Photosymbiotic ascidians we newly described

To date, we have described six photosymbiotic ascidians as new species from the Ryukyu Archipelago, Japan.

They are all belonged to the genus Diplosoma, and they are tiny, green sheet in the field. We can not identify the species based on their external morphology. Each species is discriminated by the position of the retractor muscle and the stigma numbers in the branchial sac. Molecular phylogeny based on COI gene sequences supported our classifications of these species.

Six Diplosoma species described from the Ryukyus

We also newly described one Lissoclinum harboring Prochloron in the tunic. This species, Lissoclinum midui, has so far been recorded at only one site off Kumejima Island (Ryukyu Archipelago, Japan). As a didemnid ascidian, this is very unique because the colony does not have a common cloacal aperture but each zooid has a cloacal aperture.

Lissoclinum midui

• Oka, A. T., M. Suetsugu, E. Hirose: Two new species of Diplosoma (Ascidiacea: Didemnidae) bearing prokaryotic algae Prochloron from Okinawajima (Ryukyu Archipelago, Japan). Zoological Science, 22: 367-374, 2005.

• Hirose E, Oka AT: A new species of photosymbiotic ascidian from the Ryukyu Archipelago, Japan, with remarks on the stability of stigma number in photosymbiotic Diplosoma species. Zoological Science, 25 (12) , 2008.

• Hirose E, Oka, AT, Hirose M: Two new species of photosymbiotic ascidians of the genus Diplosoma from the Ryukyu Archipelago with partial sequences of the COI gene. Zoological Science, 26(5): 362–368, 2009.

• Hirose M, Hirose E: DNA-barcoding in photosymbiotic species of the genus Diplosoma (Ascidiacea: Didemnidae) and a description of a new species from the southern Ryukyus, Japan. Zoological Science, 26(8): 564-568, 2009.

• Hirose E, Hirose M: A new didemnid ascidian Lissoclinum midui sp. nov. from Kumejima Island (Okinawa, Japan), with remarks on the absence of a common cloacal system and the presence of an unknown organ. Zoological Science, 28(6): 462–468, 2011.