Range Minimu Query: Given an array A[1,n] of n ordered objects (such as numbers), a Range Minimum Query (or RMQ) from i to j asks for the position of a minimum element in the sub-array A[i,j]. RMQs can be used to solve the lowest common ancestor problem.
The reasons that we do not eat or recommend shellfish are very similar. Shellfish are bottom feeders and feed on parasites and dead skin, many times from dead animals. They do not have appropriate digestive and filter systems to purify toxins and parasites from their body and flesh.
Shellfish such as crab and lobster do not have fins or scales and are therefore prohibited for human consumption under biblical dietary laws. However, shellfish is a multi-billion dollar business and eating such aquatic life considered a delicacy in most parts of the world.