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Babysitting Brittle Stars: Heterospecific Symbiosis between Ophiuroids (Echinodermata)
Gordon Hendler, Mark J. Grygier, Elisa Maldonado and Jessica Denton
Vol. 118, No. 2 (Spring, 1999), pp. 190-201
Stable URL: http://www.jstor.org/stable/3227060
Page Count: 12
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Juveniles of Ophiomastix annulosa live on adults of Ophiocoma scolopendrina, a confamilial broadcast-spawner, in the intertidal zone of Sesoko Is., Okinawa, Japan. This is the first reported instance of a symbiosis between heterospecific ophiuroids. In the sense that the juveniles are brooded by another species, they may be regarded as "brood parasites." There is no evidence that the symbionts physically damage the host, although they may steal its food. O. annulosa of less than 4.5 mm disk diameter primarily occupy the bursae, and also cling to the arms or disk of their hosts. The association is seen year round, usually with 4.2% or fewer of O. scolopendrina being involved. There is generally one juvenile, rarely two, on a host. The body size of the host may limit the maximum size of its symbionts. The ontogenetic transition of O. annulosa from a symbiotic to a free-living life style involves marked changes in integument, arm spine morphology, tube foot structure, disk armament, and pigmentation pattern. Adults of Ophiocoma scolopendrina harbor conspecific juveniles as well, a relatively rare behavior among ophiuroids, but only juveniles of O. annulosa occur in its bursae, the respiratory structures that in brooding and viviparous ophiuroids also serve as brood chambers. An association between adult and juvenile individuals is documented for a Panamanian population of Ophiocoma aethiops, and evidence is presented of a heterospecific symbiosis between juveniles of Ophiomastix janualis and adults of Ophiomastix flaccida in the Philippines.
Invertebrate Biology © 1999 American Microscopical Society