Meanings of many invertebrates in English

The unequivocal identification of PUFA biosynthetic pathways in many invertebrates is complicated by the presence of other organisms within them.

And we are told that these indicate "valuable internal decay" and are also a habitat themselves for many invertebrates, or the insect world.

Mucopolysaccharides (mucus) are produced by many invertebrates and have the potential to be an important source of organic carbon and nitrogen to sediment microorganisms.