( They ( mainly ( ( ( eat ( aquatic plants ) ) -LRB- ) 74 ) ) )
(ROOT (FRAG (NP (PRP They)) (VP (ADVP (RB mainly)) (VBD eat) (NP (JJ aquatic) (NNS plants)) (-LRB- -LRB-) (PP (NN 74)))))
They mainly eat aquatic plants (74
(ROOT (S (NP (DT The) (NN heterotroph)) (VP (VBZ eats) (NP (UCP (ADJP (JJ only)) (CC or) (ADVP (RB mainly))) (NNS plants))) (. .)))