We need information on Sea Slugs (Hares)

December 18, 1998
From: Jim Fitzpatrick

We are a group of children attending the Santa Barbara Montessori School (amazingly enough it's in Santa Barbara, California) and we have some basic questions about sea slugs (hares)...
the books we've been using seem to have little information on how sea slugs reproduce, can you give us some more information on their reproduction? Are they ovoviviparous? Egg ribbons?

By what means do they react to stimuli? Do they have a specialized nervous system, or would you characterize them as having a simple nervous system, and if so then how do they use that system to react to stimuli?

We have a bunch of other questions that we could ask, but we'll wait and see if these questions are too demanding.

It's Wednesday here, but we're figuring it's already Thursday where you are, so you'd better hurry up with your answers 'cause you're already a day behind!

By the way, Rincon has been overhead for the past six days, perfect conditions, and just about ideal west by northwest swell direction.

Thanks!

Jim Fitzpatrick (and students)

nosewriter@aol.com

Fitzpatrick, J., 1998 (Dec 18) We need information on Sea Slugs (Hares). [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/402

Dear Jim (and class),
If you have a look through the Sea Slug Forum you will find quite a bit on Sea Hares and other sea slugs. If you look at the GENERAL TOPICS list there are a number of entries on Sea Hares and eggs. Each page has a series of messages which are worth looking through for more information. If you go to the SPECIES LIST, all the species listed in the Order Anaspidea are Sea Hares.

For a more specialised search click on the "Search the Forum" button on the right side of the yellow panel at the top of your message and type in a word such as "mating" or "eggs" and it will list all the pages with those words.

To answer your specific questions:
1. Sea slugs are hermaphrodite, with both male and female reproductive organs. They don't self-fertilise and need a partner to mate. In some groups, including the Sea Hares you can sometimes find a string of animals forming a mating chain.
2. Sea slugs lay eggs in a jelly-like mass, often arranged in a spiral, or in the case of most Sea Hares a long tangled string. The eggs either hatch as free swimming larvae or as small crawling juveniles. Amongst those with free swimmimg larvae most spend between a few days and about a month living and feeding in the plankton before settling on to the substrate and turning into a crawling slug. Other species have larvae which only spend a short time in the plankton and don't feed until they settle and metamorphose inot a slug.
3. Sea Hares have a relatively simple nervous system but it is complex enough to have become the favorite laboratory animal amongst scientists studying how our brain works, how memory amd learning occur. Over 25,000 Californian Sea Hares are bred in captivity each year for this research.
Instead of having a single control centre (brain) in their nervous system, they have the nerve cells grouped into a number of centres (ganglia). Because the cells are large and brightly coloured, each individual cell can be mapped and its activity monitored. In this way ground-breaking research on how memory and learning occur is being undertaken. Because they have much fewer nerve cells in Sea Hares, such studies are much easier to understand than if they tried to work with our much more complicated brain.
4. Sea Slugs react to stimuli like most animals. They can feel things with all parts of their body, touch things with their oral tentacles and edge of head and they can smell chemicals in the water with their oral tentacles and rhinophores which both have nerve receptors. They are sensitive to light but their eyes, although very obvious, are unlikely to be able to see images. They seem to be able to sense light and dark and shadows passing over them.

I hope these answers help.

Best wishes,
Bill Rudman.

Rudman, W.B., 1998 (Dec 18). Comment on We need information on Sea Slugs (Hares) by Jim Fitzpatrick. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/402

Factsheet

What are Sea Hares?

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