The Echinoid Directory

Asthenosoma Grube, 1868, p. 42

[= Cyanosoma Sarasin, 1886, p. 80, type species C. urens Sarsin, p. 80 (=A. varium Grube, 1868), subjective ]

Diagnostic Features
  • Apical disc monocyclic, with ocular and genital plates forming an unbroken circle.
  • Ambulacra trigeminate, with a single large element reaching the perradial suture and two small demiplates positioned centrally and abutting one another. Only becoming adradial in position close to the apex and peristome.
  • Pore-pairs arranged in three series except adorally.
  • Primary ambulacral and interambulacral tubercles numerous on oral surface; typically slightly wider than the plate so as to make the plate edge sinuous.
  • Adapically there are no primary tubercles.
  • Ambulacra about half the width of interambulacra at the ambitus.
  • Interambulacral plates with prominent membranous gaps aborally.
  • A single primary interambulacral tubercle on every other plate only; rest of plate with just sparse granulation.
  • Shallow buccal notches.
  • Only ambulacral plates extending over the peristome, where pore-pairs are arranged uniserially.
  • Oral spines ending in expanded cone-shaped hyaline hoof.
  • Aboral spines covered in a thick, fleshy sac.
  • Sphaeridia on inner of two occluded plates only.
Recent, Indo-Pacific and Caribbean.
Name gender neuter
Asthenosoma varium Grube, 1868, by original designation.
Species Included
  • A.varium Grube, 1868; Recent, Indo-Pacific.
  • A. dilatatum Mortensen, 1934; Recent, Indo-Pacific.
  • A. ijimai Yoshiwara, 1897; Recent, southern Japan to the Moluccan Sea.
Classification and/or Status

Euechinoidea; Echinothurioida; Echinothuriidae; Echinothuriinae.



Differs from Araeosoma in having much more numerous and densely packed oral tubercles and spines. Furthermore, its aboral spines are sheathed in a large fleshy sac which is absent in Araeosoma.

A cladistic analysis of the extant species has been provided by Mooi et al. (2004).

Grube, A. E. 1868. Jahresbericht der Schlesiches Gesellschaft fur vaterlandische Cultur 45, p. 42.

Mooi, R., Constable, H., Lockhart, S. & Pearse, J. 2004. Echinothurioid phylogeny and the phylogenetic significance of Kamptosoma (Echinoidea: Echinodermata). Deep Sea Research II 51, 1903-1919.

Mortensen, T. 1935. A monograph of the Echinoidea. Volume 2, Bothriocidaroida, Melonechinoida, Lepidocentroida and Stirodonta. C.A. Reitzel, Copenhagen.

Shigei, M. 1986. The sea urchins of Sagami Bay. Maruzen Co., Tokyo.