- Atlantic populations
On pier pilings at approx 5 meters. Woods Hole, Massachusetts, USA. Approx 5 mm long. Photo: Alan Shepard.
There appear to be a number of very similar-looking species around the world which have all been identified as this species. At the moment most messages are placed on the page illustrating the southeastern Australian populations so go there for general information and links to other relevant pages.
Rudman, W.B., 2002 (April 18) Placida dendritica - Atlantic populations. [In] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/placden3
March 8, 2007
From: Erling Svensen
Svensen, E., 2007 (Mar 8) Placida dendritica? from Norway. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/19613
Unless I have totally missed the plot, this is the 'real' Placida dendritica. If you have a look at the Fact Sheet, and other messages on the Forum, you will see that there are a number of very similar looking species around the world which have been identified as P. dendritica.
In your photos we can see the white-tipped cerata and the concentrtaions of white spots? glands? in the upper half of the rhinophores. The close-up alongside nicely shows that the rhinophores are not a solid tentacular structure but are enrolled. The green branching in the body is the digestive gland - the green being chloroplasts obtained from its algal food.
November 6, 2002
From: Cynthia Trowbridge
Dear Yi Zhang and colleagues,
I would like to add to Bill's comments and ask for additional observations from Scandinavia. Here are my observations (mostly published reports) by region.
British Isles: Placida dendritica from British Isles (type location is in Southern England) eats:
Codium tomentosum (native alga)
Codium fragile tomentosoides (introduced)
C. fragile atlanticum (introduced)
Bryopsis plumosa (presumably native)
I assume that the slug may eat C. vermilara (native alga) as well. I have been working on a population of C. vermilara at Guernsey, Channel Islands this Sept. So far, I have found tons of Elysia viridis but no Placida [my visit was too late in the season]. Have any colleagues seen the slug on C. vermilara? If so, I would be keen to hear the details.
Has anyone from Norway or Sweden seen P. dendritica on C. fragile scandinavicum (introduced)? If so, it would be great to have this recorded.
Sagami Bay, Japan: Placida cf. dendritica from Sagami Bay, Japan (= Baba's Placida sp. = Marcus's Placida babai) eats:
Codium fragile (native)
C. arabicum (= C. adhaerens)
plus 3 other native Codium spp.
plus several Bryopsis spp.
Okinawa: "Placida dendritica" from Okinawa which may be Ercolania/Stiliger (according to Kathe's message in summer) eats:
Codium intricatum (confirmed)
Bryopsis harveyana (tentative)
also reported by 3 different malacologists on Caulerpa (no feeding observations)
Yoshi Hirano, Yayoi Hirano, and I have done feeding preference experiments with this sacoglossan species in July 2002.
Oregon: Placida dendritica from Oregon eats:
Codium fragile (native)
C. fragile tomentosoides (introduced)
SE Australia and New Zealand: Placida cf. dendritica from SE Australia and New Zealand eats:
Codium fragile novae-zelandiae (native)
C. fragile tasmanicum (native)
C. fragile tomentosoides (introduced)
C. convolutum (= C. adhaerens)
many other Codium spp.
many Bryopsis spp.
Other reports include:
Some of these reports are in a manuscript currently pending publication; others are already published. Please contact me directly if you wish additional details.
email@example.comTrowbridge, C., 2002 (Nov 6) Re: What does Placida dendritica eat?. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/8363
It is good to get a summary of their food preferences. There is also Jui-Sheng Chang's animal from Taiwan which is reported to feed on Codium edule. What with the difficulty of identifying the slugs, and I guess the difficulty in identifying the algae, I am amazed that you have persevered with your study of these little animals. I am sure a lesser ecologist would have retreated years ago.
November 4, 2002
From: Yi Zhang
Do you happen to know what types of algae Placida dendritica feeds on? That is where are the chloroplasts most likely from?
firstname.lastname@example.orgYi Zhang, 2002 (Nov 4) What does Placida dendritica eat?. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/8348
Dear Yi Zhang,
The first thing we need to establish is which Placida dendritica you are interested in? 'Typical' Placida dendritica was first described from Europe, and on the Forum we have a page for animals from both sides of the Atlantic. There are also pages for animals from southeastern Australia and the tropical Pacific, which have also been identified as P. dendritica. If you have a look at the messages on those pages you will see that there are scientists at the moment studying whether all the animals around the world which have been called P. denditica are in fact one species or a group of very similar-looking but quite distinct species. 'Typical' P. denditica from the British Isles feeds on Codium tomentosum and Bryopsis plumosa.
June 20, 2002
From: Jean-Pierre Bielecki
Here are some pictures of Placida dentritica from the Mediterranean. I am sure you will be interested to have this species from another part of the world.
Species found in March 2001,
Dive site: Sète, étang de Thau. [France, Mediterranean coast]
Size: between 5mm and 1cm,
Bielecki, J.P., 2002 (Jun 20) Placida dentritica from the Mediterranean. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/7295
I am indeed happy to include 'Placida dentritica' from the Mediterranean.
June 17, 2002
From: Jim Anderson
Dear Dr. Rudman,
ID'd for me by Bernard Picton, it was approx 10mm long and at 7 metres on a boulder face among Halopteris -like undergrowth. We were in Loch Leven, near Ballachulish, Scotland. water temperature 10 deg C.
I brought it out and photographed it in a tank on shore on a piece of slate with my Nik 5 and 2:1 CU.
Anderson, J., 2002 (Jun 17) Placida dendritica from Scotland. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/7149
At last a photo of the 'real' Placida dendritica from Europe. When I get a moment I should prepare a proper Fact Sheet on this species. It will be interesting to see how many species this 'species' will eventually be split into.
April 19, 2002
From: Alan Shepard
I was recently photographing the sea slugs found on pier pilings in Woods Hole, Massachusetts right in front of the Woods Hole Oceanographic Institute and I found for the first time Placida dendritica. When I searched for it on the Sea Slug Forum I noticed that you had no photos of it from our area so I'm submitting the one I took.
This one was about 5 millimeters long and was in only 5 meters of water. The most common sea slugs on the pilings were the animal you thought might be Eubranchus exiguus which were laying their eggs on hydroids.
email@example.comShepard,A., 2002 (Apr 19) Placida dendritica from Massachusetts, USA. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/6747
It's nice to get a photo of an animal from the Atlantic. I am sure Cynthia Trowbridge will be pleased. I've decided I better have a separate 'Atlantic Page' in the hope of more photos from both sides of the Atlantic.
Concerning your 'Eubranchus exiguus'. Some more photos, including some egg shots might be useful in its identification. My suggestion about it being E. exiguus was very tentative.