Thuridilla undula    Gosliner, 1995

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This species has been observed on Reunion Island


Order : Sacoglossa
Superfamily : Plakobranchoidea
Family : Plakobranchidae
Distribution : Known only from Papua New Guinea, Guam, Palau , the Philippines, the Maldives and now Réunion island
Maximal size : 20 mm
Abundance : Seldom on the fore reef zone


Species characteristics :

This sapsucker is turquoise bluish green. The undulating parapodial margin is a broad band of burnt orange, then a narrow line of black and a region of vivid blue reflective pigment.

This coloration pattern is also present on the rhinophore and on the anterior margins of the foot.

sapsucker Thuridilla undula
Showing species characteristics...

Photo Philibert Bidgrain
Reunion, "Trou d'eau" at Saint Gilles, 25 August 2010, size  10-12 mm

See more about : Sightening and mating periods
   See more about : Thuridilla phylogeny by Gosliner 1995
   See more about : Thuridilla undula variability in Southwest Indian ocean

Remarks :

Identification confirmed by Nathalie Yonow
    This sapsucker was found with specimens of Sagaminopteron psychedelicum on Dysidea sp.
    In these specimens we can observed between the burnt orange and the dark band a pale orange line (a little like in T. neona.... ), may be its a pattern variation for this species. We need other photos to confirm this hypothesis.
    Synonymous : (according Worms)
               - No other name

Bibliographic data :

A typically shaped thuridillid, long and thin, tapering posteriorly, and with a pair of rolled rhinophores anteriorly. The rhinophores are ¼ total body length.
    In T. undula the orange, blue and black markings on the rhinophores are transverse bands
    T. undula is similar in colour to T. neona. Both have a turquoise body with burnt orange, black and blue undulating parapodial bands. However T. neona has additional bright orange markings on the parapodia, anterior margin of the foot and the rhinophores. In T. undula the orange, blue and black markings on the rhinophores are transverse bands, while in T. neona they are diagonal.
    T. undula is even closer in colour to T. lineolata, the main difference being that the colour bands at the parapodial edge undulate in T. undula and are parallel to the edge in T. lineolata.
    Comparative data of the five Thuridilla with black, orange and blue margin found in our area...

 

T. multimarginata

T. indopacifica

T. livida

T. hoffae

T. undula

Parapodial margin

Narrow white edge enlarged at regular intervals, then a narrow stripes of orange, black, pale blue, and black.

Thin brownish black edge, then a broad band of yellow-orange, and an irregular band of black. In the spaces between the blackish extensions are bright blue

Black edge followed by lines of orange, black and narrow iridescent blue

Bright yellow-orange edge, followed by a thin black line and a diffuse broad light blue to blue green band.

Broad burnt orange edge, followed by lines of black and vivid blue

Head

Opaque white pigment with sometimes orange marks

Blue with a centrally placed Y-shaped opaque white patch

Dark brown to black

Black to dark blue

Black and reflective blue pigment.

Rhinophores

They have opaque white pigment with sometimes orange marks
    The tips of the rhinophores are black

The base are whitish to pale blue. At the tips are bands of blue, black, orange-yellow and black.
   Not observed in our specimens

They are dark brown to black
    The apical half has opaque white pigment

They are light blue except for the tip which is dark-blue

The base are turquoise bluish green. At the middle are narrow bands of blue and black. The apex is orange

Body

Orange or light to dark green

Translucent green with scattered opaque white spots

Dark brown to black

Black to dark blue

Turquoise bluish green

Anterior margin of the foot

It has orange, black, blue and black lines

It has black, orange-yellow , black and blue bands

It has black, orange and blue lines .

It hasn't blue and orange lines

It has orange, black and blues bands.

References :

Bill Rudman Seaslug site : Sea Slug Forum : Thuridilla undula

Publications :

  Gosliner, T.M. (1995) The genus Thuridilla (Opisthobranchia: Elysiidae) from the tropical Indo-Pacific, with a revision of the phylogeny and systematics of the Elysiidae. Proceedings of the Californian Academy of Sciences 49(1) : 1-54.
    Jensen, K.R. (2007). Biogeography of the Sacoglossa (Mollusca, Opisthobranchia). Bonner Zoologische Beiträge. 55: 255281.

Other photos of Thuridilla undula :


 

 

Sophie Darnis

Reunion, "Maison verte" at Saint Leu, 30 April 2006, size : 7-8 mm


 

Sophie Darnis

Reunion, "Cirque des Aigrettes" at Saint Gilles, 10m, 2 December 2007, size 10-12 mm

 


thuridilla undula

Philibert Bidgrain

Réunion, "Trou d'eau" at Saint Gilles, less 1 m, 6 October 2010, size 15-18 mm

A specimen with a very wavy margin parapodial


Philibert Bidgrain

Réunion, "Trou d'eau" at Saint Gilles, less 1 m, 6 October 2010, size 10-12 mm

 

A specimen with small white dots on the sides of parapodia .... like Thuridilla indopacifica

 

thuridilla undula


thuridilla undula

Philibert Bidgrain

Réunion, "Trou d'eau" at Saint Gilles, less 1 m, 11 October 2010

A specimen with a extra whitish band near the tip of the rhinophore


 More photos from Indian Ocean

See more about : Thuridilla phylogeny by Gosliner 1995

See more about : Thuridilla undula variability in Southwest Indian ocean

Maldives, Thuridilla undula, at Felidhoo Atoll, by Nathalie Yonow

Reunion, two Thuridilla undula crawling on the substrate, at Trou d'eau, by Philibert Bidgrain