Symbiosis: Entoprocta (comensal)

Ophiuroidea – Entoprocta

• Ophiuroidea: Ophioplinthus gelida: host 
• Entoprocta: Loxosomella sp : commensal

Loxosomella sp. as commensal of Ophioplinthus gelida (Koehler 1900), from which it obtains a substrate that provides its mobility to the food sources, the advantage of not being buried by the sediment as well as certain protection from predators Emschermann (1993). For Ophioplinthus it seems to be no benefits at all.

Loxosomella is mainly located at the edges of dorsal interradii as well as on the lateral plates along the arms, being able to appear with a high density of individuals. They can also appear on the ventral part of the disk, but in a scarce proportion.

Entoprocta (Kamptozoa): colonial or solitary suspensivore lophophorates whith the anus inside of the tentacle crown (lophophore), unlike the bryozoans (Ectoprocta) Loxosomella are solitary entoprocts.

1. Extended lophophorate   2. Bud    3. Contracted lophophorate

Materials studied from Expedition ANTARKTIS- XXlll / 8 Polarstern 2006/2007  in  Joinville Island (3 brittle stars with Loxosomella). They correspond to the same geographical area that the specimens studied by Emschermann to Loxosomella antarctica (Weddell Sea and Bransfield strait).

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

Collected by Pablo J. González-López.

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

References

Emschermann (1993) On antarctic Entoprocta: Nematocyst-like organs in a loxosomatid, adaptive developmental strategies, host specificity, and bipolar occurrence of species. Biol. Bull 184: 153-185

July 2010

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

Symbiosis: Hydrozoa (mutualist)

Ophiuroidea – Hydrozoa

Ophioplinthus relegata : mutualist symbiont
Hydractinia sp : mutualist symbiont

Ophioplinthus relegata (Koehler) with Hydractinia sp

One of the most beautiful symbiosis observed in the brittle stars is that of an ophiuroid covered with “flowers” (although they are carnivorous). The colonial hydrozoan Hydractinia vallini Jaederh places its hydrorhiza and polyps between and over the plates of Ophioplinthus relegata (Koehler, 1922).

1. Gastrozooids     2. Gonozooid     3. Hydrorhiza

Polyps, gastrozooids with their tentacles and globose gonozooids are located  mainly in the periphery of the disc and on the side parts of the arms.
The hydrorhizas are situated between interventrales plates, as well as in the characteristic jaw depression of  Ophioplinthus relegata, which also can give a shelter to a polyp. The dorsal part of the disk is generally free.

For Svoboda et al (1997), the ophiuroid transports the hydractinia to the new food resources and keeps it away from the sediment that would collapse it, while the hydractinia defends the brittle star from potential predators, which is similar to the symbiosis of gastropods with cnidarians, a mutualistic type of relationship.

1. Gastrozooid   2. Gonozooid   3. Hydrorhiza

In excavated jaw area of some specimens appear polyps which are larger than the rest of polyps presented in the same ophiuroid. Such specimens have very few polyps in the areas where they normally are, such as the periphery of the disc. The proximity to the mouth of the brittle star induces me to think that hydroids can feed on the remains of the food that fall off when the ophiourid is eating (commensalism), or even that it could be a case of kleptoparasitism.

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

Svoboda S, Stepanjants S, Smirnov I (1997) Two polar Hydractinia species (Cnidaria), epibiotic on two closely related brittle stars (Echinodermata): an example for a taxonomic and ecological bipolarity. Antarctic communities: species, structure, and survival edit Battaglia B ,Valencia J, Walton DWH Scientific Committee on Antarctic Research 22

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.

Pycnogonid on Ophioplinthus

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

Symbiosis: Protozoa - Ciliophora- (epibiont)

Ophiuroidea – Protozoa (Ciliophora)

• Ophiuroidea: Ophioplinthus gelida: host
• Protozoa: Folliculina sp: epibiont

On the surface of some samples of Ophioplinthus gelida may appear numerous specimens of ciliate Folliculina sp. Their presence on the ophiuroid is mostly in the radial shields, but they may also appear on any dorsal disc plate and on the dorsal and lateral arm plates. Their arrangement is both solitary and in groups of several individuals, Andrews (1914).

This relationship is an epibiosis, possibly facultative Wahl & Mark (1999). This inquilinism does not seem to affect the brittle star, while the protozoa are provided with food availability, with protection from potential predators and are save from being buried in the bottom sediments.

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

Andrews E A 1914 The Bottle – animalcule, Folliculina oecological notes.  Biol Bull  26: 245-315

Koehler R (1922) Echinodermata Ophiuroidea. Adelaide: Australas Antarct Exped (1911–1914) Sci Rep Ser C Zool Bot 8:1–98

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

Wahl M & Mark O (1999) The predominantly facultative nature of epibiosis: experimental and observational evidence. Mar Ecol Prog Ser Vol. 187: 59-66

July 2010

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