Monotheca margaretta Nutting, 1900

Calder, Dale R., 2019, On a collection of hydroids (Cnidaria, Hydrozoa) from the southwest coast of Florida, USA, Zootaxa 4689 (1), pp. 1-141 : 108-109

Monotheca margaretta Nutting, 1900

Fig. 24a

Monotheca margaretta Nutting, 1900: 72 , pl. 11, figs. 1–3.— Wallace, 1909: 137.

Plumularia margaretta .— Joyce, 1961: 70, pl. 18, figs. 1, 2.— Shier, 1965: 64, pl. 35.

Type locality. Bahamas: near Little Cat Island, shallow water ( Nutting 1900: 72) .

Material examined. Florida Keys, Bahia Honda Channel, 24°39.489’N, 81°17.198’W, 6 m, 16 June 2008, on Lytocarpia tridentata , one colony, 4 mm high, without gonophores, ROMIZ B4397.— Sanibel Island , beach at Lighthouse Point, 26°26’57”N, 82°01’06”W, on detached Thalassia in water along shore, 24°C, 35‰, 03 April 2018, fragments of one colony, 4 mm high, without gonothecae, coll. D. Calder, ROMIZ B4398 .

Remarks. The genus Monotheca Nutting, 1900 has been regarded as congeneric with Plumularia Lamarck, 1816 in some works, and as valid in others (Calder 1997: 10). While the genus as presently constituted may be polyphyletic, so too is Plumularia ( Moura et al. 2008: 98) . Herein, certain constituent species sometimes assigned to Monotheca are considered sufficiently unique morphologically to be recognized as generically discrete. Molecular studies provide evidence in support of that conclusion. Phylograms such as those of Leclère et al. (2007, 2009), Moura et al. (2008), and Maronna et al. (2016) reveal that Monotheca margaretta Nutting, 1900 , type species of Monotheca , is clearly divergent genetically from Plumularia setacea ( Linnaeus, 1758) , type species of Plumularia . While a re-definition and revision of the genus appear necessary, its validity is upheld here. The present species is therefore retained in this work under the binomen M. margaretta .

Monotheca margaretta is predominantly a hydroid of near-surface waters, and a species of tropical and warmtemperate waters. From collection records listed below, it is especially frequent in beds of the seagrass Thalassia and on algae including detached Turbinaria . It is also a constituent of the hydroid assemblage found on pelagic Sargassum in the open North Atlantic Ocean, the Caribbean Sea, and the Gulf of Mexico. Dispersal of the species has likely been facilitated by rafting on such substrates. While best known from shallow depths, the hydroid has also been found on bottoms as deep as 73 m. Other than its transport to relatively high latitudes on pelagic Sargassum in the Gulf Stream and North Atlantic Current, the known geographic range of M. margaretta in the western Atlantic extends from South Carolina ( Wenner et al. 1984) and Bermuda (Calder 1997) to the southern Caribbean Sea ( Van Gemerden-Hoogeveen 1965), and southwards to Brazil ( Oliveira et al. 2016). The species is amphi-Atlantic in distribution, having been reported from locations on the eastern side of the ocean including the Azores, the Canary Islands, the Strait of Gibraltar, the Mediterranean Sea, Senegal, and Ghana ( Ansín Agís et al. 2001). While this hydroid was collected in shelf waters off South Carolina by Wenner et al. (1984), it was never found in estuaries of the state during eight years of field work ( Calder & Hester 1978; Calder 1983).

Detailed taxonomic accounts of M. margaretta include those of Calder (1997) and Ansín Agís et al. (2001). Gonophores of this species are thought to be fixed sporosacs, although those of a closely related species from Europe, M. obliqua ( Johnston, 1847) , are liberated as very short-lived medusoids ( Motz-Kossowska 1907). The type of gonophore produced by M. margaretta thus needs to be determined.

Reported distribution. Gulf coast of Florida. Dry Tortugas ( Wallace 1909: 137).—Seahorse Key, on Thalassia ( Joyce 1961: 70, as Plumularia margaretta ).—Cape San Blas area, on Thalassia ( Shier 1965: 64, as Plumularia margaretta ).

Elsewhere in western North Atlantic. Bahamas: near Little Cat Island, shallow water ( Nutting 1900: 72).— USA: North Carolina, off Bogue Bank, on floating Sargassum ( Fraser 1912b: 381) .— Bermuda: Challenger Bank, on Campanularia insignis (= Thyroscyphus marginatus ), 55 m ( Stechow 1912: 361).— Bermuda: on floating Sargassum ( Bennitt 1922: 254) .— Bonaire: Boca Washikemba, on stranded algae + Lagoen, north coast, on stranded Sargassum ( Leloup 1935a: 54, as Plumularia margaretta ).— Curaçao: Boca Grandi, on drifting Sargassum ( Leloup 1935a: 54, as Plumularia margaretta ).— Aruba: Boca Prins, on stranded Sargassum ( Leloup 1935a: 54, as Plumularia margaretta ).—Atlantic Ocean: Gulf Stream, on pelagic Sargassum + Sargasso Sea, on pelagic Sargassum (Burkenroad, in Parr 1939: 23) .—Sargasso Sea: on Sargassum , 34°25’N, 40°05’W + 30°50’N, 54°35’W ( Timmermann 1932: 298, 300).— Dominican Republic: Monte Cristi, on Sargassum ( Timmermann 1932: 299) .— USA: Massachusetts, Gulf Stream off Martha’s Vineyard, 39°58’N, 70°06’W, on floating Sargassum ( Fraser 1944: 349, as Plumularia margaretta ).— Puerto Rico, northeast coast, 18°23’35”N, 65°37’10”W, 10 ftm (18 m) + 18°24’30”N, 65°38’30”W, 9 ftm (16 m) ( Fraser 1944: 349, as Plumularia margaretta ).— Puerto Rico: off Culebra Island, 18°19’10”N, 65°19’40”W, 10 ftm (18 m) ( Fraser 1944: 349, as Plumularia margaretta ).— Colombia: 2 miles (3 km) off Bahía Honda, 9 ftm (16 m) ( Fraser 1947b: 14, as Plumularia margaretta ).—Unstated location: on buoys ( Woods Hole Oceanographic Institution 1952: 188, as Plumularia margaretta ).— USA: Florida, Florida Current off Miami ( Adams 1960: 81, as Monotheca margaritta (sic)).— Aruba: North of Punta Braboe (=Punta Brabo), on Thalassia ( Van Gemerden-Hoogeveen 1965: 69, as Plumularia margaretta ).— Bonaire: Oranjepan (=Oranje Pan), on stranded Sargassum ( Van Gemerden-Hoogeveen 1965: 69, as Plumularia margaretta ).— Venezuela: Islote Aves, northern lagoon, on algae, near low water ( Van Gemerden-Hoogeveen 1965: 69, as Plumularia margaretta ).— Barbuda: Martello Tower Beach, on algae ( Van Gemerden-Hoogeveen 1965: 69, as Plumularia margaretta ).— St. Kitts & Nevis: St. Kitts, Frigate Bay, on algae, tidal zone ( Van Gemerden-Hoogeveen 1965: 69, as Plumularia margaretta ).— Sint Maarten: Great Bay, on algae, ca. 2 m ( Van Gemerden-Hoogeveen 1965: 69, as Plumularia margaretta ).— Virgin Islands of the United States: St. John, Turner Bay, on Turbinaria , tidal zone ( Van Gemerden-Hoogeveen 1965: 69, as Plumularia margaretta ).— USA: Texas, West Flower Garden Bank, on floating Sargassum ( Defenbaugh 1974: 102, as Plumularia margaretta ).—Gulf Stream, several stations between Florida and New Jersey, on Sargassum polyceratium , S. pteropleuron , Sargassum sp., and S. ramifolium ( Rackley 1974: 45, as Plumularia margaretta ).— Colombia: Santa Marta area ( Wedler 1975: 340, as Monotheca margareta ; Bandel & Wedler 1987: 42, as Monotheca (Plumularia) margaretta ).— Belize: Carrie Bow Cay ( Spracklin 1982: 246, as Plumularia margaretta ).— Colombia: Bahía de Cartagena ( Flórez González 1983: 121, as Plumularia margaretta ).— USA: South Carolina, middle continental shelf ( Wenner et al. 1984: 21, 40, as Plumularia margaretta ).— USA: Georgia, inner continental shelf ( Wenner et al. 1984: 40, as Plumularia margaretta ).— Belize: Twin Cays ( Calder 1991b: 223).— Belize: South Water Cut, South Water Cay, on Thalassia ( Kaehler & Hughes 1992: 331) .— Colombia: Bahía de Chengue, on Rhizophora ( Reyes & Campos 1992: 108, as Plumularia margaretta ).— Bermuda: on pelagic Sargassum fluitans and S. natans ( Calder 1995: 540) .— Bermuda: Natural Arches Beach, on stranded Sargassum fluitans + Castle Harbour, W of Castle Roads, on Thalassia , 2–3 m + Whalebone Bay, on stranded Sargassum fluitans + St. Catherine’s Beach, on stranded Sargassum fluitans + Atlantic Ocean, 2 km off Castle Roads, on rubble, 73 m + Burchall’s Cove, on stranded Sargassum fluitans + Atlantic Ocean, 2 km off Natural Arches Beach, on rhodolith, 70 m (Calder 1997: 11).— Bermuda: Argus (=Plantagenet) Bank + Challenger Bank ( Calder 2000: 1133).— Cuba: Ciudad de La Habana province, Playa Mégano, 0.5 m ( Ortiz 2001a: 64).— Panama: Bocas del Toro area, Boca del Drago, 09°25’36.3”N, 82°19’30.1”W, 1-3 m + Bocas del Toro area, Cayos Zapotilla, 09°15.564’N, 82°02.750’W, 7-8 m + Bocas del Toro area, Swan’s Key, 09°27’12.2”N, 82°18’01.8”W, 1-4 m + Bocas del Toro area, Bastimentos (front), 09°20.898’N, 82°09.959’W, 1-4 m + Bocas del Toro area, Bastimentos (north), 09°20.898’N, 82°09.959’W, 1-4 m ( Calder & Kirkendale 2005: 482).—French Lesser Antilles: Guadeloupe, Grande-Terre, Les Arches, 16°27.529’N, 61°32.021’W, 17 m + Grande-Terre, Pointe d’Antigues, 16°26.251’N, 61°32.523’W, 10–15 m, on an alga + Grande-Terre, harbor of Port-Louis, 16°24.720’N, 61°31.910’W, on red algae ( Galea 2010: 29, as Plumularia margaretta ).— Cuba: Golfo de Batabanó, Cayo Real, Cayería San Felipe ( Castellanos-Iglesias et al. 2011: 25).—French Lesser Antilles: Martinique ( Galea 2013: 50, as Plumularia margaretta ).—Caribbean Sea ( Wedler 2017b: 163, figs. 206A, B, 207A, B, 208).— Mexico: Alacranes Reef, on algae, soft coral ( Mendoza-Becerril et al. 2018b: 131).— Panama: Bocas del Toro area, near Bocatorito Bay ( Miglietta et al. 2018b: 108, as Plumularia margaretta ).

Figures

FIGURE 24. a, Monotheca margaretta: part of a hydrocaulus with a hydrocladium and hydrotheca, Florida Keys, Bahia Honda Channel, ROMIZ B4397. Scale equals 0.05 mm. b, Nemertesia nigra: part of hydrocaulus and proximal ends of hydrocladia, Southwest Florida Shelf, ROMIZ B2138. Scale equals 0.1 mm. c, Nemertesia nigra: part of a hydrocladium with a hydrotheca and nematothecae, Southwest Florida Shelf, ROMIZ B2138. Scale equals 0.05 mm. d, Nemertesia simplex: apophysis of hydrocaulus and proximal end of a hydrocladium, Southwest Florida Shelf, ROMIZ B2113. Scale equals 0.1 mm. e, Nemertesia simplex: part of a hydrocladium with a hydrotheca and nematothecae, Southwest Florida Shelf, ROMIZ B2113. Scale equals 0.1 mm. f, Plumularia floridana: part of a hydrocaulus with proximal end of a hydrocladium and two hydrothecae, Fort Myers Beach, ROMIZ B4399. Scale equals 0.1 mm.