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?	No
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 To ingest food, a tentacle is inserted into the mouth, the buccal membrane constricts and the tentacle withdrawn, scraping off any adherent food particles.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 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	No
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
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