Quahog parasite unknown

The life stages of thalli, endospores, and sporangia have been observed.[3] It somewhat resembles the unrelated protist haplosporidian parasite Haplosporidium nelsoni (MPX), a pathogen of the eastern oyster.[2]

QPX was originally considered a chytrid, but has now been provisionally assigned to the phylum Labyrinthulomycota in either the families Thraustochytriidae or Labyrinthulidae, based on the organism having a "uninucleate biflagellate zoospore stage, a loose multilaminar cell wall, and particularly an intracellular sagenogen-like structure".[4] However, much about it is still unknown.[1] QPX-like organisms also may not be all of the same species.[2]

Molecular phylogenetic on the SSU rRNA of QPX was able to produce the same phylum-level identification, and more precisely down to the family Thraustochytriidae next to Thraustochytrium pachydermum. A PCR primer targeting this region that detects QPX infection has been constructed.[5]

QPX can be cultured in laboratories, with the optimal temperature being 20 to 23 °C. It produces a mucus that causes inflammation in the clam and shields itself from clam immune response.[6]

The partial genome of QPX has been sequenced by the shotgun method in 2013, along with the transcriptome to identify genes important in stress response (mainly temperature). A few interesting proteins and a wide range of genetic polymorphisms have been identified. It expresses some genes involved in the synthesis of antibiotics that are also toxic to clams.[6] Further experimental characterisation in 2018 of these single-nucleotide polymorphisms shows variations in genes related to virulence and environmental (salinity and temperature) adaptation.[7]