Step 1Cut 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 2Combine 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.