In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: As anticipated , animals exhibited a progressive increase in levodopa - induced motor fluctuations , dyskinesia and wearing - off , that correlated with the duration of levodopa therapy .
### Output Text:
As anticipated , animals exhibited a progressive increase in <span class="chemical">levodopa</span> - induced motor fluctuations , dyskinesia and wearing - off , that correlated with the duration of <span class="chemical">levodopa</span> therapy . 