Chemolithotrophs (sulfur/iron oxidizers), cave fungi, detritivores processing allochthonous organic material entering through cracks
Troglobites (obligate cave dwellers): isopods, amphipods, cave spiders. Troglophiles occasionally enter; trogloxenes (bats) import organic matter
Cavefish lose eyes (costly to maintain in darkness) and pigment. Enhanced lateral line senses water pressure waves. Regressive evolution via relaxed selection + pleiotropy