BIOTIC

BIOTIC Species Information for Neopentadactyla mixta

Researched by

Angus Jackson

Data supplied by

MarLIN

Refereed by

Dr Andrew C. Campbell

Taxonomy

Scientific name

Neopentadactyla mixta

Common name

Gravel sea cucumber

MCS Code

ZB260

Recent Synonyms

Pseudocucumis mixta

Phylum

Echinodermata

Subphylum

Echinozoa

Superclass

Class

Holothurioidea

Subclass

Order

Dendrochirotida

Suborder

Family

Phyllophoridae

Genus

Neopentadactyla

Species

mixta

Subspecies

Additional Information

Various 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 form

Cylindrical

Feeding method

Passive suspension feeder

Mobility/Movement

Burrower

Environmental position

Infaunal

Typical food types

Seston

Habit

Burrow dwelling

Bioturbator

Flexibility

High (>45 degrees)

Fragility

Fragile

Size

Medium-large(21-50cm)

Height

Insufficient information

Growth Rate

Insufficient information

Adult dispersal potential

10-100m

Dependency

Independent

Sociability

Gregarious

Toxic/Poisonous?

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 To ingest food, a tentacle is inserted into the mouth, the buccal membrane constricts and the tentacle withdrawn, scraping off any adherent food particles.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 & Ireland

All 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 distribution

South, west and north coasts of the British Isles, the Faeroe Islands, the west coast of Norway (Molde) and the Atlantic coasts of France.

Biogeographic range

Not researched

Depth range

15-70m

Migratory

See additional information

Distribution Additional Information

Although 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 preferences

Gravel / shingle
Maerl

Physiographic preferences

Open coast
Strait / sound
Sealoch
Ria / Voe

Biological zone

Lower Infralittoral
Upper Circalittoral

Wave exposure

Exposed
Moderately Exposed
Sheltered
Very Sheltered

Tidal stream strength/Water flow

Moderately Strong (1-3 kn)
Weak (<1 kn)

Salinity

Full (30-40 psu)

Habitat Preferences Additional Information

Distribution References

Mortensen, 1927, Konnecker & Keegan, 1973, Keegan, 1974,

Reproduction/Life History

Reproductive type

Insufficient information

Developmental mechanism

Insufficient information

Reproductive Season

Insufficient information

Reproductive Location

Insufficient information

Reproductive frequency

Insufficient information

Regeneration potential

Life span

Insufficient information

Age at reproductive maturity

Insufficient information

Generation time

Insufficient information

Fecundity

Insufficient information

Egg/propagule size

Insufficient information

Fertilization type

Insufficient information

Larvae/Juveniles
Larval/Juvenile dispersal potential	Insufficient information	Larval settlement period	Insufficient information
Duration of larval stage	Insufficient information

Reproduction Preferences Additional Information

No 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