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