Chop the shrimp into 1/2 inch pieces and transfer to a bowl. Set aside. In a small bowl, whisk together the lemon, lime and orange juice to combine. Pour 1/2 cup of the citrus juice over the shrimp and toss to combine. Allow the shrimp to marinade in the juice for 15 minutes. Add the tomato, jalapeño, jicama (or apple), cilantro and red onion to the shrimp. Toss the ingredients to combine and allow to marinade for an additional 10 minutes. Stir in the avocado and remaining juices. Season the ceviche with salt and pepper, to taste. Serve immediately with tortilla chips, if desired.