A developmental chimera: co-option of appendage, secretory and myogenic programs underlies spider venom gland evolution
This study reveals that the spider venom gland evolved as a developmental chimera through the hierarchical co-option of three ancestral programs: an appendage-patterning gene (*Distal-less*) establishing spatial coordinates, a transcription factor (*sage*) that represses a latent neural program to maintain secretory identity, and a myogenic factor (*sum-1*) that drives muscle-mediated metabolic support, thereby illustrating how complex organs arise by integrating distinct tissue modules.