Symbiosis: Cancerilla - Ophioika (parasitism)

Ophiuroidea – Copepoda

First the ectoparasites copepods of Antarctic ofiuroids were cited by Mortensen (1936), but without identifying the species, it was Heegaard (1951) who identified them. In the taxonomic literature they have also been cited by Madsen (1967).

Ophiacantha antarctica: host

Cancerilla sp: ectoparasite

The copepods are adhered to the dorsal surface of the disc. Females are carrying their bags of eggs like balls, males have not been found.

Ophiacantha antarctica: host

Ophioika sp: endoparasite

Copepods with modified morphology occupy nearly an entire interradius of the disk. In this species very small males are situated inside of females brood-pouch.

In his review of Ophiuroidea reproduction, Hendler (1991), cites a work of Bartsch (1975) in which he described a castration as a consequence of an ectoparasite copepod (Cancerilla oblonga) in Amphiura capensis. This is an issue to investigate whether in Antarctic ofiuroids there are similar consequences.

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.

References

Heegaard, P (1951) Antarctic parasitic copepods and an ascothoracid cirriped from brittle-stars. Vidensk. Medd. Dan. Naturhist. Foren. 113, 171-190

Hendler, G (1991) Echinodermata: Ophiuroidea. In: Giese, A.C., 

Pearse, J.S. & Pearse, V.B. (Eds.), Reproduction of marine invertebrates: echinoderms and lophophorates. The Boxwood Press, Pacific Grove, CA, pp. 355–511

Madsen FJ (1967) Ophiuroidea. B.A.N.Z. Antarctic Research Expedition (1929–1931) under the Command of Sir Douglas Mawson Rep Ser B 9:123–145

Mortensen T (1936) Echinoidea and Ophiuroidea. Discovery Reports, National Institute of Oceanography Cambridge 12:199–348

July 2010

A day at the Natural History Museum

One typical August morning in London (that means drizzling) Elena and me, accompanied by Chester Sands (molecular ecologist at the British Antarctic Survey BAS) found ourselves at the gates of the British Natural History Museum (NHM).

In the NHM, an architectural ensemble of unique and spectacular beauty, which blends a “cathedral” museum with modern research facilities, we were welcomed by Mr Andrew Cabrinovic, echinoderms curator of the Department of Zoology of the NHM. His kindness and attention to every single detail of our work were really praiseworthy.

The collections, magnificently preserved and neat, were at our disposal, and our “temporary” place of work was equipped with a great stereomicroscopy and a camera to take pictures of the specimens.

The research project which I participate in as ophiuroids taxonomist is about phylogeny and biogeography of Southern Ocean benthos. I’ve already identified several thousand of specimens from several expeditions made by the BAS. During my second stay in Cambridge, I identified the ophiuroids collected by Chester Sands during the expedition ANT XXVII / 3  to South Georgia, Larsen and Bouvet Island on board the German ship Polarstern, organized by the Alfred Wegener Institute (AWI).

To make the identifications reliable, it was necessary to compare our specimens with the specimens preserved in museums, either because some species are represented only by the holotype, or because of the variability or the lack of information of the original descriptions. Thus the aim of the visit was to see the specimens of the ophiuroids collected during expeditions Discovery I (1925) and Discovery II (1936) that constituted the base for one of the major monographs on the Southern Ocean ophiuroids, the work of Theodor Mortensen 1936. I also had the opportunity to see specimens from other expeditions (Challenger 1873-1876 and Quest 1921-1922).

What did that experience mean to me? I mean, the fact of spending a day working in one of the most important zoological research centers worldwide and having in my hands those specimens from the Discovery expeditions after years of rereading the work of Mortensen. Well, I suppose that, besides of a mere fact of collecting information necessary for identification, it could be comparable to the feelings of a Treki in a Star Trek convention being able to take a picture with Leonard Nimoy. Yes, just a day, but a day to remember.

Agosto 2011.

Symbiosis: Nematoda (parasitism)

Ophioplinthus / Ophionotus - Nematoda

Ophioplinthus gelida (Koehler, 1901): host
Ophionotus victoriae Bell, 1902: host
Nematoda (unidentified): coelomic cavity and bursae endoparasites 

Nematodes identified as parasites of Antarctic ofiuroids belong to Thalassonema genus; they have been found in Ophiocten amitinum, although mentioned in sub-Antarctic waters, and in Ophiacantha antarctica. Mortensen 1936, cites the presence of nematodes, unidentified, in Amphiura microplax disjunta.

  


Nematodes, in some cases, can be seen going out from the openings in the disc and, on opening some ofiuroids, several nematodes can be seen spread all over the body cavity.

References

Jangoux M (1987) Diseases of Echinodermata. II: Agents metazoans (Mesozoa to Bryozoa) Dis aquat org, vol. 2: 205-234

Mortensen T (1936) Echinoidea and Ophiuroidea. Discovery Reports, National Institute of Oceanography Cambridge 12:199–348

Collected by Pablo J. González-López. Cruiser ANTARKTIS XXIII/8  Polarstern.
The study was made using Motic SMZ-168 TL stereo microscope.

July 2010