Partners for life: a brittle star and its octocoral host

Abstract

Throughout the New England and Corner Rise seamounts of the western North Atlantic Ocean, several ophiuroid species are conspicuously epizoic on octocorals. One species, Ophiocreas oedipus, was found only on the chrysogorgiid octocoral Metallogorgia melanotrichos. Colonies of M. melanotrichos were collected from 11 seamounts during expeditions in 2003, 2004, and 2005 at depths between 1300 and 2200 m. O. oedipus is obligately associated with M. melanotrichos, leading a solitary existence on all octocorals observed. Evidence suggests that a young brittle star settles directly on a young octocoral and the 2 species then grow, mature, and senesce together. The brittle star benefits directly by being above the bottom for suspension feeding and is passively protected by the octocoral, but the latter, as far as we have been able to determine, seems neither to benefit nor be disadvantaged by the relationship.

Redescription of Hemieuryale pustulata von Martens, 1867 (Echinodermata, Ophiuroidea) based on Brazilian specimens, with notes on systematics and habitat association

“…Similar to the observations of Mosher & Watling (2009) on O. oedipus and Metallogorgia melanotrichos, we also believe that the relationship between H. pustulata and N. guadalupensis is not mutualistic, since no benefit to the coral has been perceived. However, further studies are necessary to clarify this issue.…”

Host species of the non-indigenous brittle star Ophiothela mirabilis (Echinodermata: Ophiuroidea): an invasive generalist in Brazil?

“…Notwithstanding, further studies are needed to confirm this because the biological invasion is ongoing and the density on a single host individual may be more a function of how long ago O. mirabilis established rather than the basibiont species. Some authors suggest a commensal relationship between octocorals and brittle stars, since no benefit or disadvantaged to the octocoral has been reported and the brittle stars benefit from protection and more efficient suspension feeding by being above the bottom (Mosher and Watling 2009). Other species of the genus Ophiothela have also been recorded on gorgonians, as on the Karachi coast in the North Arabian Sea, with "no indication that they affect host survival" (Tahera 2001).…”

“…Other species of the genus Ophiothela have also been recorded on gorgonians, as on the Karachi coast in the North Arabian Sea, with "no indication that they affect host survival" (Tahera 2001). Furthermore, brittle stars can feed on mucus from the coral colony or capture small planktonic organisms with their tube feet and arm spines (Mosher and Watling 2009). The ophiuroids may benefit from host sponges by more efficient suspension feeding by making use of their internal currents (Sivadas et al 2014).…”

“…The species does reproduce asexually by fissiparity, which permits an individual to split the disc in two parts and regenerate the missing part, what facilitates its proliferation (Hendler and Brugneaux 2013) and which can allow it to achieve high densities on its hosts. In general the most commonly observed hosts of brittle stars include sponges, cnidarians, bryozoans, sea urchins and algae (Mladenov et al 1983;Mladenov and Emson 1988;Hickman 1998;Tahera 2001;Mosher and Watling 2009;Hendler and Brugneaux 2013) which may provide refugia from predation, habitat and feeding space. After colonization it is possible that the ophiuroids crawl out and disperse short distances to other nearby species and may also disperse by rafting on algal and invertebrate fragments (Mladenov and Emson 1988;Hendler et al 1999).…”

INTRODUCTION Recent advances in deep-sea coral science and emerging links to conservation and management of deep-sea ecosystems Karen Miller1,*, Helen Neil2, Di Tracey2

“…One area where multidisciplinary research is particularly apparent is in the emerging links between environmental parameters and the distribution and biology of deep-sea corals. (2009) (all this volume) utilise cross-disciplinary approaches to link factors such as substrate or oceanography with food supply, growth, or ecophysiology to provide an improved understanding of deep-sea coral diversity, distributions, and the role and functioning of ecosystems (Bo et al 2009, Mosher & Watling 2009.…”