BIOTIC Species Information for Neopentadactyla mixta
Researched byAngus Jackson Data supplied byMarLIN
Refereed byDr Andrew C. Campbell
Scientific nameNeopentadactyla mixta Common nameGravel sea cucumber
MCS CodeZB260 Recent SynonymsPseudocucumis mixta

PhylumEchinodermata SubphylumEchinozoa
Superclass ClassHolothurioidea
Subclass OrderDendrochirotida
Suborder FamilyPhyllophoridae
GenusNeopentadactyla Speciesmixta

Additional InformationVarious descriptions of the tentacles have been made regarding the layout and size of the rings. One of the most recent states that there are twenty in total arranged pentaradially around the mouth. There are ten large outer tentacles arranged as five pairs, then within these, five single intermediate tentacles and then the inside ring is of five small tentacles. Tube feet are usually confined to the radii and may be crowded in the middle of the body.
Taxonomy References Howson & Picton, 1997, Mortensen, 1927, Smith, 1983, Konnecker & Keegan, 1973,
General Biology
Growth formCylindrical
Feeding methodPassive suspension feeder
Environmental positionInfaunal
Typical food typesSeston HabitBurrow dwelling
Bioturbator FlexibilityHigh (>45 degrees)
FragilityFragile SizeMedium-large(21-50cm)
HeightInsufficient information Growth RateInsufficient information
Adult dispersal potential10-100m DependencyIndependent
General Biology Additional Information
  • In suitable habitat, densities have been recorded as high as 400 per square metre. In 1973, the population in Kilkieran Bay appeared to be increasing.
  • Most sea cucumbers are gonochoristic although some species are hermaphrodite.
  • The values for length apply to body length excluding the tentacular crown. When extended, the tentacular crown can be up to a quarter of the body length and have a spread of 140 square cm. The gravel sea cucumber is an infaunal burrower and is only visible when the tentacles are projected above the surface. The body is generally held in a u-shape within the sediment with the tentacles held in the water column and the terminal anus just at the surface.
  • Food particles are trapped using special adhesive areas at the tips of the tentacles. To ingest food, a tentacle is inserted into the mouth, the buccal membrane constricts and the tentacle withdrawn, scraping off any adherent food particles.
  • Melanella alba, a eulimid gastropod is a temporary ectoparasite on Neopentadactyla mixta, piercing the skin and feeding on the internal organs.
Biology References Mortensen, 1927, Smith, 1983, Smith & Keegan, 1984, Konnecker & Keegan, 1973, Smith, 1984, Hansen & McKenzie, 1991,
Distribution and Habitat
Distribution in Britain & IrelandAll up the west coast of Scotland to Orkney and Shetland. A few isolated records from the east coast. Also from SW England, SW and NW Wales. In Ireland, particularly Kilkieran Bay, round the north and north-east, also the SE and SW corners.
Global distributionSouth, west and north coasts of the British Isles, the Faeroe Islands, the west coast of Norway (Molde) and the Atlantic coasts of France.
Biogeographic rangeNot researched Depth range15-70m
MigratorySee additional information   
Distribution Additional InformationAlthough not necessarily representative of all populations, Neopentadactyla mixta exhibits regular daily and seasonal movements within the substratum. In the Kilkieran Bay population, individuals withdraw further into the sediment between 1 or 4 hours after sunrise and remain in the substratum for 1 or 2 hours, re-emerging over a period of up to four hours. In September/October the entire population withdraws into the substratum and re-emerges in March/April. They remain buried in aerobic conditions at depths of up to 60 cm with tentacles retracted and not feeding. Considerable loss of condition occurs during this time. Direct absorption of dissolved organic matter may be important for nutrition. This state of torpor is not complete, respiration and activity is greatly reduced but some movement within the substratum still occurs. Depth of burial is maintained despite surface changes in gravel with water movement.

Substratum preferencesGravel / shingle
Physiographic preferencesOpen coast
Strait / sound
Ria / Voe
Biological zoneLower Infralittoral
Upper Circalittoral
Wave exposureExposed
Moderately Exposed
Very Sheltered
Tidal stream strength/Water flowModerately Strong (1-3 kn)
Weak (<1 kn)
SalinityFull (30-40 psu)
Habitat Preferences Additional Information
Distribution References Mortensen, 1927, Konnecker & Keegan, 1973, Keegan, 1974,
Reproduction/Life History
Reproductive typeInsufficient information
Developmental mechanismInsufficient information
Reproductive SeasonInsufficient information Reproductive LocationInsufficient information
Reproductive frequencyInsufficient information Regeneration potential No
Life spanInsufficient information Age at reproductive maturityInsufficient information
Generation timeInsufficient information FecundityInsufficient information
Egg/propagule sizeInsufficient information Fertilization typeInsufficient information
Larval/Juvenile dispersal potentialInsufficient information Larval settlement periodInsufficient information
Duration of larval stageInsufficient information   
Reproduction Preferences Additional InformationNo information has been found in relation to longevity or reproduction. Breeding is presumed to occur between April and September when the population is at the substratum surface. Most holothurians are gonochoristic and are broadcast spawners (although some species brood their larvae). The larvae of some species show planktotrophy, others lecithotrophy, some direct development, others indirect.
Reproduction References
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