Un momento natural

En una poza mareal en la rasa de El Médano (Sur de Tenerife): abrigados por el alga parda Lobophora variegata permanecen semiocultos, en una pequeña oquedad, un erizo (Paracentrotus lividus) y una ofiura (Ophioderma longicauda) que saca uno de sus brazos.

Symbiosis: Amphiura - Eulimidae (parasitism)

Amphiura joubini: host

Eulimids: endoparasite

In a Amphiura belgicae specimen, caught in South Georgia, Mortensen (1936) described a gastropod that could belong to the same species as the one from the present study. Mortensen described as a possible mechanism of parasite infestation its entrance through an orifice. He also indicated that the adult looked like a sack and had no visible shell.

In the examined specimens of Amphiura joubini from South Shetland we can  see externally one or two large whitish interradios. When we opened the animals, we saw a bag with numerous white or flesh colored shells inside the coelom, the adult being globular.

There is no observable orifice through which the gastropod entered, so there is a possibility of its regeneration. However, in one of the specimens that had two parasites in contiguous interradios, the other interradios are open ventrally, which leads us to think that this would be an “exit” mechanism for the gastropods.

This parasitism does not necessarily mean the death of the brittle star, possibly due to its great regenerative capacity. Although this is only a supposition, based on the large number of examined specimens of Amphiura joubini with badly damaged interradios due to the process of youth parasitic forms leaving their host.

There have also been numerous open specimens of Ophiolimna antarctica, without most of the aboral disk, it is hard to find a “whole” specimen in our collection. In one of the specimens a pair of juvenile gastropods were found, so it does not seem to be a specific Amphiura genus parasitism.

Although there is a reference in the literature on the presence of internal eulimidae parasites, not yet been identified at specific level (Anders Waren, pers. Comm.)

Live Amphiura jouvini

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

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

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.

Soy Rafael Martín

Profesor de Biología y Geología en el I.E.S. Santa Bárbara de Málaga. Licenciado en Ciencias Biológicas con especialidad en Zoología y Master en Investigación Científica. 
Estudio organismos marinos de bentos; con especialización en la taxonomía y biogeografía de ofiuroideos (equinodermos) antárticos.

Con un estereomicroscopio (Zeiss Discovery V8) en el Natural History Museum de Londres; viendo especímenes de la expedición Challenger (1872-1876) . 

Así es como llegan los especímenes de las expediciones, conservados en formaldehído o etanol, a la espera de una ardua labor de identificación.

BAS (British Antarctic Survey -Cambridge-).

He realizado estancias de investigación en la British Antarctic Survey (Cambridge; Inglaterra), para el estudio de diversas colecciones de ofiuroideos pertenecientes a expediciones británicas y alemanas al Océano Sur alrededor Antártida.

En el laboratorio de BAS con Chester Sand, ecólogo molecular y Huw Griffths, biogeógrafo marino.

En el laboratorio de BAS con los botes de muestras de ofiuroideos de una expedición británica en aguas del Arco de Scotia en la Antártida; el estereomicroscopio es un Zeiss Stemi SV 6.

En el laboratorio de BAS con estereomicroscopio Leica M65

Ophiosteira bullivanti, fotografía tomada con cámara CCD en un estereomicroscopio Leica M65.

Microscopio electrónico (Quanta 3D FEG/FEI SEM) en la Universidad de Extremadura.

Fotografías SEM (microscopía electrónica de barrido) de Ophiacanta wolftarntzi. Una nueva especie descrita, por el que esto escribe, colectada por el buque de investigación alemán Polarstern en aguas antárticas.

Ofiuroideos antárticos vivos. Estos, conservando su color original, fueron fotografiados momentos después de ser recogidos con una draga Agassiz.

Publicaciones como primer autor:

Brittle stars from Southern Ocean (Echinodermata: Ophiuroidea)

A new brooding species of brittle star (Echinodermata: Ophiuroidea) from Antarctic waters

Publicaciones como coautor:

The macro- and megabenthic fauna on the continental shelf of the eastern Amundsen Sea, Antarctica

Observations of the ophiuroids from the West Antarctic sector of the Southern Ocean

Against the flow: evidence of multiple recent invasions of warmer continental shelf waters by a Southern Ocean brittle star

Para saber más sobre los ofiuroideos antárticos puedes hacer click sobre la siguiente imagen:

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

Ophiosparte gigas, the monster

Among the specimens that were captured during Australian expedition in 1922, there were three examples of what Koehler considered at that time, apart from the unpleasant appearance due to its thick fleshy skin , as one of the largest ophiuroids ever seen till then, the biggest one of those three had a disk of 48 mm. He assigned it a new genus, Ophiosparte and, due to its size, called it gigas, perhaps he intuited that in future expeditions there would be caught larger specimens, though I doubt he thought that there would have been samples of up to 70 mm of the disk.

Ophiosparte gigas, is one of the most fearsome predators of the Antarctic benthos. Where there is no sharks, crabs and few teleosts, the echinoderms are one of the dominant groups and amog them the brittle stars that, forming dense swarms, cover with their arms large extentions of the bottom. Ophiosparte is not the most abundant species, that role is left to Ophionotus victoriae, something like half fox and half wolf, but once Ophiosparte – the bear – appears, that fox-wolf will not hesitate to run away, crestfallen . Wandering through the soft-bottom, using spatulate brachial spines as oars and helping itself with the chemoreceptors of its brachial tentacles, it tracks its prey and, if starving, it will not be averse to a corpse.

Males and females, probably bad-tempered, will have to meet and be close one to another for spawning to give rise to large larvae, which in Ross and Weddell seas and around the Antarctic Peninsula will be the future of the species, which will remain a mystery for taxonomists who come across it and challenge the traditional systematic doubting whether it is a Ophiacanthidae or Ophiomyxidae, reminding us that those are just the rails of our mind which want to pigeonhole such a marine monster.

The photos was made using Motic SMZ-168 TL stereo microscope.

References

Bernasconi I, D’Agostino MM (1974) Equinodermos antárticos. III. Ofiuroideos. 1. Ofiuroideos del extremo norte de la Peninsula Antartica. Revista Museo Argentino de Ciencias Naturales ‘Bernardino Rivadavia’. Hidrobiologia 4(2):80-133

Dearborn JH, Hendler G, Edwards KC (1996) The diet of Ophiosparte gigas (Echinodermata: Ophiuroidea) along the Antarctic Peninsula, with comments on its taxonomic status. Polar Biol 16: 309-320

Fell HB (1961) The Fauna of the Ross Sea: Ophiuroidea. Memoirs of the New Zealand Oceanographic Institute, 18, 1–79.

Koehler R (1922) Echinodermata Ophiuroidea. Scientific Reports Australasian Antarctic Expedition 1911–1914, 8, 1–98

February 2010

Ophiacanthidae or Ophiomyxidae?

Sometimes we have it just in front of our eyes, but only with the help of an open mind and a new form of seeing things it makes apparent.

Alexander Martynov from Zoological Museum of Moscow State University, carrying out a revolutionary systematic work in accordance with the structures of the arm-spine articulation ridges, establishes a surprising and convincing change: Ophiosparte gigas is an archaic member of Ophiuridae family.

Reference

Martynov AV (2010) Structure of the arm spine articulation ridges as a basis for taxonomy of Ophiuroidea (a preliminary report). Echinoderms: Durham. Proceedings of the 12th International Echinoderm Conference. 233-239

April 2010