1 in 5,000 north Atlantic lobsters are born bright blue.

Lobsters, like snails and spiders, have blue blood due to the presence of haemocyanin which contains copper (in contrast, vertebrates and many other animals have red blood from iron-rich haemoglobin). Lobsters possess a green hepatopancreas, called the tomalley by chefs, which functions as the animal’s liver and pancreas.

Lobsters of the family Nephropidae are similar in overall form to a number of other related groups. They differ from freshwater crayfish in lacking the joint between the last two segments of the thorax, and they differ from the reef lobsters of the family Enoplometopidae in having full claws on the first three pairs of legs, rather than just one. The distinctions from fossil families such as Chilenophoberidae are based on the pattern of grooves on the carapace.