member vs pleopod

member and pleopod both are nouns.

Word	Noun	Adjective	Verb	Adverb
member	Yes	No	No	No
pleopod	Yes	No	No	No

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

member: an external body part that projects from the body
pleopod: one of the paired abdominal appendages of certain aquatic crustaceans that function primarily for carrying the eggs in females and are usually adapted for swimming

Other hyponyms of member include chelicera, mouthpart, fang, chela, claw, nipper, pincer, parapodium, fin, swimmeret, limb, dactyl, digit.

member (noun)	pleopod (noun)
an external body part that projects from the body	one of the paired abdominal appendages of certain aquatic crustaceans that function primarily for carrying the eggs in females and are usually adapted for swimming
the male sex organ
an organization that is a member of another organization (especially a state that belongs to a group of nations)
one of the persons who compose a social group (especially individuals who have joined and participate in a group organization)
anything that belongs to a set or class