Invasion History

First Non-native North American Tidal Record: 1950
First Non-native West Coast Tidal Record: 1950
First Non-native East/Gulf Coast Tidal Record:

General Invasion History:

The native region of Caecijaera horvathi is unknown. It occurs solely in the burrows of the wood-boring gribbles, Limnoria spp. (possibly only L. tripunctata), also of unknown origin. Limnoria tripunctata is now widely distributed throughout the world and is considered introduced on the West Coast, where it was first reported in 1871 (Menzies 1951; Carlton 1979). Caecijaera horvathi was described from Los Angeles-Long Beach harbor, California (Menzies 1951), and has been subsequently found in Hawaii (Cooke 1977) and Cuba (Kensley et al. 1997).

North American Invasion History:

Invasion History on the West Coast:

The only collections of Caecijaera horvathi from the West Coast, of which we are aware, are the collections made by Menzies for the species' description on Dec. 6 1950, when a total of 29 specimens were collected from wood infested with Limnoria tripunctata (Menzies 1951; Carlton 1979). Given the small size and obscure habitat of this isopod, and the absence of recent studies of the ecology of Limnoria in California, we presume that it is still established. However, more collections and further research are needed.

Invasion History in Hawaii:

Caecijaera horvathi was collected in test blocks of wood, infested with Limnoria tripunctata, at Makai Range Pier, near Honolulu, on March 13, 1975, and continued to be collected through 1975. It was not collected at other test sites in Hawaii (Cooke 1977). Carlton and Eldredge (2009) cite no further reports of this isopod in the Hawaiian Islands, but treat it as established.

Invasion History Elsewhere in the World:

Caecijaera horvathi was collected on April 10, 1994, in Limnoria sp. burrows, in the hulls of decaying barges at Cayo Mendoza, on the northwestern coast of Cuba. Five male specimens were preserved (Kensley et al. 1997; USNM 1083189, US National Museum of Natural History 2007). We have no further records of this isopod from the western Atlantic.


Caecijaera horvathi has a roughly oblong body, which is usually twice as wide as it is long, with a rounded head and telson. Coxal plates are not visible in dorsal view. Antenna 1 has an inflated basal segment and 5 subsequent segments. The first segment of Antenna 2 is extended laterally, and the third segment bears an oval scale. The flagellum has 14 segments and is about equal to half the width of the head. In males, Pleopods 1 and 2 are modified for copulation. Pleopods 1 are fused to form a narrow appendage (the sympod), widening near the tip and ending in a knob (Menzies 1951, California) or in thick curved outer spines, and finer inner spines (Cooke 1977, Hawaii; Kensley et al. 1997, Cuba). Pleopods 2 are not fused, but the inner ramus is modified into a needle-like stylus. The pleotelson is shield-shaped, and the short biramous uropods protrude from notches. Specimens from Hawaii and Cuba differed from those from California, in having the basal segment of Antenna 1 with a more extended lobe, reaching the distal joint of the second segment, and in the differences in the form of Pleopods 1, as noted above (Cooke 1977; Kensley et al. 1997). Wilson and Wagele (1994) and Kensley et al. (1997) suggest that the Hawaiian and Cuban forms could represent a separate species. Adults are about 1.6-1.8 mm long. Description based on: Menzies 1951, Schultz 1969, Cooke 1977, Kensley et al. 1997, and Brusca et al. 2007.


Taxonomic Tree

Kingdom:   Animalia
Phylum:   Arthropoda
Subphylum:   Crustacea
Class:   Malacostraca
Subclass:   Eumalacostraca
Superorder:   Peracarida
Order:   Isopoda
Suborder:   Asellota
Family:   Janiridae
Genus:   Caecijaera
Species:   horvathi


Potentially Misidentified Species

Caecijaera kussakini
Caecijaera kussakini (Malyutina 1994), from Vietnam, is very similar to C. horvathi (Kensley et al. 1997).

Caecijaera cojimarensis
Caecijaera cojimarensis (Ortiz & Lalana 1993) is a very similar species, differing in small features of the pleopods and uropods (Kensley et al. 1997).



Caecijaera horvathi has separate sexes and development is direct (Schultz 1969). Caecijaera horvathi presumably feeds on the detritus and microbial community created by Limnoria's consumption and digestion of wood. Svavarsson (1982) suggested that Caecijaera spp. feeds on fungi growing on the walls of Limnoria's burrows.


Wood; Detrtus (Commensal with Limnoria sp.)

Trophic Status:




General HabitatCoarse Woody DebrisNone
General HabitatMarinas & DocksNone
General HabitatVessel HullNone
Salinity RangePolyhaline18-30 PSU
Salinity RangeEuhaline30-40 PSU
Tidal RangeSubtidalNone
Tidal RangeLow IntertidalNone
Vertical HabitatEpibenthicNone

Tolerances and Life History Parameters

Maximum Length (mm)1.8Hawaii (Cooke 1977)
Broad Temperature RangeNoneWarm temperate-Subtropical
Broad Salinity RangeNonePolyhaline-Euhaline

General Impacts

No impacts have been reported for Caecijaera horvathi.

Regional Distribution Map

Bioregion Region Name Year Invasion Status Population Status
SP-XXI None 1975 Def Estab
NEP-VI Pt. Conception to Southern Baja California 1951 Def Estab
CAR-V None 1994 Def Estab
P050 San Pedro Bay 1950 Def Estab

Occurrence Map

OCC_ID Author Year Date Locality Status Latitude Longitude


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

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

Cooke, William J. (1977) On the occurrence of the commensal asellote Caecijaera horvathi Menzies, 1951 in Hawaii., Crustacean 110(1): 74-98

Kensley, Brian; Ortiz, Manuel; Schotte, Marilyn (1997) New records of marine Isopoda from Cuba (Crustacea: Peracarida., Proceedings of the Biological Society of Washington. 110(1): 74-98

Menzies, Robert James (1951) A new genus and new species of asellote isopod, Caecijaera horvathi, from Los Angeles-Long Beach Harbor, American Museum Novitates 1542: 1-7

Ortiz, Manuel; Lalana R., Rogelio (1993) [Caecijaera (Caecijaera) cojimarensis, a new species of isopod (Asellota, Janiridae) Associated with Limnoria sp. Flabellifera), in Cuba], Caribbean Journal of Science 29(1-2): 44-49

Schultz, G.A. (1969) The Marine Isopod Crustaceans, Wm. C. Brown Company, Dubuque, Iowa. Pp. <missing location>

Svavarsson, Jorundir (1982) Limnoria borealis and its commensal Caecijaea borealis (Isopoda, Asellota) in Icelandic waters, Sarsia 67: 223-236

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

Wilson, George D. F.; Wagele, Johann-Wolfgang (1994) Review of the family Ianiridae (Crustacea: Isopoda: Asellota), Invertebrate Taxonomy 8: 683-747