Asteronotus madrasensis   O'Donoghue,  1932 (Sea Slug)
Organism information awaits expert curation
Class: Gastropoda

Size: 76 mm long by 41 mm wide and 39 mm high. The foot measures 72 mm long by 42 mm wide, but its margin is greatly crumpled. The radula is large, and measures 9 mm long by 11 mm wide.

Color in life: Black spots, papillae are partly black and the branchiae are brown. The dorsal surface of the foot flange and the ventral surface of the foot have black spots and blotches.

The body is doridiform but it is much contracted and plump, almost rectangular in cross section. The mantle is not wide and the dorsum is very smooth and almost slimy. The mantle is bluntly rounded in front and behind, and thrown into a series of low, wide, transverse folds. Behind the rhinophore sheath on each side is a small group of flattened papillae, those on the right being more numerous and further from the sheath. On the right side also there is a second, similar but smaller group.
The head is a low sub-spherical process buried in the groove between mantle and foot. It bears well to each side a small cylindrico-conical tentacle. The foot is oval, bluntly rounded in front and more sharply rounded behind. It has an outstanding flange-like margin, which is much wrinkled and folded. It is widely bilabiate at the front end back to between one-quarter and one-third of its length, and upper lip is deeply notched in the middle line, but the cleft is narrow. The rhinophore is clavate with a short cylindrical stalk and a cylindrico-conical, multiperfoliate clavus. It is deeply retractile within a deep sheath with a rounded margin. The branchico consist of six large quadripinnate plumes arranged in a circle; they are joined at their bases, but the junction between the posterior pair is lower than the others. They can be retracted into a deep sheath with a smooth sheath on which, however, are a few blunt points. The anus lies in the centre of the circle of branchiae upon a well-marked papilla with a flattened top, which bears a series of radiating ridges. The renal aperture is on a small papilla, just behind the anal papilla.
The reproductive aperture lies well forward on the right side of the body slightly behind the level of the rhinophore. Behind it is a membranous fold passing down to the upper surface of the foot flange. The buccal mass is large and consists of two parts, an anterior chamber immediately inside the mouth and a muscular portion containing the radula. The inside of the anterior chamber contains a number of papillae; near the mouth they are long and packed into about six longitudinal ridges, which practically occlude the cavity. Behind this they are low and irregularly scattered, so that they leave a cavity which forms a sort of antechamber to the muscular portion. Although all the papillae are hard they do not appear to have a chitinous covering.
There are 46 rows of teeth, of which the last two are not fully formed, and there is no rachidial tooth. The formula of the first row is 9.0.16, of the second 32.0.40, and of a complete row 98.0.98. The innermost tooth has a basal plate in the form of a round angled parallelogram with a thickened anterior margin. From this arises a simple, spine-shaped, backwardly directed blade. In lateral view there is a characteristic rounded shoulder above the union of the blade and basal plate. The remaining teeth are all simply hamate with rather a long blade, and increase in size to a maximum about two-thirds of the way out. The outermost three decreases rapidly in size and the last is partly degenerate and curiously curved.

Synonym (s)

Common Name (s)
Economic Importance and Threats



• Tamil Nadu, Krusadai Island INDIA

Literature Source(s)
  • O'Donoghue, CH (1932) Notes on Nudibranchiata from southern India Journal of Molluscan Studies The Malacological Society of London 20(3) 141-166 Available at -
  • Society for the Management of European Biodiversity Data (2009) World Register of Marine Species (WoRMS) Available at -

Page last updated on:2010-11-30

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