Haplozoon

Haplozoon
Light micrograph of Haplozoon axiothellae in its trophont stage
Scientific classification Edit this classification
Domain: Eukaryota
Clade: Diaphoretickes
Clade: SAR
Clade: Alveolata
Phylum: Myzozoa
Superclass: Dinoflagellata
Class: Dinophyceae
Order: Peridiniales
Poche
Family: Haplozoonaceae
Poche
Genus: Haplozoon
Dogiel

Haplozoon (/hæploʊ’zoʊən/) are unicellular endo-parasites, primarily infecting maldanid polychaetes. They belong to Dinoflagellata but differ from typical dinoflagellates. Most dinoflagellates are free-living and possess two flagella. Instead, Haplozoon belong to a 5% minority of parasitic dinoflagellates that are not free-living. Additionally, the Haplozoon trophont stage is particularly unique due to an apparent lack of flagella. The presence of flagella or remnant structures is the subject of ongoing research.

At first glance, Haplozoon also do not appear unicellular – in fact they were originally classified as a possible transitional stage between protists and multicellular organisms.[1] They have more recently been classified as compartmentalized syncytia – single cells with multiple nuclei that have been subdivided by internal membranes.[2] Their life cycle is also largely unknown; while there is a well-observed adult trophont stage, understanding of other life stages is speculative at best.

There is a single published case of Haplozoon infecting an appendicularian.[3] Otherwise, they are almost exclusively documented as infecting Maldanidae, and the extent to which they are an appendicularian parasite has not been investigated.

  1. ^ Shumway, W. (1924). The genus Haplozoon, Dogiel. Observations on the life history and systematic position. The Journal of Parasitology, 11(2), 59-74.
  2. ^ Leander, B., Saldarriaga, J., & Keeling, P. (2002). Surface morphology of the marine parasite Haplozoon axiothellae Siebert (Dinoflagellata). European Journal of Protistology, 38(3), 287–297. doi: 10.1078/0932-4739-00882
  3. ^ Cachon J. (1964). Contribution a l’étude des Péridiniens parasites. Cytologie. Cycles évolutifs. Ann. Sci. Nat. Zool. 12: 1-158.