Rafael Microfauna Marina: Iophon

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

This morning, after a delicious breakfast at Vicente’s, I was in my laboratory ready to observe specimens, when I suddenly found a beautiful composition: a pycnogonid (Austrodecus sp) grasping the spicules of the Iophon sponge which covers the disk of a Ophioplinthus gelida.

The pycnogonids, sea spiders, are marine arthropods that feed mainly on hydroids, bryozoans, anemones and other soft-bodied animals in which insert their proboscis to suck their fluids. In Antarctic waters there are about 175 species, which amounts to be 18% of the pycnogonids on a world scale.

Hardly any brittle star can be found among their prey because of having the body covered with calcareous plates which, like an armor-plate, may dissuade many predators who are not armed with appropriate dentition or stylet (pricker).

So, this picture might seem to be a portrait of a process of micropredation or even ectoparasitism, but I tend to consider it just an accident, although there can appear a supposition that what the pycnogonid might have been really looking for could have been the abundat offspring of gemmules of the Iophon sponge.

Specimens conserved in 70% ethanol, all photographs were made in ethanol.

Collected by Pablo J. González-López. Cruiser ANTARKTIS XXIII/8 Polarstern

Identified by Rafael Martín-Ledo
The study was made using Motic SMZ-168 TL stereo microscope.

March 2010