Symbiosis: Ophioplinthus - Ascothorax (parasitism)

Ophioplinthus brevirima: Host
Ascothorax sp: endoparasite

Inside there were several parasites (Ascothorax sp) with globose aspect; the smaller ones (probably males) with better distinguished morphology having two valve, while the larger specimens are possibly females. This difference in size, and better conservation of structures in male specimens is a common phenomenon in many parasitic crustaceans.

Ophioplinthus brevirima has short genital  slits, hence its specific epithet. In the studied specimens one of the slits, which coincides with the deformed area of the disc has a deformation making it larger, and the proximate plates look abnormal. It is likely had been caused when the endoparasites were leaving their host.

This is supposedly the first record of endoparasites for Ophioplinthus brevirima.

Materials studied from Expediton ANTARKTIS-XXIII/8 Polarstern 2006/2007 in Snow Hill and Dundee Islands. Specimens conserved in 70% ethanol, all photography were made in ethanol using Motic SMZ-168 TL  stereo microscope.
Collected by Pablo J. González-López
Identified by Rafael Martín-Ledo
July 2010

Live Ophioplinthus brevirima, covered by Iophon sponge