Vol. 60, 2021

(update: 2021.06.03)
 

Contact Reactions between Individuals of the Coral-killing sponge, Terpios hoshinota

Yurika Hirose^1,2, Siti Nurul Aini¹, and Hideyuki Yamashiro^3,*

¹Graduate School of Engineering and Science, University of the Ryukyus, Japan. E-mail: florida2004yrk@gmail.com (Hirose)
²Environmental Partnership Council, Tokyo, Japan. E-mail: sitinurulandaini@gmail.com (Aini)
³Sesoko Station, Tropical Biosphere Research Center, University of the Ryukyus, Japan. *Correspondence: hyama@lab.u-ryukyu.ac.jp (Yamashiro). Phone +81-980-47-6072; Fax +81-980-47-4919.

Received 14 January 2021 / Accepted 21 May 2021
Communicated by Yoko Nozawa

Outbreaks of the coral-killing sponge Terpios hoshinota Rützler and Muzik, 1993 have become a threat to corals and result in coral reef deterioration. This species has an increasing distribution in the Indo-Pacific Ocean and thrives in patches on some reefs in Okinawa, Japan. However, the dispersal process and mechanisms involved remain unknown. We observed the self and non-self recognition capabilities of T. hoshinota by performing contact assays in aquarium and in the field. In the contact assays (indirect and direct contact), allogeneic sets did not fuse and showed a rejection reaction as they formed boundaries (approx. 0.2 mm width) between their tissues. Although the initial reaction between individuals involved adhesion in allogeneic sets, the two individuals remained distant from each other. Histological observations showed that soft tissues (such as collagen) were not present in the boundary zones. These boundaries were maintained for more than 2 weeks before being encroached by other specimens. Boundary formations were also confirmed in three field sites in Okinawa, Japan. Our results suggest that T. hoshinota can distinguish self and non-self individuals. Contact assays are a useful method for evaluating the spatial distribution and local population structures of T. hoshinota in coral reefs.

Key words: Self recognition, Tissue reaction, Rejection, Coral reef, Histoincompatibility.

Citation: Hirose Y, Aini SN, Yamashiro H. 2021. Contact reactions between individuals of the coral-killing sponge, Terpios hoshinota. Zool Stud 60:41. doi:10.6620/ZS.2021.60-41.

Supplementary Materials: Video S1