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Speckled Camouflage Anemone

Oulactis muscosa

Description 3

A large common anemone, also known as the "sand anemone". Its colours often serve to camouflage it, but close up it can be seen as a rainbow of colours. It feeds on mussels that have been dislodged from their rocks by waves.
Habitat
Rocky shore often nestles in crevices.

Column
Appears to be short and squat, but its column is usually hidden in a crevice, 45mm high. Column brown, orange or greenish brown with lines of white or cream verrucae adhesive pads running up the column, more numerous towards the top. The column is often hidden by the fragments of shell and grit sticking to the verrucae.

Oral disc
The oral disc colour is often primarily red or brown with a complex, 12 way symmetrical, radiating pattern of rings and zig-zags of colour, 40mm diameter. In the South Island it is tends to be larger, often with a red oral disc.

Tentacles
Tentacles towards the centre are brown with mottled white spots, tentacles on the outer edges are mauve/pink. The mottled spots give it a banded appearance. 96 short, 10-15mm long, tentacles in 4 whorls - 12+12+24+48.
Otago card says: tentacles inner green with pale patches, outer deep gray with pink patches, or almost unbarred
24 bright pink or orange spherules encircle the crown.

Distribution
Found throughout NZ.

Reproduction
Can split in half or produce off-spring sexually.

Australian descriptions tend to be a bit different, no mention of pink outer tentacles. Tentacles described as grouped into three rows,transparent to pale brown or pale greenish to greyish-white, marked with horizontal black bands.
Otago card says: "Distinctive features: Tentacles 1/2 - 1/3 width of oral disc. Marginal spherules (pink or orange). Verrucae (suckers on column) in longitudinal rows."


Edited version of Records of the Canterbury Museum, Vol 6, No 1, p102-3, Nov 1951
Article: The Actiniaria of New Zealand - a check-list of recorded and new species, a review of the literature, and a key to the commoner forms Part 1
By G. Parry. :

Genus OULACTIS Milne-Edwards and Haime,, 1851. Actiniidae with well-developed pedal disc. Column smooth in its lowest part, otherwise provided with longitudinal rows of verrucae which, below the margin are small and very close set on small lobes of the column, forming frond-like formations. Fosse distinct. Marginal spherules present.
Tentacles rather short, hexamerously arranged.

Oulactis muscosa (Drayton, 1846)
The base is firmly adherent in rock crevices, so that it is difficult to remove the animal without damage. Column is straight, covered with numerous verrucae in longitudinal rows. These verrucae become more numerous towards the upper part of the column, where the last few of each row (about 12) are carried on a ridge. Their colour is white or cream, the column between them being brown, orange, or a green-brown. There is a circle of bright pink or orange marginal spherules, usually 24.

The tentacles are in 4 cycles, 12, 12, 24, 48. The inner two cycles are mottled brown, the outer a rosy, transparent pink. They all bear on their oral faces a line of brown, with lenticular white patches running across the tentacles, giving it the appearance of being barred with white. The outer sides of the inner, brown, tentacles have a similar brown streak, flanked by white. The tentacles are all rather short and arranged near the outer edge of the disc. They do not differ in size, all being about half or one-third width of the disc.

When the disc is expanded it is held flat, though it may be saucer-shaped, with the inner cycle of tentacles held over it. Its colour is very variable, and may be all one colour, or more commonly, has a complex radiating pattern. Usually its ground colour is within the range of red to brown. There is a slight peristome, usually darker in colour, with white tubercles at the siphonoglyphs. The ground colour of the disc is generally broken up by radial lines and rings of colour. First there is a series of radial brown markings along the mesenterial insertions, from the peristome to the bases of the tentacles. Just beyond the peristome there is a zig-zag ring of darker colour. At the bases of the tentacles the colour usually changes to brown, broken by a V-shaped patch of white at the base of the inner cycle of 12 tentacles. There are similar patches at the bases of the second cycle of 12, but further out, and these patches are all linked with white markings to form a complex ring of white round the tentacles. The outer cycles of tentacles have a ring of white running round the base of each tentacle. The marginal spherules are armed with atrichs; the tentacles with spirocysts, basitrichs and microbasic p-mastigophors.

Size of a large specimen is height, 4.5 cm.; width of disc, 4 cm.; length of tentacles, 1-1.5 cm.

Distributed throughout New Zealand. Rocky shores and reefs, in rock crevices or pools just above low tide level.

References 3

Synonyms:

  • Cradactis plicatus
  • Metridium muscosum
  • Oulactis muscosa
  • Oulactis plicata
  • Oulactis plicatus
  • Tealidium cinctum (Ambiguous synonym)

Comments 3

joe_fish comments (on https://inaturalist.nz/observations/94678616)
those speckles seem to be a surprisingly robust diagnostic trait for these species. also useful is the color of the marginal vesicles and acrorhagi.

dark and white versus white and pink

i haven't looked to thoroughly to see what sort of variation there might be for those traits, but i'd suggest you clearly document them for any suspected magna that you photograph. looks like the vesicles are dark in this specimen, so what do i know...

[edit: looks like vesicle coloration is varied is muscosa. here's a specimen from New South Wales with dark ones. not sure if the pink acrorhagi are of any use]

Sources and Credits

  1. (c) Tony Wills, some rights reserved (CC BY-SA), uploaded by Tony Wills
  2. Tony Wills, no known copyright restrictions (public domain), uploaded by Tony Wills
  3. (c) Tony Wills, some rights reserved (CC BY-SA)

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