Dear Rajesh,

This is a Sea Hare rather than a nudibranch. If you follow the links on the Sea Hare Fact Sheet you will find quite a bit of background information on the family. I have labelled your animal so you can get a basic idea of its anatomy. The purplish colour at the back is the remains of the purple ink many sea hares produce.

It is a species of Aplysia but I am afraid its not possible to identify it to species in this state.

Best wishes,
Bill Rudman

Dear Kate,

I am not an expert on keeping algae in aquaria, but as a general rule, brown and red algae in small aquarium systems where the water is not continually changed are not a good idea - especially if the algae are being eaten alive.

Best wishes,
Bill Rudman

Dear Kate,

Your photos aren't that clear but it looks like you have a sea hare. Sea hares do eat algae, but they are pretty choosy on which species they eat. Just because they were washed up at the same time as a lot of algae it doesn't necessarily mean they algae they washed up with is their food. Often it just means that the algae and the sea hares were caught up in the same storm.  One fairly common algae that most species of Sea Hare like is the green algae Ulva, which is commonly called 'sea lettuce' because it looks quite like a leaf of lettuce from the garden.

However most algae is difficult to keep alive in aquaria, and as they die they exude very poisonous chemicals into the aquarium water. Unless you can find some Ulva to try - which appears to be aquarium safe - my advice would be to put the Sea Hare back in a  rock pool at the beach

Best wishes,
Bill Rudman

Dear Georgia,

You have certainly seen a Sea Hare, but it won't be Aplysia brasiliana, which is found only in the Atlantic. There are a number of species of Aplysia found in New South Wales. I suspect the two most likely ones you ave seen are Aplysia dactylomela and Aplysia sydneyensis. If you have a look at the Sea Hares Fact Sheet you will find links to a lot of general information on these fascinating animals.

Best wishes,
Bill Rudman

Dear Ute,

The strange spiral 'thing' is its penis. Usually it is sitting in a sac inside the body and is only everted like this when it is about to mate. Unfortunately they sometimes do this when they are 'sick'. I hope in the time it has taken me to answer your message it has recovered rather than died.

If you look carefully at your photo just where the penis attached to the side of the head you should be able to see a line running diagonally up to just below the rhight rhinophore or head tentacle. This is the sperm grrove which carries sperm from the reproductive opening at the front of the mantle cavity forward to the penis. You will see a better picture on the Sea Hare head Fact Sheet.

Best wishes,
Bill Rudman

Dear Hugues,

Thanks for this. I'm afraid I cant get a good enough look at the slug to identify it. I'm surprised there is not some sign of purple ink. Perhaps the animal was already dead when the crab began to eat it?

Best wishes,
Bill Rudman

Thanks Jeff,
Bill Rudman

Dear Alicia,
I am sure someone with local knowldege of the area should be able to ientify your Sea Hares
Best wishes,
Bill Rudman

Dear John,
Species of Sea Hares are found throughout the world, often in large numbers. In Florida, the two common species are Aplysia brasiliana and Aplysia morio. The strange thing is that it is only the Western Australian species, Aplysia gigantea, which has been accused of poisoning dogs. There have been a few accounts of Dolabella auricularia causing food poisoning, but it is suspected that it the result of some posionous algae in the internal organs. In general, Sea Hares are quite harmless, and are often favourite items in 'touch tanks' for children in aquarium displays. In our litigious world I am sure if there was any evidence of them causing harm to kids, someone would have sued by now. I don't know how many I have picked up alive without gloves or how many students over the years I have been with who have picked them up, but except for the special cases mentioned above, I would have no hesitation in saying they are harmless.
Best wishes,
Bill Rudman

Dear Rick.
I am pretty sure this is the tangled egg ribbon of a Sea Hare. Have a look at photos on the Forum of the egg ribbon of Aplysia juliana [see #10759]. I can't see enough detail to be sure, but if it is a Sea hare egg ribbon you will see tiny eggs inside the pink cylinder much as in the photos of Aplysia fasciata [see #8159].
Best wishes
Bill Rudman

Dear Krista,
This doesn't sound like mass mortality to me. I'm afraid I can't give you an answer to why they were doing this but I can suggest a few possibilities.
The first possibility is that this has something to do with the heat. As you know we have been having many days over 30 deg C recently and this makes living intertidally a fairly risky business for animals which live there. At first sight, rockpools seem to be a good place to escape from the heat and the possibility of drying out, but unfortunately its not that simple. The water in rockpools heats up at low tide on a hot day. This means that there is less oxygen in the water and it also means that the sea weeds in the pool become quite stressed and can secrete chemicals into the water which are sometimes quite unhealthy for animal life. My first bet would be that the sea hares were finding life in the pools fairly uncomfortable and so were attempting to escape a slow cooking.

Another possibility is that they were responding to their normal biological rhythms or 'biologcial clock'. Many tidepool animals seem to become very active just before the the tide turns. Animals that have been hiding for 3 or 4 hours will suddenly appear and start crawling around. I know of no studies on why they do this but I suspect it is part of an activity rhythm they have which coincides with the return of fresh seawater as the tide returns.

People often make the mistake of thinking that we know everything about the environment. In fact as your strange sea hares show us, we still have a lot to learn.
Best wishes
Bill Rudman

Dear Dunyaporn,
There are certainly species of all that group that live in Thai waters but there are no guarantees that you could find an appropriate number of animals when you needed them. To provide a guaranteed supply of Aplysia for research was the main reason that facilities like the NIH-Aplysia Resource Facility in Miami, Florida were established. [http://www.rsmas.miami.edu/groups/sea-hares/]. They ship more than 25,000 captive bred animals a year to laboratories. I am not an expert in the field of nervous system research but I understand there are problems with using wild-collected animals because they habituate differently to captivity and so it is difficult to have suitable control specimens. It is also difficult to make comparisons between specimens whose history is unknown.

It is probably not possible to import captive bred animals when you return to Thailand so I would think it would be valuable if you were to spend some time before you returned to Thailand learning some basic techniques on keeping and breeding some of these animals in captivity. This would mean that when you returned to Thailand, you could collect some material locally and start your own captive bred colony.
Best wishes
Bill Rudman

Dear Josh,
I guess you want a quick answer. I'm afraid the red tide part of the story is a bit outside my field of expertise other than to say it is caused be microscopic phytoplankton - ie one-celled plants floating in the sea. I've listed a couple of web sites below but there are many
more:
• http://www.marinelab.sarasota.fl.us/~mhenry/WREDTIDE.phtml
• http://www.whoi.edu/redtide/

Sea Hares don't eat phytoplankton - they feed on macroalgae - that is seaweeds attached to the bottom. See Sea Hares Page for links to much more information.

So basically they would have no interest in red tides and in the low oxygen conditions caused by the red tide organisms they would most likely die and their carcases would add to any pollution

Hope that helps
Good Luck with your debate
Bill

Dear Angie,
I'm not sure what question you are trying to answer but I suspect there is no conflict in the information you have found. I have no idea how many eggs a Sunfish lays but I am happy to accept that it 'the most eggs of all fish'. Since Sea Hares are not fish then the number of eggs are Sea Hare lays does not conflict with anything you say about the Sunfish. Sea Hares are specialised snails, which are Molluscs [including, squid, octopus, clams, snails etc, etc]. Sea Hares certainly can lay a lot of eggs - See the earlier message discussing the number of eggs one species of Sea Hare lays.
Best wishes,
Bill Rudman

Dear Dee,
This is a Sea Hare. It is definitely dead and beginning to swell as decomposition occurs. The flap on the back is the mantle, and the hard plate inside is the thin shell. The mantle and shell are usually covered, or partially enclosed by parapodial flaps, but I guess they have partly rotted away. From the lower photo you can see a sort of disc at the back of the foot. This would suggest this is Aplysia juliana, but I can't be 100% sure. If you follow the links indicated you will find planty on the Forum about Sea Hares
Best wishes,
Bill

Dear Pepe,
I suspect if Sea Hares in Mexico were edible then people would already be eating them. Some communities in the Pacific eat Dolabella auricularia, but as you will see if your look at the messages on that page, some cases of poisoning have occurred. In Western Australia, a large Sea Hare Aplysia gigantea has caused the deaths of dogs when they are washed up on beaches, so all things considered I think it would be best to leave them alone. For other information of eating sea slugs, go to the Recipes? Page.
Best wishes,
Bill Rudman

Dear Stephen,
Your question raises the interesting question about whether Sea Hares actually migrate inshore for breeding. Have a look at the Mass Mortality Page for some discussion and links on the topic.
Best wishes,
Bill Rudman

Dear Stephen,
Perhaps you should contact Mónica Medina [details on the Participants Page] who has looked at population genetics in Aplysia californica.

Best wishes,
Bill Rudman

Dear Eric,
Does your genetics study have to be a study of animal behaviour? I thought the relationship between genes and behaviour, at least in humans, was still a field of continuing debate if not open warfare. To attempt to study it amongst invertebrates, whose behaviour we scarcely understand, may be a bit much. I am sure you are aware of the work of the pioneering work of Kandel and many others who have used Aplysia californica to investigate how brains function and 'learn' and cause 'behaviour' but I don't know of any work where the brains of different genetic strains of Aplysia have been compared.

If on the other hand you are interested in any genetic study, and cost is no object, why not look at some of the Sea Hares which are thought to have worldwide distributions. Are they really the same species or not? Take a 'species' that is today found in the Caribbean, the Mediterranean, the Indo-West Pacific and east Pacific. While populations on both sides of the Panama isthmus may still be reproductively viable, the Atlantic and Pacific populations have been isolated for a much longer period. It would certainly be interestng to study.

A few Sea Hares which have very large distributions include:
•Aplysia dactylomela
•Aplysia juliana
•Bursatella leachi
•Stylocheilus striata
•Stylocheilus longicauda

Perhaps you should contact Mónica Medina [details on the Participants Page] who has looked at population genetics in Aplysia californica.

Best wishes,
Bill Rudman

Dear Ray and Danny,
Good question. Have a look at the Sea Hares Page for some general information. Basically they are herbivores, feeding on various sea weeds. They can grow very quickly if conditions are right and there is a species in California called Aplysia vaccaria which can grow to about 1 metre long and can weigh nearly 14kg [approx 30 pounds].

I am not sure where in the world you were fishing, but sometimes storms can wash large numbers of these animals up on to beaches where they unfortunately die. If you look at the page on Aplysia morio you will see there have been a lot of messages from Florida reporting just such a washup.

Now to your male & female question. Like all sea slugs, Sea Hares are hermaphrodites, which means they have fully functional male and female parts. During mating they can act as either the male or the female partner, and sometimes they mate in chains of three or more. When mating in chains the anterior animal acts just as a female and the most posterior animal as a male, but the ones in between act simultaneously as male and female. Have a look at the Sea Hares mating page.

Best wishes,
Bill Rudman

Dear Moira,
When you say you are writing a paper does that mean you are going to publish a research paper or is this for a university assignment?

Normally I would offer to help but I have a huge backlog of questions on the Forum so am reluctant to spend time on someone else's research. Here are a few references worth looking at

• Audesirk, TE (1979) A field study of growth and reproduction in Aplysia californica. Biol. Bull. 157(3): 407-421.
• Bebbington, A., Thompson, TE. (1969) Reproduction in Aplysia (Gastropoda, Opisthobranchia). Malacologia, 9(1): 253.
• Dudek, FE., Soutar, B., Tobe,S S. (1980) Reproduction in Aplysia californica: correlations between egg laying in vivo and egg release in vitro. Can. J. Zool., 58(11): 2163-2166.
• Painter, SD., Chong,MG., Wong,MA., Gray,A., Cormier,JG., Nagle,GT. (1991) Relative contributions of the egg layer and egg cordon to pheromonal attraction and the induction of mating and egg-laying behaviour in Aplysia. Biol. Bull., 181: 81-94.
• Switzer-Dunlap, M., Hadfield, MG., (1979) Reproductive patterns of Hawaiian Aplysiid gastropods. In: Reproductive Ecology of Marine Invertebrates, Belle W. Baruch Library in Marine Science, No 9. (Ed: Stancyk,SE),, 199-210.
• Thompson, TE., Bebbington, A. (1969) Structure and function of the reproductive organs of three species of Aplysia (Gastropoda: Opisthobranchia). Malacologia, 7(2-3): 347-380.
• Susswein, AJ., Markovitch, S., Achituv, Y. (1993) Asymmetry of male and female mating in mixed-species groups of Aplysia fasciata Poiret and Aplysia brasiliana Rang (Mollusca: Gastropoda). Isr. J. Zool., 39: 213-229.
• Yusa, Y (1996) The effects of body size on mating features in a field population of the hermaphroditic sea hare Aplysia kurodai Baba, 1937 (Gastropoda: Opisthobranchia). J. Moll. Stud., 62: 381-386.

It would also be worth looking at Kandel's two books for a general overview and the place of the nervous system in reproduction.
Best wishes,
Bill Rudman

Dear L. Rivard,
By coincidence I have just posted a message on the Forum today about an article on how to culture Sea Hare larvae in an aquarium.

I am not sure if you have visited the Forum before but there is quite a lot of information on Sea Hares, about various aspects of their biology and about a number of different species. The information is not all neatly ordered because the Forum grows in areas determined mainly by the immediate interests of the participants.

If you go to the General Topics Index you will find a list of pages about Sea Hares. All those pages have attached messages and discussions which are worth a look at.

Best wishes,
Bill Rudman.

Dear Sara,
I've added you to the Participants Page. I usually just add such details to the Participants List without including the information amongst the daily messages. However it seems a good time to advertise the list and ask any one who is not on it to seriously consider sending some details. There is no cost and no obligation, but it is a good way to let other like-minded people know you exist. Have a look at the 'visitor stats' I have posted today to show just how many people read the Forum regularly.

And Sara, your research on Aplysia sounds very fascinating. If you would like to share any background information on your work, photos of your species etc, it would be very welcome.

Best wishes,
Bill Rudman.

Dear Suzanne,
You will find references to Kandel's two books throughout the Forum. You'll find full references in an earlier message if you need them.

Since they were published over 20 years ago it is unlikely they will still be in stock but I guess you should just go to a good bookstore and see if they can track it down for you. Or contact the publisher. Out of curiosity I had a look at the Amazon online site and they say its out of print but you can ask them to try and find a used copy for you at no obligation.

Best wishes,
Bill Rudman.

Dear Will,
Although we often find Sea Hares in the intertidal region they are not really well adapted for life there. They can survive being exposed at low tide if they are in the shade and kept damp, by being covered with sea weeds. Apparently as long as their skin is damp they can still breathe. However they can't live long like this and will die in a few hours or if caught exposed to the sun where they dry out. Sometimes after storms large numbers are found washed up on beaches at low tide where they die before the tide returns.

Basically all slugs are snails that have lost their shells. Snails that live in the intertidal region often have special adaptations to stops them drying out and getting overheated. For exmaple, many snails have an operculum or door which closes tightly to prevent water loss at low tide. One special example are the periwinkle snails (Littorinidae) which live high on the shore and are often uncovered for 10 days or more on hot rocks. They survive by sealing their shells to the rocks with a sticky mucus and then they withdraw their foot further into the shell so it is no longer in contact with the hot rock.

When you are a slug unfortunately, there is no way to stop drying out if you are caught uncovered at low tide. If you look at the Sea Hare shell Page you will see it is just a flat plate hidden in the skin. Certainly no use for protection. It is a bit like the few bones at the base of our backbone called the coccyx. They are all that is left of our tail, but not much use for swinging through the trees.

Also have a look at the pages on What is a Slug? and How snails became slugs.

Good Luck with you report,
Bill Rudman.

Dear Andrew,
If you see the messages about Scutus it looks like grazing herbivores are quite good at surviving great upheavals in their lives.

I am pretty sure your animals are juvenile Sea Hares, probably species of Aplysia. It is possible the blackish one is a sacoglossan (Elysia?) but I can't be sure. I am sure they will survive in your aquarium feeding on algae so why don't you just keep an eye on them and when they grow a bit bigger send me another photo.

Best wishes,
Bill Rudman.

Dear Chantelle,
I guess you have an assignment to do for school? or university? However without some indication from you it is difficult for me to decide how much you already know.

There is quite a lot of information on Sea Hares in the Forum. If you go to the Sea Hares page you will find some background information and a list of other pages with more information. Make sure to read the messages and answers on each page because they also have a lot more information. (Don't forget the messages below yours on this page).

If, after reading all those pages, there are some points you are not clear on, please let me know and I will try and help.

Best wishes,
Bill Rudman.

Dear Raphaël,
I appreciate your thought that I can answer any question on Sea Hares, but the truth is that although research on how brains work fascinates me, I must admit I have no time to keep up with it. I have relied on the comprehensive, but somewhat dated reviews of Kandel, which I have referred to in an earlier message, and the occasional article in magazines such as Science. To those of you who at a complete loss with the question, LTP or long term potentiation is a name for a process that increases the strength of the synaptic connections between neurons. In one model of how memory and learning works it is thought that 'learning' is the result of the build up of specific synaptic connections or pathways between neurons and through the accumulation of such connections, brains learn things and memories develop.

As I've have said elsewhere in the Forum, Aplysia, with a relatively simple nervous system and large nerve cells has proved an ideal animal for use in the study of learning.

Unfortunately Raphaël, I can't help with any recent reviews on the subject. If you find one, could you let me know so I can add it to the Forum. Or perhaps when you finish your review you could write us a summary on the subject, remembering of course that most of us have never developed neural pathways to deal with this area of science.

Best wishes,
Bill Rudman.

Thanks Erwin,
It could be Aplysia oculifera but I am not sure. Whatever the species is, it is certainly a good shot of one swimming.
Best wishes,
Bill Rudman.

Dear Mark,
If you are trying to identify a Sea Hare you have found in the Galapagos Ids it would be better if we could see a photo of it. There may be more than one species found there, and even if I could give you a list of those that have been found there, it does not necessarily mean that other species do not also live there.

I haven't a list of those that have been found there but perhaps someone reading this can help us.

Best wishes,
Bill Rudman.

Dear Alaa,
I am glad to hear of your interest in Sea Hares. Any questions, observation, photos etc are welcome.

I am also sure that now other workers know of your interest they will contact you directly.

Look forward to hearing from you,
Bill Rudman.

Dear Jack,
The gut of the sea hares follows a very similar design throughout the Order. I have used a very old drawing of Cuvier's (1803) of the opened gizzard region to illustrate the arrangement [mainly because most people don't get a chance to see these old figures]. The inset is a sketch of mine to show the whole gut. In Cuvier's drawing many of the hooks in the filter chamber (C) are missing. They should form a dense band right around the chamber.

There is a muscular buccal bulb (bb), opening at the mouth, and it contains the broad rasping radular ribbon used to break off pieces of the algae it feeds. A pair of long salivary glands (sg) open into it. the oesophagus is a large extensible sac or crop (cr) in which pieces of algal food are stored before being crushed in the gizzard, which is broken into 3 regions (ABC). The first (A) is unarmed and presumably is just an anterior holding sac for partially digested food forced down from the crop. The second part of the gizzard (B) has a basal layer of circular muscle encircling the gizzard, and is lined with large chitinous pyramidal crushing plates which reduce the algal plates to fine pieces and a slurry of algal 'juice'. The third region (C) is lined with find recurved chitinous hooks which filter the crushed slurry of food, preventing large particles from moving further down the gut.

The stomach (st) is a very small chamber into which the ducts (D) of the digestive gland open. Also opening into the stomach are the caecum (F) and the intestine (E). Then stomach and caecum are lined with ciliated ridges and there is obviously a very complicated sorting process going on in the stomach, separating edible and inedible particles from the gizzard, and faecal and excretory products from the digestive gland. The caecum seems to be where the faecal pellets are formed.

This is probably more than you wanted to know. Suffice to say that the gizzard plates are of two sorts. A band of large crushing plates and then a region of relatively fine hooks packed close together to form a filter chamber.

Best wishes,
Bill Rudman.

Best wishes,
Bill Rudman.

Dear Myrtle,
The short answer is that Sea Hares, like all molluscs have a kidney whose main function, as in vertebrates, is to maintain the constancy of the internal environment by governing the body's water content, regulating the electrolyte balance of the body fluids, excreting wastes and conserving nutrients.

If you want a fuller account you should find a good book on mollusc physiology. A good summary can be found in Kandel, E. R. (1979): Behavioural Biology of Aplysia. San Francisco, W.H.Freeman & Co. 463pp.
Best wishes,
Bill Rudman.

Dear Yasuhiro,
Yes this is a Sea Hare. It is a bit difficult identifying which species of Aplysia it is without a better idea of its shape. Both Aplysia juliana and Aplysia cf. parvula can have very dark, almost black, bodies and a horny brown coloured shell like in your photo.

Best wishes,
Bill Rudman.

Dear Sylvia,
The best background book for Aplysia is:
Kandel,E. R. (1979): Behavioural Biology of Aplysia. San Francisco, W.H.Freeman & Co. 463pp

It will probably be more than you need but the value of the book is that it puts the anatomy of the animal into its functional context and it also puts Sea Hares into their place in molluscan evolution. It should be available in university libraries, especially if they have Pyschology Department, as Sea Hares are now an important subject for behavioural studies.

I guess you have looked at the Sea Hare page in the Forum. It will lead you to the other relevant pages. You can either use my email address to write to the Forum or click the SEND A MESSAGE button on the Navigation Bar at the top and bottom of each page.

Best wishes,
Bill Rudman.

Dear Fabienne,

I'm not sure if ypu have given me enough information to identify your animal but if it was swimming then it was possibly a Sea Hare, some species of which can swim. Have a look at the information in the Forum on Sea Hares and have a look at the message today from Stephanie Clark which has a photo of a swimming Sea Hare.

If your animal didn't look like a Sea Hare, a rough sketch or drawing would help us identify it.

Best wishes,
Bill Rudman.

Dear Alexis,
Looks like you left it to the last minute - a common student disease. I can't drop everything to meet your deadline but there is lots of information on Sea Hares throughout the Forum. As a first step go to the Sea Hares Page where you'll find a list of links to other related pages. At the bottom of each page [and below your message] you will find a series of messages and answers which you should look at because they contain quite a lot of material.
Also use the Search the Forum button in the yellow bar at the top of each message and the bottom of each page.

Good luck with your assignment,
I guess there is no point in saying start earlier next time,

Bill Rudman.