Invasion History

First Non-native North American Tidal Record: 2001
First Non-native West Coast Tidal Record: 2001
First Non-native East/Gulf Coast Tidal Record:

General Invasion History:

Myrianida convoluta was described from the Bay of Naples, in the Mediterranean Sea (Cognetti 1953, cited by Cinar and Gambi 2005), but its native region is unknown. It has been reported from the East Atlantic (Spain, Madeira, Canary Islands, Cape Verde Islands; Nygren 2004), the Caribbean (Liñero-Arana et al. 2011), Korea (Lee 1998), Japan (Imajima 1966b), Pacific Russia (Buzhinskaja and Nekrasova 2007), and California (Nygren 2004). Small variations in morphology of populations in different regions (see 'Taxonomy') suggest that 'M. convoluta' could be a complex of cryptic species.

North American Invasion History:

Invasion History on the West Coast:

Myrianida convoluta was first collected in North American waters in 2001 off Bird Rock, near Santa Catalina Island, California. Six specimens were collected and a population is presumed to be established. The worms were found at 20 m depth, among hydroids on Laminaria kelp (Nygren 2004). In 2011, four specimens were found in epifauna collections in Los Angeles-Long Beach Harbor (California Department of Fish and Wildlife 2014). Reproductive adults could be transported in ballast water, while non-reproductive worms are likely to occur with sponges, algae, and seaweeds in fouling communities (Nygren 2004).

Invasion History Elsewhere in the World:

The native range of Myrianida convoluta is unknown, but the earliest records are from the Mediterranean Sea (Cognetti 1953, cited by Cinar and Gambi 2005). It is known from the Mediterranean coast of Spain (San Martin 1984, cited by Cinar and Gambi 2005) and the Aegean coast of Turkey (Cinar and Ergen 2002). Records from the Mediterranean coast of Israel and the Suez Canal (Ben-Eliahu 1972) are uncertain, on morphological grounds (Cinar and Gambi 2005). In the Atlantic, M. convoluta was reported from Cape Trafalgar, Spain (in 2000, Nygren 2004), the Canary Islands (Pascual 1999), the Cape Verde Islands (Lopez and San Martin 1994), Cuba (San Martin 1994) and Venezuela (Liñero-Arana and Díaz Díaz 2011). Records of Myrianida convoluta in the Northwest Pacific are scattered, including the northern Pacific coast of Japan (Imajima 1966b), the southern coast of Korea (Lee 1998), and the Russian coast of the northern sea of Japan (Buzhinskaja and Nekrasova, 2007). As noted above, small variations in morphology of the worms in different regions could indicate that 'M. convoluta' is a widely distributed species complex, or could represent phenotypic responses to local environments by a widespread invader.


Myrianida convoluta is a syllid polychaete. Family characteristics of the Syllidae include: a relatively small and slender body; a prostomium with two pairs of eyes, and sometimes a couple of eyespots; three antennae and paired palps; an eversible pharynx and proventricle; the anterior-most segment (peristomium) lacking chaetae, but bearing 1-2 pairs of tentacles; uniramous parapodia (biramous in reproductive individuals); dorsal and ventral cirri on each chaetiger; and a pygidium (anal segment) with 2-3 anal cirri (Pettibone 1963; Blake and Ruff 2007).

During its atokous (non-reproductive) stage, Myrianida convoluta is slender and slightly tapered anteriorly. The prostomium is oval to pentagonal in shape, being wider than it is long, with four eyes arranged in a trapezoid. The anterior pair of eyes is larger and bears three antennae, one located medially. The median antenna emerges between the anterior pair of eyes. It reaches back to chaetigers 6-12 and is 1.5-2X as long as the lateral antennae. The palps are small and fused throughout- they do not project beyond the prostomium. The anterior-most segment (peristomium) bears two pairs of tentacular cirri, with the dorsal pair being longer at 1/2 to 2/3X the length of the median antenna. The ventral tentacular cirri are about 1/2 of the length of the dorsal ones. The nuchal organs appear to vary in size and shape among populations, extending from the posterior end of the prostomium to the middle of chaetiger 1 in populations from the Mediterranean (Cinar and Gambi 2005); the Sea of Japan, Russia (Buzhinskaja and Nekrasova 2007); and the East China Sea, Korea (Lee 1998). In other populations, the nuchal organs extend to the 2rd chaetiger, as seen in Pacific Japan (Imajima 1966b), or to the 7th chaetiger in California (Nygren 2004). The pharynx is long and very convoluted, with many bends before it reaches the proventriculus. The anterior end of the pharynx is a circlet (trepan) of 9 or 15-16 equal triangular teeth, in 1 ring (Nygren 2004). The proventricle is located between chaetigers 7 and 14 (Imajima 1996b; Lee 1998; Nygren 2004; Cinar and Gambi 2005; Buzhinskaja and Nekrasova 2007).

The dorsal cirri of the 1st chaetiger can range in size, from being as long as the median antenna (Nygren 2004; Buzhinskaja and Nekrasova 2007), to being longer (Lee 1998) or slightly shorter (Imajima 1966b; Cinar and Gambi 2005). The dorsal cirri on chaetiger 2 and the subsequent chaetigers are much shorter than the pair on chaetiger 1. All of the tentacular and dorsal cirri arise from cirriphores. The parapodia are blunt and rounded, but with a pointed neuropodial lobe. The parapodia each bear a bundle of 5-8 compound setae (with two teeth) and a single simple seta. The atokous section, or the last stolon, ends in a rectangular pygidium which terminates in a pair of anal cirri. Atokous M. convoluta range from 2.4 to 2.5 mm and 39 - 45 chaetigers in size. Their color ranges from faintly yellowish to pale orange, with red eyes (Imajima 1966b; Nygren 2004; Cinar and Gambi 2005; Buzhinskaja and Nekrasova 2007).

In one adult female worm, the epitokous segments (stolons) began at chaetiger 5. Females had large eyes with lenses. The palps were absent, as were notopodia and swimming chaetae. Females swam carrying broods of larvae (and presumably eggs) on chaetigers 5 to 30 (Buzhinskaja and Nekrasova 2007), as is seen in species of Autolytus (Pettibone 1963). Male epitokes have been more frequently described than females. In Imajima's (1966b) specimens, stolons formed after the 22nd chaetiger and consisted of 16-20 chaetigers. Worms with stolons measured 4.7- 6.5 mm (Imajima 1966b). Nygren's (2004) specimens ranged from 3.2 to 5.9 mm, including stolons. A single male stolon was 1.8 mm long and greenish. The lateral antennae are bifid (two branches). The parapodia have prominent swimming chaetae in bundles of ~15 (Nygren 2004).

Numerous small differences occur in descriptions of M. convoluta from different regions of the world, including the size and shape of the nuchal organs, the size of the proventricle, and the number of teeth in the trepan (Imajima 1996b; Lee 1998; Nygren 2004; Cinar and Gambi 2005; Buzhinskaja and Nekrasova 2007). The significance of these differences is not clear.


Taxonomic Tree

Kingdom:   Animalia
Phylum:   Annelida
Class:   Polychaeta
Subclass:   Palpata
Order:   Aciculata
Suborder:   Phyllodocida
Family:   Syllidae
SubFamily:   Autolytinae
Genus:   Myrianida
Species:   convoluta


Autolytus convolutus (Cognetti, 1953)
Autolytus (Regulatus) convolutus (Imajima, 1966)
Myrianida convoluta (Nygrens, 2004)

Potentially Misidentified Species



Myrianida convoluta, like other members of the Syllidae, reproduces by epitoky. During epitoky the worm undergoes stolonization, in which segments of the body become modified for carrying gametes and swimming (modified chaetae, enlarged eyes). The sexes are separate, and stolons break off from the stem portion of the worm's body and swim in the water column as epitokes, with a new head, three antennae, and well-developed eyes. Then, the stem portion of the body regenerates a new stolon. Male and female stolons are morphologically distinguishable (Imajima 1966b; Nygren 2004). The details of fertilization are not known for M. convoluta, but the female swims in the water column, carrying the fertilized eggs and larvae in a long ventral egg mass (Buzhinskaja and Nekrasova 2007).

Myrianida convoluta occurs in cold-temperate to tropical climates over its known range (Lopez and San Martin 1994; Nygren 2004; Cinar and Gambi 2005; Buzhinskaja and Nekrasova 2007). It is found in the intertidal and shallow subtidal zones among seaweeds, seagrasses, hydroids, sponges, and fire corals (Imajima 1966b; Nygren 2004; Liñero-Arana, and Díaz Díaz 2011). It has also been found on marina and dock fouling (California Department of Fish and Wildlife 2014) and on plastic pipes (Liñero-Arana and Díaz Díaz 2011). Syllids have been considered exclusively carnivorous, including members of the subfamily Autolytinae (such as Myrianida) feeding largely on hydroids (Fauchald and Jumars 1979). However, studies of fecal pellets indicate that many Syllids, including one species of Autolytus, are omnivorous (Giangrande et al. 2000).

Trophic Status:




General HabitatRockyNone
General HabitatMarinas & DocksNone
General HabitatGrass BedNone
Salinity RangePolyhaline18-30 PSU
Salinity RangeEuhaline30-40 PSU
Tidal RangeSubtidalNone
Tidal RangeLow IntertidalNone
Vertical HabitatEpibenthicNone
Vertical HabitatPlanktonicNone

Tolerances and Life History Parameters

Minimum Length (mm)1.7Nygren 2004, smallest collected
Maximum Length (mm)6.5Imajima 1996b, length including stolons
Broad Temperature RangeNoneCold Temperate-Tropical
Broad Salinity RangeNonePolyhaline-Euhaline

General Impacts

No ecological or economic impacts are known for Myrianida convoluta in North American waters.

Regional Distribution Map

Bioregion Region Name Year Invasion Status Population Status
MED-III None 1953 Crypto Estab
NEA-V None 2000 Crypto Estab
MED-VI None 0 Crypto Estab
MED-II None 1984 Crypto Estab
NWP-3a None 1995 Crypto Estab
CAR-III None 2001 Crypto Estab
NWP-4b None 0 Crypto Estab
WA-I None 1999 Crypto Estab
WA-VI None 1994 Crypto Estab
CAR-II None 1994 Crypto Estab
NWP-4a None 2006 Crypto Estab
NEP-VI Pt. Conception to Southern Baja California 2001 Def Estab
P058 _CDA_P058 (San Pedro Channel Islands) 2001 Def Estab
P050 San Pedro Bay 0 Def Estab
P020 San Diego Bay 2013 Def Estab

Occurrence Map

OCC_ID Author Year Date Locality Status Latitude Longitude


Ben-Eliahu, M. N. (1972) Polychaeta errantia of the Suez Canal, Israel Journal of Zoology 21: 189-237

Blake, James A.; Ruff, R. Eugene (2007) The Light and Smith Manual: Intertidal invertebrates from Central California to Oregon (4th edition), University of California, Berkeley CA. Pp. 309-410

Buzhinskaja, G. N.; Nekrasova, M. I. (2007) Description of Myrianida convoluta (Cognetti) form the Bay of Peter the Great (the Sea of Japan), first finding in the Russian Seas (Polychaeta, Syllidae, Autolytinae), Zoosystematic Rossica 16(2): 147-151

California Department of Fish and Wildlife (2014) Introduced Aquatic Species in California Bays and Harbors, 2011 Survey, California Department of Fish and Wildlife, Sacramento CA. Pp. 1-36

Çinar, Melih Ertan; Gambi, Maria Cristina (2005) Cognetti's syllid collection (Polychaeta: Syllidae) deposited at the Museum of the Stazione Zoologica “Anton Dohrn” (Naples, Italy), with descriptions of two new species of Autolytus, Journal of Natural History 39(10): 725-762

Cinar, Melin Ertan; Ergen, Zeki (2002) Faunistic analysis of Syllidae (Annelida: Polychaeta) from the Aegean Sea, Cahiers de Biologie Marine 43: 171-178

Fauchald, Kristian; Jumars, Peter A. (1979) The diet of worms : A study of polychaete feeding guilds, Oceanography and Marine Biology, an Annual Review 17: 193-284

Giangrande, Adriana; Licciano, Margheritia; Pagliaria, Patrizia (2000) The diversity of diets in Syllidae (Annelida: Polychaeta), Cahiers de Biologie Marine 41: 55-65

Imajima, Minoru (1966b) The Syllidae (polychaetous annelids) from Japan II. Autolytinae, Publications of the Seto Marine Biological Laboratory 14(1): 27-83

Lee, Jong-Wui (1998) Systematic study of polychaetes (Annelida) from offshore waters of Geojedo Island, Korea, Korean Journal of Systematic Zoology Molluscan Research 14(3): 243-255

Liñero-Arana, Ildefonso; Díaz Díaz, Oscar (2011) Syllidae (Annelida, Polychaeta) from the Caribbean coast of Venezuela, ZooKeys 117: 1-28

Lopez, Eduardo; San Martin, Guillermo (1994) [Syllidae (Polychaeta) collected in the Cape Verde Islands by the 1st Iberian Expedition], Revista Biologia Tropical 42(1/2): 129-139

Nygren, Arne (2004) Revision of Autolytinae (Syllidae: Polychaeta)., Zootaxa 680: 1-314

Pascual, Mariano; Nunez, Jorge (1999) [Syllids (Polychaeta: Annelida) endobionts of sponges from Canaries and Madeira], Avicennia 10/11: 73-80

Pettibone, Marian H. (1963) Marine polychaete worms of the New England region. 1. Aphroditidae through Trochochaetidae., Bulletin of the United States National Museum 227(Part 1.): 1-356

Ruiz, Gregory; Geller, Jonathan (2021) Spatial and temporal analysis of marine invasions: supplemental studies to evaluate detection through quantitative and molecular methodologies, Marine Invasive Species Program, California Department of Fish and Wildlife, Sacramento CA. Pp. 153 ppl.

San Martin, Guillermo (1994) Autolytinae (Polychaeta, Syllidae) from Cuba and North American Atlantic Ocean, Memoires da Museum d'Histoire Naturelle 162: 269-277