Proboscidactyla Brandt, 1835

Schuchert, Peter & Collins, Richard, 2021, Hydromedusae observed during night dives in the Gulf Stream, Revue suisse de Zoologie 128 (2), pp. 237-356 : 260-261

Genus Proboscidactyla Brandt, 1835

Synonymy: See Schuchert (2009).

Diagnosis: Medusa umbrella mostly hemispherical; with exumbrellar nematocyst patches or linear arrays of patches alternating with tentacles; radial canals branched; usually instead of circular canal a solid gastrodermal marginal strand; manubrium base with four, six or more radial gastric pouches, extending along proximal portions of radial canals, pouches in some species inconspicuous; gonads surrounding manubrium and extending onto gastric pouches; tentacles with swollen hollow base connected to the lumen of radial canals.

Hydroid on rims of sabellid polychaete tubes, with creeping, naked stolons; hydranths almost sessile, polymorphic; gastrozooid with rounded hypostome, separated from body by a constriction; hypostome with large pad of nematocysts somewhat displaced onto one side, two filiform tentacles arising close together beneath hypostomial constriction and opposite to nematocyst cluster; gonozooids and dactylozooids without tentacles, mouth-less and smaller than gastrozooids; medusa buds close to gonozooid tip.

Remarks: Species delimitation in this genus has a long history of discussions and especially the status of the various variants of P. ornata are unclear [comp. Schuchert (2009) and references therein]. The medusae of P. ornata are quite variable and a number of species and subspecies have been proposed, mainly based on the presence and position of vegetative medusa buds. Kramp (1957, 1965) examined numerous specimens and concluded that these variants likely belong to the same species, the number of canal ramifications and the place of medusa budding being variable even within the same population.

However, as seen in other medusa-based species – e.g. Clytia or Zanclea – once also the polyp stage is considered, many morphospecies can sometimes be distinguished (for Zanclea see e.g. Boero et al., 2000). Hand (1954), using complete data of the medusa and polyp stage of Pacific Proboscidactyla species as well as host data of the polyp colony, found that they differ in minute details. This makes it likely that other widely distributed Proboscidactyla species which are solely based on the medusa stage could represent species complexes. DNA sequence results obtained in this study indeed indicate that this seems to be the case for at least P. ornata .