''Dicyema shimantoense'' is a

parasitic Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson ha ...

worm of the phylum Dicyemida. It is a

vermiform Vermiform (ˈvərməˌfôrm) describes something shaped like a worm. The expression is often employed in biology and anatomy to describe usually soft body parts or animals that are more or less tubular or cylindrical. The word root is Latin, ''ve ...

mesozoan parasite that infects the renal appendages of the cephalopod ''

Octopus sasakii ''Octopus sasakii'' is a species of octopus found only in salt water. This species is a taxon inquirendum. Physical description It is able to change its color. It moves forward by vigorously squeezing water in its cloak and pumping it throu ...

''. The name is derived from the

Shimanto River The is a river in western Kōchi Prefecture, Japan. 196 km in length, it has a watershed of 2,270 km². Its name is written with kanji meaning "forty thousand and ten". Since the river is remote from major cities and does not have a ...

, which is the longest river in

Shikoku is the smallest of the four main islands of Japan. It is long and between wide. It has a population of 3.8 million (, 3.1%). It is south of Honshu and northeast of Kyushu. Shikoku's ancient names include ''Iyo-no-futana-shima'' (), '' ...

, and flows into

Tosa Bay Tosa Bay () is a bay north of the line connecting Cape Muroto and Cape Ashizuri in Kochi Prefecture, Japan. Tosa Bay is better fishing grounds in Japan, which is strongly affected by the Kuroshio Current The , also known as the Black or or t ...

. A 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''. There are many species of dicyemids. Examination of the calotte (the anterior ends of dicyemids ) is required to distinguish them. ''D. shimantoense'' inserts the conical calottes into intracellular folds of renal appendages.

Characteristics

The body length of ''D. shimantoense'' can reach up to 3000μm. Peripheral cells consist of 4 propolars, 5 metapolars, 2-4 parapolars, and 10-12 trunk cells. There are infusoriform embryos of up to 37 cells. There are 2 nuclei in each cell, and 22 peripheral cells.

Life cycle

The Dicyemids have three stages of life. 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 (there is an independent infection of each kidney). In '' O. sasakii'', however, the mode of transmission is currently unknown.

References

* * {{Taxonbar, from=Q2379308 Parasites of molluscs Parasitic protostomes Dicyemida Animals described in 2008