- Ophioplinthus [O. gelida (Koehler), O. brevirima (Mortensen)]: host
- Iophon radiatus Topsent: epibiont
When Koehler described the species Ohioplinthus gelida in 1900 (Ophioglypha gelida), he did not cite the presence of Iophon. Some years later, in his description from 1912 (Ophiurolepis gelida), he writes about Iophon (I. flabellum-digitatus Kirkpatrick) indicating that it covers the disc and arms dorsally and it partly extends to the ventral part. At being manifested as an exclusive character, the presence of the sponge could be identifying for the species (taxonomic character).
Ophioplinthus gelida, arm with Iophon sp
Mortensen (1936) describes the species Ophiurolepis brevirima, which also carries the sponge Iophon radiatus Topsent in a symbiosis. Until then, says Mortensen, this species had possibly been confused with O. gelida.
Ophioplinthus brevirima with Iophon sp
Fell (1961) writes that the relationship Iophon radiatus Topsent / or Ophiurolepis gelida, Ophiurolepis brevirima is a case of parasitic infestation. Cherbonnier (1962) writes that the morphology of O. gelida is partly due to the presence or absence of Iophon, so it stands out that the symbiosis may alter the development of O. gelida, changing the plates disposition.
How far this relationship has affected the two species?
There is no specific studies which establish the degree of symbiosis that the two species show .
If we consider:
- the modifications in the plates of the ophiuroids caused by the presence of Iophon
- that the two Ophiuroids are Antarctic and Magellanic circumpolar ones (Fell 1961), which can be found massively and in some cases as dominant (Ross Sea Fell 1961, Weddell Sea Dahm 1996) (this means that we are not talking about ecologically fragile species with scarce evolutionary success).
So, the deformation of the plates, as a sign of infestation, may be just a right price to be paid for the potential benefits that the association would bring to Ophioplinthus (read protection from predators), as it might have contributed to the survival and dominance of both species . So, it might be more a mutual relationship than an infestation. For Gutt (1998) it is an obligatory relationship for Iophon, indicating that this is a phase previous to the mutualism, a proto-cooperation. Perhaps the association Ophioplinthus / Iophon, would be a good study model for understanding of the evolution of symbiotic relationships.
References
Cherbonnier G (1962) Ophiures de l’expedition Antarctique Belge (1960-1961) Bulletin Institut Royal des Sciences Naturelles de Belgique. Vol 38:1-31 / Dahm C (1996) Ophiuroids (Echinodermata) of southern Chile and theAntarctic: Taxonomy, biomass, diet and growth of dominant species SCI. MAR., 63 (Supl. 1): 427-432 / Fell HB (1961) The fauna of the Ross Sea. Part 1. Ophiuroidea. N Z Dep Sci Ind Res Bull 142 / Gutt J, Schickan T (1998) Epibiotic relationships in the Antarctic benthos. Antarctic Science 10 (4): 398-405 / Koehler R (1901) Echinides et Ophiures. Resultats du voyage du S.Y. Belgica en (1897–99):1–42 / Koehler R (1912) Échinodermes (Astéries, Ophiures et Échinides). Deuxième Expéd Antarct Fr (1908–1910):1–270 / Mortensen T (1936) Echinoidea and Ophiuroidea. Discovery Reports, National Institute of Oceanography Cambridge 12:199–348
©Rafael Martín-Ledo 2010