sea spider vs arthropod

sea spider and arthropod both are nouns.

Word	Noun	Adjective	Verb	Adverb
sea spider	Yes	No	No	No
arthropod	Yes	No	No	No

As nouns, arthropod is a hypernym of sea spider; that is, arthropod is a word with a broader meaning than sea spider:

sea spider: any of various small spiderlike marine arthropods having small thin bodies and long slender legs
arthropod: invertebrate having jointed limbs and a segmented body with an exoskeleton made of chitin

sea spider (noun)	arthropod (noun)
any of various small spiderlike marine arthropods having small thin bodies and long slender legs	invertebrate having jointed limbs and a segmented body with an exoskeleton made of chitin