Preheat oven to 350 degrees. In a small bowl combine tomato ketchup, 2 tablespoons lemon juice, lemon zest, horseradish, worchestershire and parsley. Set aside in refrigerator. In a ziploc bag, add shrimp, salt and pepper, 3 tablespoons olive oil, remaining lemon juice and the crushed red pepper. Seal and refrigerate for one hour. Slice the baquette into 1/2 inch slices on the diagonal. Place bread slices in a ziploc bag. Add olive oil to coat. Place bread on a baking sheet and cook until slightly brown, about 5 minutes. Remove and set aside. In a medium skillet set on high, saute' the shrimp unitl pink, about 3 minutes. Remove form heat and set aside to cool. To assemble - Top each crostini bread slice with about 1 tablespoon of the ketchuo mixture. Add a few leaves of arugula. Top each slice with a piece of shrimp. Serve.