Microsporidosis of Lobsters


Category 3 (Host Not in Canada)

Common, generally accepted names of the organism or disease agent

Microsporidosis of palinurid lobsters.

Scientific name or taxonomic affiliation

Ameson sp.

Geographic distribution

South-west Australia and Torres Strait between Australia and New Guinea.

Host species

Panulirus ornatus and Panulirus cygnus. Similar parasites occur in many species of crabs, shrimp and prawns.

Impact on the host

Numerous microsporidian spores occur in the muscle fibres causing the muscle to appears "milky" or "cooked" in living specimens. Prevalence is low (1/1000-3000) and thus the disease does not appear to be a threat to lobsters in endemic areas. The prevalence of inapparent infections (presumably identifyable by histological examination) is not known.

Diagnostic techniques

Gross Observations: Muscle appears white or "cooked" in living specimens.

Histology: Microsporidial spores (1.4-1.8 by 2.0-2.4 µm) aggregated in packets in muscle fibers. Reproductive stages consisted of sporonts that divided equally to produce two thick walled sporoblasts which differentiated into spores. Infected muscle fibers were hypertrophied with a mean width of 15 µm in comparison to 8.5 µm for unaffected fibers.

Electron Microscopy: Exospore (about 0.1 µm thick) was covered by microvilli. Endospore (about 0.2 µm thick) encapsulated the sporoplasm which contained an isofilar, singly coiled polar filament, a polaroplast with four to six tubular elements and a granular posterior portion, and a posteriorly located nucleus.

Methods of control

No known methods of prevention or control.


Dennis, D.M. and B.L. Munday. 1994. Microsporidiosis of palinurid lobsters from Australian waters. Bulletin of the European Association of Fish Pathologists 14: 16-18.

Citation Information

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

Date last revised: Fall 1996
Comments to Susan Bower

Date modified: