Why do crustaceans and insects look so much alike? There has got to be some kind of connection...?

Answer 1

They both belong to the phylum Arthropoda meaning jointed appendages. They both contain an open circulatory system made up of a dorsal tubular heart and blood called hemolymph. Their dorsal brain is connected to a ventral running nerve cord. Their bodies are segmented: insects containing 3 (head, thorax, and abdomen), while the crustaceans contain 2 (head and cephalothorax). Their mouth parts are also jointed and flexible. As far as their origins there embryos developed mush in the same way. They are duterostomes meaning there anus developed before their mouths. They contain bilateral symmetry and reproduce sexually.

Answer 2

Yes, indeed they share a phylogenetic (ancestor-descendant) relationship.
Both insects and crustaceans are arthropods, and their similarities include having an exoskeleton (made of chitin in insects, and reinforced with calcium carbonate in many crustaceans), paired articulated limbs, and body divided in sectors called "tagmata". The body parts of Insects are 3: head, thorax and abdomen; and those of crustaceans are head, pereion (=thorax) and pleon (=abdomen). Although most crustaceans are aquatic and most insects are terrestrial, there are some terrestrial crustaceans that look like insects, such as the pill bugs or sow bugs (there are also aquatic insects, of course, such as the Dytiscid water beetles).
Some phylogenetic schemes place the crustaceans and insects together because they have mandibles. Yet other hypotheses indicate that Crustaceans are more closely related to the Chelicerates (spiders, scorpions and the like) than to the Insects, because of the possession of birramous limbs (with two "branches"), whereas the Insects have primitively unirramous limbs.

More on their relationships:
http://www.mcz.harvard.edu/Departments/InvertZoo/pdf_files/Giribet%20et%20al.%202001b.pdf
http://www.amonline.net.au/pdf/publications/cladistics2000.pdf

Answer 3

SOME crustaceans look like SOME insects. It seems to me that you have a lot more to learn about insects and crustaceans.

Answer 4

They are members of the largest phylum, Arthropoda which includes insects and crustaceans. Organization into phylums implies genetic/evolutionary relationships, but it isn't necessarily the case with all members.

Answer 5

Well, they're the same phylum... Arthropoda consists of crustaceans, hexapods (insects), myriapods (millipedes, centipedes), and Chelicerata (spiders etc...)

Answer 6

You're right. They do look alike. So much so that I won't eat shrimp. I call them 'sea roaches'. Yuck.

Answer 7

Because they both have exoskeletons

Answer 8

well they are related. good eyes!!