sentences:  This increases its usefulness as a valuable model organism for studying the evolution of innate immunity.The sequencing also revealed that while some genes were thought to be limited to vertebrates, there were also innovations that have previously never been seen outside the chordate classification, such as immune transcription factors PU.1 and SPIB.The gonads of both male and female sea urchins, usually called sea urchin roe or corals, are culinary delicacies in many parts of the world.