Step 1 Cut each cucumber segment in half on the diagonal. Using a melon baller or small spoon, make a small cavity by scooping out and discarding seeds from each piece. Cover with plastic wrap and refrigerate until needed.
Step 2 Combine the crab, mango, lime juice, oil and half the peanuts in a small bowl. Season to taste with salt and pepper.
Step 3Season each cucumber cavity with salt and pepper and fill with crab-mango mixture, compressing to hold the mixture together. (Cover and refrigerate if not using right away.)
Step 4Garnish each hors d'oeuvre with chopped mint and a cilantro leaf and sprinkle the remaining peanuts on top. Serve immediately.