Invasion History

First Non-native North American Tidal Record: 1977
First Non-native West Coast Tidal Record: 1977
First Non-native East/Gulf Coast Tidal Record:

General Invasion History:

Dynoides dentisinus is native to the Northwest Pacific where it is found from the Sea of Japan and the southern Kuril Islands, Russia, to the coast of the East China Sea (Huang 2001). In 1977 it was found in San Francisco Bay, California in the Oakland estuary (Carlton 1979). It has subsequently been found at several locations in the South and Central portions of the bay (Cohen and Carlton 1995; Cohen et al. 2005).

North American Invasion History:

Invasion History on the West Coast:

Dynoides dentisinus was first collected on the West coast in fouling on dock floats, in the Oakland estuary, in 1977. It was found among the introduced tunicates Ciona robusta and Styela plicta and with the introduced isopod Ianiropsis serricaudis (Carlton 1979). During subsequent surveys, it was found at several locations in the Central Bay (e.g. Richmond Marina in 1993, Cohen and Carlton 1995; Presidio Yacht Club in 2004, Cohen et al. 2005) and South Bay (San Leandro Marina in 2004, Cohen et al. 2005; San Mateo Bridge Pylon in 2005, Cohen and Chapman 2005). This isopod has not been reported from other locations on the West Coast.


Dynoides dentisinus is a marine isopod found in subtidal and intertidal mussel and seaweed beds, in fouling communities, and sometimes swimming at night in the plankton (Bruce 1980; Cohen and Carlton 1995; Iwasaki 1996; Li 2000). Isopods of the genus Dynoides have a crescent-shaped head, which is wider than it is long, with prominent eyes, an oval-rectangular body, and a broad, bilobed heart-shaped pleotelson with a slit in the apex. In D. dentisinus, the pleon has a triangular process, which divides the anterior portion of the telson, and the apical slit in the telson is expanded anteriorly and narrows towards the apex. The slit is lined with small teeth. The uropods are broad, biramous, and fan outwards. The pleotelson and uropods are covered with small tubercles. In lateral view, the pleotelson has a half-dome like shape. The lateral edges of the peraonal segments are lined with bristly setae. Maximum length is about 8 mm (Iwasaki 1996). In photographs from Japan, Dynoides dentisinus, has varying patterns of dark brown and white, with red bordering the body segments (Oriyama 2010; Saito 2012). Description based on: Nunomura and Nishimura 1976, Bruce 1980, Harrison and Ellis 1991, Cohen and Carlton 1995, Iwasaki 1996, and Li 2000.


Taxonomic Tree

Kingdom:   Animalia
Phylum:   Arthropoda
Subphylum:   Crustacea
Class:   Malacostraca
Subclass:   Eumalacostraca
Superorder:   Peracarida
Order:   Isopoda
Suborder:   Flabellifera
Family:   Sphaeromatidae
Genus:   Dynoides
Species:   dentisinus


Potentially Misidentified Species



Dynoides dentisinus is a marine isopod found in intertidal and subtidal mussel, barnacle, and seaweed beds, and in fouling communities. It has separate sexes and fertilization is internal. Females brood up to 2 to 19 juveniles, with fecundity increasing with body size (Iwasaki 1996). This isopod occurs in intertidal areas of Asia, which are prone to a wide seasonal fluctuations in temperature (Iwasaki 1996; Ivanova et al. 2008). We have not found reports of this isopod from strongly brackish water. In mussel beds in Japan, it was most abundant from 10 cm below to 60 cm above mean sea level (Iwasaki 1996). Dynoides dentisinus was common in beds of the surfgrass Phyllospadix japonicus in South Korea (Kang and Yun 1988). We have not found information on the feeding of this isopod; however, most sphaeratomids are herbivorous (Brusca et al. 2007).

Trophic Status:




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

Tolerances and Life History Parameters

Maximum Length (mm)8Iwasaki (1996)
Broad Temperature RangeNoneCold temperate-Warm Temperate
Broad Salinity RangeNonePolyhaline-Euhaline

General Impacts

We have found no reported impacts for introduced populations of Dynoides dentisinus.

Regional Distribution Map

Bioregion Region Name Year Invasion Status Population Status
NWP-4a None 1929 Native Estab
NWP-3b None 0 Native Estab
NEP-V Northern California to Mid Channel Islands 1977 Def Estab
P090 San Francisco Bay 1977 Def Estab
NWP-3a None 0 Native Estab
NWP-4b None 0 Native Estab
NWP-5 None 0 Native Estab

Occurrence Map

OCC_ID Author Year Date Locality Status Latitude Longitude


Bruce, Niel L. (1980) The systematics of some Japanese marine isopods (fam. Sphaeromatidae) of the genera Dynoides Barnard, 1914 and Cymodocella Pfeffer, 1887, with descriptions of two new species, Crustaceana 38(2): 199-211

Brusca, Richard C.; Coeljo, Vania R. Taiti, Stefano (2007) The Light and Smith Manual: Intertidal invertebrates from Central California to Oregon (4th edition), University of Calfiornia Press, Berkeley CA. Pp. 503-542

Carlton, James T. (1979) History, biogeography, and ecology of the introduced marine and estuarine invertebrates of the Pacific Coast of North America., Ph.D. dissertation, University of California, Davis. Pp. 1-904

Cohen, Andrew N. and 10 authors (2005) <missing title>, San Francisco Estuary Institute, Oakland CA. Pp. <missing location>

Cohen, Andrew N.; Carlton, James T. (1995) Nonindigenous aquatic species in a United States estuary: a case study of the biological invasions of the San Francisco Bay and Delta, U.S. Fish and Wildlife Service and National Sea Grant College Program (Connecticut Sea Grant), Washington DC, Silver Spring MD.. Pp. <missing location>

Cohen, Andrew N.; Chapman, John T. (2005) <missing title>, San Francisco Estuary Institute, San Francisco. Pp. <missing location>

Harrison, K.; Ellis, J. P. (1991) The genera of the Sphaeromatidae (Crustacea: Isopoda): a key and distribution list, Invertebrate Taxonomy 5: 915-952

Huang, Zongguo (Ed.), Junda Lin (Translator) (2001) Marine Species and Their Distributions in China's Seas, Krieger, Malabar, FL. Pp. <missing location>

Ivanova, M. B.; Belogurova, L. S.; Tsurpalo, A. P. (2008) Ecological studies and the state of the ecosystem of Amursky Bay and the estuarine zone of the Razdolnaya River (Sea of Japan) Vol. 1., Dalnauka, Vladivostok, Russia. Pp. 1-140

Iwasaki, K. (1995) Comparison of mussel bed community between two intertidal mytilids Septifer virgatus and Hromomya mutibilis, Marine Biology 123: 109-119

Iwasaki, Keiji (1996) Vertical distribution and life cycle of two isopod crustaceans within intertidal mussel beds, Benthos Research 51(2): 21-32

Kang, Yong Joo; Yun, Sung Gyu (1988) Ecological study on isopods crustaceans in surfgrass beds around Tongbacksum, Haeudae, Pusan, Ocean Research 10(1): 23-31

Li, Li (2000) A new species of Dynoides (Crustacea: Isopoda: Sphaeromatidae) from the Cape d’Aguilar Marine Reserve, Hong Kong, Records of the Australian Museum 52: 137-149

Miron, Gilles; Audet, Dominique; Landry, Thomas; Moriyasu, Mikio (2005) Predation potential of the invasive green crab Carcinus maenas and other common predators on commercial bivalve species found on Prince Edward Island., Journal of Shellfish Research 24(2): 579-586

Nunomura, Noburu; Nishimura, Saburo (1976) Marine Isopoda from the rocky shore of Osaka Bay, middle Japan (2), Bulletin of the Osaka Museum of Natual History 30: 19-26

Oriyama, Tetsuro 2010 Observation of <em>Dynoides dentisinus</em> Shen, 1929 (Crustacea: Isopoda: Sphaeromatidae). <missing URL>

Saito, Atsushi 2012 28S rDNA partial sequence of<em> Dynoides dentisinus</em> (Crustacea: Isopoda: Sphaeromatidae). <missing URL>

U.S. National Museum of Natural History 2002-2021 Invertebrate Zoology Collections Database.

Zenkevitch, L. (1963) <missing title>, Allen & Unwin, London. Pp. <missing location>