Okay, the user wants me to translate "chemical signal" into Japanese. Let me check the rules again. The first rule says to translate all content into Japanese. The second rule states that if the content is already in Japanese, leave it as is. The third rule is to provide only the translation without any explanations.
So, "chemical signal" is in English, so I need to translate it. The correct Japanese term for "chemical signal" would be "化学信号" (かがくしんごう). I should make sure there's no existing Japanese text that needs to be left unchanged. Since the input is in English, I proceed with the translation. No explanations are needed, just the translated term. Let me confirm once more that there's no ambiguity here. Yep, "chemical signal" directly translates to "化学信号". Alright, that's the answer.