This is caused by an unidentified, possibly species-specific factor, emitted into the water by growing tadpoles.
(This; is caused; by an unidentified, possibly species-specific factor) (an unidentified, possibly species-specific factor; emitted; by growing tadpoles)
This an unidentified, possibly species-specific factor
is caused emitted
by an unidentified, possibly species-specific factor
by growing tadpoles