Nematodes in Lobsters


Category 4 (Negligible Regulatory Significance in Canada)

Common, generally accepted names of the organism or disease agent

Larval nematodes.

Scientific name or taxonomic affiliation

Ascarophis sp. (family Spiruroidea) and Hysterothylacium sp.(family Secernentea).

Geographic distribution

Eastern Canada and south off Cape Cod, USA.

Host species

Homarus americanus.

Impact on the host

Ascerophis apparently infects the lobster via the gills (Boghen 1978) and encysts along the anterior wall of the rectum. During a comparison of parasite fauna of offshore and coastal lobsters off Cape Cod, Uzmann (1970) observed Ascarophis sp. almost exclusively restricted to offshore lobsters. Unhealthy looking Hysterothylacium sp.were encapsulated in the stomach wall and were observed in the lumen of the stomach, suggesting that they were acquired from fish used as bait in the lobster traps and lobsters are not an important host in the transmission of this nematode.

Diagnostic techniques

Squash Preparations: Larval nematodes from about 2 to 12 mm in length associated with the gills or intestine where they may be encapsulated. Ascarophis may be coiled in lenticular cysts about 1 mm wide in the anterior wall of the rectum.

Methods of control

No known methods of prevention or control.


Boghen, A.D. 1978. A parasitological survey of the American lobster Homarus americanus from the Northumberland Strait, southern Gulf of St. Lawrence. Canadian Journal of Zoology 56: 2460-2462.

Brattey, J. and A. Campbell. 1986. A survey of parasites of the American lobster, Homarus americanus (Crustacea: Decapoda), from the Canadian Maritimes. Canadian Journal of Zoology 64: 1998-2003.

Uzmann, J.R. 1967. Juvenile Ascarophis (Nematoda: Spiruroidea) in the American lobster, Homarus americanus. The Journal of Parasitology 53: 218.

Uzmann, J.R. 1970. Use of parasites in identifying lobster stocks. The Journal of Parasitology 56: 349. (abstract).

Citation Information

Bower, S.M. (1996): Synopsis of Infectious Diseases and Parasites of Commercially Exploited Shellfish: Nematodes in Lobsters.

Date last revised: September 1996
Comments to Susan Bower

Date modified: