Content area
Full Text
KEY WORDS
Monocystis
Amynthas
Gregarines
Apicomplexans
Monocystis perplexa
Species Descriptions
Earthworm Parasites
18S rRNA Gene
Invasive Earthworms
Parasite Life Stages
ABSTRACT
Monocystis perplexa n. sp., a parasite of an important invasive Japanese earthworm in North America, Amynthas agrestis, is described from a site in Vermont. An improved standard for Monocystis species descriptions is proposed including a standard nomenclature to reduce synonymies, a standard set of biometrics and shape descriptions for living cells, and a DNA genomic sequence for the 18S rRNA (~1,700 base pairs). Comparing morphologies of Monocystis parasites in sympatric earthworm species indicates that M. perplexa is specific to A. agrestis in the study region. Also, polymerase chain reaction primers specific to M. perplexa amplified samples of A. agrestis earthworms taken from several sites in Japan. This suggests the parasite entered North America from Japan, the origin of the invasive Amynthas earthworm, and thus M. perplexa would be the first Monocystis described from the diverse Japanese Amynthas earthworms and the first from East Asia. Monocystis perplexa was found in every population of A. agrestis surveyed in Vermont, always reaching 100% prevalence by late summer (the host has an annual life cycle in Vermont). The 18S gene sequence differed from that of Monocystis agilis from the sympatric earthworm Lumbricus terrestris (the only other sequence available for Monocystis), and a genetic similarity tree places them closest among other gregarines. Many of the 95 described species of Monocystis are very similar in morphology (based on species descriptions), so the 18S gene can act as a barcode for Monocystis species and thus will help to eliminate both synonymies and reveal cryptic species.
The gregarines are a clade of early-branching apicomplexan parasites that infect a broad diversity of invertebrate animals from marine, freshwater, and terrestrial environments (Desportes and Schrevel, 2013). Cavalier-Smith (2014), using molecular, cell structural, and life cycle data, found the classical gregarines are polyphyletic and erected a new class, Gregarinomorphea, to hold most of the overall diversity (here we term "gregarines"). Like other apicomplexans, the gregarine life cycle includes sexual reproduction to produce the transmission stage (oocysts) but differs in lacking merogony (asexual replication) in most species. The genus Monocystis (Monocystidae) can stand as an exemplar in many positive ways for the gregarines. Fully 95 described...