Zanclea alba ( Meyen, 1834 )

Calder, Dale R., 2013, Some shallow-water hydroids (Cnidaria: Hydrozoa) from the central east coast of Florida, USA, Zootaxa 3648 (1), pp. 1-72 : 10

Zanclea alba ( Meyen, 1834)

Fig. 1d

Acrochordium album Meyen, 1834: 165 , pl. 28, fig. 8.

Type locality. North Atlantic Ocean: near the Azores, on Fucus natans (= Sargassum natans ) ( Meyen 1834).

Voucher material. Fort Pierce Inlet State Park , 27°28’29.5”N, 80°17’25.8”W, on stranded Sargassum fluitans , 14.vii.2012, 28° C, 35‰, collected manually, two colonies, with medusa buds, coll. D.R. Calder, ROMIZ B3961 .

Remarks. The generic name Zanclea Gegenbaur, 1856 , although predated by Acrochordium Meyen, 1834 and Mnestra Krohn, 1853 , has been conserved by the International Commission on Zoological Nomenclature (1994). A genus once erroneously thought monospecific ( Calder 1988), 14 nominal species have been assigned to it by Bouillon et al. (2006) and 34 by Schuchert (2012a). One of these, Z. alba ( Meyen, 1834) , is common on the holopelagic gulfweeds Sargassum natans and especially S. fluitans in the North Atlantic ( Calder 1995), and is recorded here from the study area. Colonies of Z. alba usually occur within inner and older parts of the algal thallus (e.g., on “stems”), and especially on colonies of the cheilostome bryozoan Membranipora tuberculata . That microhabitat on gulfweed may offer increased shelter and reduced risk of desiccation. Species of Zanclea tend to be substrate specialists, occurring in association with bryozoans, bivalves, or corals (e.g., Boero et al. 2000; Fontana et al. 2012).

The binomen Zanclea alba is still relatively obscure, having been largely overlooked until the late 20 th century ( Calder 1988). The following original reports of hydroids from Sargassum are likely to have been based on this species: Clava amphorata Bosc, 1797 from the North Atlantic ( Bosc 1797: 9); Zanclea alba ( Meyen, 1834) from Bermuda ( Calder 1988, 1995) and Belize ( Calder 1991b, c); Zanclea costata Gegenbaur, 1856 from the Tortugas ( Mayer 1910: 88), Texas ( Deevey 1950: 349; Defenbaugh & Hopkins 1973: 47), Colombia ( Fraser 1947: 3), and Belize ( Spracklin 1982: 240); Gemmaria costata ( Gegenbaur, 1856) from North Carolina ( Fraser 1912b: 346) and the Atlantic Ocean off both Nantucket and Cape Hatteras ( Fraser 1943: 86); Zanclea gemmosa McCrady, 1859 from off Martha’s Vineyard ( Fraser 1944: 44); Gemmaria gemmosa ( McCrady, 1859) from the Tortugas ( Mayer 1900: 35) and from Woods Hole ( Hargitt 1908: 105); Zanclea sp. from Puerto Rico ( Wedler & Larson 1986); Gemmaria from the western North Atlantic (Burkenroad, in Parr 1939: 24). So too is Murbach’s (1899) mistaken report of Corynitis agassizii McCrady, 1859 from pelagic Sargassum in Vineyard Sound. Hargitt (1908) correctly determined that Murbach’s hydroid was a species of Gemmaria McCrady, 1859 (= Zanclea ) and not C. agassizii (= Sphaerocoryne agassizii ).

The life cycle of Zanclea alba includes a medusa having two well-developed tentacles, with cnidophores, at liberation ( Calder 1988). At that stage, gonads were undeveloped. Medusae have not been reared further in the laboratory, and hydroids of Z. alba have not been clearly linked as yet to any known adult medusa. While such medusae must exist in the Sargasso Sea, given the abundance and pelagic substrate of the hydroid, no medusoid species of Zanclea were reported from the oceanic realm of the North Atlantic by Kramp (1959, 1961). Medusae described as Zanclea costata from the plankton at the Tortugas by Mayer (1910) may be Z. alba , but they could also be from hydroids of another species of Zanclea in the region.

The nematocyst complement of this hydroid comprises stenoteles of two size classes, while that of its juvenile medusa includes stenoteles and macrobasic euryteles ( Calder 1988; Galea 2008).

Reported distribution. Atlantic coast of Florida. First record.

Western Atlantic. New England, on floating Sargassum ( Hargitt 1908, as Gemmaria gemmosa ), to the Caribbean Sea ( Calder 1991c), including Bermuda ( Calder 1988) and the Gulf of Mexico ( Defenbaugh & Hopkins 1973, as Zanclea costata ).

Elsewhere. Eastern Atlantic , near the Azores ( Meyen 1834) .