Dicyema shimantoense

Dicyema shimantoense
Scientific classification
Kingdom:	Animalia
Phylum:	Mesozoa
Class:	Rhombozoa
Order:	Dicyemida
Family:	Dicyemidae
Genus:	Dicyema
Species:	D. shimantoense
Binomial name
Dicyema shimantoense Furuya, 2008[1]

Dicyema shimantoense of the Phylum Dicyemida. It is a vermiform mesozoan parasite that infects the renal appendages of the cephalopod Octopus sasakii. The name is derived from the longest river in Shikoku called the Shimanto River which begins at Tosa Bay. A present study from 2000-06 used 59 specimens obtained from fishermen at Tosa Bay and Kii Strait Japan. O. sasakii is a cephalopod found mainly in the shallow-water of Southern Japan. Research found that only those of certain sizes and geographical locations can be infected by D.shimantoense.

The following procedures were performed for collection of the specimen. 1)small pieces of the O. sasakii’s renal organ infected with the parasite were mounted on slides 2)smears were then fixed on Bouin’s fluid and preserved in Et2O 3)Erlich’s hematoxylin was used to stained and counterstained with eosin 4)mounted slides were then observed with a light microscope

There are many species of dicyemids. In order to distinguish them apart, you need to observe the shape of the calotte (anterior ends of dicyemids: conical or elongation). D. shimantoense inserts the conical calottes into intracellular folds of renal appendages.

Characteristics

· Body length up to 3000 μm

· Peripheral cells consist of 4 proplars, 5 metapolars, 2-4 parapolars, 10-12 trunk cells

· Infusoriform embryos up to 37 cells

· 2 nuclei in each cell

· 22 peripheral cells

Life cycle:Stages of dicyemids

1. The nematogen is the asexual stage of dicyemids which produce vermiform larvae in the axial cells

2. Nematogens continue to reproduce in the kidneys until the vermiform matures into rhombogens

3. Rhombogens contain hermaphroditic gonads within the axial cell called the infusorigens (gonads which produce gametes of various sizes)

Transmission

The infection of the parasite are found in the kidneys (independent infection of each kidneys) in O. sasakii, however mode of transmission is currently unknown.

References

1. ^ Furuya, H (2008). "Three new dicyemids from Octopus sasakii (Mollusca: Cephalopoda: Octopoda)". The Journal of parasitology 94 (5): 1071–81. doi:10.1645/GE-1580.1. PMID 18576860. 

• Furuya, H., F. G. Hochberg, and K. Tsuneki (2001). "Developmental patterns and cell lineages of vermiform embryos in dicyemid mesozoans". Biological Bulletin 201 (3): 405–416. PMID 11751252. http://www.biolbull.org/cgi/content/full/201/3/405. 
• Furuya, Hidetaka; Tsuneki, Kazuhiko (2003). "Biology of Dicyemid Mesozoans". Zoological Science 20 (5): 519–32. doi:10.2108/zsj.20.519. PMID 12777824.