Imagine you were hired by a pharmaceutical company to create membranes for genetically engineered animals that are different from all previous life forms found on earth. You need to choose an epithelium optimized for an animal that lives in a sterile aquarium. The animal has no gastrointestinal tract, so absorbs all nutrients from the fluid surrounding it. The fluid surrounding the animal is different from the blood of the animal. The best tissue to use for the most superficial layer of the skin would be