Sponges do not undergo metamorphosis in the traditional sense. Unlike insects, amphibians, or many marine invertebrates, sponges lack a larval stage in their life cycle.

Here's how sponge reproduction and development work:

* Sexual Reproduction: Most sponges reproduce sexually, releasing sperm and eggs into the water. Fertilization occurs externally, forming a zygote.

* Direct Development: The zygote develops directly into a small sponge without going through a free-swimming larval stage. This means there's no dramatic transformation like we see in other animals.

Therefore, sponges don't exhibit metamorphosis. Their development is direct, with the zygote progressing directly to a miniature version of the adult sponge.

However, some sponges do undergo a process called gemmulation, which is a form of asexual reproduction and might be mistaken for metamorphosis by some. Gemmulation involves the formation of internal buds (gemmules) that can survive harsh conditions like drought or freezing. These gemmules can later develop into new sponges when conditions are favorable.

While gemmulation allows for a form of regeneration, it's not considered true metamorphosis as it lacks a larval stage and doesn't involve a fundamental change in body structure.