Invasion History

First Non-native North American Tidal Record: 1965
First Non-native West Coast Tidal Record:
First Non-native East/Gulf Coast Tidal Record: 1965

General Invasion History:

Paradella dianae was described from Bahia de San Quintin, on the Pacific Coast of Mexico, and is known from San Diego Bay, California to Mazatlan, Mexico, including the Gulf of California. An occurrence in Pisco, Peru could be part of the natural range, or an introduction (Menzies 1962; García-Guerrero and Hendrickx 2005; U.S. National Museum of Natural History 2016). Paradella dianae has been widely introduced in warm-temperate and tropical harbors and coastal waters around the world. It is found on the coasts of every continent except Antarctica, and on oceanic islands (e.g. Hawaii, the Marshall Islands, and Bermuda). Early introductions include Fernandina Beach and Key West, Florida in 1965 and 1968, respectively (US National Museum of Natural History 2016); Puerto Rico in 1966 (Glynn 1970); Eniwetok Atoll in 1967 (Glynn 1970); Queensland, Australia in 1971 (Harrison and Holdich 1982); Brazil in 1978 (Pires 1980); and Italy in 1985 (Forniz and Maggiore 1985).

North American Invasion History:

Invasion History on the East Coast:

The earliest record of Paradella dianae in the Atlantic Ocean is from Fernandina Beach, in northeast Florida, in 1965 (USNM 84387, US National Museum of Natural History 2016). Subsequently, P. dianae has been found north to Charlestown, South Carolina (Knott et al. 2011), and south to Key Biscayne, Florida (USNM 205734, US National Museum of Natural History 2016). In the Gulf of Mexico, it was collected at Key West in 1969 (USNM 205734, US National Museum of Natural History 2016) and from Matagorda Bay to South Padre Island, Texas in 1978 (Clark and Robertson 1982). Kensley and Schotte (1999) collected many specimens from a wide variety of habitats in the Indian River Lagoon, Florida.

Invasion History in Hawaii:

In 2002-2003, Paradella dianae was found in Port Allen Harbor, Kauai, and Kahului Harbor, Maui (Coles et al. 2004; Carlton and Eldredge 2009). It is probably more widespread in the islands than currently reported.

Invasion History Elsewhere in the World:

In the Caribbean Sea, Paradella dianae was collected in Mayaguez, Puerto Rico in 1966 (Menzies and Glynn 1968; USNM 128324, US National Museum of Natural History 2016). It was found in Santos, Sao Paulo State, Brazil in 1978, and Cabo Frio, in Rio de Janeiro State (Pires 1980; Pires 1982). In 1981, it was collected on Bermuda (USNM 236261, US National Museum of Natural History 2016).

In European waters, P. dianae was first reported from Civitavecchia, Italy, on the Tyrrhenian Sea (Forniz and Maggiore 1985). It was subsequently found in other parts of the Mediterranean (from west to east): Bay of Algeciras, Spain in 1992 (Castello and Carballo 2002); Lake of Tunis, Tunisia (Bey 2001 cited by Amor et al.2016); Izmir, Turkey, Aegean Sea (Cinar et al. 2008, cited by Ates et al. 2013); Cyprus in 2002 (Kirkim et al. 2010); and Alexandria, Egypt (Atta 1991; Ramadan et al. 2006). In 1988, it was first collected on the open Atlantic coast of Europe, in Cadiz Harbor, Spain (Rodriguez et al.1992).

In the Indo-Pacific region, it was first seen on Eniwetok Atoll, in the Marshall Islands in 1967 (Glynn 1979). This was a site of naval operations and nuclear testing, so transport by military vessels is likely. Other appearances were mostly near shipping ports. The first record in Australia is from Brisbane, Queensland in 1971 (Harrison and Holdich 1982). It was later found in Townsville, Queensland in 1976 (Harrison and Holdich 1982); in the Swan River estuary, Western Australia in 1978 (Harrison and Holdich 1982); and in 1995 in Bunbury Harbor, also in Western Australia (Hass and Knott 1998). Elsewhere in the Indo-West Pacific, it was found in Buleji, near Karachi, Pakistan, on the Arabian Sea in 1984 (Javed and Ahmed, 1987); Hong Kong in 1986 (Bruce 1992); and Singapore in 2003 (Bruce and Wong 2015).


Paradella dianae has a rectangular-ovoid body shape, with a crescent-shaped cephalon and prominent eyes. Especially in the, male, the posterior border of the cephalon is a shelf-like ridge. The flagellum of Antenna 1 has 12 segments; while the flagellum of antenna 2 has 13 segments. The posterior edge of peraeonite 7 is bilobed, with a small central indentation and two ovoid lateral lobes. Pleonite 1 has two rounded median tubercles. In the male, the pleotelson is roughly triangular, with a heart-shaped opening (foramen) at the apex. Anterior to the cleft are 4 elongated tubercles, arranged in a rectangle- the male also has a small tubercle anterior to the foramen. Pleopods 2 of the male bear a long extension, twice the length of the endopod. The rami of the uropods are broad, oval, and paddle-like, and broader in males than in females. The endopods of the uropods extend beyond the tip of the pleotelson. In the female, the apex of the pleotelson has a simple notch, with no anterior tubercle. The endopod of the uropod ends level with the apex of the pleotelson. Males reach 3.5-5.6 mm in size, while females are usually smaller (2.1-5.6 mm). Live animals are mottled brown and yellowish white, with a broad yellowish white patch, and two black or orange dots in the center of Pleonite 1. This description is based on: Menzies 1962; Glynn 1970; Pires 1980; Harrison and Holdich 1983; Forniz and Maggiore 1985; Kensley and Schotte 1989; Atta 1991; Garcia-Guerero and Hendrickx 2005; and Knott et al. 2011.


Taxonomic Tree

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


Dynamenella dianae (Menzies and Glynn, 1968)
Dynamenopsis dianae (Menzies, 1962)
Paradella dianae (Harrison and Holdich, 1982)

Potentially Misidentified Species

Paradella plicatura
Tropical West Atlantic, Jamaica-Venezuela (Glynn 1970; Kensley and Schotte 1989).

Paradella quadripunctata
Florida-Caribbean (Kensley and Schotte 1989).



As with most isopods, Paradella dianae has separate sexes and fertilization is internal. However, an unusual feature of this isopod is that this species is a protogynous hermaphrodite. The young mature as females, brood and bear young, and then transform into males. Females are generally smaller (2.1-4.0mm) than males (3.5-5.6 mm) (Menzies 1962; Glynn 1970; Pires 1980; Harrison and Holdich 1983; Forniz and Maggiore 1985; Kensley and Schotte 1989; Kensley and Schotte 1999; Atta 1991; Knott et al. 2011). Ovigerous females have penises similar to those of subadult males. The young are brooded by the female and development is direct (Kensley and Schotte 1999). The number of embryos increases with body size, from 14 to 24, over a size range of 2.4 to 5.6 mm (Garcia-Guerrero and Hendrickx 2005).

Paradella dianae is widespread in warm-temperate to tropical climates (13-30°C) and tidal fresh to euhaline salinities (0-39 PSU, Nelson and Demetriades 1992; Rodriguez et al. 1992; Kensley and Schotte 1999). It is known from a wide range of intertidal and shallow-water habitats, including invertebrate fouling communities, seaweeds, mangrove roots, wharf pilings, rock crevices, and tubeworm colonies, but also from soft sediments (Clark and Robertson 1982; Forniz and Maggiore 1985; Nelson and Demeriades 1994; Hass and Knott 1998; Kensley and Schotte 1999; Garcia-Guerrero and Hendrickx 2005). Paradella dianae feeds by scraping algae and biofilms from surfaces (Harrison and Holdich 1982; Mungia and Alenius 2016).


Algal-Bacterial Films; Filamentous algae

Trophic Status:




General HabitatCoarse Woody DebrisNone
General HabitatMarinas & DocksNone
General HabitatRockyNone
General HabitatMangrovesNone
Salinity RangeLimnetic0-0.5 PSU
Salinity RangeOligohaline0.5-5 PSU
Salinity RangeMesohaline5-18 PSU
Salinity RangePolyhaline18-30 PSU
Salinity RangeEuhaline30-40 PSU
Tidal RangeSubtidalNone
Tidal RangeLow IntertidalNone
Vertical HabitatEpibenthicNone
Vertical HabitatEndobenthicNone

Tolerances and Life History Parameters

Minimum Temperature (ºC)13Field data, Cadiz, Spain (Rodriguez et al. 1992)
Maximum Temperature (ºC)30Field data, Indian River Lagoon FL (Nelson and Demetriades 1992)
Minimum Salinity (‰)0Field data, Indian River Lagoon FL (Kensley and Schotte 1999)
Maximum Salinity (‰)39Field data, Cadiz, Spain (Rodriguez et al. 1992)
Minimum pH7.670% survival
Maximum pH8.2Natural pH, control (Munguia and Alenius 2016)
Maximum Length (mm)5.6Male, Brazil (Pires 1980)
Broad Temperature RangeNoneWarm temperate-Subtropical
Broad Salinity RangeNoneTidal Limnetic-Euhaline

General Impacts

On jetties in the Gulf of Mexico, Paradella dianae 'seems to replace Sphaeroma quadridentatum, the most abundant isopod on the northern jetties' (Clark and Robertson 1982). However, interactions between the two species, have not been quantified, to our knowledge.

Regional Impacts

CAR-INorthern Yucatan, Gulf of Mexico, Florida Straits, to Middle Eastern FloridaEcological ImpactCompetition
Paradella dianae 'seems to replace Sphaeroma quadridentatum, as the most abundant isopod on the northern jetties' on the Texas coast (Clark and Robertson 1982).

Regional Distribution Map

Bioregion Region Name Year Invasion Status Population Status
NEP-VI Pt. Conception to Southern Baja California 1962 Native Estab
CAR-IV None 1966 Def Estab
SA-II None 1978 Def Estab
CAR-I Northern Yucatan, Gulf of Mexico, Florida Straits, to Middle Eastern Florida 1968 Def Estab
NEP-VII None 1952 Native Estab
CAR-VII Cape Hatteras to Mid-East Florida 1965 Def Estab
NA-ET4 Bermuda 1981 Def Estab
MED-III None 1985 Def Estab
IP-1 None 1984 Def Estab
MED-V None 1991 Def Estab
SP-XIII None 1967 Def Estab
NEA-V None 1988 Def Estab
AUS-XII None 1971 Def Estab
AUS-IV None 1978 Def Estab
NWP-2 None 1986 Def Estab
S190 Indian River 1984 Def Estab
S080 Charleston Harbor 2007 Def Estab
S183 _CDA_S183 (Daytona-St. Augustine) 1965 Def Estab
S180 St. Johns River 1965 Def Estab
S206 _CDA_S206 (Vero Beach) 1968 Def Estab
S200 Biscayne Bay 1988 Def Estab
MED-I None 1992 Def Estab
G280 Matagorda Bay 1978 Def Estab
G290 San Antonio Bay 1978 Def Estab
G300 Aransas Bay 1978 Def Estab
G310 Corpus Christi Bay 1978 Def Estab
G320 Upper Laguna Madre 1978 Def Estab
G330 Lower Laguna Madre 1978 Def Estab
P020 San Diego Bay 0 Native Estab
SP-XXI None 2002 Def Estab
S175 _CDA_S175 (Nassau) 1965 Def Estab
MED-VI None 2008 Def Estab
MED-IV None 2012 Def Unk
SA-II None 1978 Def Estab
SA-III None 1982 Def Estab
EAS-VI None 2003 Def Estab
SEP-C None 2009 Crypto Estab
NEP-VIII None 0 Native Estab
AUS-XI None 0 Native Estab
MED-IV None 206 Def Unk

Occurrence Map

OCC_ID Author Year Date Locality Status Latitude Longitude


Amor, Kounofi-Ben; Rifi, M.; Ghanem, R.; Draief, I.; Zouali, J.; Souissi, J. Ben (2016) Update of alien fauna and new records of Tunisian marine fauna, Mediterranean Marine Science 17(1): 124-143

Ates, A. Suat; Katagan, Tuncer; Sezgin, Murat; Özcan, Tahir (2013) Exotic crustaceans of the Turkish coast, Arthropods 2(1): 20-25

Atta, Manal M. (1991) The occurrence of Paradella dianae in Mediterranean waters of Alexandria., Crustaceana 60(2): 213-218

Bazairi, H. and 7 authors (2013) Alien marine species of Libya: first inventory and new records in El-Kouf National Park (Cyrenaica) and the neighbouring areas, Mediterranean Marine Science 14(2): 451-462

Bruce, Niel L.; Wong, Helen P.-S. (2015) An overview of the marine Isopoda (Crustacea) of Singapore, Raffles Bulletin of Zoology Supplement No. 31:: 152-168

Carlton, James T.; Iverson, Ernest W. (1981) Biogeography and natural history of Sphaeroma walkeri Stebbing (Crustacea: Isopoda) and its introduction to San Diego Bay, California, Journal of Natural History 15: 31-48

Carlton, James T.; Eldredge, Lucius (2009) Marine bioinvasions of Hawaii: The introduced and cryptogenic marine and estuarine animals and plants of the Hawaiian archipelago., Bishop Museum Bulletin in Cultural and Environmental Studies 4: 1-202

Castelló, José; Carballo, José Luis (2001) Isopod fauna, excluding Epicaridea, from the Strait of Gibraltar and nearby areas (Southern Iberian Peninsula)*, Scientia Marina 65(3): 221-241

Çinar, Melih Ertan and 7 authors (2021) Current status (as of end of 2020) of marine alien species in Turkey, PLOS ONE 16: Published online

Clark, Scott T.; Robertson, Philip B. (1982) Shallow water marine isopods of Texas., Contributions in Marine Science 25: 45-59

Coles, S. L.; Reath, P. R.; Longenecker, K.; Bolick, Holly; Eldredge, L. G. (2004) <missing title>, Hawai‘i Community Foundation and the U. S. Fish and Wildlife Service, Honolulu. Pp. 1-187

Farrapeira, Cristiane Maria Rocha; Tenório, Deusinete de Oliveira ; do Amaral, Fernanda Duar (2011) Vessel biofouling as an inadvertent vector of benthic invertebrates occurring in Brazil, Marine Pollution Bulletin 62: 832-839

Forniz, C.; Maggiore, F. (1985) New records of Sphaeromatidae from the Mediterranean Sea (Crustacea, Isopoda )., Oebalia 11(3): 779-783

Furlani, Dianne M. (1996) A guide to the introduced marine species in Australian waters., In: (Eds.) . , Hobart, Australia. Pp. <missing location>

García-Guerrero, Marcelo; Hendrickx, Michel E. (2005) Fecundity and reproductive period of Paradella dianae and Uromunna sp. (Peracarida, Isopoda) associated with prop roots of Rhizophora mangle in a tropical coastal lagoon, SE Gulf of California, Mexico, Crustaceana 78(7): 769-780

Glynn, Peter W. (1970) A systematic study of the Sphaeromatidae (Crustacea: Isopoda) of Isla Margarita, Venezuela, with descriptions of three new species., Memoria de la Sociedad de Ciencias Narturales La Salle 30: 5-48

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

Harrison, K.; Holdich, D. M. (1984) Hemibranchiate sphaeromatids (Crustacea: Isopoda) from Queensland, Australia, with a world-wide review of the genera discussed, Zoological Journal of the Linnean Society 81: 275-387

Harrison, K.: Holdich, D. M. (1982) Revision of the genera Dynamenella. Ischyromene, Dynamenopsis, and Cymodocella (Crustacea: Isopoda), including a new genus and five new species of Eubranchiate Sphaeromatids from Queensland waters., Journal of Crustacean Biology 2(1): 84-119

Hass, C. G.; Knott, B. (2000) Sphaeromatid isopods (Crustacea: Isopoda from the Leschenault estuary, Collie River and Bunbury Harbour., Journal of the Royal Society of Western Australia 83(4): <missing location>

Hass, Christine G.; Knott, Brenton (1998) Sphaeromatid isopods from the Swan River, Western Australia: diversity, distribution, and geographic sources., Crustaceana 71(1): <missing location>

Henricksen, Summer; Bollens, Stephen M. (2021) Abundance and growth of the invasive Asian clam, Corbicula fluminea, in the lower Columbia River, USA, Aquatic Invasions 17: In press

Javed, Waquar; Ahmed, Roshan (1987) On the occurrence of Paradella dianae, a genus and species of Sphaeromatidae (Isopoda, Flabellifera) in the Arabian Sea., Crustaceana 53(2): 215-217

Junoy, J.; J. Castelló (2003) Catálogo de las especies ibéricas y baleares de isópodos marinos (Crustacea: Isopoda)., Boletin Insitituto Espanol de Oceanografia 19(1-4): 293-325

Kensley, Brian; Nelson, Walter G.; Schotte, Marilyn (1995) Marine isopod biodiversity of the Indian River Lagoon, Florida, Bulletin of Marine Science 57(1): 136-142

Kensley, Brian; Schotte, Marilyn (1989) <missing title>, Smithsonian Institution Press, Washington, D.C.. Pp. <missing location>

Kensley, Brian; Schotte, Marilyn (1999) New records of isopods from the Indian River Lagoon, Florida (Crustacea: Peracarida)., Proceedings of the Biological Society of Washington 112(4): 695-713

Knott, David M.; DeVictor, Susan T.; Crickenberger, Sam 2011 <i>Paradella dianae</i>- around the world in 20 years. <missing URL>

Liu, Wenliang; Liang, Xiaoli ; Zhu, Xiaojing (2015) A new record and mitochondrial identification of Synidotea laticauda Benedict, 1897 (Crustacea: Isopoda: Valvifera: Idoteidae) from the Yangtze Estuary, China, Zootaxa 4294: 371-380

Mathieson, Arthur C.; Dawes, Clinton J. (2017) Seaweeds of the Northwest Atlantic, University of Massachusetts Press, Amherst MA. Pp. <missing location>

Menzies, Robert J. (1962a) The marine isopod fauna of Bahia de San Quintin,Baja California, Mexico, Pacific Naturalist 3(11): 337-348

Menzies, Robert J.; Glynn, Peter W. (1968) The common marine custaceans of Puerto Rico, Studies of the Fauna of Curacao and other Caribbean Islands 27: 1-33

Morgan, David L.; Gill, ;Howard S.; Maddern, Mark G; Beatty. .; Stephen J. (2004) Distribution and impacts of introduced freshwater fishes in Western Australia, New Zealand Journal of Marine and Freshwater Research 38: 511-523

Nelson, Walter G.; Demetriades, Leandros (1992) Peracarids associated with Sabellariid worm rock (Phragmatopoma lapidosa) at Sebastian inlet, Florida, Journal of Crustacean Biology 12(4): 647-654

Pires, Ana Maria Setubal (1980) New record of Sphaeromatidae (Isopoda) from the Brazilian southern coast: Dynamenella dianae (Menzies, 1962), Crustaceana 39(2): 133-140

Pires, Ana Maria Setubal (1982) [Sphaeromatidae (Isopoda:Flabellifera) of the intertidal and shallow depths of the states of Sao Paulo and Rio de Janeiro, Boletim do Instituto Oceanográfico 31(2): 43-55

Ramadan, Sh. E.; Kheirallah, A. M.; Abdel-salam, Kh. M. (2006) Marine fouling community in the Eastern harbour of Alexandria, Egypt compared with four decades of previous studies, Mediterranean Marine Science 7/2: 19-29

Rodriguez, A.; Drake, P.; Aris, A. M. (1992) First records of Paracerceis sculpta (Holmes, 1904) and Paradella dianae (Isopoda, Sphaeromatidae) at the Atlantic Coast of Europe,, Crustaceana 63(1): 94-97

Santos, Cinthya S. G. (2007) Nereididae from Rocas Atoll (North-East, Brazil)., Arq. Mus. Nac., Rio de Janeiro 65(3): 369-380

Soors, Jan; Faasse, Marco; Stevens, Maarten; Verbessem, Ingrid; De Regge, Nico;Van den Bergh, Ericia (2010) New crustacean invaders in the Schelde estuary (Belgium), Belgian Journal of Zoology 140: 3-10

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

Ulman, Aylin and 17 authors (2017) A massive update of non-indigenous species records in Mediterranean marinas, PeerJ 5( e3954): <missing location>

Wetzer, Regina; Bruce, Niel L. (2007) A new species of Paradella Harrison & Holdich, 1982 (Crustacea: Isopoda: Sphaeromatidae) from Baja California, Mexico, with a key to East Pacific species., Zootaxa 1512: 39-49