Their species have the similiar evolutionary developments to creatures with bioluminescence like cephalopods and jellyfish. Meaning they are partly made out of water. Their cells developed a harder layer of skin around their bodies after leaving the waters. Seeing as they are unable to move around outside aquatic enviroments they were given bio-engineered enviromental suits. The spider-like legs would help them maintain balance and long arms to grab hold of objects. The Yu'Jal's elongated can reach the height of a human adult.