Researchers have discovered that Psolus fabricii, a cold-water sea cucumber, produces severed tissues that survive indefinitely in ordinary seawater. These tissues, named LiPfe (Living immortal P. fabricii explants), challenge biological limits. Scientists made the accidental finding when amputated tube feet and tentacles continued living without special conditions, unlike typical separated tissues.

LiPfe explants actively reorganize after separation. They shrink initially by 23%, then regrow to original size within months. The tissues absorb dissolved amino acids directly from seawater, fueling survival. Over a year, they transform into translucent orbs with red cores, dismantling muscle tissue while expanding connective tissue to maintain basic functions without developing organs.

This tissue immortality appears unique to P. fabricii. Unlike HeLa cells, LiPfe represents structured animal tissue with natural immortality. The discovery offers researchers an experimental model avoiding ethical concerns of live animal testing. These "zombie tissues" challenge fundamental perceptions of life while providing new possibilities for biological research.