Arnold Ross

A review of the Pyrgoma cancellatum species complex (Cirripedia: Pyrgomatidae)

The coral-inhabiting barnacle Pyrgoma cancellatum Leach, 1818 was considered the sole representative of Pyrgoma Leach, 1817 as previously defined. It now appears there are at least four other species that should be included within this genus, i.e. P. japonica Weltner, 1897, Paranobia kuri (Hoek, 1913), Paranobia projectum (Nilsson-Cantell, 1938) and Nobia sinica Ren, 1986. These re-assignments are based, in addition to the opercular morphology, on the presence in the basis of passageways to the external surface that develop between calcareous ladder to arch-like structures similar to those found in bryozobiines and certain armatobalanines. Pyrgoma lobata Gray, 1825, was considered a junior subjective synonym of P. cancellatum. However, it has a uniquely derived type of wall architecture resembling a torus suspended by flying buttresses, and therefore it is assigned herein to a new genus, Neopyrgoma.

A new sessile barnacle symbiotic with bryozoans from Madagascar and Mauritius(Cirripedia : Balanomorpha) : a unique case of co-evolution?

Bryozobia synaptos n. gen., n. sp., from the Grand Recif of Madagascar and the Mascarene Plateau north of Mauritius, is the only cirriped known that has evolved an intimate association with cheilostome bryozoans. This small barnacle settles on a bryozoan colony and in time overgrows a number of zooids, modifying its shell to accommodate them by developing numerous passages (atria) through its basis and wall by a process involving substrate replication. Calcareous, tubular passages formed in the basis of the barnacle grow radially, keeping pace with marginal growth of the barnacles wall. Eventually, the openings to the zooecial tubes at the wall margin are encircled by the barnacle, thereby forming the first whorl of atria through which the bryozoan deploys its lophophores. During subsequent growth the process is repeated

DEEP-WATER SCALPELLOMORPH/CORAL SYMBIOSIS (CIRRIPEDIA, PEDUNCULATA/HEXACORALLIA, SCLERACTINIA) IN THE NORTH ATLANTIC

The heavily armored peduncles of four species of deep-water calanticid scalpellomorphs, from three distant localities across the North Atlantic, are partially overgrown by the branching scleractinian corals on which they had settled. We infer the association and overgrowths benefit the barnacles in isolating them from competitors and predators. These barnacles and their hosts represent relatively old groups (early Mesozoic and Paleogene, respectively) and therefore the relationship could have been established during their early radiation. Because the corals are capable of at least partially if not completely entombing the scaly remains of the peduncles when the barnacles die, recognizable traces of this symbiotic relationship are probably present in the fossil record.