Version française...

This species has been observed on Reunion Island

Order : Cephalaspidea Superfamily : Philinoidea Family : Gastropteridae Distribution : Western indian ocean to western pacific Maximal size : 16 mm Abundance : Seldom if ever on the reef flat zone Species characteristics : The basic body color is a transparent grey covered with numerous black punctate markings and light grey to cream coloured pustules The posterior rim of the funnel, the tip of the cephalic tentacles, the tip of the dorso-median crest and the flagellar appendage are lined in orange. In different specimens varying numbers of other orange specks can be found.
	Showing species characteristics...	Photo Christophe Cadet Reunion, Etang Salé lagoon, less 1 m, 29 October 2009, size : 15 mm

See more about : Sightening and mating periods

Remarks :

Identification confirmed by Bill Rudman and Nathalie Yonow
    The general body shape is that of a member of the family Gastropteridae in that it has paired parapodia which extend up over the dorsum, an elongate tapered tail, a posterior funnel on the cephalic shield, an internal shell and a relatively short free mantle margin on the right side
    Synonymous : (according Worms)
               - No other name

Bibliographic data :

The cephalic shield is short (C.s), about one third the length of the body, broadened anteriorly with short cephalic tentacles (C.t) projecting forward     The cephalic shield gradually narrows to form a posterior funnel (F) which is raised and projects forward almost to the anterior limit of the head when seen from a dorsal view.The funnel is relatively short and is heavy at the base.     The dorso-median crest (M.c) is long extending through the center of and projecting beyong the edge of the funnel.     The dorsal hump (D. h) is broad, flattened and gradually slopes to the tail (T)     The free mantle margin (M. m) originates about one third to one half of the way back on the right side of the body becomes wider posteriorly and terminates in a long flagellar appendage (F. a) which normally projects upward

There is some variation in the background colour
               - Some animals appearing translucent cream, and the black speckling varies from dense to very sparse in different animals.
               - The edges of the siphon are usually orange, and sometimes the tip of the siphon as well.
               - There are two distinctive orange spots on the headshield, one at each anterior corner, and the flagellum is also often edged with orange.
               - In different specimens varying numbers of other orange specks can be found.
    The black eye spots are near the anterior base of the funnel and are not clearly visible
    Numerous small pustulose protuberances cover much of the dorsum, tail, and parapodia and are most obvious at the posterior of the dorsal hump. The head has a few small protuberances. Those on the parapodia are much smaller than those on the body and tail
    The ctenidium is hidden by the free mantle margin and the parapodia except for the tips which are sometimes visible just below the flagellar appendage. They are transparent with black punctuations.
    The host is a demosponge, Dysidea spp. The gray colored D. granulosa, and also occasionally another sponge, D. herbacea, which is sometimes a pale blue-gray color on parts of the sponge not exposed to sunlight.
    Specimens of S. nigropunctatum tend to match the color "intensity" of the host, darker on darker forms of D. granulosa, paler on paler forms of D. herbacea.
    The animal is capable of extending the parapodia when attempting to swim.
    Ethymology :
               -The genus is named for Sagami Bay, Japan, where Emperor Hirohito collected so many opisthobranchs that have been studied by Kikutaro Baba
               - The authors named this species nigropunctatum because of the numerous small black punctate markings which cover its body.
    Chemical defense strategy :
               - On Guam, the gastropterids Sagaminopteron nigropunctatum and S. psychedelicum feed on the sponge Dysidea granulosa.
               - They seem to rely on contrasting defense strategies as S. psychedelicum has vivid colors, consistent with the warning coloration found in many chemically defended opisthobranchs, whereas S. nigropunctatum is highly cryptic on the sponge.
               - S. nigropunctatum is avoided by the pufferfish Canthigaster solandri in aquarium assays.
               - The secondary metabolites of the two species both share polybrominated diphenyl ethers (BDEs) with their host sponge D. granulosa.
               - S. psychedelicum and S. nigropunctatum sequester the major BDE in the sponge and accumulate it in the mantle at approximately the same concentration as in the sponge (4.03 and 2.37%, respectively), and concentrate it in their parapodia at over twice the sponge concentration (7.97 and 10.10%, respectively).
               - This metabolite is also transferred to the egg masses of S. nigropunctatum (2.22%) where is may offer protection from bacteria                - Despite contrasting color patterns displayed by the two gastropterid species, they seem to share a similar chemical defense strategy, they feed on D. granulosa and accumulate the major BDE of the sponge in their tissues

References :

Site de Bill Rudman : Sea Slug Forum : Sagaminopteron nigropunctatum

Publications :

Carlson, C.H. & Hoff, P.J. (1973). Two new species of Gastropteridae from Guam, Marianas Islands (Opisthobranchia: Cephalaspidea). Publications of the Seto Marine Biological Laboratory, 21(2) : 141-151
    Gosliner T.M. (1989) Revision of the Gastropteridae (Opisthobranchia: Cephalaspidea) with descriptions of a new genus and six new species. The Veliger 32(4): 333-381
    Gribble, Gordon W. (2010). Naturally Occurring Organohalogen Compounds - A Comprehensive Update SpringerWienNewYork : 1-613
    Mikel A. Becerro, John A. Starmer & Valerie J. Paul. (2006). Chemical Defenses of Cryptic and Aposematic Gastropterid Molluscs Feeding on their Host Sponge Dysidea granulosa. Journal of Chemical Ecology. 12(7) : 1491-1500

Other photos of Sagaminopteron nigropunctatum :

Christophe Cadet Reunion, Etang Salé lagoon, less 1 m, 12 December 2009, size : 20 mm Two specimens with their spawns.

The free mantle margin (M. m) originates about one third to one half of the way back on the right side of the body becomes wider posteriorly and terminates in a long flagellar appendage (F. a) which normally projects upward The dorso-median crest (M. c) is long extending through the center of and projecting beyong the edge of the funnel (F). The ctenidium (C) is hidden by the free mantle margin and the parapodia except for the tips which are sometimes visible just below the flagellar appendage. They are transparent with black punctuations. The posterior rim of the funnel (F) , the tip of the cephalic tentacles (C. t), the tip of the dorso-median crest (M. c) and the flagellar appendage (F. a) are lined in orange.

Philibert Bidgrain Reunion, Etang Salé lagoon, less 1 m, 27 November 2005, size : 10-13 mm Two specimens with their spawns.

Eva Fontaine Reunion, Etang Salé lagoon, less 1 m, 11 April 2011, size : 10-12 mm Several specimens and spawns have been observed on this day... The basic body color is a transparent grey covered with numerous black punctate markings (a) and light grey to cream coloured pustules

Reunion, two Sagaminopteron nigropunctatum and their spawns, at Etang salé, by Christophe Cadet