Re: What is the mantle cavity in the barnacle used for?

Hello Adriana!

What an interesting question! Let's see if I can come up with a good answer for you.

A barnacle's mantle is a thin layer of tissue that lines the inside of the animal's shell. The space between the mantle and the rest of the body parts is called the mantle cavity. In the drawing below, the mantle cavity is indicated by the black area:

The mantle cavity is just that -- a cavity, or empty space. However, it plays a crucial role in barnacle reproduction. You see, barnacles are what we zoologists call hermaphrodites. That means they have both male and female reproductive structures. If you take a closer look at the drawing above, you'll see that this barnacle has both an ovary (female reproductive organ) and a penis (male reproductive organ).

Barnacles reproduce by copulation. In other words, a barnacle functioning as a male will use its penis to introduce sperm into the mantle cavity of a barnacle that is functioning as a female (remember, barnacles are both male and female at the same time). The eggs are fertilized and develop within the mantle cavity of the "female". Thus, a barnacle's mantle cavity serves as a brood chamber, or nursery for the embryos. The eggs hatch when the developing embryos have reached a stage called a nauplius larva, then they are released from their mother's mantle cavity to continue growing in the plankton.

I hope this answers your question. The information and the drawing I included in this answer were taken from the following textbook:

Ruppert and Barnes, 1994. Invertebrate Zoology. Saunders College Publishing.

Allison J. Gong
Mad Scientist