Carcinonemertes spp. of Crabs


Category 2 (In Canada and of Regional Concern)

Common, generally accepted names of the organism or disease agent

Nemertean worm predation of crustacean eggs.

Scientific name or taxonomic affiliation

Carcinonemertes carcinophila, Carcinonemertes errans, Carcinonemertes sp.

Geographic distribution


Host species

Cancer magister, Paralithodes camtschatica, Chionoecetes bairdi, and Callinectes sapidus. Forty-eight other host species of Carcinonemertes spp. and related species of nemerteans, including various lobsters (Panulirus spp. and Homarus americanus), have been reported world wide.

Impact on the host

Adult worms (cream to orange, 4-7 mm long) feed on eggs of hosts causing egg loss up to 100% and overgrowth with epibionts such as fungus (e.g. Lagenidium) and bacteria. Significant egg loss has been reported from various crustacean hosts. Juvenile worms (pink, 0.2-1.0 mm long) live on exoskeleton, including gills, of non­ovigerous crabs, but cause no harm and may encyst between gill lamellae. Worms settle from a planktonic stage, may be transferred during copulation, or transferred from old exoskelton to new during molt.

Diagnostic techniques

Gross Observations: Juvenile worms can be seen under the abdomen of non-ovigerous crabs or encysted between the gills. Mature worms range through egg masses of ovigerous females and may return to the gills.

Methods of control

May possibly be removed by dipping briefly in fresh water as most Carcinonemertes appear quite sensitive to osmotic shock.


McCabe, G.T., R.L. Emmett, T.C. Coley and R.J. McConnell. 1987. Effect of a river-dominated estuary on the prevalence of Carcinonemertes errans, an egg predator of the Dungeness crab, Cancer magister. Fishery Bulletin 85: 140-142.

Messick, G.A. and C.J. Sindermann. 1992. Synopsis of principal diseases of the blue crab, Callinectes sapidus. NOAA Technical Memorandum NMFS-F/NEC-88. 24 p.

Wickham, D.E. 1986. Epizootic infestations by nemertean brood parasites on commercially important crustaceans. Canadian Journal of Fisheries and Aquatic Sciences 43: 2295-2302.

Wickham, D.E. 1988. Nemertean worm predation. In: C.J. Sindermann and D.V. Lightner (eds.). Disease Diagnosis and Control in North American Aquaculture. Developments in Aquaculture and Fisheries Science 17. Elsevier, Amsterdam, p. 226-229.

Wickham, D.E. and A.M. Kuris. 1985. The comparative ecology of nemertean egg predators. American Zoologist 25: 127-134.

Citation Information

Bower, S.M. (1996): Synopsis of Infectious Diseases and Parasites of Commercially Exploited Shellfish: Carcinonemertes spp. of Crabs.

Date last revised: September 1996
Comments to Susan Bower

Date modified: