Iniciando una aventura

Medusa (Hydrozoa - Cnidaria): freza (liberación de espermatozoides desde la gónada). 20x, campo oscuro.

Espermatozoides. 40x, campo oscuro.


Equipo utilizado:
- Microscopio Zeiss Axio Scope A1, objetivos Plan-Neofluar. 
- Canon 80D, adaptador DSLR 1,6x.

Procedimiento:
Organismo capturado por la noche con una red de plancton en la bahía de Santander. Observación en vivo con estereomicroscopio Motic SMZ 168 en placa de petri tras narcotizar con 5 g (en 100 ml de muestra) de cloruro de magnesio; separado con pipeta Pasteur, porta y cubre-objeto para ser observado al microscopio.  



Para saber más...
Otto Larink & Wilfried Westheide (2011) Coastal Plankton. Verlag Dr. Friedrich Pfeil. München

Pennaria disticha (Cnidarios: Hidrozoo)

Pennaria disticha. Un hidrozoo colonial.

Hidrozoo colonial (pertenece al filo Cnidaria) que crece en el mismo plano de forma alterna respecto a un eje vertical. Con sus pólipos blancos recuerda a un árbol de navidad.

A los hidrozoos coloniales debido a su pequeño tamaño, donde los pólipos apenas son distinguibles y por su aspecto de planta, se les confunde frecuentemente con algas.

Hidrante (pólipo) con medusoide (cuando se desprenda será una medusa), en la parte inferior el hidrocaule (rama de la colonia). Fotografía realizada con Nikon Coolpix P5100 a través de un estereomicroscopio Motic SMZ 168 (x40).

Están emparentados  con la carabela portuguesa y con el velero (clase Hidrozoa del filo Cnidaria).

Tres hidrantes con medusoides sobre el hidrocaule. Fotografía realizada con Nikon Coolpix P5100 a través de un estereomicroscopio Motic SMZ 168 (x30).

Los hidrozoos, como Pennaria disticha, son animales que presentan un ciclo de vida complejo. Una etapa de pólipos que viven en colonias fijas al sustrato y que se reproducirán, de forma asexual, dando lugar a medusas. Las medusas de vida libre se reproducirán, de forma sexual, dando lugar a la fase de pólipos coloniales.

Los pólipos tienen tentáculos con células urticantes (cnidocitos) con las cuales se alimentará cazando organismos del plancton.

Pennaria disticha está presente en todas las aguas cálidas del mundo, habitando sobre rocas a poca profundidad.

Los especímenes fueron fotografiados en charcas mareales de El Médano (sur de Tenerife), octubre del 2014.

Fuentes
- Bouillon et al. (2004) Fauna of the Mediterranean Hydrozoa. Scientia Marina 68

- Riedl (1986) Fauna y flora del mar Mediterráneo. Edit. Omega

- Ruppert & Barnes (1996) Zoología de los invertebrados. Edit. McGraw-Hill Interamericana

Para saber más...
Hayward, Nelson-Smith & Shields (1999) Flora y fauna de las costas de España y de Europa. Edit. Omega

Microfósiles

Estereomicroscopio triocular (Motic SMZ-168) y parte de la colección de preparaciones de microfósiles.

Los microfósiles se corresponden a organismos de muy diversa clasificación biológica, que van desde algas, protozoos, crustáceos o briozoos hasta restos de esponjas y holoturias.
Para su estudio hay que usar un stereomicroscopio (lupa binocular) y si los microfósiles son muy pequeños habrá que recurrir a un microscopio.

En el Departamento de Biología y Geología del IES Leonardo Torres Quevedo -Santander- contamos con una interesante colección de preparaciones de microfósiles. Colección que posiblemente sea de los inicios del Instituto, allá por los años 70 del siglo pasado (no viene indicación alguna sobre su origen).
Las siguientes imágenes son fotocomposiciones con la preparación y lo que se ve en ella usando el estereomicroscopio.
Entre los microfósiles podemos hacer una pequeña clasificación:

Charofitas (Algas verdes)
Se conservan sus estructuras reproductoras femeninas (oogonios). Son buenos fósiles guía para realizar dataciones en estratigrafía del Paleozoico superior, Mesozoico y Terciario.
Haciendo click sobre la imagen podrás verlo a mayor tamaño.

Foraminíferos (Protozoos, Rizópodos)
El grupo de protozoos con mayor número de especies y posiblemente el mejor estudiado. Son buenos fósiles guía para realizar dataciones estratigráficas. Su concha puede ser arenosa o aglutinada, hialina o calcárea.

Ostrácodos (Artrópodos, Crustáceos)
Su estudio como fósiles guía es para realizar dataciones desde el Paleozoico a épocas actuales, según las especies. Complementan a los foraminíferos en medio marino y son los principales fósiles guía para el medio dulceacuícola.

Briozoos
Los llamados "musgos marinos" son animales coloniales cuyos fósiles proceden desde el Ordovícico y sus grupos son numerosos en la actualidad.

Las fotografías fueron tomadas con una Nikon Coolpix P5100.

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

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

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