polychaete vs bloodworm

polychaete and bloodworm both are nouns.

Word	Noun	Adjective	Verb	Adverb
polychaete	Yes	No	No	No
bloodworm	Yes	No	No	No

As nouns, bloodworm is a hyponym of polychaete; that is, bloodworm is a word with a more specific, narrower meaning than polychaete:

polychaete: chiefly marine annelids possessing both sexes and having paired appendages (parapodia) bearing bristles
bloodworm: a segmented marine worm with bright red body; often used for bait

Other hyponyms of polychaete include lobworm, lug, lugworm, sea mouse.

polychaete (noun)	bloodworm (noun)
chiefly marine annelids possessing both sexes and having paired appendages (parapodia) bearing bristles	a segmented marine worm with bright red body; often used for bait