A natural polymer found in the exoskeletons of crustaceans can keep your car cleaner. Researchers in the School of Fashion and Textiles at RMIT are using the biopolymer, found in the exoskeletons of crustaceans such as crabs and shrimp, to coat the 100% polyester fabric used in automobiles. Combining fragrance oils with the polymer, which has the ability to form an antimicrobial film, creates a durable, fragrant finish in the fabric.

Based on the prefix “exo-,” and prior knowledge about crabs and shrimp, an exoskeleton is probably: ______________.