Pseudocarcinonemertes homari of Lobsters
Category 2 (In Canada and of Regional Concern)
Common, generally accepted names of the organism or disease agent
Nemertean worm predation of crustacean eggs, Lobster egg worm.
Scientific name or taxonomic affiliation
Pseudocarcinonemertes homari. Other species of nemertean worms (e.g., Carcinomertes spp.) have also been reported from Homarus americanus as well as from other crustaceans such as Palinurid lobsters and crabs.
Northeastern United States and Canada.
Impact on the host
Worms (4-8 mm long) feed on eggs of lobsters and can cause up to 100% egg loss and overgrowth with epibionts when present in high intensities (> 4, but several hundred can occur on a single lobster) during the early stages of egg incubation. Immature worms (0.2-1.0 mm) live in low intensity on exoskeleton, including gills, of nonovigerous lobsters, but cause no harm. Observations of Fleming and Gibson (1981) indicate that the gills of immature male lobsters can be experimentally infected with the nemerteans but natural infections have only been obtained from female hosts. Also, P. homari can release eggs at any time whilst the lobster host is gravid (berried), but they are unable to produce eggs on non-ovigerous hosts. Other species of nemertean worms (Carcinomertes sp.) may also infect the egg clusters on lobsters. These other species are similar in size and can cause similar damage to the eggs as P. homari.
Gross Observations: Living worms are up to 8 mm long and 1-1.25 mm wide. The head is rounded without cephalic furrows and bears four distinct eyes. Mature females contain many yellow eggs interspersed between the intestinal diverticula, giving a general yellowish-orange hue to the nemertean. Mature males are orange in colour, whilst immature worms of both sexes are white or cream coloured (Fleming and Gibson 1981).
Methods of control
Control is not an issue unless berried lobsters are transported for experimental purposes. Nemerteans readily move to berried lobsters that are placed in a tank with infected hosts. The nemerteans may possibly be removed by dipping the lobsters briefly in fresh water.
Aiken, D.E., S.L. Waddy, L.S. Uhazy and A. Campbell. 1983. A nemertean destructive to the eggs of the lobster Homarus americanus. Rapports Procès-verbaux Réunion Conseil Permanent International pour l'Exploration de la Mer 182: 120-133.
Campbell, A. and J. Brattey. 1986. Egg loss from the American lobster, Homarus americanus, in relation to nemertean, Pseudocarcinonemertes homari infestation. Canadian Journal of Fisheries and Aquatic Sciences 43: 772-780.
Fleming, L.C. and R. Gibson. 1981. A new genus and species of monostiliferous hoplonemerteans, ectohabitant on lobsters. Journal of Experimental Marine Biology and Ecology 52: 79-93.
Sindermann, C.J. 1988. Nemertean worm predation on lobster eggs. 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. 264-265.
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.
Bower, S.M. (2003): Synopsis of Infectious Diseases and Parasites of Commercially Exploited Shellfish: Pseudocarcinonemertes homari of Lobsters.
Date last revised: April 2003
Comments to Susan Bower
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