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:

Proceraea okadai was described using specimens from Asamushi and Onagawa in northern Japan, and Seto in southern Japan (Imajima 1966b). It is thought to be native to this region. Introduced populations were reported from Friday Harbor, Washington in 2001 (Nygren 2004) and San Francisco Bay, California in 2003 (California Academy of Sciences 2015).

North American Invasion History:

Invasion History on the West Coast:

In January 2001, Nygren (2004) collected 35 specimens of Proceraea okadai from a fouling community (sponges, hydroids, barnacles) on a floating dock in Friday Harbor, in the San Juan Islands, Washington. In April 2003, Leslie Harris collected specimens of this worm from floating docks and piers at marinas in the vicinity of San Francisco, California (California Academy of Sciences 2015). Proceraea okadai appears to be introduced on the West Coast of North America. Likely vectors are ballast water transport of the swimming epitokes, or transport of atokous (asexual) organisms in fouling. Larvae and atokous adults of a related species, P. rzhavskyi are specialized predators on hydroids (Britayev and San Martin 2001). However, the larval development and life history of P. okadai are unknown.


Proceraea okadai 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, P. okadai is slender and slightly tapered anteriorly. The prostomium is oval, being wider than it is long, with four eyes arranged in a trapezoid. The anterior and posterior pairs of eyes are very close together or confluent, but the anterior pair is larger. The prostomium bears three antennae, one located medially. The median antenna emerges from the center of the prostomium, reaches back to chaetigers 11-14, and is 1.5-2x as long as the lateral antennae. The palps project 1/3 to 1/2 of the prostomial length, beyond the prostomium. The anterior-most segment (peristomium) bears two pairs of tentacular cirri, with the dorsal pair being longer and 1/2 to 2/3 the length of the median antenna. The ventral tentacular cirri are about 1/3 to 1/2 of the length of the dorsal ones. The nuchal organs are leaf-shaped, pigmented in the center, and extend to the middle of the peristomium. The pharynx is S-shaped and is surrounded by nine soft papillae. The anterior end of the pharynx is a circlet (trepan) of 18 unequal triangular teeth (9 large and 9 small). The proventricle is 1-2 chaetigers long and is located on chaetigers 6-7.

The dorsal cirri of the 1st chaetiger are as long (Imajima 1966b), or 3/4 as long (Nygren 2004), as the median antenna. The second dorsal cirri are about two-thirds as long as the first one. The subsequent dorsal cirri are shorter and of equal length. The parapodia are bluntly conical, but with a pointed neuropodial lobe. Each parapodium bears a bundle of 6-10 compound chaetae (with two teeth). The first 15 parapodia also bear a single simple chaeta, above the bundle. The atokous section, or the last stolon, ends in a rectangular pygidium which terminates in a pair of anal cirri. Atokous specimens range from 34 to 65 chaetigers and 3.6 to 13 mm in length. The color is pale yellow, with two black lines along the sides of body, and two distinct black lines on the dorsal side (Imajima 1966b; Nygren 2004).

Epitokous females form a single stolon, with a developing head. Swimming chaetae develop beyond the 7th chaetiger of the developing stolon. Female specimens had six pre-epitokal segments, 11 epitokous segments, and were ~3 mm long. The median antenna reaches back to the 4th chaetiger, and the lateral antennae are of equal length. Dorsal cirri of epitokal segments are longer than those of the pre-epitokal ones and each has a long cirrophore, lacking in the pre-epitokal segments. The epitokal segments bear long swimming chaetae, emerging from beneath the dorsal cirri. Female epitokes were filled with pink eggs (Imajima 1966b; Nygren 2004).

Male epitokes consist of the prostomium, peristomium, six pre-epitokous segments, 26-28 epitokal segments, 10-12 post-epitokal segments, and a pygidium which is 5-6 mm long. The eyes are enlarged, especially the anterior pair. The antennae are greatly enlarged, with the median antenna stretching back to the 28th chaetiger. The lateral antennae are also long, and have two branches, dividing at about mid-length. The epitokal segments have long parapodia, with bundles of long swimming chaetae. The post-epitokal segments have short cirri, parapodia, and chaetae (Imajima 1966b; Nygren 2004).


Taxonomic Tree

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


Autolytus (Regulatus) okadai (Imajima 1966, 1966)

Potentially Misidentified Species


Proceraea cornuta
North Atlantic and North Pacific (Pettibone 1963; Nygren 2004)

Proceraea nigropuncta
Northeast Pacific (Nygren 2004)



Proceraea okadai, 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). In P. okadai, 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 P. okadai. In many species of the subfamily Autolytinae, the female epitoke swims in the water column and carries the fertilized eggs and larvae in a long ventral egg mass (Pettibone 1963). However, in Proceraea rzhavskyi, eggs may be deposited or the larvae settle on the hydroid Abietinaria turgida, where they feed and develop.

Proceraea okadai is known to occur in cold-temperate to warm-temperate climates over its known range (Imajima 1966b; Nygren 2004). It is found in the intertidal and shallow subtidal zones, among hydroids, sponges, and bryozoans (Imajima 1966b; Nygren 2004). It has been found on marina and dock fouling (Nygren 2004; California Academy of Sciences 2015). Another member of the genus, P. rzhavskyi, is a specialized parasite/predator of hydroids, using the polyps as food and shelter (Britayev and San Martin 2001). Syllids of the subfamily Autolytinae have been considered exclusively carnivorous, feeding largely on hydroids (Fauchald and Jumars 1979).


Hydroids, bryozoans

Trophic Status:




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

Tolerances and Life History Parameters

Minimum Length (mm)3.5For an atokous specimen, An incomplete epitokous female was 3 mm long. Males were 5-6 mm long (Imajima 1966b; Nygren 2004).
Maximum Length (mm)13For the largest atokous specimen (Nygren 2004)
Broad Temperature RangeNoneCold temperate-Warm Temperate
Broad Salinity RangeNonePolyhaline-Euhaline

General Impacts

No ecological or economic impacts are known for Proceraea okadai in North American waters.

Regional Distribution Map

Bioregion Region Name Year Invasion Status Population Status
NWP-4b None 0 Native Estab
NWP-3b None 0 Native Estab
NEP-III Alaskan panhandle to N. of Puget Sound 2001 Def Estab
P292 _CDA_P292 (San Juan Islands) 2001 Def Estab
NEP-V Northern California to Mid Channel Islands 2003 Def Estab
P090 San Francisco Bay 2003 Def Estab

Occurrence Map

OCC_ID Author Year Date Locality Status Latitude Longitude


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

Britayev, Temir A.; San Martin, Guillermo L. A. (2001) Description and life-history traits of a new species of Proceraea with larvae infecting Abietinaria turgida (Polychaeta, Syllidae & Hydrozoa, Sertulariidae), Ophelia 54(2): 105-113

California Academy of Sciences 2005-2015 Invertebrate Zoology Collection Database. <missing URL>

California Academy of Sciences 2015 <i>Proceraea okadai</i> (Imajima, 1966). <missing URL>

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

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

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

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