté the garlic and chili pepper in the extra virgin olive oil in a frying pan until golden, then add the shellfish, the chopped squids and shelled prawns. Sauté for a few minutes and then add the pureed tomato and salt to taste.
In the meantime, cook the pasta in plenty of boiling, salted water. Drain al dente. Toss the pasta with the seafood sauce and taste, add salt as needed.
Serve the pasta garnished with the herb pesto made by pulsing parsley, basil, virgin olive oil and a pinch of salt in a blender.