Plakobranchus ocellatus    van Hasselt, 1824

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This species has been observed on Reunion, Mayotte, Madagascar and Seychelles Islands


Order : Sacoglossa
Superfamily : Plakobranchoidea
Family : Plakobranchidae
Distribution : Tropical Indo-West Pacific
Maximal size : 50 mm
Abundance : (Run) Seldom on the reef flat zone (May) Frequently on the reef flat zone


Species characteristics :

The head, outsides of the parapodia and the foot are dirty white to pale grey with numerous slightly darker spots each surrounded with a pale ring (ocellated) .
   The long and thin rhinophores extend horizontally from the sides of the head.
   The rhinophores are creamish and their tips are sometimes mauve. The edge of the tail is also tinged with mauve

plakobranchus ocellatus
Showing species characteristics...

Photo Maurice Jay
Réunion, La saline lagoon, under a dead coral, 16 July 1989,
size 40 mm

See more about : Sightening and mating periods
   See more about : Plakobranchus ocellatus variability in Southwest Indian ocean

Remarks :

Identification confirmed by Kathe Jensen and Bill Rudman
    Synonymous : (according Worms)
               - Very numerous synonymous see worms

Bibliographic data :

The color pattern and distribution of spots varies considerably, but the internal anatomy shows so few differences that it must be considered one species with a wide distribution.
    It has a very soft body which is dorso-ventrally flattened. The thin, smooth parapodia, which completely covered the body, meet along the dorsal midline and they can only separated with difficulty.
    The sacoglossans feed by sucking the cell sap out of algae. Some, such as P. ocellatus, keep the chloroplasts from the algae alive in their own bodies, where they continue to photosynthesize - converting the sun's energy into sugars. It stores huge numbers of bright green chloroplasts in ridges hidden from view beneath the parapodial flaps.
    According Jensen, it is never found in close association with any particular alga, indeed its natural food is unknown. It will feed on Chlorodesmis sp (Udoteaceae) and Udotea sp (Udoteaceae) in the laboratory.
    P. ocellatus is a common inhabitant of shallow coral reef pools and lagoons. It is seldom seen as it is well-camouflaged, half buried in the coral sand
    The egg mass is rather different from most elysiid masses. It forms an irregular band containing numerous small eggs

References :

Bill Rudman Seaslug site : Sea Slug Forum : Plakobranchus ocellatus
    Nudipixel Plakobranchus ocellatus

Publications :

Hasselt , J.C.v. (1824). In Andre Férussac. Extrait d'une lettre du Dr. J.C. van Hasselt au Prof. van Swinderen sur mollusques de Java (traduit de l'Allemand. konst en letterbode, 1824, nos. 2,3,4) Tjuringe (île Java) le 25 Mai 1823 (1). Bulletin des Sciences Naturelle et de Géologie, 3 : 237-248
    Jensen, K.R. (1992) Anatomy of some Indo-Pacific Elysiidae (Opisthobranchia: Sacoglossa (=Ascoglossa), with a discussion of the generic division and phylogeny. Journal of Molluscan Studies, 58(3) : 257-296
    Jensen, K.R. (2007). Biogeography of the Sacoglossa (Mollusca, Opisthobranchia). Bonner Zoologische Beiträge. 55: 255281

Other photos of Plakobranchus ocellatus :


Maurice Jay

Réunion, La saline lagoon, under a dead coral, 16 July 1989,
size 40 mm

Detail of the head were :

   - The long and thin rhinophores extend horizontally from the sides of the head.
   - The rhinophores are creamish and their tips are sometimes mauve.
   - There are also some larger ocelli surrounded by a black ring,

plakobranchus ocellatus


Sonia Ribes Beaudemoulin

Réunion, flat reef of l'hermitage, Saint Gilles, less 1 m, 18 May 2007.

Several specimens find in little sandy area on the flat reef.

 

Detail of the head were :

   - The long and thin rhinophores extend horizontally from the sides of the head.
   - The rhinophores are creamish and their tips are sometimes mauve.
   - There are also some larger ocelli surrounded by a black ring,

 

Three specimens on a little sandy area on the flat reef

 


 

Eva Fontaine

Tsoha at Mayotte, crawling on the reef flat zone, less 1 m, 31 July 2008, size 20 mm.

They keep the chloroplasts from the algae alive in their own bodies, where they continue to photosynthesize. It stores huge numbers of bright green chloroplasts in ridges hidden from view beneath the parapodial flaps.


Philibert Bidgrain

Réunion, La saline lagoon, less 1 m, 18 June 2009, size : 25 mm

 


Philippe Bourjon

Réunion, Trou d'eau lagoon, less 1 m, 27 September 2010, size : 20 mm

It stores huge numbers of bright green chloroplasts in ridges (a) hidden from view beneath the parapodial flaps.


 

Eva Fontaine

Mayotte, Mtsanga Tanaraki, crawling on the reef flat zone, less 1 m, 25 July 2010, size 15-20 mm.

 


 

Philibert Bidgrain

Mayotte, Mtsanga Tanaraki, on the reef flat zone, less 1 m, 25 July 2010, size 15 mm.

Try to found the rhinophores...

A well camouflated specimen isn't it???


 More photos from Indian Ocean

See more about : Plakobranchus ocellatus variability in Southwest Indian ocean

Mayotte, underside of Plakobranchus ocellatus, at Sakouli, by Philibert Bidgrain

Madagascar, Plakobranchus ocellatus, at Andavadoaka, by Alain Barrère

Seychelles, Plakobranchus ocellatus, at Mahé, by Christophe Mason-Parker