The etiological agent of 'bumper car' disease in lobsters Homarus americanus is described as a new species of ciliate, Anophryoides haemophila (Scuticociliatida: Orchitophryidae). A. haemophila n, sp, is distinguished from other species in the genus by the curved rectangular oral polykinetid 2, a somatic kinety range of 16 to 18, and its relatively small size. The parasite is easy to maintain in vivo and in vitro for extended periods at 2 to 5°C. Apparently the ciliate can be a significant impediment to the economic viability of coldwater lobster impoundments in eastern North America. However, factors inducing epizootics of 'bumper car' disease are unknown.

A combination of 16S rRNA sequencing and random amplified polymorphic DNA (RAPD) analysis was used to evaluate the genetic diversity within Aerococcus viridans var. homari, the causative agent of gaffkemia in lobsters. A collection of 7 A. viridans var. homari strains and 2 avirulent A. viridans-like cocci isolated from homarid lobsters harvested from different regions on the Atlantic Coast of North America were analyzed. The isolates are separated geographically and temporally between the years 1947 and 2000. Sequencing of 16S rRNA genes confirmed the inclusion of all 9 isolates in the monophyletic A. viridans clade (99.8 to 100% similarity). RAPD analysis revealed that the 9 A. viridans var. homari isolates could be separated into 2 distinct subtypes. Subtype 1 included the 7 pathogenic lobster isolates and constituted a homogeneous group regardless of their geographical, temporal or virulence differences. Subtype 2 contained the 2 avirulent A. viridans-like cocci that had distinct RAPD patterns and clustered separately with the non-marine A. viridans. RAPD analysis represented a useful method for determining molecular subtyping for the intraspecific classification and epidemiological investigations of A. viridans var. homari.

Neoparamoeba pemaquidensis, the etiological agent of amoebic gill disease, has shown surprising sequence variability among different copies of the 18S ribosomal RNA gene within an isolate. This intra-genomic microheterogeneity was confirmed and extended to an analysis of the internal transcribed spacer (ITS) region. High levels of intra-genomic nucleotide diversity (Pi=0.0201-0.0313) were found among sequenced ITS regions from individual host amoeba isolates. In contrast, the ITS region of its endosymbiont revealed significantly lower levels of intra-genomic nucleotide diversity (Pi=0.0028-0.0056) compared with the host N. pemaquidensis. Phylogenetic and ParaFit coevolution analyses involving N. pemaquidensis isolates and their respective endosymbionts confirmed a significant coevolutionary relationship between the two protists. The observation of non-shared microheterogeneity and coevolution emphasizes the complexity of the interactions between N. pemaquidensis and its obligate endosymbiont.

Anophryoides haemophila is a ciliated protozoan and the causative agent of bumper car disease in lobsters. An in vitro system was developed to assess the effects of chemotherapeutants on c~liate motility and morphology. Monensin, formaldehyde and pyrimethamine + sulphaquinoxaline caused a dose-dependent reduction in ciliate motility and induced cell lysis The effects of oxytetracycline were dependent upon the incubat~on solut~on; no effect was observed on ciliates in seawater and a dose-dependent decrease in ciliate motility and cell rounding occurred in 0.8 M NaCI. Amprolium had no effect on ciliate motility or morphology. This system can be used to rapidly screen antiprotozoan compounds for efficacy against A. haemophila prior to selecting compounds for in vivo efficacy and safety studies.

We have determined the nucleotide sequence of the nuclear gene encoding small-subunit ribosomal ribonucleic acid of the ciliate Anophryoides haemophila, a parasite of the American lobster Homarus americanus. The gene is 1763 bp in length, and has a guanosine-plus-cytosine content of 43.9%. Inferred phylogenetic frameworks strongly support the monophyly of the scuticociliates, and suggest that order Scuticociliatida should be elevated to at least subclass rank. Oligonucleotide probes based on A. haemophila ssurDNA can discriminate between DNAs of A. haemophila and other investigated hymenostome ciliates, and effectively prime polymerase chain reaction-based detection of A. haemophila deoxyribonucleic acid against at least a 1600-fold excess of total deoxyribonucleic acid from H. americanus. GENBANK/U51554