Alderia modesta
(Loven, 1844)

Order: SACOGLOSSA
Superfamily: LIMAPONTIOIDEA
Family: Limapontiidae

DISTRIBUTION

Nthn Atlantic (NW Europe from Norway to Atlantic France, British Isles; Nth America from Newfoundland to New York State). Nthn Pacific (Nth America from British Columbia to California; NW Pacific - Peter the Great Bay, Russia, Yellow Sea, China).

PHOTO

Peter the Great Bay, Russia, Pacific Ocean, Sea of Japan. Depth: 0-0.2 m. Length: 10-12 mm. 1-5 June 2003. on Vaucheria mats. Photographer: A. V. Chernyshev

Relatively small slug, usually 5-8 mm long but can grow to 15 mm. Usually translucent with mottled green or brown and sometimes some white patching. Foot much wider than body, and rhinophores are either absent or reduced to small rounded bumps or 'ears' on each side of the head. The front third of the body lacks cerata but on the posterior two-thirds, cerata are arranged along each side of the body, leaving the dorsal midline clear. In small animals the cerata appear to be arranged in rows but a pattern is impossible to see in larger individuals. The anal papillae is relatively long and lies in the posterior dorsal midline, level with the most posterior cerata. Branches of the digestive gland ramify throughout the skin of the body wall, the foot, and the cerata. There is also a central digestive gland duct in each ceras.

The heart and pericardium are absent in all members of the genus, blood being pumped through the body by rhythmic pulsations of the cerata. Alderia modesta mates by hypodermic insemination, a spine on the tip of the penis, piercing the skin of the partner's body wall and injecting sperm into the body cavity, from where it finds it way to the reproductive system to fertilise the eggs. It is found in estuarine localities and tidal marshes where it feeds exclusively on the mat-forming alga Vaucheria.

• Bleakney, J. S. (1988) The radula and penial style of Alderia modesta (Lovén, 1844) (Opistobranchia: Ascoglossa) from populations in North America and Europe. The Veliger 31: 226-235.
• Bleakney, J.S. (1996) Sea Slugs of Atlantic Canada and the Gulf of Maine. The Nova Scotia Museum Field Guide Series, Nimbus Publishing & Nova Scotia Museum, Halifax, Nova Scotia. .216 pages.
• Chernyshev A.V., Chaban E.M. (2005) The first findings of Alderia modesta (Loven, 1844) (Opistobranchia, Ascoglossa) in the Sea of Japan. Ruthenica, 14(2): 131-134 (in Russian).
• Evans, T. J. (1951) The alimentary and vascular systems of Alderia modesta Lovén in relation to its ecology. Proceedings of the Malacological Society of London 29: 249-258.
• Graves, D. A., Gibson, M. A., and Bleakney, J. S. (1979) The digestive diverticula of Alderia modesta and Elysia chlorotica (Opisthobranchia: Sacoglossa). The Veliger 21: 415-422.
• Hand, C. and Steinberg, J. (1955) On the occurrence of the nudibranch Alderia modesta (Lovén, 1844) on the central Californian coast. The Nautilus 69: 22-28.
• Hartog, C. D. and Swennen, C. (1952) On the occurrence of Alderia modesta (Lovén) and Limapontia depressa A. & H. on the salt marshes of the Dutch Waddenzee (Gastropoda, Nudibranchia).  Beaufortia, Zoological Museum, Amsterdam 19: 1-3.
• Jensen, K. R. (1981) Observations on feeding methods in some Florida ascoglossans. Journal of Molluscan Studies 47: 190-199.
• Krug, P. J. (1998) Poecilogony in an estuarine opisthobranch: planktotrophy, lecithotrophy, and mixed clutches in a population of the ascoglossan Alderia modesta. Marine Biology 132: 483-494.
• Qi Z., Ma X., Wang Z., Lin G., Xu F., Dong Z., Lu D. 1989. Mollusca of Haunghai and Bohai. Beijing: Agricultural Publ. House: 309 p. (in Chinese).
• Thompson, T.E. (1976) Biology of Opisthobranch Molluscs, Volume I. The Ray Society, London. 207 pages.
• Trowbridge, C. D. (1993) Local and regional abundance patterns of the Ascoglossan (=Sacoglossan) Opisthobranch Alderia modesta (Loven, 1844) in the Northeastern Pacific. The Veliger 36: 303-310.
• Trowbridge, C. D. (1993) Population structure of two common species of Ascoglossan (= Sacoglossan) Opisthobranchs on the central coast of Oregon, USA. The Veliger 36: 99-106.
• Trowbridge, C. D. (1994) Defensive Responses and palatability of specialist herbivores: predation on NE Pacific ascoglossan gastropods. Marine Ecology Progress Series 105: 61-70.

Authorship details
Rudman, W.B., 2005 (March 22) Alderia modesta (Loven, 1844). [In] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/aldemode

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Related messages

Photographs of 2 Sacoglossans of the Dutch saltmarshes [1]

November 27, 2009
From: Marianne Ligthart

Dear Bill.

I understand from your earlier comments [message #22783] that you regret there are too few photographs of Alderia modesta on the Forum. So I am sending you some recent photographs of Alderia modesta and Limapontia depressa [message #22863] taken in the field (on the saltmarshes in the south-west part of our country near estuarine coastal waters). I regularly find both species throughout the year, exept in periods when it is very cold or dry.

The animals mostly are very small in size: 2 - 3 mm and they live on Vaucheria spec.

Locality: saltmarshes in the south-west part of the country near estuarine, coastal waters, / on saltmarshes, the Netherlands, estuarine waters of the North Sea, autumn 2008, on saltmarshes on Vaucheria spec.. Length: 2 - 3 mm. Photographer: Marianne Ligthart.

With greetings:
Marianne Ligthart

ahmligthart@hetnet.nl

Ligthart, M., 2009 (Nov 27) Photographs of 2 Sacoglossans of the Dutch saltmarshes [1]. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/22841

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Re: Alderia modesta living sublittorally in Holland

November 19, 2009
From: Skip Pierce

Concerning message #22783:

Hi Bill
I'm sitting here berating myself for not taking a picture of them, but this message reminded me to report to you the reappearance last spring of Alderia modesta in Woods Hole. I have been collecting Elysia chlorotica for decades in the Woods Hole area and, for many years, we routinely encountered a few A. modesta in the same marshes as E. chlorotica - both eat Vaucheria.

Other than noticing the A. modesta, we never paid much attention to them until colleague Pat Krug, who works on A. modesta as you know, called me, asked where to get them in Woods Hole, and then could not find any where I confidently sent him. I, of course, blamed Pat, but when I went to look, not only couldn't I find them either, but we have not seen any there in 20 years of casual looking. This spring, my collector, who lives in Woods Hole, went out to get us some E. chlorotica, which, unusually, he failed at, but instead he sent 3 or 4 tiny green slugs, which turned out to be A. modesta, which I immediately sent to Pat.

I have just returned to Tampa from a 2 month sojourn to Woods Hole (probably the last sabbatical of my career) and we collected E. chlorotica there a couple of weeks ago, and again found no A. modesta. Now, they are pretty small, but we looked especially for them in the Vaucheria mats. I am not at all sure what these observations mean - maybe only that A. modesta is just an occasional visitor to Woods Hole, maybe is only around in the spring, maybe is harbinger of climate change, maybe we just missed them - or something else - but here's another note for your distribution list - and I'll remember to photograph them if we ever see them again.

Skip

pierce@cas.usf.edu

Pierce, S. K., 2009 (Nov 19) Re: Alderia modesta living sublittorally in Holland. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/22803

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Alderia modesta living sublittorally in Holland

November 16, 2009
From: Marianne Ligthart

Dear Bill,

Maybe some interesting news from the Netherlands related to message #22765 on Limapontia and Vaucheria

Another sacoglossan from the saltmarshes, Alderia modesta, has found a complete new habitat in the sublittoral zone of the coastal waters in the south-west part of our country. The animals have been found by my buddy Marco Faasse and myself during summer and autumn from 2006 till now.
The animals are living and feeding on the exotic alga Vaucheria longicaulis (introduced in the Netherlands since 1993).
The size is very small: 1-2 mm.
Only the eggs are visible under water. Until now this habitat below the low water mark in a totally marine environment was unknown in our country for Alderia modesta.

Vaucheria longicaulis only grows in summer and autumn. We don't know how the animals survive the other seasons.

Also on the saltmarshes in the south-west of our country Alderia modesta and Limapontia depressa are still present. They live on Vaucheria spec. often mixed with other alga.

Locality: The Oosterschelde and Grevelingen, two estuarine, coastal waters in the south-west of the country, 1 - 5 m, the Netherlands, estuarine waters of the North Sea, 2006 till now, summer and autumn, not intertidal but sublittoral. Length: 1 - 2 mm

we have no photographs.

With greetings,
Marianne Ligthart

ahmligthart@hetnet.nl

Ligthart, M., 2009 (Nov 16) Alderia modesta living sublittorally in Holland. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/22783

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Alderia modesta from eastern Russia

March 22, 2005
From: A. V. Chernyshev, E. M. Chaban

Dear Bill,
Alderia modesta (Loven, 1844) is the fourth sacoglossan species reported from the north-west part of Sea of Japan. It was found upon Vaucheria algal mats in the semi-enclosed reservoir of the Amurskiy Bay (Peter the Great Bay, Sea of Japan) in 2003 and 2004 (Chernyshev & Chaban, 2005). The adult specimens are up to 14 mm long. In late May and early June the density of A. modesta varied from 10-20 to 1000-2000/m2. The numerous egg masses hatch planktotrophic veligers. From July to April both A. modesta and Vaucheria sp. are absent. It is the second finding of A. modesta in the Asian seas. This species has also been found in the Yellow Sea (Qi et al., 1989).

Locality: Peter the Great Bay, Russia, Pacific Ocean, Sea of Japan. Depth: 0-0.2 m. Length: 10-12 mm. 1-5 June 2003. on Vaucheria mats. Photographer: A. V. Chernyshev

• Chernyshev A.V., Chaban E.M. (2005) The first findings of Alderia modesta (Loven, 1844) (Opistobranchia, Ascoglossa) in the Sea of Japan. Ruthenica, 14(2): 131-134 (in Russian).
• Qi Z., Ma X., Wang Z., Lin G., Xu F., Dong Z., Lu D. 1989. Mollusca of Haunghai and Bohai. Beijing: Agricultural Publ. House: 309 p. (in Chinese).

Alexei V. Chernyshev
Institute of Marine Biology, Vladivostok, Russia,
tsher@bio.dvgu.ru

Elena M. Chaban
Zoological Institution, St.-Petersburg, Russia,
cem@EC2579.spb.edu

Chernyshev, A.V. & Chaban, E.M., 2005 (Mar 22) Alderia modesta from eastern Russia. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/13381

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