Association with vessel vectors

Actual evidence of being found in samples in a particular vector from any world region.

Anchor and anchor chains. Organisms found on anchors, anchor chain or within attached sediments, including anchor chain lockers.

Ballast water. Ballast water means water with its suspended matter taken on board a ship to control trim, list, draught, stability or stresses of the ship.

Biofouling. Biofouling means the accumulation of aquatic organisms such as micro-organisms, plants, and animals on surfaces and structures immersed in or exposed to the aquatic environment. Biofouling can include microfouling and macrofouling.

  • Macrofouling means large, distinct multicellular organisms visible to the human eye such as barnacles, tubeworms, or fronds of algae.
  • Microfouling means microscopic organisms including bacteria and diatoms and the slimy substances that they produce.
Biofouling comprised of only microfouling is commonly referred to as a slime layer.

Sea chest. The sea chests are cavities (an opening with protection grid) at the bottom side of the ships’ hull (an opening for pumping in and out water for, e.g., ballasting, firefighting) where aquatic organisms may settle and be transported.

Tank sediments. Matter settled out of ballast water within a ship.

Bioaccumulation association

Natural toxins. An organism that accumulates toxins naturally produced by other organisms, such as phytotoxins, in its tissues.

Anthropogenic chemical compounds. An organism that accumulates human-produced chemicals, such as pharmaceuticals, heavy metals, pesticides, dioxins, in its tissues.

Characteristic feeding method

Chemoautotroph. An organism that obtains metabolic energy by oxidation of inorganic substrates such as sulphur, nitrogen or iron.

Deposit feeder – Subsurface. Synonym: detritivore. An organism feeding on fragmented particulate organic matter in the substratum.

Deposit feeder – Surface. Synonym: detritivore. An organism feeding on fragmented particulate organic matter from the surface of the substratum.

Grazer. An organism feeding on plants (higher aquatic plants, benthic algae and phytoplankton) and/or sessile animals organisms.

Herbivore. An organism feeding on plants (higher aquatic plants, benthic algae and phytoplankton).

Mixotroph. An organism both autotrophic and heterotrophic.

Omnivore. An organism feeding on mixed diet of plant and animal material.

Parasite. Feeding on the tissues, blood or other substances of a host.

Photoautotroph. An organism that obtains metabolic energy from light by photosynthesis (e.g. seaweeds, phytoplankton).

Planktotroph. An organism feeding on plankton.

Predator. An organism that feeds by preying on other organisms, killing them for food.

Scavenger. An organism feeding on dead and decaying organic material.

Suspension feeder – Active. An organism feeding on particulate organic matter, including plankton, suspended in the water column, collecting it actively by sweeping or pumping (creating feeding currents).

Suspension feeder – Passive. An organism feeding on particulate organic matter, including plankton, suspended in the water column, utilizing the natural flow to bring particles in contact with feeding structures.

Symbiont contribution. Where some dietary component(s) are provided by symbiotic organisms (e.g. Anemonia with zooxanthellae).

Developmental trait

Brooding. The incubation of eggs either inside or outside the body. Eggs may be brooded to a variety of developmental stages. Males or females may be responsible for brooding.

Direct development. A life cycle lacking a larval stage.

Spawning. The release of gametes into the water.

Lecithotrophy. Development at the expense of internal resources (i.e. yolk) provided by the female.

Parental care. Any form of parental behaviour that is likely to increase the fitness of offspring.

Planktotrophy. Feeding on plankton.

Resting stages. The quiescent stage in the life cycle (dormancy, diapause).

Viviparous. Producing live offspring from within parental body.

Habitat modifying ability potential

Autogenic ecosystem engineers. Organisms which change the environment via their own physical structures (i.e. their living and dead tissues) such as corals, oysters, kelps, sea grasses, etc.

Allogenic ecosystem engineers. Organisms which modify the environment by causing physical state changes in biotic and abiotic materials that, directly or indirectly, modulate the availability of resources to other species (e.g. excavating deep burrows which other organisms co-occupy, damming the water flow, etc).

Keystone species. A keystone species is crucial in maintaining the organization and diversity of its ecological community, by determining the types and numbers of other species.

Life form

Neuston. Organisms that live on (epineuston) or under (hyponeuston) the surface film of water bodies.

Zoobenthos. Animals living on or in the seabed.

Phytobenthos. Algae and higher plants living on or in the seabed.

Zooplankton. Animals living in the water column, unable to maintain their position independent of water movements.

Phytoplankton. Microscopic plankton algae and cyanobacteria.

Benthopelagos. Synonyms: hyperbenthic, benthopelagic, nektobenthic, demersal. An organism living at, in or near the bottom of the sea, but having the ability to swim.

Nekton. Actively swimming aquatic organisms able to move independently of water currents.

Parasite. An organism intimately associated with and metabolically dependent on another living organism (host) for completion of its life cycle.

Symbiont (nonparasitic). An organism living mutually with another species without harming it. Association of two species (symbionts) may be mutually beneficial.


Boring. An organism capable of penetrating a solid substrate by mechanical scraping or chemical dissolution.

Burrowing. An organism capable of digging in sediment.

Crawling. An organism moving slowly along on the substrate.

Drifting. An organism whose movement is dependent on wind or water currents.

Permanent attachment. Non-motile; permanently attached at the base. Also includes permanent attachment to a host.

Swimming. An organism capable of moving through the water by means of fins, limbs or appendages.

Temporary attachment. Temporary / sporadic attachment. Attached to a substratum but capable of movement across (or through) it (e.g. Actinia). Also includes temporary attachment to a host.

Native origin

The region the species originates from.


References should follow the standard of Biological invasions:

Journal article
Gamelin FX, Baquet G, Berthoin S, Thevenet D, Nourry C, Nottin S, Bosquet L (2009) Effect of high intensity intermittent training on heart rate variability in prepubescent children. Eur J Appl Physiol 105:731-738. doi: 10.1007/s00421-008-0955-8
Ideally, the names of all authors should be provided, but the usage of “et al” in long author lists will also be accepted:
Smith J, Jones M Jr, Houghton L et al (1999) Future of health insurance. N Engl J Med 965:325–329

Article by DOI

Slifka MK, Whitton JL (2000) Clinical implications of dysregulated cytokine production. J Mol Med. doi:10.1007/s001090000086

South J, Blass B (2001) The future of modern genomics. Blackwell, London

Book chapter
Brown B, Aaron M (2001) The politics of nature. In: Smith J (ed) The rise of modern genomics, 3rd edn. Wiley, New York, pp 230-257

Online document
Cartwright J (2007) Big stars have weather too. IOP Publishing PhysicsWeb. Accessed 26 June 2007

Trent JW (1975) Experimental acute renal failure. Dissertation, University of California

Reproductive frequency

Iteroparous. Organisms breeding more than once in their lifetime.

Semelparous. Organisms breeding once in their lifetime.

Reproductive type

Asexual. Budding, Fission, Fragmentaion, including parthenogenesis. A form of asexual multiplication in which:
a) a new individual begins life as an outgrowth from the body of the parent. It may then separate to lead an independent existence or remain connected or otherwise associated to form a colonial organism;
b) the ovum develops into a new individual without fertilization;
c) division of the body into two or more parts each or all of which can grow into new individuals is involved.

Self-fertilization. Selfing or autogamy. The union of a male and female gamete produced by the same individual.

Sexual. Permanent hermaphrodite, Protandrous hermaphrodite, Protogynous hermaphrodite, Gonochoristic.
Capable of producing both ova and spermatozoa either at the same time. A condition of hermaphroditism in plants and animals where male gametes mature and are shed before female gametes mature or vice versa.
Having separate sexes.


The exact salinity range if known (psu), else salinity zone(s) according to the Venice system:
1. Limnetic [<0.5psu]
2. β-Oligohaline [0.5-3psu]
3. α-Oligohaline [3-5psu]
4. β-Mesohaline [5-10psu]
5. α-Mesohaline [10-18psu]
6. Polymixohaline [18-30psu]
7. Euhaline [30-40psu]
8. Hypersaline [>40psu]


Colonial. Descriptive of organisms produced asexually which remain associated with each other; in many animals, retaining tissue contact with other polyps or zooids as a result of incomplete budding.

Gregarious. Organisms living in groups or communities, growing in clusters.

Solitary. Living alone, not gregarious.

Sub-species level

A geographical subset of a species showing discrete differences in morphology, coloration or other features when compared with other members of the species. Subspecies may also differ in their habitat or behavior, but they can interbreed. Often the lowest taxonomic level within a classification system.


Valid synonyms of a species (not all of them).


Poisonous. An organism capable of producing poison that gains entry to another organism body via the gastrointestinal tract, the respiratory tract, or via absorption through intact body layers.

Venomous. An organism capable of producing poison, usually injected through another organism intact skin by bite or sting.

Not relevant. Neither poisonous nor venomous.

Public domain: Species account

Species Ensis leei [WoRMS]
Authority M. Huber, 2015
Family Pharidae  
Order Adapedonta  
Class Bivalvia  
Phylum Mollusca  
Synonym (?) Ensis americanus (Gould, 1870)
Ensis arcuatus var. directus
Ensis directus (Conrad, 1843)
Solen directus (Conrad, 1843)
Solen ensis americana (Gould & Binney, 1870)

References (not structured):
Von Costel R, Gofas S (2011) Ensis directus (Conrad, 1843). Accessed through: World Register of Marine Species. Accesed November 18 2011

Species can be found in BINPAS database as 'Ensis Americanus'
Sub-species level (?) Not entered
Native origin (?) Country: USA
--> LME: 6. Southeast U.S. Continental Shelf
--> LME: 7. Northeast U.S. Continental Shelf

References (not structured):
Bousfield EL (1960) Canadian Atlantic Seashells. National Museum of Canada Ottawa, 72 pp.
Gosnel K (1978) Atlantic seashore. New York: Harcourt, Brace and Company.

NW Atlantic.
Ensis directus lives in sandy bottoms in the intertidal or subtidal zones along the Atlantic coast from Labrador to South Carolina. It is usually found in colonies. E. directus is not migratory and remains in its habitat year round
Life form / Life stage (?)
 AdultJuvenileLarvaeEggsResting stage
Symbiont (non parasitic)

References (not structured):
Kindersley D, Molluca-Anatomy online. Accessed 10 November 2011 at

Amos G. Winter V, Robin LH Deits &Hosoi; AE, (2012). Localized fluidization burrowing mechanics of Ensis directus. J Exp Biol. 215:2072-2080.
Sociability / Life stage (?)
 AdultJuvenileLarvaeEggsResting stage

References (not structured):
Amos G. Winter V, Robin LH Deits &Hosoi; AE, (2012). Localized fluidization burrowing mechanics of Ensis directus. J Exp Biol. 215:2072-2080.

E. directus can be colonial in adult phase.
Reproductive frequency (?) Iteroparous

References (not structured):
Sullivan CM, (1948). Bivalve larvae of Malpeque Bay, P.E.I. Fish. Res. Bd. Canada, N°77

Kenchington E, Duggan R, Riddell T (1998) Early life history characteristics of tile razor clam (Etzsis directus) and the moonsnails (Euspiru spp.) with applications to fisheries and aquaculture. Can. Tech. Rep. Fish. Aquat. Sci. 2223: vii + 32

Most E. directus individuals will be sexually mature between the third and seventh growing season. Mating can occur between May and September and is associated with the water temperature.
Reproductive type (?) Sexual

Sullivan CM, (1948). Bivalve larvae of Malpeque Bay, P.E.I. Fish. Res. Bd. Canada, N°77
Ensis directus Atlantic jackknife clam(Also: Atlantic jackknife; common jackknife clam) Camponelli, K. 2001. "Ensis directus" (On-line), Animal Diversity Web. Accessed 19 November 2011.

Ensis directus has separate males and females. The males release their sperm into the water and the sperm enters the females through openings. The eggs are fertilized in the interior of the gill and the newly fertilized zygotes develop into larvae, which are released in the water. There are two larval stages. The first stage is the trocophore stage that has small larvae that are free swimming. They are pear shaped, translucent and cilicated. The second stage is the veliger stage, which is also freeswimming. Ensis directus has a very long pelagic or plantonic stage, which means that the larvae can spread over greater distances. After the larval stage, the species settles onto the sand or mud and begins the development to adult stage.
Developmental trait (?) Planktotrophy

Sullivan CM, (1948). Bivalve larvae of Malpeque Bay, P.E.I. Fish. Res. Bd. Canada, N°77

First larval stage: ciliated trocophore larvae
Second larval stage: veliger larvae
Adult: benthic
Characteristic feeding method / Life stage (?)
 AdultJuvenileLarvaeEggsResting stage
Suspension feeder – ActiveXX
Suspension feeder – Passive
Deposit feeder – Surface
Deposit feeder – Sub-surface
Symbiont contribution

References (not structured):
Ensis directus Atlantic jackknife clam(Also: Atlantic jackknife; common jackknife clam) Camponelli, K. 2001. "Ensis directus" (On-line), Animal Diversity Web. Accessed 19 November 2011.

E. directus is a filter feeders that draws its food from the water around it. When feeding, E. directus will stay close to the surface and expose its siphons. Cilia covering the gills pull the food particles into the shell. As the food passes along the gills (ctenidia) they combine with mucous and become trapped. The cilia along the gills then move the food towards the digestive tract. E. directus mainly feeds upon small phyto- and zooplankton.
Mobility / Life stage (?)
 AdultJuvenileLarvaeEggsResting stage
Temporary attachment
Permanent attachment

References (not structured):
Luczak C, Dewarumez JM, Essink K, (1993) First record record of the american jack knife clam Ensis derictus on the French coast of the North Sea. Mar. Biol. Assoc. 73, 233-235.

Swennen C, Leopold MF, Stock M (1985) Notes on growth and behavior of the American razor clam Ensis directus in the Wadden Sea and the predation on it by birds.-Helgoländer Meeresunters. 39, 255-261

Leewis R (2002) Flora en fauna van de zee [Marine flora and fauna] Veldgids, 16. KNNV Uitgeverij: Utrecht, The Netherlands. ISBN 90-5011-153-X. 320pp

The free-swimming larvae are distributed by currents in spring. Secondary dispersal of post-larval stages in summer.
First larval stage: free swimming
Second larval stage: free swimming
The very long pelagic or planktonic larval stage, allow the larvae to spread over larger distances.
Adult: E. directus are very rapid burrowers with short siphons and usually live near the surface but are able to disappear rapidly to great depths when disturbed.
Remark: E. directus is also able to swim or use byssus threats for drifting. They show a diurnal rhythm, being more abundant in the water column at night.
Salinity tolerance range (?) Exact range: 7 - 32

Maurer D, Watling L, Aprill G, (1974). The distribution and ecology of common marine and estuarine pelecypods in the Delaware Bay Area. The Nautilus. 88(2): 38-46
Habitat modifying ability potential (?) Allogenic ecosystem engineers
Autogenic ecosystem engineers

References: (accessed June 2012)

Ecosystem engineer

Ecosystem engineer: The species is remarkable in both the speed in which new areas are colonized and its dominance in abundance over all other shellfish species, causing competition for food and space. If its population in an area becomes very large, it can affect the overall structure of the benthic community. The fact that these clams dig burrows for themselves can, in areas with dense populations, influence the character of the sediments and hence the habitats of other species.
Toxicity / Life stage (?) Unknown

Not available.
Bioaccumulation association (?) Unknown

Not available.
Known human health impact? Not known

Not available.
Known economic impact? Not known

Not available.
Known measurable environmental impact? Known

Gollasch, S., Kerckhof, F., Craeymeersch, J., Goulletquer, P., Jensen, K., Jelmert, A., and Minchin, D., 2015. Alien Species Alert: Ensis directus. Current status of invasions by the marine bivalve Ensis directus. ICES Cooperative Research Report No. 323. 32 pp.
Witbaard, R., Duineveld, G.C.A., Bergman, M.J.N., Witte, H.I.J., Groot, L., and Rozemeijer, M.J.C., 2015. The growth and dynamics of Ensis directus in the near-shore Dutch coastal zone of the North Sea. J. Sea Res. 95, 95-105.

Impacts on species and habitats, potentially also ecosystem functioning (Gollasch et al. 2015 and references within).
Included in the Target Species list? Yes

Assessed by the COMPLETE project experts (2021), included in target species list.
Association with vessel vectors (?) Ballast waters
Tank sediments

Kerckhof F, Haelters J, Gollasch S, 2007. Alien species in the marine and brackish ecosystem: the situation in Belgian waters. Aquatic Invasions, 2(3):243-257.
Molecular information Available consulted on 19 November 2011.

Several genes of Ensis directus (including cytochrome c oxidase subunit I) are present in Gen bank(TM).
Last update byMonika Pelėdienė, 2022-01-18