Didemnum vexillum

Overview

Scientific Name: Didemnum vexillum

Phylum: Chordata

Class: Ascidiacea

Order: Aplousobranchia

Family: Didemnidae

Genus: Didemnum

Species:

vexillum [Describe here as A. iricolor]

Native Distribution

Origin Realm:

Temperate Northern Pacific

Native Region:

Origin Location:

Temperate Northern Pacific Japan (Lambert 2009, cited in Dijkstra 2015) STATED AS LIKELY Northwest Pacific, possibly Japan (NEMESIS 2015) STATED AS PROBABLE Northwest Pacific (Lee II & Reusser 2012) STATED Japan (Stefaniak & Whitlatch 2014) STATED Japan (Lambert 2009) STATED Kamome-jima, Esashi City, Hokkaido. (as D. pardum, Nishikawa 1990) STATUS NOT STATED Natsudomari Peninsula, Mutsu Bay. (as D. pardum, Nishikawa 1990) STATUS NOT STATED Okirai Bay and Otsuchi Bay, Iwate Prefecture, northern Honshu of the Pacific side. (as D. pardum, Nishikawa 1995) STATUS NOT STATED Oga Peninsula, Akita Prefecture, northern Honshu of the Japan Sea side. (as D. moseleyi which is misidentified of D. vexillum, Nishikawa 1990) STATUS NOT STATED Off Nagai, Sagami Bay. (as D. pardum, Tokioka 1962) STATUS NOT STATED Oki Islands, Shimane Prefecture, western Honshu at the Japan Sea side. (as D. pardum, Biodiversity Center of Japan 2007) STATUS NOT STATED [Korea] Geojedo Island. (as D. pardum, Rho & Park 1998) STATUS NOT STATED (It cannot be judged whether D. pardum in Korea is native or introduced.) RELATED: [Didemnum spp.] Puget Sound (Kozloff 1993) STATUS NOT STATED

Geographic Range:

-135.400009155273 35.0999984741211,-67 57.1000022888184 (OBIS 2016) Mutsu Bay, Japan to Hiroshima Bay, Japan (Lambert 2009) Oga Peninsula: 39º 48.55'N, 139º 44.51'E to 39º 48.19'N, 139º 44.56'E. (Nisihikawa 1984)

General Diversity:

There are two distinct clades of D.v. based on mitochondrial cytochrome c oxidase 1 (COX1): one in the northwest Pacific (native region), and a second that has been introduced around the world. When the whole mitochondrial genome is analysed, there is a relatively high level of diversity and there was divergence across almost all genes (Smith et al. 2015) There are three haplotypes of D.v. in the Ebro Delta and two in Venice Lagoon (Ordonez et al. 2015) Introduced populations are limited to six haplotypes, while there are 22 in the NW Pacific (assumed native region). All three haplotypes found in the Mediterranean were found in the native region (Stefaniak et al. 2012, cited in Ordonez et al. 2015)

Non-native Distribution

Invasion History:

Yes (Dijkstra 2015; NEMESIS 2015; NIMPIS 2015)

Non-native Region:

Northeast Pacific, Northeast Atlantic, Northwest Atlantic, Mediterranean Sea, Tropical Eastern Pacific, Southern Australia and New Zealand

Invasion Propens:

Temperate Northern Pacific Northeast Pacific (British Columbia to Southern California) (multiple authors, cited in Dijkstra 2015) *Invasive West coast of North America, including Alaska, California, Mexico (NEMESIS 2015) *Introduced Northeast Pacific (Lee II & Reusser 2012) *Non-indigenous Canada (BC), USA (west coast) (Daniel & Therriault 2007) *Invasive Sitka, Alaska, USA to Bahia San Quintin, Mexico (mulitple authors, cited in NEMESIS 2015) *Introduced Morro Bay, California (Needles & Wendt 2013) *Introduced Puget Sound, Washington, USA (Cordell et al. 2013) *Non-native and invasive West coast of the USA, British Columbia (Canada) (multiple authors, cited in Forrest et al. 2013) *Non-indigenous Temperate Northern Atlantic Northeast of the USA, northwest Atlantic, the Netherlands, northwest France, Ireland, England, North Wales (multiple authors, cited in Dijkstra 2015) *Invasive East coast of North America, including Maine, Massachusetts, and New York (NEMESIS 2015) *Introduced Netherlands; Brittany and Port of Le Havre, France; Ireland; Spain; Adriatic Sea (NEMESIS 2015) *Introduced Northwest Atlantic, Northeast Atlantic (Lee II & Reusser 2012) *Non-indigenous Found at ports connected to Montéal, Québec; Québec city, Québec; and Sorel-Tracy, Québec in Canada (Bailey et al. 2011) *Non-indigenous Ireland, France, the Netherlands, USA (east coast) (Daniel & Therriault 2007) *Invasive Bay of Fundy, Nova Scotia, Canada to Shinnecock Bay, NY, USA (mulitple authors, cited in NEMESIS 2015) *Introduced Northern Ireland (Minchin & Nunn 2013) *Non-indigenous East coast of the USA, the United Kingdom, Ireland, northern France, the Netherlands, northern Italy (multiple authors, cited in Forrest et al. 2013) *Non-indigenous Ebro Delta, Western Mediterranean (Ordonez et al. 2015) *Non-indigenous and invasive Temperate Australasia New Zealand (multiple authors, cited in Dijkstra 2015) *Invasive New Zealand (NEMESIS 2015) *Introduced New Zealand (Lee II & Reusser 2012) *Non-indigenous New Zealand (Daniel & Therriault 2007) *Invasive New Zealand (multiple authors, cited in Forrest et al. 2013) *Non-indigenous Tauranga, northern New Zealand. (Lambert 2009) *Global invader Whangamata Harbour in northern New Zealand and Shakespeare Bay in southern New Zealand. (Coutts & Forrest 2007) *Non-indigenous and invasive Tropical Eastern Pacific Ecuador (Ordonez et al. 2015) *Non-indigenous and invasive RELATED: Temperate Northern Pacific [Didemnum sp.] Introduced to west coast of North America; origin unknown. Abundant on marina floats and subtidal hard surfaces at scattered locations from northern California to British Columbia (Carlton 2007) *Introduced

Status Date Non-native:

Puget Sound, Washington, USA: June - October 2010 (Cordell et al. 2013) Netherlands: first reported in 1991, population exploded in 1996 (NEMESIS 2015) Port of Le Havre, France: 2001; Brittany, France: 2002 (NEMESIS 2015) Malahide Estuary, Ireland: 2005 (NEMESIS 2015) Santander, Baiona, Moana, Corme-Porto, Gijon, Spain: 2008-2009 (NEMESIS 2015) Adriatic Sea: 2010 (NEMESIS 2015) Fangar Bay, Spain: 2012 (NEMESIS 2015) New Zealand: 2001 (NEMESIS 2015) Port Nelson, New Zealand: 2008 and 2009 (Fletcher & Forrest 2011) Ebro Delta, Western Mediterranean: May 2012 (Ordonez et al. 2015)

Vectors and Spread

Initial Vector:

Ballast water, Hull fouling (unspecified), Aquaculture and Fisheries, Natural dispersal, Other

Second Vector:

Hull fouling (recreational and commercial), Aquaculture and Fisheries, Natural dispersal, Recreation, Other

Vector Details:

Introduction vector: fisheries and aquaculture; introduced accidentally with oysters, with discarded bait, and non-mollusc fisheries (NIMPIS 2015) Introduction vectors: hull fouling, ballast water (noted as unlikely), aquaculture, rafting (e.g. on broken leaves, debris), live seafood, ship bilge water (multiple authors, cited in Dijkstra 2015) Introduction and spread vectors: hull fouling, fouling of fishing gear, fishing trawls, dredges, colony fragments in ballast water, movement of oyster and other shellfish stock or gear, natural processes (e.g. currents) (multiple authors, cited in Therriault & Herborg 2007) Spread through hull fouling on local boat traffic and commercial vessels (Dijkstra 2015); interconnected waterways; live seafood (Pederson et al. 2005, cited in Dijkstra 2015) Vectors: hull fouling, associated with Pacific oyster aquaculture (Lee II & Reusser 2012) Introduction vector: oyster bags (Minchin & Nunn 2013) Spread by leisure craft (Minchin & Nunn 2013) Introduction vectors: hull fouling and ballast water (multiple authors, cited in Lambert 2009) Spread regionally and locally through hull fouling of recreational vessels and barges (Wasson et al. 2001, cited in Lambert 2009) and movement of aquaculture products and gear (Lambert 2009) Spread regionally through hull fouling of barge in New Zealand. (Coutts & Forrest 2007)

Spread Rate:

[West coast of North America] First reported in San Francisco Bay, California in 1993; reported from Okeover Inlet, BC in 2003 and Puget Sound, Washington in 2004; reported from Sitka, Alaska, in 2010. In 2005, D.v. was found fouling oysters in Bahia San Quintin, Mexico (mulitple authors, cited in NEMESIS 2015) [Georges Bank, USA] covered 103.6 km^2 in 2003 and 2004, 259 km^2 in 2005, and had doubled at 75% of survey sites in 2006 (multiple authors, cited in Daniel & Therriault 2007) [East coast of North America] Reported from Damariscotta River estuary, Maine in 1982; collected from Tillies Bank, MA in 1996; Eel Pond at Woods Hole, MA in 2000; Bay of Fundy, Nova Scotia, Canada in 2014. Most southern extent is reported to be Shinnecock Bay, NY in 2004 (mulitple authors, cited in NEMESIS 2015) [New Zealand] Two months later from the first record in Whangamata Harbour in northern New Zealand, the ascidian was found on the hull of a barge moored in Shakespeare Bay in southern New Zealand. (Coutts & Forrest 2007)

Date First Observed in Japan:

Not applicable

Date First Observed on West coast North America:

1993; San Francisco, USA; though fishermen in British Columbia, Canada assert that it was present a decade earlier (NEMESIS 2015) RELATED: [Didemnum sp.] Appeared in California in the 1990s (Carlton 2007)

Impacts

Impact in Japan:

Not applicable

Global Impact:

Able to overgrow benthic organisms; spread quickly through high reproductive output and fragmentation (NIMPIS 2015) Once established, D.v. is able to overgrow shellfish and other sessile invertebrate species, and inhibits the settlement of invertebrate species. This also makes it a pest to mussel farmers (multiple authors, cited in Dijkstra 2015) [New Zealand] Economic impact on aquaculture industry due to fouling of equipment (Dijkstra 2015) [Maine, USA] Overgrowth of aquaculture target species (Valentine et al 2007b, cited in Dijkstra 2015) Impacts: ecosystem change/habitat alteration, modification of natural benthic communities, monoculture formation, negatively impacts aquaculture/fisheries, threat to/loss of native species. Through: competition (monopolizing resources and smothering), filtration, fouling, interacting with other invasive species, rapid growth (Dijkstra 2015) [New Zealand] Overgrows and smothers mussels, resulting in crop losses. Fouling pest to the commercial fishing industry and ports (Coutts & Forest 2007, cited in NEMESIS 2015) Economic: Reduced abundance of wild fisheries, such as bottom fishes, scallops and lobsters is expected due to habitat change. Eradication attempts have been expensive. Cost of removal from aquaculture facilities, notably shellfish cages but also salmon aquaculture cages (multiple authors, cited in NEMESIS 2015) Competition: Changes to community structure, reduced resources available for other species (e.g. food, space), overgrows other species. Sea scallops fouled with D.v. have reduced swimming speeds, and may be less able to escape predation. Some species die when overgrown (multiple authors, cited in NEMESIS 2015) Habitat change: Overgrows gravel, seaweed, scallops, mussels, other invertebrates, and so alters the structure of habitat and reduces available space for larval settlement, and reduces suitable shelter for juvenile fish and other prey organisms (multiple authors, cited in NEMESIS 2015) Food/prey: D.v. mats may form a physical barrier between fish and benthic prey resources (Valentine et al. 2007, cited in NEMESIS 2015) Toxicity: Chemical defenses result in a lower surface pH of 2-3 (Bullard et al. 2007, cited in NEMESIS 2015) Outcompetes native organisms; overgrows and smothers seaweeds; lowers quantity of suspended organic particles in the wter column; reduces the amount or change the composition of plankton; overgrows sponges, hydroids, anemones, limpets, oysters, mussels, scallops, barnacles, bryozons, corals, coelentrates, ascidians, other fouling species; mussels and oysters populations may decrease in condition and suffer from increased mortality; casuses increased competition for food; prevents benthic larval settlement; out competes native species for space; changes species composition in fouling communities; reduces available prey for fish; reduces refuges for juvenile rockfish; acidic tunic could kill fish eggs or larval fish settling on its surface (multiple authors, cited in Daniel & Therriault 2007) Has potential to cause physical, economic, and ecological damage through fouling of clean surfaces, damage and loss of efficiency due to increased drag, and reduced benthic biodiversity, respectively (Aldred & Clare 2014) Negatively impacted mussel length, condition, growth, and shell thickness (Auker 2010, cited in Cordell et al. 2013) Changes in community structure and composition (multiple authors, cited in Cordell et al. 2013) Mussel shell thickness was greater at one site where D.v. was present (Cordell et al. 2013) Increased abundance of benthic polychaetes (Lengyel et al. 2009, cited in Morris Jr. & Carman 2012; Mercer et al. 2009, cited in Morris Jr. & Carman 2012); potential decrease in densities of bivalves, including commercially important bay scallop (Argopecten irradians irradians) and sea scallop (Placopecten magellanicus) (Morris et al. 2009, cited in Morris Jr. & Carman 2012) [Mediterranean] Reduces the price of oysters due to loss of visual appeal; cleaning pre-sale is expensive and time consuming (Ordonez et al. 2015) [New Zealand] Overgrows and smothers mussels, resulting in crop losses. Fouling pest to the commercial fishing industry and ports (Coutts & Forest 2007)

Tolerences

Native Temperature Regime:

See details

Native Temperature Range:

[Ise Bay, Japan] 6.0 - 31.1 ºC (Japan Oceanographic Data Center 2006, cited in Daniel & Therriault 2007)

Non-native Temperature Regime:

Subtropical, see details

Non-native Temperature Range:

[Maine, USA] Summer temperatures range from 10 - 18 ºC (Bullard et al. 2013) [Ebro Delta, western Mediterranean] 8 - 28 ºC (Ordonez et al. 2015) [Venice Lagoon, Adriatic Sea] 0 to >30 ºC (Ordonez et al. 2015) [New Zealand] 9 - 23 ºC (Ordonez et al. 2015) [Western Mediterranean] Temperate areas to warmer, subtropical waters (Ordonez et al. 2015)

Native Salinity Regime:

Polyhaline, Euhaline

Native Salinity Range:

[Ise Bay, Japan] 29.28 - 34.99 psu (Japan Oceanographic Data Center 2006, cited in Daniel & Therriault 2007)

Non-native Salinity Regime:

Polyhaline, Euhaline

Temperature Regime Survival:

Cool temperate, See details

Temperature Range Survival:

1.0 - 31.0 ºC (lab-based study shows 31 ºC, but field observations report 24 ºC; multiple authors, cited in NIMPIS 2015) Observed from 0 - 28 ºC (multiple authors, cited in Dijkstra 2015) Optimal growing temperature 14 - 18 ºC; nearly all colonies died below 4 ºC (Gittenberger 2007, cited in Dijkstra 2015) -2 to 24 ºC (field data; Bullard et al. 2007, cited in NEMESIS 2015). Cold temperate (NEMESIS 2015) -2 to 24 ºC, with 4 ºC possibly representing a critical lower threshold where growth is limited. However, they may hibernate and resume growth and reproduction when favourable conditions return (multiple authors, cited in Therriault & Herborg 2007) Can tolerate a daily fluctuation of 9 ºC (Valentine et al. 2005a, cited in Daniel & Therriault 2007) -2 to 25 ºC (noted that likely survive above 25 ºC) (Valentine et al. 2009) Cool-water temperate species; 0 - 28 ºC temperature range (multiple authors, cited in Lambert 2009)

Temperature Regime Reproduction:

Cool temperate, Mild temperate, See details

Temperature Range Reproduction:

Recruitment occurred from 14.0 - 20.0 ºC; ceased at 9 - 11 ºC (Valentine et al. 2009) [New Zealand] Recruitment not detected below 12 ºC, but some larvae were present in colony tissues (Fletcher et al. 2013, cited in NEMESIS 2015) [Ebro Delta, western Mediterranean] Mature larvae present in all colonies when temperatures ranged from 18 - 27 ºC from May - July (Ordonez et al. 2015) Cool temperate, Mild temperate (Judging from specimens with embryo and/or ovary being from Hokkaido to Sagami Bay, these climate zone may be applied.) (Otani pers. comm.)

Salinity Regime Survival:

Mesohaline, Polyhaline, Euhaline

Salinity Range Survival:

10.0 - 33.0 psu (NIMPIS 2015) Marine waters (33psu); also present in estuaries and areas with fluctuating salinity regimes (Dijkstra 2015) Highest growth at 26 - 30 psu, but survived down to 20 psu (field and laboratory data; mulitple authors, cited in NEMESIS 2015). HIghest observed salinity was 35 psu (NEMESIS 2015) Observed at 26 - 36 psu (Lee II & Reusser 2012) Can tolerate a fluctuation in salinity, but will close siphons at 20 psu and lower (which can lead to zooid death), and is rarely found below 25 psu (multiple authors, cited in Therriault & Herborg 2007)

Salintiy Regime Reproduction:

Polyhaline, Euhaline

Salinity Range Reproduction:

[CT, USA] Salinity ranged from 27 - 32 psu while zooids produced gametes in the field (Stefaniak & Whitlatch 2014)

Depth Regime:

Upper intertidal, Mid intertidal, Lower intertidal, Shallow subtidal, Deep subtidal

Depth Range:

1 - 81 m depth; high tide, mid tide, low tide, subtidal (NIMPIS 2015) Low intertidal, subtidal (NEMESIS 2015) 0 - 65 m (Lee II & Reusser 2012) Intertidal to 65 m (multiple authors, cited in Therriault & Herborg 2007) Found 0.5 m below surface (Minchin & Nunn 2013) Esashi, Hokkaido: 3-7 m deep. (Nishikawa 1990) Oga Peninsula: 6 m to 102 and 104 m deep. (Nishikawa 1984) Sagami Bay: In shallow pools near low water mark of the intertidal zone. (Tokioka 1962) Geojedo Island, Korea: 8 - 10 m. (Rho & Park 1998)

Non-native Salinity Range:

Native Abundance:

Common

Reproduction

Fertilization Mode:

internal

Reproduction Mode:

Hermaphrodite/ monoecious

Spawning Type:

NA

Development Mode:

Lecithotrophic planktonic larva (non-feeding)

Asexual Reproduction:

See details

Reproduction Details:

Reproduces asexually by budding (Kozloff 1990; Dijkstra 2015) Hermaphroditic, ovoviviparous; asexual reporduction through budding and fragmentation; internal fertilization: sperm released into the sea is taken in through the oral siphon of another zooid where the egg is fertilized; larvae brooded in tunic below the zooid until developed and released; eggs mature within the colony in several weeks; typical zooid produces one to 20 eggs (Daniel and Therriault 2007; cited in NIMPIS 2015). Lecithotrophic larvae that spend less than 24 hours in the water column before settling; can disperse as larvae or through fragmentation (Dijkstra 2015) Hermaphroditic; Lecithotrophic larvae; larvae usually swim for less than 24 hours before settling, but may remain longer in the plankton if water temperature is low (10% survival after 36 hour delay); most settle within 250 m of parent population, but possible up to 1 km or more. Fragments of populations can reattach after suspension of up to three weeks, and reproduce while suspended in the water column (mulitple authors, cited in NEMESIS 2015) Hermaphroditic; ovoviviparous; non-feeding planktonic larvae remain in the water column for minutes to hours before settling (multiple authors, cited in Therriault & Herborg 2007) Unhatched larvae are ~600 - 700 µm long (Lambert & Lambert 2005, cited in Daniel & Therriault 2007). Sperm are released into the sea and taken into another zooid where the egg is fertilized internally. Egg is released into the tunic for fertilization; larvae brood in the tunic below the zooid. Non-feeding larvae are released into the water column when fully developed (multiple authors, cited in Daniel & Therriault 2007) Larvae are positively phototactic and negatively geotactic once released from the adult colony, then become negatively phototactic and positively geotactic before settling; larvae remain the water column for less than 24 hours (multiple authors, cited in Daniel & Therriault 2007) Larvae are viable for up to 36 hours after release, and may spread ~10km before settling. Colony fragments may spread 100 m before reattaching (Fletcher et al. 2013) A full reproductive cycle (settlement to recruitment) takes a minimum of 4 months. If colony is under stress (competition or predation) that reduces its growth rate, it could take a year (Stefaniak & Whitlatch 2014) RELATED: [Didemnum spp.] Can bud while the gonads are maturing (Monniot et al. 1991, cited in Therriault & Herborg 2007); can undergo precocious budding where blastozooids are produced in the larvae within the tunic (Kott 2001, cited in Therriault & Herborg 2007)

Adult Mobility:

Sessile

Adult Mobility Details:

Non-motile (Lee II & Reusser 2012) Sessile. Colony can expand by fragmentation or rafting (moving with its habitat) (Therriault & Herbord 2007)

Maturity Size:

Zooids are 1 - 2 mm long (multiple authors, cited in Daniel & Therriault 2007); colonies in New Zealand averaged 22 cm circumference and 50 - 100 cm in length, with some as long as 220 cm (Coutts 2002, cited in Daniel and Therriault 2007)

Maturity Age:

[CT, USA] Recruits reached sexual maturity in 50 to 62 days at 19 to 20 ºC (Stefaniak & Whitlatch 2014) One to three years, with reproduction after the first year (Berrill 1950, cited in NIMPIS 2015; O'Clair and O'Clair 1998, cited in NIMPIS 2015)

Reproduction Lifespan:

NF

Longevity:

NOTE: two sources (NIMPIS 2015 and Therriault & Herborg 2007), citing the same sources, but one specifies D.v. while the other states that it's colonial ascidians One to three years (Berrill 1950, cited in NIMPIS 2015; O'Clair and O'Clair 1998, cited in NIMPIS 2015) RELATED: [Colonial ascidians] Typically 1 to 3 years (Berrill 1950, cited in Therriault & Herborg 2007, O’Clair and O’Clair 1998, cited in Therriault & Herborg 2007)

Broods per Year:

Annual reproductive cycle (multiple authors, cited in Stefaniak & Whitlatch 2014)

Reproduction Cues:

Larval release in the morning after a period of darkness (multiple authors, cited in Daniel & Therriault 2007) A period of darkness induces larval release (Fletcher et al. 2013) 48 hours of darkness, followed by exposure to bright light (Fletcher & Forrest 2011) RELATED: [Class Ascidiacea] Gonad development and spawning are controlled by light and temperature (multiple authors, cited in Therriault & Herborg 2007). Food concentration is also important (Lambert 2005b, cited in Daniel & Therriault 2007) [Class Ascidiacea] Larval release controlled by underwater irradiance, which is influenced by water turbidity, depth, cloud cover, season, etc. (Svane & Young 1989, cited in Daniel & Therriault 2007)

Reproduction Time:

[Maine, USA] Settlement begins in late July or beginning of August (Bullard et al. 2013) Recruitment lasted from 3.5 to 5 months (Valentine et al. 2009) [CT, USA] Reproductive structures developed in May; recruits found on panels 7 weeks later (Stefaniak & Whitlatch 2014) [Temperate waters] Recruitment occurs from summer to early autumn (multiple authors, cited in Ordonez et al. 2015) [New Zealand] Recruitment occurs from late spring to early winter; interrupted during the austral winter (Fletcher et al. 2013a, cited in Ordonez et al. 2015) [Ebro Delta, western Mediterranean] Mature larvae present in all colonies from May - July (Ordonez et al. 2015) RELATED: [Class Ascidiacea] [Temperate waters] Summer months (Cohen 2005, cited in Therriault & Herborg 2007; Lambert 2005b, cited in Therriault & Herborg 2007) [Class Ascidiacea] [Alaska] Spring or summer (O'Clair & O'Clair 1998, cited in Daniel & Therriault 2007) [Class Ascidiacea] [Tropical waters] Fall (Cohen 2005, cited in Daniel & Therriault 2007; Lambert 2005b, cited in Daniel & Therriault 2007)

Fecundity:

A typical zooid produces one to 20 eggs (Berrill 1950, cited in Daniel and Therriault 2007; Lambert & Lambert 2005, cited in Daniel & Therriault 2007) Colonies release huge numbers of larvae over the several month reproductive season (Valentine and Carman, unpub. obs. cited in Lambert 2009)

Egg Size:

300 - 400 µm in diameter with specimens from Hokkaido, Mutsu Bay and Oga Peninsula. (as D. pardum, Nishikawa 1990) 280 - 350 µm in diameter with specimens from Geojedo Island, Korea. (as D. pardum, Rho & Park 1998)

Egg Duration:

Eggs mature within the colony in several weeks (Daniel and Therriault 2007; cited in NIMPIS 2015).

Early Life Growth Rate:

Fragments 5 - 9 cm^2 grew 6 - 11 fold in the first 15 days (Valentine et al. 2005a, cited in Daniel & Therriault 2007) ~56 % of larvae settled onto the substratum and metamorphosed into juveniles 24 hours after release from the colony; only ~18 % of the remaining swimming larvae (6.1 % of released larvae) metamorphosed after another 24 hours (which adds only another ~1.1 % to the initial 56 %) (Fletcher & Forrest 2011)

Adult Growth Rate:

[Maine, USA] Colonies grew faster in the summer months than the winter months, when they reduce mass to a dormant bud to hibernate until conditions improve (multiple authors, cited in Daniel & Therriault 2007)

Population Growth Rate:

Recruits formed juvenile colonies with, on average, 4 to 6 zooids after 4 weeks (Fletcher & Forrest 2011)

Population Variablity:

In coastal zones, there is a seasonal cycle of regression during the coldest months (Dijkstra et al. 2007a, cited in Dijkstra 2015) [Ebro Delta, Mediterranean Sea] Regresses in the warmest months (beginning when temperatures exceed 18 ºC) and reappears during winter (growth begins again when waters cool below 14 ºC), with maximum abundance in spring and a peak in reproduction just before regression (Ordonez et al. 2015) [Temperate waters] Where winters are cold, D.v. regresses in the winter (multiple authors, cited in Ordonez et al. 2015) [Venice Lagoon, Adriatic Sea] Growth peaks in spring; one period of arrested growth in winter and one in summer (Tagliapietra et al. 2012, cited in Ordonez et al. 2015)

Habitat

Ecosystem:

Sediment subtidal, Rocky intertidal, Rocky subtidal, SAV, Worm reef, Mussel reef, Oyster reef, Macroalgal beds, Kelp forest, Fouling, Flotsam, Other

Habitat Type:

Epibenthic, Epizoic, Epiphytic

Substrate:

Mixed sediments, Gravel, Cobble, Rock, Hardpan, Biogenic, Artificial substrate

Exposure:

Exposed, semi-exposed, protected

Habitat Expansion:

Expansion

Habitat Details:

Lives on concrete, wood, boulder, cobble, gravel; found in both calm and rough (e.g. strong currents) conditions (NIMPIS 2015) Grows on horizontal and vertical surfaces; rocky intertidal and subtidal; man-made substrates; high current velocities (multiple authors, cited in Dijkstra 2015) Grass bed, coarse woody debris, unstructured bottom, oyster reef, marinas & docks, rocky, bedrock, vessel hull, gravel, bivalve colonies, seaweeds, eelgrass; epibenthic (multiple authors, cited in NEMESIS 2015) Epibenthic and epizoic. Observed in semi-enclosed bays and estuaries; subtidal, unvegetated soft sediments (gravel, cobble, mixed sediments); rocky intertidal; rocky subtidal; oyster and mussel reef; fouling of artificial substrates (Lee II & Reusser 2012) Rock, gravel, pebbles, cobble, boulders, animals (e.g. sponges, worms, mussels and oysters, etc.), algae, shell, hard clay with stones, artificial substrates (multiple authors, cited in Therriault & Herborg 2007) Found in protected areas with reduced wave action and on the open coast (mulitple authors, cited in Daniel & Therriault 2007) Found on blades of Fucus serratus; overgrowing mussels; kelp stipes; stones; rocks; boulders (Minchin & Nunn 2013) Found on rocky substrata, macroalgal beds, seagrass habitats, tide pools, estuaries, lagoons, and open coastal areas (multiple authors, cited in Forrest et al. 2013) [New Zealand] Found on mussel farms, salmon farms, floating pontoons and mooring lines, wharf piles, horse mussels, finger sponges, hydroid trees, macroalgae (Carpophyllum flexuosum, Macrocystis pyrifera), decorator crabs, submerged logs, cables, other debris (Forrest et al. 2013) Expanding from temperate areas to warmer, subtropical waters (e.g. western Mediterranean) (Ordonez et al. 2015) Rafting (e.g. found on broken leaves, debris) (multiple authors, cited in Dijkstra 2015) Found on the buoys of the net cages for fish rearing set. (Nishikawa 1984) Found under side of stones. (Tokioka 1962) Covered leaves of Zostera sp. algal stems or other materials. Some encrusting Mytilus galloprovincialis and Styela clava. (Nishikawa 1990) Found on the worm tubes, Geojedo Island, Korea. (Rho & Park 1998)

Trophic Level:

Suspension feeder

Trophic Details:

Suspension feeder (NIMPIS 2015) Filter feeds for phytoplankton, bacteria, and detritus; suspension feeder (NEMESIS 2015) Filter-feeder; eats phytoplankton, suspended particulate matter, diatoms, invertebrate larvae, suspended bacteria (mulitple authors, cited in Therriault & Herborg 2007)

Forage Mode:

Selective

Forage Details:

Large particles are removed before entering the branchial sac (multiple authors, cited in Daniel & Therriault 2007)

Natural Control:

COMPETITION [Competition] Competes with Mytilus edulis for space and food, but is a strong competitor and can grow on the mussel shell, which restricts its valve movement (Auker & Oviatt 2007, cited in NIMPIS 2015) PREDATION [Predation] Few known predators (Lambert 2009, cited in Dijkstra 2015). Photographic evidence has been collected of D.v. being consumed by a sea star, a sea urchin (Notechinus albocinctus), a chiton (Cryptoconchus porosus), and an intertidal snail (Littorina littorea) (multiple authors, cited in Dijkstra 2015) [Predation] Eaten by the generalist snail Trivia arctica, and a specialist snail, Lamellaria (Gittenberger 2007, cited in Dijkstra 2015) [Predation] Seastars, urchins (NEMESIS 2015) [Predation} Few known predators, but Littorina littorea, chitons, sea urchins, and sea stars have been reported preying on D.v. (Valentine 2003, cited in Therriault & Herborg 2007) [Predation] Littorina littoria, chitons, sea urchins, sea stars, fish, flatworms, polychaete worms, echinoderms, gastropods, seals, other cetaceans (multiple authors, cited in Daniel & Therriault 2007) [Predation] Preyed on by the native bloodstar, Henricia sanuinolenta (Dijkstra et al. 2007, cited in Dijkstra et al. 2013) [Predation] cushion stars, Patiriella regularis, and sea urchins, Evechinus chloroticus consumed D.v., eleven-arm sea stars (Coscinasterias muricata), top shells (Turbo smaragdus), chitons (Cryptoconchus porosus) and hermit crabs (Paguridae) were presumed to be eating D.v. (Forrest et al. 2013) DISTURBANCE [Disturbance] [Class Ascidiacea] High sedimentation causes ascidians to defensively close their oral siphons to prevent harm, which ceases respiration (Monniot et al. 1991, cited in Daniel & Therriault 2007; Tyree 2001, cited in Daniel & Therriault 2007) PARASITES [Parasites] Apicomplexan parasite Lankesteria didemni found in D.v. intestines (Reuckert et al. 2015)

Associated Species:

PARASITES [Parasites] Apicomplexan parasite Lankesteria didemni found in D.v. intestines (Reuckert et al. 2015) HITCHHIKERS [Possible hitchhikers] Six harmful algal species, Prorocentrum minimum, Alexandrium fundyense, Heterosigma akashiwo, Aureococcus anophagefferens, Karenia brevis, and Alexandrium monilatum, were able to pass in tact through the gut and re-establish boom populations, which suggests a possibility of introducing them to newly invaded regions (Rosa et al. 2013) RELATED: EPIBIONTS [Epibionts] [Class Ascidiacea] Copepods, amphipods, shrimps, polychaetes, molluscs, decapods, hydroids, algae, nematodes, ciliates, protozoans (gregarines), suctorian ciliates, and pea crabs live harmlessly on ascidians (multiple authors, cited in Daniel & Therriault 2007)

References and Notes

References:

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Literature:

Extensive scientific information; peer-reviewed information; data specific to the location; supported by long-term datasets (10 years or more)

Notes:

NA