What eats sea slugs?
One big gap in our knowledge is what actually eats Sea Slugs. Except in rare cases such information, where it exists, is published not in the malacological literature, where we would look, but in the literature associated with predator, for example fish biology journals, often in stomach contents lists which don't appear as keywords or any easily searchable form. I think this is a good time to add a page for predation records where we can gradually accumulate such information on who/what eats sea slugs. So here is the page. It's basically empty at present, so any records/observations, either personal observations or from the literature, would be appreciated.
All observations in the list below are linked to a message containing details.
ANASPIDEA (Sea Hares)
Johnson & Willows, 1999 - List of reported predators on Sea Hares.
Johnson, S. 1999 - Gymnodoris ceylonica eating Stylocheilus striata.
Bonnet, 2006 - Gymnodoris ceylonica eating Stylocheilus striata.
Roberts, M. 2005 - Puffer fish and and Philinopsis cyanea eating Stylocheilus striata.
Miller, 2000 - Turtles eating Sea Hares.
Rogers, et al, 2000 Pycnogonids, 'Sea Spiders' eating Sea Hares and assorted opisthobranchs.
Rogers, C., 2000. Labrid fishes or wrasses eating adult Aplysia parvula and juvenile Aplysia dactylomela.
Koh, D.B., 2005. Nemertine worm eating Aplysia parvula.
Koh, D.B., 2005. crab eating; Aplysia juliana.
Wright, W.G., 2006 Navanax inermis eating Aplysia californica
Kirkendale, L, 2006 Flatworm eating Aplysia juliana
NOTASPIDEA (Pleurobranchs, etc)
Rudman, 1999 - turtles eating Pleurobranchus forskalii
Johnson, 1999 - Gymnodoris striata eating Plakobranchus ocellatus
Trowbridge, 2001 predation on Stiliger fuscovittatus, Alderia modesta & Placida dendritica.
Horst, 2009. Hermit crab attacking Thuridilla hopei.
Arango & Brodie, 2003 - Pycnogonid eating Okenia virginiae.
Johnson, 2000 - Gymnodoris citrina eating other Gymnodoris citrina.
Anderson, 2006 - Roboastra luteolineata eating Nembrotha kubaryana
Gudgeon, 2006 - Roboastra gracilis eating Nembrotha kubaryana
Ogden, 2008 - Roboastra luteolineata eating Nembrotha aurea
Penney, 2001 - Predation experiments on Cadlina luteomarginata
Hildering & Miller, 2007 - Starfish eating ?Cadlina luteomarginata
Elayani, 2006 - Polychaete attacking Chromodoris purpurea
Hösel, 2007 - Gymnodoris rubropapulosa? juvenile eating Pectenodoris trilineata.
Cobb, 2008 - Gymnodoris sp. 5 juv. eating? Glossodoris atromarginata.
Anderson, 2008 - Gymnodoris rubropapulosa eating Chromodoris westraliensis.
Toh, 2008 - Gymnodoris rubropapulosa eating Chromodoris lineolata.
Penney, 2001 - Crow attacking Archidoris montereyensis.
Harris, 2006 - Fish attacking Peltodoris nobilis
Koh, D.B., 2006. Nemertine worm eating Atagema intecta.
Chuk, 2007. Starfish holding Doris cameroni.
Horst, 2009 . possible crab attack on Peltodoris atromaculata.
Yokes, 2009 . crabs attacking nudibranchs in aquaria .
Seiko Kuroe & Akira Mada, 2007 - Crab attacking Tritoniopsis elegans.
Whitacre, 2001 - pycnogonids feeding on Berghia verrucicornis.
Silva, 2008 - crab eating Spurilla neapolitana.
Hermosillo, 2002 - fish & Navanax feeding on Phidiana lascrucensis.
Rudman, W.B., 2000 (May 3) What eats sea slugs?. [In] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/predrecord
March 26, 2009
From: Shelby Beckham
I was hoping that you knew what the natural enemy is to a Bullina lineata.
email@example.comBeckham, S., 2009 (Mar 26) What eats Bullina lineata. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/22363
I may be wrong, but this question sounds as though your are doing a school project. Are you interested in other aspects of its biology as well? If you look at the Fact Sheet and earlier messages on this species you will get an idea of what we know about its natural history.
I'm afraid we know very little about what eats sea slugs. This is also the case with lots of other animals simply because we don't often see one animal eating another, and even if we do we don't immediately alert a biologist to what we have seen. Most research on feeding is the other way around. Someone wants to know what a particular animal eats so observations are made on that animal, or its stomach contents are studied, and an article is published with the details. With modern electronic search methods it is possible to see if someone has published an article on what a particular species eats, but as yet, there is no easy way to find if Bullina lineata was one of the unfortunate animals in the list of things eaten.
We have a What eats Slugs? page on the Forum, which is an attempt to build up information on this topic, but we have a long way to go.
January 24, 2002
I have had trouble finding this out using other sites and books, and was wondering if you could help me. I was wondering if you knew of any sea stars that ate sea slugs (such as Flabellina iodinea) in the Point Reyes area (North of San Francisco in northern California). Any info would be greatly appreciated.
firstname.lastname@example.orgDaniel, 2002 (Jan 24) Sea Stars that eat Sea Slugs. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/6086
Have a look at the page on Predation where I list known records of animals eating sea slugs. The only reference we have to starfish eating them is Brian Penney's message. Hopefully someone from California can give us some more information. I am not sure if you are more interested in the starfish or the sea slugs. If it is the sea slugs have a look at the Sea Slug Defence page for some more information. You will find that aeolid nuidbranchs, like Flabellina have quite good defence organs called cnidosacs.
September 6, 2001
From: Brian K. Penney
Good idea on the predation page. In five years at Bamfield (west coast of Vancouver Island in British Columbia, Canada) I have only seen one instance of predation on local dorids in the field. About three years ago I saw a crow pick up an Archidoris montereyensis from the shore in front of the marine station. The bird soon dropped the slug, but I am not sure if it was truly rejecting the slug, or annoyed at me frantically following behind. When I recovered the slug, its viscera had been pecked around a fair bit, but were all still there. The slug died the next day.
I have tried some lab predation experiments with live Cadlina luteomarginata against various generalist molluscivores: crabs (Cancer sp.), anemones (Anthopleura sp.), sea stars (Pycnopodia helianthoides) and fish (Hexagrammos decagrammus). Crabs and fish would taste the slugs with their mouthparts, and then throw them away; when tested a second time, they wouldn't even pick up the slug! Anemones and sea stars would consume the slug, then spit it out by the following day. Most of these slugs (>50%) lived at least one more week in the lab.
If anyone is interested in more detail on the latter results, I should be submitting them for publication within the next year or so. But it seems:
• dorid defenses work well against numerous predator types,
• some predators learn to avoid dorids after one sample and
• predator sampling does not invariably lead to the slug's death.
Hope this is helpful.
email@example.comPenney, B.K., 2001 (Sep 6) Predation on dorids. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/5113
Building up feeding observations is a slow business, so any reports are of great value and will hopefully encourage more. Please let me know when your paper is published.
February 7, 2001
From: Cynthia Trowbridge
I am delighted to see that you are accumulating a page on predation on sea slugs.
A casual perusal of the slug literature indicates that there has been considerable work done on apparent defenses against predators (e.g., autotomizing cerata, lowered pH, viscous white secretions, etc.). Yet, there is a surprising lack of experimental evidence in the field or lab to test the effectiveness of the defenses.
About 10 years ago, I investigated the palatability of 4 common sacoglossan species on the Oregon coast to a suite of ecologically relevant predators including different sculpins, surfperch, shore crabs, Dungeness crabs, and nemerteans. Three small, cryptic sacoglossan species (Stiliger fuscovittatus, Alderia modesta, and Placida dendritica) were readily eaten by various fishes and crabs. In contrast, the larger, black and white sacoglossan Aplysiopsis enteromorphae was not readily eaten by predators.
Furthermore, I also tested the role of predation on the shore for Alderia modesta in a traditional predator-exclusion experiment (with exclusion cages, 2 types of cage controls, and unmanipulated controls). Predators significantly reduced densities of the slugs (relative to the exclusion controls) in my 12-day experiment in Yaquina Bay, Oregon (USA).
This study has not been widely cited, in part because it refutes the traditional - but largely untested - assumption that sea slugs are unpalatable. The role of predation is far more complex than researchers have traditionally assumed. Thank you for considering my comments.
• Trowbridge, C.D. 1994. Defensive responses and palatability of specialist herbivores: predation on N.E. Pacific ascoglossan gastropods. Marine Ecology Progress Series, 105: 61-70.
firstname.lastname@example.orgTrowbridge, C., 2001 (Feb 7) Predation on sacoglossans. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/3724
I wish we could get more researchers interested in this type of study. It is a very complex set of questions. Some species appear well camouflaged and others are brightly coloured at least to our eyes. Many have nasty chemicals and at least on initial contact are avoided by fish. It seems there will be no general or simple rule that covers all species. I have suggested, when discussing chromodorids, (Rudman, 19) that defensive chemicals are probably the last line of defence. By the time the predator is experiencing your nasty secretions, your chances of survival are probably quite low.
January 9, 2001
From: Cary Rogers
I thought you could add these to the predator list. The pycnogonid (sea spider) Anoplodactylus evansi which ate sea hares, sacoglossans and nudibranchs in aquaria, and labrid fishes or wrasses which ate adult Aplysia parvula and juvenile Aplysia dactylomela in subtidal field experiments near Sydney, Australia.
email@example.comRogers, C., 2001 (Jan 9) Pycnogonids - Sea Slug predators. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/3407
I've added them to the list and prepared a page on Anoplodactylus evansi as promised.
These observations are the result of studies Cary has been conducting over recent years on various aspects of the biology of Sea Hares around Sydney, especially defence and chemical ecology. This particular aspect of his work has been recently published in an interesting paper I have cited below.
•Rogers, C.N., de Nys, R. & Steinberg, P.D. (2000) Predation on juvenile Aplysia parvula and other small Anaspidean, Ascoglossan and Nudibranch Gastropods by Pycnogonids. The Veliger, 43(4): 330-337.
July 1, 2000
From: Lorna Travers age 8
What eats sea slugs?
Lorna Travers (age 8)
firstname.lastname@example.orgTravers, L., 2000 (Jul 1) Food chain. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/2643
Snails and Sea Slugs are very closely related. The shell, which is often very strong, helps to protect snails from being eaten by other animals. Slugs however have had to find other ways to try and protect their soft bodies from attack. In case you don't have much experience with using the world wide web, perhaps I should say that if you click on any word in my message which is underlined, you will be taken to a page on that subject.
If you go to the page on Opisthobranch Defence you will find a list of pages which have information on different aspects of their defence. Many sea slugs have nasty tasting chemicals in their skin to protect them, and some have become brightly coloured to warn fish that they are very bad tasting. One group, the aeolids, take stinging cells from their sea anemone (and other cnidarian) prey and store these up to use in their own defence. Have a look at all the pages listed as they all have interesting stories to tell.
Now to you question about who or what eats sea slugs. It is very difficult to collect this sort of information because sea slugs don't leave much trace behind. They don't have a shell or bones, so a biologist studying the food of an animal by looking at the undigested remains in its stomach or its faeces will find no recognsiable traces of seas slugs except in rare cases. The only other way to find what eats them is to observe them being eaten in the field, and that is very difficult. I have listed the few records I know of other animals eating sea slugs at the top of this page.
One group in the list that eats sea slugs is the Genus Gymnodoris which are themselves nudibranch sea slugs, specialised in eating other sea slugs. If you look at the relevant Gymnodoris pages you will see some great photos of them feeding.
May 4, 2000
From: Bill Rudman
In today's message from Bob Bolland he mentions observing possible bite marks (predation damage) on many of the Pleurobranchus mamillatus and I mentioned my observations in Tanzania of large Pleurobranchus forskalii being eaten by turtles.
As I say there, one big gap in our knowledge is what actually eats Sea Slugs. Except in rare cases such information, where it exists, is published not in the malacological literature, where we would look, but in the literature associated with predator, for example fish biology journals. I think this is a good time to add a page for predation records where we can gradually accumulate such information on who/what eats sea slugs. So here is the page. It's basically empty at present, so any records/observations would be appreciated.
Bill Rudman.Rudman, W.B., 2000 (May 4) A new page - Predation Records. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/2358