Opisthobranch Mollusca


BMLSS Records
(Numbers in brackets are Glaucus  reference numbers).
In alphabetical order by scientific names.

Acanthodoris pilosa

Acanthodoris pilosa, brown specimen. (photograph by Andy Horton)Regular occurrence in spring on east Brighton beach under rocks on the lower shore. Numbers vary from a dozen to hundreds from year to year. White specimens exceed brown-black specimens. (A.Horton). Photographed.  Estimated at up to 32 mm long.
(05.03.26*, 06.01.04)
Also recorded at Worthing.

Salcombe at 21 metres in July, and Dale, Pembrokeshire. at 12 metres in June (J.Lilley).

Acanthodoris pilosa (white specimen) from the Isle of Wight (Photograph by Luke Richards)

12  + specimens, brown form, mating with eggs, on a Lundy dive, north end of Jenny's Cove, 2 July 1998 (J Lilley).
Acanthodoris pilosa, a nudibranch (Photograph by Richard Lord, Guernsey)

5 January 2007
The nudibranch, Acanthodoris pilosa, was discovered in Belle Greve Bay under a large boulder on the edge of the Fucus serratus zone on Guernsey's east coast, Channel Islands.

Report & Photograph by Richard Lord (Guernsey)
Sealord Photography

7 May 2008
The shore with rocks uncovered on the low spring tide by the Half Brick, east Worthing, was ordinary with the usual fare of with sea anemones and crabs. The only thing vaguely unusual was the first nudibranch sea slug, a small Acanthodoris pilosa in a fawn colour and larger than normal. I had not seen one for several years. The fawn colour was unusual, possibly unprecedented in my experience.
Lancing & Worthing Beach 2008

Aeolidiella alderi

Aeolidiella alderi  (Photograph  ©  by Richard Lord of Guernsey)

18 October 2005
I found two Aeolidiella alderi under rocks on the mid-shore of La Valette, east coast of Guernsey.  The smaller of the two specimens appears to be parasitized by a copepod. What I find interesting is that I found another specimen of Aeolidiella
alderi on 28 October 2004.  It seems that Aeolidiella alderi may arrive on the east Guernsey shore in October.  I have not found it inter-tidally at any other time of year.

Report and Photograph ©  by Richard Lord (Guernsey)
Aeolidia glauca

In the earlier books this species is not included and some records of A. papillosa may have been this species.
A single specimen recorded from Hannafore, Looe, by Jon Makeham in March 1999.
When compared side by side with the next species, it is distinguished because:
1)  no white patches on the sea slug.
2)  much smaller size = 35 mm.
3)  a thin line through the centre of the cerata instead of the bald patch on A.papillosa.
4) cerata closely packed and most of them were curled inwards in a distinctive way.

Aeolidia papillosa

Occurs in spring on east Brighton beach under rocks on the lower shore. Numbers vary from absent altogether up to 50  from year to year. Spawn spirals on the underside of rocks.  (A.Horton). Photographed.
Frequent east Brighton under flint cobbles with spawn up to 5 cm long 1982  (D.Ventham).

Found under Worthing pier in spring, more often than at Brighton, numbers extremely variable: absent altogether most years, or occasional specimens in shallow pools or moribund; some years hundreds scattered over lower shore in conjunction with the sea anemone Sagartia troglodytes, present in thousands and confirmed to be its prey (A.Horton). Photographed. (03.01.31, 03.03.11, 04.03.21*,26*, 04.04.41*, 05.01.46*)

1993 recorded as a spawning year for this species at Worthing, reaching a maximum size of only 50 mm. (A.Horton). (04.03.21*)

    (1) Spawn (2) Grey Sea Slug feeding on a Beadlet Anemone


Recorded at Manorbier beach, near Tenby, south Wales (C.Batt) (05.02.10).
Recorded in Fowey estuary, Cornwall (05.02.14) (R.Stokes).

Front cover photographs (monochrome) in Glaucus, feeding on sea anemone Actinia equina, and spawn.

Recorded at Broad Ledge, Lyme Regis, in 1995 (A.Brokenshire) (06.02.45).

Battery Rocks Penzance  1968/1971 in Oarweed. CBRU records supplied by Dr Ian Lancaster.

Abundant at Fleet narrows, Dorset 1996 (P.Glanvill).

3 specimens together, only 9 mm long, Caherdaniel, SW Ireland dive. 1998 (J.Lilley).
10 mm long young specimens has exhibited a striking "startle response", the cerata were raised very rapidly, making it look much larger and prickly, when touched, making me jump. (Jane Lilley).

16 March 1999. Spawn and an individual (a single one discovered attempting to spawn by dying in the attempt) under Worthing Pier. (Andy Horton).

Hannafore, Looe:  Occasional specimens grow to 110 mm, but they are usually 50-60 mm. Remain until July laying spawn. Most specimens have white patches on the head &/or middle.  Jon Makeham (April 1999)

One adult specimen a long way up the Tyne in October 1999  (Helen Marshall) .

For more information on this nudibranch as well as the Sea Hares, Aplysia and Elysia, the Sea Slug Forum  site is recommended.

Aeolidia papillosa references

Archidoris pseudoargus

Photograph by Ron Barrett

Colourful specimen discovered on Kingston beach at the entrance of Shoreham harbour on one occasion. Assumed to be a fishermen's discard (A.Horton). Photographed.
A single all yellow specimen discovered in a crevice on my only visit to Hope's Nose, a rocky beach in south Devon (A.Horton).
Solitary specimens found on two occasions on the shore at East Brighton 1982 (D.Ventham).

Solitary specimen under a rock on the shore at the Mumbles, Gower, south Wales (J.Hall).(04.04.31).

Specimen found at low spring tide at Gelliswick Bay, Milford Haven (C.Batt).(05.02.17, 05.03.21).

Specimens at Fleet narrows 1996 (P.Glanvill).

Battery Rocks Penzance 1968/71. CBRU records supplied by Dr Ian Lancaster.

Hallsands, Devon at 20 metres. Plymouth at 15 metres. St. Bride's Bay, Pembrokeshire. at 16 metres. Littlehampton, Sussex, at 13 metres. Shelly Rocks, Bognor at 7 metres. Skomer, laying eggs 3 June 1995.
Several on chalk platform, north side of Swanage Bay at 6 to 7 metres.
Out of Bognor, two mating pairs 28 April 1996. (J.Lilley).

A 4 mm specimen collected from Tenby beach in August 1998 (W. Thomas).

Cadlina laevis

Seen twice, once at Skomer and two together at Porthoustock, Cornwall. (J.Lilley).

A single specimen on a Lundy dive, Knoll Pine, 30 June 1998  (J Lilley).

A single specimen on a Lundy dive, north end of Jenny's Cove, 2 July 1998 (J Lilley).

A single specimen discovered on a Caherdaniel, SW Ireland dive. 1998 (J.Lilley).

Recorded on a Farne Island dive, 15 August 1998 (Jane Lilley).

27 November 2003
Hi Andy........Yes I went down to the Mumbles yesterday, the last day
possible on this big tide.  Then I found a sea slug.  I
believe that it is Cadlina laevis, 5mm in length.  (Jim Hall)

Calma glaucoides

At Battery Rocks, Penzance (SW477298) 1977. CBRU records supplied by Dr Ian Lancaster.

Coryphella lineata

One specimen seen on a dive near Oban, W Scotland. (J.Lilley).

Crimora papillata

Two tiny specimens seen on a dive at Hallsands, off Devon at 20 metres in late May.
Observed at 15 or 20  metres near Salcombe, Devon, in July. (J.Lilley).

3 specimens on a Portland Bill, west side, south of Blacknor Point dive, 7 July 1998 (J.Lilley).

Cuthona nana

Recorded at Anstey's Cove, south Devon on one occasion. Feeds on the hydroid  Hydractinia commensal with Hermit Crabs (C.Proctor). (05.02.12*).

Dendronotus frondosus

Recorded in Fowey estuary (R.Stokes).
(05.02.14, 05.03.26*)

Observed  at Hand Marks, St. Bride's Bay, Pembrokeshire. at 16 metres, on an unidentified hydroid; seabed rocky with some overlying sediment. (J.Lilley).

Large specimens on Isle of Man dive (early July 2000) (J.Lilley)

Diaphorodoris luteocincta

Several recorded on a dive near Oban, 1996.
Also off Plymouth and dives at Skomer and Pembrokeshire. several times.(J.Lilley).

A single specimen on a Lundy dive, Knoll Pine, 30 June 1998  (J Lilley).

A single specimen on a Lundy dive, north side of Jenny's Cove, 1 July 1998 (J Lilley).

A single specimen on a Lundy dive, north end of Jenny's Cove, 2 July 1998 (J Lilley).

Several, including one pair mating, and var. alba twice, on a Lundy dive, wreck of the MV Robert, 3 July 1998 (J Lilley).

Both the normal species and the var. alba were very numerous on a Lundy dive, Knoll Pins, 3 July 1998 (J Lilley).

Mating pair, Caherdaniel, SW Ireland dive. 1998 (J.Lilley).

Doto coronata

Recorded on small hydroids attached to mussels under Worthing pier, Sussex (A Horton).
Photographed. (06.01.42)  Picture Link

Found on 3 occasions at least 7 specimens to 4 mm long on the shore at Roedean, east Brighton. On hydroid Sertularia argentea, gravid and spawn coils, 1982.
Also at Kemp Town, intertidal (D.Ventham).

Recorded from the Mumbles, near Swansea, in 2002.  (Jim Hall)

Doto maculata

28 November 2004
The record of the miniature nudibranch Doto maculata from Loch Fyne (a sea loch on west coast of Scotland) at depth of 16 metres could be because this small mollusc is rarely recorded rather than being uncommon. The problem is that it could be confused with other sea slugs of the same genus, especially the common species Doto coronata.

Report by Jim Anderson on the Sea Slug Forum
Doto pinnatifida

5 specimens (probable identification) on a Lundy dive, at Gull Rock, 11-16 metres, 29 June 1998 (J Lilley).
Frequently discovered with eggs at 16-21 metres off Portland Bill, east side, The Ledge, 10 July 1998 (J Lilley).

Eubranchus farrani

Seen on an Isle of Man dive (early July 2000) (J.Lilley)

Facelina auriculata

Occasional occurrence in spring on Worthing beach under rocks on the lower shore.  (A.Horton). Very small.
Very small specimens at East Beach and Broad Ledge, Lyme Regis, Dorset, 1996 (Robert Jones). Photographed and included on front cover of Glaucus (Vernal/Summer 1996).

Specimens recorded in rock pools very high up on the shore, virtually the splash zone. at Portuarick, Ardamurchen peninsula, west Scotland. Identification not confirmed (T.Taylor).

Juvenile specimen at Abbots Reef, Mountís Bay, Cornwall, (50 03 .1 N 05 18.04 W), June 1999. 10 mm long and electric blue - a colour found only in juveniles  (John Putley).

25 May 2010
I made an unplanned visit to Worthing Pier as the tide was out.  The most notable discovery on the underside of a rock was a tiny nudibranch sea slug Facelina auriculata. Its cerata and overall appearance were bright crimson.

Flabellina pedata

Tiny specimens in purple livery in the Fleet narrows, near Ferrybridge, Dorset, 1996. [Large numbers spawning in the same location in August 1998.] (P.Glanvill).

Photograph by Robert Jones (Trowbridge)

Up to 15 mm long, intertidally, at East Beach and Broad Ledge, Lyme Regis, Dorset, 1996 (Robert Jones).

Recorded at Salcombe, Devon, twice at 20 and 26 metres.
Several solitary individuals at Skomer and St. Bride's Bay, S W Wales, between 6 and 20 metres. (J.Lilley).

Six specimens (probable identification) in Swanage Bay close to Ballard Point, Dorset, 9 May 1998, at 9 metres depth. (J.Lilley)
Large numbers of again spawning in the Fleet narrows, near Ferrybridge, Dorset, i.e. much later in the year than when I last reported them doing this, 22 August 1998 (Peter Glanvill)

4 May 2000
2 x Flabellina pedata, (approx. 20 mm) together on brown seaweed, Lifeboat ramp, Selsey, West Sussex.
(Clive Bremner)

Geitodoris planata

News Report Link

Geitodoris planata from Devon, UK.

Goniodoris castanea

30 August 2005
Photograph  ©   Richard Lord (Guernsey)
           Goniodoris castanea

Whilst accompanying the biologists in St. Peter Port Harbour, I found many Goniodoris castanea sea slugs with their spawn. They were feeding on the colonial Star Ascidian, Botryllus schlosseri,  and were cryptic.  On one 5 x 5 cm
square colony of Botryllus schlosseri I found six of these nudibranchs. Dr. Charles David, President of La Société Guernesiaise, tells me this species is a new record for Guernsey.

Report and Photograph by Richard Lord (Guernsey)
on the Marine Wildlife of the North-east Atlantic Ocean Group
BMLSS Tunicata

10 May 2009

The nudibranch Goniodoris castanea
discovered on the south of Lihou Island causeway, west coast of Guernsey
 on a colony of the Sea Squirt (Tunicata) Botrylloides leachi with two species of Flatworms (Platyhelminthes)

Report & Photograph © by Richard Lord (Guernsey)
Sea Lord Photography

Goniodoris nodosa

Seen twice at Milford Haven where it is supposed to be common. (J.Lilley).

24 November 2003
At the Mumbles (near Swansea) found a few Goniodoris nodosa but no spawn.
Helen Marshall

Janolus cristatus

Specimen given to me by John Barker. Collection probably in Hayling Island area, Hants. (A.Horton) Photographed.

Recorded sublittorally in kelp forest, Torbay (C.Proctor). (05.01.23).

Abundant sublittorally at several sites near Oban, Scotland, 1996. Usually on a bryozoan resembling a miniature Hornwrack, Flustra foliacea. (J.Lilley).

Photograph © Richard Lord (Guernsey)

Nudibranchs from Guernsey
Photograph ©Richard Lord (Guernsey)

Janolus cristatus which I photographed from the Queen Elizabeth II marina in St. Peter Port, Guernsey.  This specimen was crawling just below the water-line on one of the pontoons adjacent to the eastern wall of the marina.  I found one specimen on 19 September 2004 which I collected for photography and another with spawn on 20 September 2004. I took the adults home to photograph and then returned them to the marina the following day.  Both specimens were about 3 cm long.

One specimen caught with Thecacera pennigera in south Wales 1996 (J. Hall). Photographed.

South of Bognor, West Sussex, on pebble and Crepidula substrate at 16 metres.
Off Salcombe, Devon at 22 metres.
Skomer, S W Wales, several specimens at different sites at depths of 5 metres and 20 metres. (J.Lilley).

Very large specimen with eggs in Swanage Bay close to Ballard Point, Dorset, 9 May 1998, at 9 metres depth. (J.Lilley)

Janolus hyalinus

17 February 2007
I found what I think is Janolus hyalinus in a warm, shallow, sandy-bottomed pool in Belle Greve Bay on Guernsey's east coast.
The shallow pool has coralline algae covered boulders sitting in it and this specimen was found underneath one of those boulders.  This pool is within one hundred yards of the Salerie Corner quay on the south side of Belle Greve Bay.  Low tide was at about 12:50 at 1.3 metres.  I found this nudibranch at about 15:15.

Report and Photographs by Richard Lord (Guernsey)
Jorunna tomentosa

At Battery Rocks, Penzance (SW477298) 1965. CBRU records supplied by Dr Ian Lancaster.

Observed off Swanage, Dorset, at a depth of 8 metres in August. (J.Lilley)

One specimen in Swanage Bay close to Ballard Point, Dorset, 9 May 1998, at 9 metres depth. (J.Lilley)

10 March 2001 at the Mumbles, Swansea.
It was 25mm, pale beige in colour, with velvety skin and with the ability to withdraw the rhinophore's completely also the gills.  Undoubtedly it had done this when captured, hence my failure to recognise what it was at the time.

2002  Jorunna tomentosa found on Japanese weed at Les Écréhous (Channel Islands) by Nicolas Jouault.

Limacia clavigera

Details to be extracted from archives. (02.04.07*)

Recorded in kelp forest, Torbay (C.Proctor).(05.01.23)

Two specimens washed up on the beach at Anstey's Cove, near Torquay in 1995 (C.Proctor).
At Battery Rocks, Penzance (SW477298) 1978/1986. CBRU records supplied by Dr Ian Lancaster.

Castlebeach, Dale, Pembrokeshire. at 12 metres.
Great Mew Stone, Plymouth, 15-19 metres, very common, usually on encrusting bryozoans on red algae.
Eddystone, south of Plymouth at 20 metres: one on red algae, one on Membranipora on kelp frond.
Also, found on a dive near Oban, west Scotland. (J.Lilley).

2 discovered on a dive at Portland Bill, west side, on 6 July 1998. (J.Lilley)
3 discovered on the bryozoan Electra pilosa (probably) on the red seaweed Delesseria sanguinea off Portland Bill, west side, north of Blacknor Point dive. (J.Lilley).

Discovered on the bryozoan Membranipora growing on a kelp stipe and elsewhere, quite often. Caherdaniel, SW Ireland dive. 1998 (J.Lilley).

Frequently discovered on a Farne Island dive, 15 August 1998 (Jane Lilley).

Lomanotus genei

Recorded at 20 metres depth, S.W. Gateholm, Pembrokeshire, on hydroid Nemertina ramosa with small coil of eggs present at the base of the hydroid. Sea bed ascidian/bryozoan/hydroid turf dominant and sponge-rich area on mixed bed.
This species has been only seen once or twice by divers in this area.
Grid ref: SM 768068 (K.Lock). Video-Photographed.

One specimen seen at Hand Marks, St. Bride's Bay, Pembrokeshire. at 16 metres, on an unidentified hydroid; seabed rocky with some overlying sediment. (J.Lilley).

Okenia elegans

A single specimen on a Lundy dive, at Gull Rock, 11-16 metres, 29 June 1998 (J Lilley).

Onchidoris bilamellata

Regular occurrence in spring on east Brighton beach under rocks on the lower shore. Numbers vary from a few pairs to hundreds from year to year. (A.Horton). Photographed.

Onchidoris bilamellata laying spawn

Occasional specimens at East Brighton, on shore,  next to barnacles 1982 (D.Ventham).

10 specimens together, each about 13 mm long, normal speckled cream and brown coloration (see photograph) on a dive at Caherdaniel, SW Ireland 1998 (J.Lilley).

Spawn laid by this species photographed in aquaria from a specimen collected from under Worthing Pier in the spring of 1998. (A. Horton).

Spawn recorded in large quantities under Worthing Pier in March 1999. No adults found but it looks like a breeding year. (Chris Everson).
16 March 1999. Spawn and individuals (just one pair discovered) under Worthing Pier. (Andy Horton).

13 May 1999:  Spawn recorded in even larger quantities than March under Worthing Pier. On the top of about 20 boulders under the actual pier. On one boulder, 16 nudibranchs in two groups of 8 were beginning to lay spawn. (Andy Horton).

A considerable way up the Tyne in October 1999,  lots of Onchidoris bilamellata on rocks which we trawled up (consuming large quantities of barnacles). The salinity was around 20 psu.  I was pleasantly surprised, however I am not expecting that they are going to survive as they were found in the Tyne.  Do you have any idea when they die off?  The individuals I have are around 20 mm long. (Helen Marshall).

Three 20 mm individuals at the Mumbles, late February 2001. More specimens on 10 March 2001. (Jim Hall)

4 March 2002. A single specimen at Kingston beach, Shoreham. On this inner harbour shore, such occurences are unusual.

5 March 2002
On a calm day the low spring tide at Shoreham was forecasted at 1.1 metres. The tide receded to lap against the lowest of the Worthing pier supports at its lowest ebb. Fauna was not particularly special. Plumose, Beadlet and Sagartia troglodytes sea anemones were recorded. Very small Blennies (x 50+) and Rock Gobies (x 12) were under rocks. The most notable report was of the spawn of the nudibranch Onchidoris bilamellatabut no adults were seen.

Onchidoris sparsa


A specimen photographed by Sean Clark under the West Pier, Brighton in year 2000.

Palio nothus

One specimen seen on a dive on a reef on the south side of Castlebeach Bay, Dale, Pembrokeshire.  (J.Lilley).

Polycera faeroensis

Common sublittorally at Skomer Marine Nature Reserve. Yellow appendages. Up to 23 mm long only. Mating. June and August. (J.Lilley).
Observed mating on a dive near Oban, west Scotland, June 1996 (J.Lilley).
On wreck of James Egan Layne, near Plymouth, about 15 metres; and near Eddystone lighthouse, south of Plymouth.

One at the Farne Islands on 16 August 1998.  (J.Lilley).

3 specimens, 1 pair mating, Portland Bill, west side, south of Blacknor Point dive, 7 July 1998 (J.Lilley).

2 specimens on a Lundy dive, at Gull Rock, 11-16 metres, 29 June 1998 (J Lilley).

A single specimen on a Lundy dive, Knoll Pine, 30 June 1998  (J Lilley).

5 specimens on a Lundy dive, north side of Jenny's Cove, 1 July 1998 (J Lilley).

3 specimens on a Lundy dive, north end of Jenny's Cove, 2 July 1998 (J Lilley).

Frequent including 3 mating pairs on a Lundy dive, wreck of the MV Robert, 3 July 1998 (J Lilley).

Quite often found (but not as common as the next species), including mating pairs, Caherdaniel, SW Ireland dive. 1998 (J.Lilley).

Polycera quadrilineata

Recorded on bryozoans attached to mussels under Worthing pier, Sussex (A Horton).
Young specimens collected with Sea-Mat bryozoan Membranipora membranacea at east Brighton beach (A.Horton).  (06.01.42*)

Occasional specimens at East Brighton 1982. More details available. (D.Ventham)

Out of Bognor at 9 metres: mating pair 28 April 1996.
Opposite westernmost of Seven Sisters, East Sussex, at 5 metres on red algae.
Salcombe, Devon at 30 metres +.
South of Littlehampton, West Sussex, at 15 metres, numerous small specimens on a smallish rock covered with Membranipora-like encrusting bryozoan. (J.Lilley).

One off Purbeck, immediately, south of Durleston Head, at 9 metres  (J.Lilley).
Frequently found on kelp, including a mating pair of 1 normal-coloured and 1 finely spotted all over with black; another black-spotted individual nearby; spawn, at the Farne Islands 15 August 1998, another very black-spotted on at the Farne Islands on 16 August 1998.  (J.Lilley).

Quite often found, including mating pairs, Caherdaniel, SW Ireland dive. 1998 (J.Lilley).

June 2000: 6 mm specimen discovered by Jim Hall at Mumbles Pier, Swansea, amongst the mussel beds.

Rostanga rubra

At Battery Rocks, Penzance (SW477298) 1965. CBRU records supplied by Dr Ian Lancaster.

14 August 2003
A Rostanga rubra was discovered in a rockpool at Les Écréhous, Jersey. News item. This species feeds on red sponges.

Rostanga rubra from Devon, UK

Thecacera pennigera

Reputably rare species recorded at Skomer Marine Reserve.
One specimen on one occasion, and two on another dive at South Haven, Skomer at 20 metres. (J.Lilley).
Also at Castlebeach, Dale, Milford Haven, Pembrokeshire. at 12 metres. (J.Lilley).

Numerous sea slugs of this species caught on the shore (south Wales) whilst fishing for prawns in 1995 and 1996. Identification verified at Swansea University. (Jim Hall). (05.03.40*)

One specimen Portland Bill, west side, south of Blacknor Point dive, 7 July 1998 (J.Lilley).

Dozens of specimens at low tide near Mumbles Pier, Swansea in May 2000 (Jim Hall).

c. 17 September 2003
A specimen of the nudibranch Thecacera pennigera is observed on the Brooklands outfall pipe, on the Lancing/Worthing border, West Sussex.

Report by David Cropp via Paul Parsons
24 November 2003
Nothing too interesting to report except that I am still finding Thecacera pennigera at Mumbles (near Swansea) though in much smaller numbers (just five today) all between 4-10 mm in length. The interesting bit:  I found them on Bugula
plumosa which had started growing. I found quite a lot at Mumbles today (two
months ago there was nothing there), mainly it was new growth on older stems
that had apparently "died back". Found a few Goniodoris nodosa but no spawn.
Helen Marshall

Trapania pallida

18 June 2000
Small specimens seen on a dive out of Bracklesham Bay, East Sussex. (J.Lilley)
Probably also out of Poole, Dorset, on 1 May 1999. (J.Lilley)

Trapania pallida enquiry:
Not quite Poole Bay, but I have seen two, in very close contact, in Swanage Bay.  31 May 99, in 8 m of water, on a reef with a mixture of red algae, hydroids and bryozoan.  They were both around 12 mm long. Identification was from underwater observation + a rather poor photograph, but I noted at the time that there was enough detail to be certain.  I don't have the photo to hand (it's in a file on the boat),but will check it to see if possible food sources can  be identified.
Mike Markey

I have never seen this animal, despite having dived Loch Sunart 15-20 times, but I'll keep an eye out for it next week when we are up there.
Jim A

Tritonia hombergi

Nudibranch recorded feeding on soft coral Alcyonium digitatum at Castlebeach Bay, Dale, Pembrokeshire. at about 12 metres; and at Rye Rocks, North Haven, Skomer, Pembrokeshire. below 30 metres; both in June (J.Lilley).
(05.03.26*, 06.02.24).

Small, but numerous in places, Caherdaniel, SW Ireland dive. 1998 (J.Lilley).

Several 13 mm long specimens discovered on a Farne Island dive, 16 August 1998 (Jane Lilley).

28 January 2000
A crab fisherman gave me a live nudibranch Tritonia hombergi.  I placed it in a black bucket with aeration and it spawned on 1 February 2000. It weighed 35 grams after spawning and it was 12 cm long when crawling... quite a frilly beautiful animal.  The crab fisherman who gave it to me said that he was noticing a lot of spawn on his crab potting gear.  It appears the Tritonia hombergi crawled into his pot to spawn.                                                  Report by Richard Lord (Guernsey)
Eggs on on Isle of Man dive. No adults. (early July 2000) (J.Lilley)

Tritonia lineata

Single specimens seen repeatedly around Skomer, Milford Haven, and on one rock with lots of small specimens at Stack Rock, out of Broad Haven, Pembrokeshire. (J.Lilley).

   Illustration  by Chris Hicks (Northolt)

1 August 1999: A single specimen of the nudibranch Tritonia lineata was discovered by Gavin Bushell diving alone off Porth Eilian, Isle of Anglesey, NW Wales. It was discovered on the west side of Point Linas, over a sea bottom that had large boulders scattered around, but generally was covered in a dense fine silt. And it was on a patch of this silt between the boulders that the nudibranch was discovered at a depth of 8 metres. The species is probably not rare, but it is rarely reported from any location other than around the islands of Skomer (SW Wales) and Lundy (Bristol Channel). It has not been recorded intertidally, and its infrequency of reporting by divers maybe because it inhabits silty conditions which tend to be unpopular with divers because of their poor visibility when the silt is churned up, and because such sites do not prove as interesting as hard rock areas. The diet of this nudibranch is not known and all observations are of interest. This species has a local distribution, but seems to be widespread and is found of almost all British coasts.

The following info may add something to your data on Tritonia lineata (Report of 25 March 2000).

I have logged the following observations of T. lineata in Poole Bay:
15 Jun 97 depth 14m rather poor photo taken
11 Sep 99 depth 11m several, up to 15mm long
7 Nov 99 depth 11m ditto
21 Nov 99 depth 11m  just one seen, approx. 15mm
19 Mar 00 depth 11m at least 6 seen, 10/12mm long

There are two separate sites here (1997, and 99/00), both of which are typical Poole Bay reefs - silty rock surfaces with lots of holes, gullies etc, and some current at some stages of the tide (mainly the ebb) and quite slack water at other times.  The Tritonia lineata have usually been seen on fairly vertical surfaces.

The observations listed are only those which I have logged - Tritonia lineata is common enough in Poole Bay to be seen without being noted!

Report by Mike Markey
Dive in Poole Bay on Sunday 20 August 2000.

The site is a small offshore reef surrounded by silty sand, with depths 13-16 m at high water.  There are other similar reefs nearby.  There will be some current on the ebb tide, running approximately south west, but considerably less on the flood.  The rocks are generally covered with a silty 'turf'.

Observation 1:
There are a lot of Tritonia lineata there at the moment (I stopped counting after 20, which included 8 spread out over just a couple of square metres).  They are mostly around 15 mm in length, and one was in the process of laying eggs - there was no clear target that the eggs were being laid on.  I took some photos, which are not very satisfactory, but one of them does show one of the Tritonia close to and heading towards a group of what I am told are Sarcodictyon sp., said to be a possible food source.

Report by Mike Markey
Tritonia nilsodhneri

Observed at Eddystone Rocks, near Plymouth, on Eunicella verrucosa at 25 metres, with eggs: a tight spiral of pink-beige thread wound around the arms of a sea fan on 8 July 1995. Also nearby on 27 July 1996 with eggs. (J.Lilley).

Low numbers on sea fans Eunicella verrucosa, (up to one specimen on a fan), around the island of Lundy in the summer of 1997 (J. Lilley). (09.01.31**).

3 specimens with eggs on a Lundy dive, north side of Quarry's Bay, 30 June 1998 (J Lilley).

On a Lundy dive near Gannet's Rock on 2 July 1998, 41 sea fans Eunicella verrucosa inspected to discover 5 of these nudibranchs, no more than one on a fan, except for one fan which had two plus the eggs (J Lilley).

Further Information

One problem until recently was that there was no popular book in print that identified more than a handful of species, but this has now been remedied:'


A Field Guide to the Nudibranchs of the British Isles', by Bernard Picton and Christine Morrow, published by Immel Publishing, 1994, cost £15.95. It contains beautiful colour photographs of all the British species.
ISBN 1-898162-05-0.

Any bookshop should be able to obtain a copy, but if you have any difficulties you can order direct from Immel Publishing Tel: 071 491 1799.


British Opisthobranch Molluscs by T E Thompson & Gregory H Brown
 Field Studies Society   Synopses of the British Fauna No.8
 Academic Press [1976]   ISBN 0.12.689350.0
Revised to:  Molluscs:  Benthic Opisthobranchs  by T E Thompson

This book describes all the external features and general structure of these molluscs as well as the basic internal anatomy.

Sea Slugs: Locomotion

The BIOMAR CD-ROM contains information on British opisthobranchs.

Link for more information


Molluscs of the English Channel and
Atlantic Coasts

P. Bouchet, F. Danrigal and C. Huyghens
National Museum of Natural History, Paris
Translated and Edited by
B. F. Picton

Department of Botany and Zoology
The Ulster Museum, Belfast

ISBN   0 7137 1031 4

An interesting little book, but not a comprehensive identification guide. Available in second-hand shops sometimes.

Please send in Reports by EMail


Bernard Picton's Nudibranch Site 
Jim Anderson's Scottish Nudibranch pages
Sea Slug International Page
Sea Slug Forum
Sea Slug Forum Species Index
Nudibranchs (Australia)
Mediterranean Opisthobranchs
Opisthobranchs from north-eastern Atlantic and North Sea
More Nudibranch Links (International)  including the 
Australasian Nudibranch Newsletter
Okinawa Slug Site
Nudibranchs of Heron Island, Great Barrier Reef (Book)
Opisthobranch Mollusks
Slug Site

British Mollusca
BMLSS Species List
Nudibranch Food Preferences
TORPEDO Electronic News Bulletin (All Species)

British Marine Life Study Society Home Page
News 2020
News 2018
Main Links
Membership Form
Top of the Page
Use these links if your are familiar with the scientific classifications of marine life


Uncommon Species Notes (not Nudibranchs)