Dynamena disticha ( Bosc, 1802 )

Calder, Dale R., 2019, On a collection of hydroids (Cnidaria, Hydrozoa) from the southwest coast of Florida, USA, Zootaxa 4689 (1), pp. 1-141 : 80-81

Dynamena disticha ( Bosc, 1802)

Fig. 21c

Sertularia disticha Bosc, 1802: 101 , pl. 29, fig. 2.

Sertularia cornicina .— Nutting, 1904: 58.— Fraser, 1943: 92; 1944: 279.

Sertularia mayeri .— Nutting, 1904: 58.— Leloup, 1935a: 49.— Fraser, 1943: 93.— Shier, 1965: 51, pl. 28.

Sertularia exigua .— Fraser, 1944: 281.

Sertularia erasmoi .— Joyce, 1961: 67, pl. 17, figs. 1, 2.

Dynamena cornicina .— Van Gemerden-Hoogeveen, 1965: 25.

Dynamena mayeri .— Van Gemerden-Hoogeveen, 1965: 30.

Sertularia sp.— Shier, 1965: 52, pl. 29.

Type locality. Atlantic Ocean: “...sur le fucus natans ( Sargassum natans ) dans la haute mer…” ( Bosc 1802: 101).

Material examined. Sanibel Island, beach at Lighthouse Point, 26°26’57”N, 82°01’07”W, on detached Thalassia in water along shore, 21 February 2013, one colony, 9 mm high, with gonothecae, coll. D. Calder, ROMIZ B4410.— Sanibel Island , beach at Lighthouse Point, detached and stranded in tidepool, 30 March 2013, one colony, 8 mm high, without gonophores, coll. D. Calder, ROMIZ B4411 .— Sanibel Island , beach at Lighthouse Point, 26°26’55”N, 82°01’08”W, on detached Thalassia in water along shore, 21° C, 34.5‰, 19 March 2018, three colony fragments, up to 8 mm high, with gonothecae, coll. D. Calder, ROMIZ B4408 .— Sanibel Island , beach at Lighthouse Point, 26°26’58”N, 82°01’04.5”W, on detached Idiellana pristis at water’s edge, 21 March 2018, 22° C, 34.5‰, three colony fragments, up to 1.1 cm high, without gonophores, coll. D. Calder, ROMIZ B4407 .

Remarks. Hydroids identified under either the binomen Dynamena disticha ( Bosc, 1802) or one of its various synonyms are widespread and of frequent occurrence in the tropical and warm-temperate western North Atlantic. The reported range of the species extends from southern New England ( Nutting 1904) and Bermuda (Calder 1990 [1991a]) to the Caribbean coast of northern South America ( Wedler 1975), and on to Argentina in the southwest Atlantic ( Oliveira et al. 2016). Well-known as part of the Sargassum fauna, it is found in the Sargasso Sea and the Gulf of Mexico, and is carried far northwards in the warm Gulf Stream on gulfweed to waters east of Atlantic Canada ( Fraser 1918). As apparent from distribution records below, it has been collected several times previously on the Gulf coast of Florida. Dynamena disticha has been reported over a bathymetric range of 0–256 m ( Fernandez & Marques 2018), but the species is much more frequent in near-surface waters.

Molecular analyses ( Moura et al. 2011; Maronna et al. 2016) reveal that Dynamena Lamouroux, 1812 as presently constituted is polyphyletic and in need of significant revision. Indeed, Dynamena disticha is shown in such studies to be genetically distant from the type species of the genus, D. pumila ( Linnaeus, 1758) . Sertularia quadridentata Ellis & Solander, 1786 , another species likewise remote from D. pumila but formerly included in Dynamena , was referred earlier ( Calder 2013) to Pasya Stechow, 1922 , as P. quadridentata . Dynamena disticha needs to be reassigned, along with any closely related species, to another genus. Such re-classification needs careful consideration and is beyond the scope of this study.

Moura et al. (2011) detected potential cryptic species within populations identified as D. disticha from western Europe. Questions also exist about possible taxonomic differences between two forms assigned to the species in the western Atlantic ( Calder 2013). One of these, a stunted form usually 1 cm high or less, is common on pelagic Sargassum as originally described by Bosc (1802). The other morphotype, more robust and reaching 5 cm high, has been reported largely from inshore waters on various benthic substrates.

Hydroids of D. disticha are typically bright yellow in colour ( Bosc 1802; Calder 1971, 1983). While seldom branched, a single hydrocladium may occur on large colonies ( Calder 1971). In this character it differs from the closely related but alternately branched D. moluccana ( Pictet, 1893) . Dynamena dimorpha Galea, in Galea & Ferry 2015 , a species much resembling D. disticha , has recently been described from Martinique in the Caribbean Sea. It differs in having both unbranched and pinnately branched colonies, thicker and less collapsable perisarc, and hydrothecae that are shallower and wider ( Galea & Ferry 2015). From the original account of that species, symbiotic zooxanthellae may be present.

Gonothecae in D. disticha , resembling inverted Chinese lanterns, usually occur on the hydrorhiza. They may also arise from internodes of the hydrocaulus or even from old hydrothecae ( Calder 1971; Galea 2008). In the latter case, their morphology is atypical in being sac-shaped with a rounded distal end, they vary in length and width, and their walls are smooth or only slightly undulated ( Galea 2008).

While believed to be a substrate generalist ( Calder 1971, 1991c; Oliveira 2016), this hydroid often occurs on seagrasses and especially on pelagic Sargassum . If estuarine populations have been correctly assigned to this species, D. disticha is both euryhaline and eurythermal. It extends from coastal waters up-estuary to about the 18‰ isohaline ( Calder 1976), and it tolerates temperatures as low as about 9° C before becoming dormant (Calder 1990). Hydroids, including D. cornicina (= D. disticha ), were found to be the primary food of Atlantic spadefish ( Chaetodipterus faber ) in estuarine areas and offshore reefs of South Carolina ( Hayse 1990).

The nomenclature of D. disticha has been reviewed elsewhere (Calder 1990 [1991a]). A detailed synonymy of the species exists in Medel & Vervoort (1998).

Reported distribution. Gulf coast of Florida. Pourtales Plateau ( Nutting 1904: 58, as Sertularia cornicina ).— Off Cape San Blas, 29°16’30”N, 85°32’W (Albatross Station 2369), 26 ftm (48 m) ( Nutting 1904: 59, as Sertularia mayeri ).—Off Cape Romanes (Cape Romano) ( Nutting 1904: 59, as Sertularia mayeri ).—Dry Tortugas, 27 ft (8 m) ( Leloup 1935a: 49, as Sertularia mayeri ).—W of Florida, 20 ftm (37 m) ( Fraser 1943: 92; 1944: 280, as Sertularia cornicina , “robust type ”).—Dry Tortugas ( Fraser 1943: 93, as Sertularia mayeri ).—Between Biscayne and Duck keys, on Sargassum ( Fraser 1943: 93, as Sertularia mayeri ).—W of Cape Romano, 2 miles (3 km) ( Fraser 1944: 282, as Sertularia exigua ).—Seahorse Key, on Sargassum ( Joyce 1961: 67, as Sertularia erasmoi ).—Dry Tortugas, on shells, coral debris ( Van Gemerden-Hoogeveen 1965: 25, as Dynamena cornicina ).—Dry Tortugas ( Van Gemerden-Hoogeveen 1965: 30, as Dynamena mayeri ).—Cape San Blas area ( Shier 1965: 51, as Sertularia mayeri ).—Cape San Blas area, on Syringodium , Thalassia , Sargassum , Diplanthera (= Halodule ), and Codium ( Shier 1965: 99, as Sertularia sp.).

Elsewhere in western North Atlantic. Atlantic Ocean: high seas, on Fucus natans (= Sargassum natans ) ( Bosc 1802: 101, as Sertularia disticha ).— USA: South Carolina, Charleston Harbor ( McCrady 1859: 204, as Dynamena cornicina ).— USA: South Carolina, Charleston (A. Agassiz 1865: 142, as Dynamena cornicina ).— USA: North Carolina, coast (Verrill 1872: 437, as Dynamena cornicina ).— USA: Massachusetts, Vineyard Sound, on Halecium and floating Zostera , 1–8 ftm (2–15 m) ( Verrill 1874d: 733, as Sertularia cornicina ).— USA: North Carolina, off Cape Fear, 9 ftm (16 m) ( Allman 1877: 24, as Sertularia exigua ).— USA: North Carolina, Fort Macon area ( Coues & Yarrow 1878: 308, as Sertularia cornicina ).— Mexico: Yucatan, on an alga ( Clarke 1879: 246, as Sertularia complexa ).— USA: North Carolina, Beaufort ( Brooks 1882: 142, as Dynamena bilatteralis ; 1884: 711, as Dinamena bilateralis ).— USA: Massachusetts, Woods Hole area ( Nutting 1901: 359, as Sertularia cornicina ).— USA: Massachusetts, Woods Hole area + near Nobska Point, on seaweed ( Nutting 1901: 360, as Sertularia complexa ).—Atlantic Ocean: beyond the Antilles, on Sargassum ( Jäderholm 1903: 287, as Sertularia exigua ).— USA: Massachusetts, Woods Hole area ( Nutting 1904: 58, as Sertularia cornicina ).— Bahamas: between Eleuthera and Little Cat islands, shoal water + Great Bahama Bank, on floating seaweed ( Nutting 1904: 59, as Sertularia mayeri ).— USA: North Carolina, off Cape Fear, 33°37’30”N, 77°36’30”W, 14 ftm (26 m) ( Nutting 1904: 59, as Sertularia mayeri ).— USA: North Carolina, Bogue Sound, on floating algae and Sargassum + North River + Straits, 10 ft (3 m) + off Beaufort, on sponge ( Fraser 1912b: 374, as Sertularia cornicina ).— USA: Massachusetts, Georges Bank, floating colonies ( Fraser 1915: 308, as Sertularia cornicina ).—Gulf Stream: E of Nova Scotia, on Sargassum ( Fraser 1918: 359, as Sertularia cornicina ).— Bermuda: Agar’s Island, on ledges and Sargassum + Somerset Bridge, on ledges and Sargassum + Challenger Bank, on a gorgonian, 32 ftm (59 m) ( Bennitt 1922: 251, as Sertularia cornicina ).— Sargasso Sea, on Sargassum ( Hentschel 1922: 4, as Sertularia mayeri ).— Bonaire: Kralendijk, Pasanggrahan, 0.2 m, on algae + Plaja Witte Pan, on stranded algae + Plaja Oranje Pan, on stranded algae + Lac, mouth, back of reef, on detached Sargassum , 1.5 m + Boca Washikemba, on stranded algae + Boca Onima, on stranded Sargassum ( Leloup 1935a: 40, as Dynamena cornicina ).— Curaçao: Boca Grandi, on Sargassum ( Leloup 1935a: 40, as Dynamena cornicina ).— Aruba: Boca Prins, on stranded Sargassum ( Leloup 1935a: 40, as Dynamena cornicina ).—Sargasso Sea: on pelagic Sargassum , 23°57’N, 67°45’W + 27°13’N, 62°16’W ( Leloup 1935b: 4, as Dynamena cornicina ).— Bahamas: Elbow Cay, south coast ( Leloup 1937: 106, as Dynamena cornicina ).—Atlantic Ocean: Gulf Stream, on pelagic Sargassum + Sargasso Sea, on pelagic Sargassum (Burkenroad, in Parr 1939: 23) .— Trinidad & Tobago: Trinidad, Maguaripe Bay (=Macqueripe Bay) ( Fraser 1943: 93, Sertularia mayeri ).—Sargasso Sea: NE of the Bahamas, on Sargassum ( Fraser 1944: 280, as Sertularia cornicina ).— USA: North Carolina, offshore ( Fraser 1944: 280, as Sertularia cornicina ).—Sargasso Sea: 34°N, 38°W, on Sargassum ( Vervoort 1946: 307, as Dynamena cornicina ).— Aruba: 8 miles (13 km) SW of San Nicolaas Bay (Sint Nicolaas Baai), 23–24 ftm (42–44 m) ( Fraser 1947b: 10, as Sertularia cornicina ).— Colombia: 2 miles (3 km) off Bahía Honda, 9 ftm (16 m) ( Fraser 1947b: 10, as Sertularia exigua ).— Venezuela: off Isla Tortuga ( Fraser 1947b: 10, as Sertularia exigua ).— USA: Texas, Port Isabel + Port Aransas, on Sargassum ( Deevey 1950: 346, as Sertularia cornicina ).— Aruba: Boca Prins, on stranded Sargassum ( Van Gemerden-Hoogeveen 1965: 25, as Dynamena cornicina ).— Curaçao: Klein Curaçao, western shore, on Sargassum ( Van Gemerden-Hoogeveen 1965: 25, as Dynamena cornicina ).— Bonaire: Kralendijk, Pasanggrahan, near low tide, on small stone + De Hoop, 1–3 m + Punt Vierkant, on algae, coral, & detached, low tide to 2 m + Oranjepan, on Sargassum + Boca Washikemba, on stranded brown algae + Boca Onima, on Sargassum ( Van Gemerden-Hoogeveen 1965: 25, as Dynamena cornicina ).— Venezuela: Isla La Blanquilla, Playa Valuchu, 2.5 m, on wood fragments + Islas Los Frailes, La Pecha, SW shore, 1–2 m, on algae + Islas Los Testigos, Puerto Tamarindo, ca. 2 m, on seaweed ( Van Gemerden-Hoogeveen 1965: 25, as Dynamena cornicina ).— Trinidad & Tobago: Trinidad, Monos, Avalon Bay, ca. 1 m, on stones, shells + Tobago, Buccoo Bay, 2 m, on coral ( Van Gemerden-Hoogeveen 1965: 25, as Dynamena cornicina ).— Grenada: between Grenada and Trinidad, on floating Sargassum ( Van Gemerden-Hoogeveen 1965: 25, as Dynamena cornicina ).— St. Kitts & Nevis: St. Kitts, Frigate Bay, near low tide, on algae and other hydroids ( Van Gemerden-Hoogeveen 1965: 25, as Dynamena cornicina ).— Sint Maarten: Simson Lagoon, outlet, near low tide, on algae ( Van Gemerden-Hoogeveen 1965: 65, as Dynamena cornicina ).— USA: Virginia, York River (Tue Marsh Light; Perrin; Gloucester Point; Page’s Rock) + James River (Hampton Bar) + southern Chesapeake Bay (Little Creek jetty; Cape Charles) ( Calder 1971: 70, as Dynamena cornicina ).— USA: Virginia, York River, Big Mumford Island, 37°16’N, 76°31’W, on Zostera ( Marsh 1973: 93, as Dynamena cornicina ).— USA: Texas, Galveston, front beach, on floating Sargassum ( Defenbaugh & Hopkins 1973: 107, as Sertularia mayeri ).— USA: Texas, West Flower Garden Bank, on floating Sargassum ( Defenbaugh 1974, as Sertularia mayeri ).—Sargasso Sea + Gulf Stream, several stations between Florida and North Carolina, on Sargassum fluitans III, S. fluitans X, S. pteropleuron ( Rackley 1974: 35, as Dynamena mayeri ).— Colombia: Santa Marta area, rocky littoral ( Wedler 1975: 340, as Dynamena cornicina ).— USA: Florida, southeast coast ( Mergner 1977: 122, as Dynamena cornicina ; 1987: 187, as Dynamena cornicina ).— USA: South Carolina, numerous areas across the coastal zone ( Calder & Hester 1978: 91, as Dynamena cornicina ).— Belize: Carrie Bow Cay ( Spracklin 1982: 246, as Dynamena cornicina ).— Barbados: on Thalassia ( Lewis & Hollingworth 1982: 43, as Sertularia mayeri ).—? Colombia: Bahía de Cartagena ( Flórez González 1983: 123, as Dynamena cornicina ).— USA: South Carolina, Murrells Inlet, 1–3 m + Sewee Bay, 2–4 m + Bulls Bay, 5 m + Prices Creek, 8 m + Inlet Creek, 4 m + Charleston Harbor entrance, 10 m + Kiawah River, 2–6 m + North Edisto River, 7–10 m + South Edisto River, 7 m + Beaufort River, 6 m ( Calder 1983: 10, as Dynamena cornicina ).— USA: continental shelf of South Carolina and Georgia ( Wenner et al. 1983: 148, as Dynamena cornicina ).— USA: South Carolina, inner (17–18 m), middle (32–36 m) and outer (46–69 m) continental shelf + Georgia, inner (17–22 m), middle (23–29 m) and outer (59–67 m) continental shelf ( Wenner et al. 1984: 21, 40, as Dynamena cornicina ).— USA: South Carolina, North Inlet area, Town Creek and tributaries + Murrells Inlet, jetties + Charleston area + Folly River area, Oak Island, oyster reef + Breach Inlet, jetties ( Fox & Ruppert 1985: 61, 92, 140, 152, 167, as Dynamena cornicina ).— Bermuda: inshore shallow waters + reefs + offshore banks + pelagic Sargassum ( Calder 1986: 137) .— Colombia, Santa Marta area, rocky littoral, near low tide, on algae, other hydroids, Thalassia , Syringodium ( Bandel & Wedler 1987: 42, as Dynamena cornicina ).— USA: South Carolina and Georgia, inner continental shelf, on artificial reefs ( Wendt et al. 1989: 1112, as Dynamena cornicina ).— USA: South Carolina, coastal areas, in stomachs of Atlantic spadefish ( Hayse 1990: 81, as Dynamena cornicina ).— Bermuda: Flatts Inlet, on Thalassia , 1 m + Whalebone Bay, on algae, 1–4 m + Natural Arches Beach, on Sargassum (Calder 1990 [1991a]: 93, 94).— Belize:Twin Cays ( Calder, 1991b: 223).— USA: North Carolina, Onslow Bay, in fish stomachs ( Pike & Lindquist 1994: 366, as Dynamena cornicina ).— Bermuda: on pelagic Sargassum fluitans ( Calder 1995: 540) .— Bermuda: Challenger Bank + Argus (=Plantagenet) Bank ( Calder 2000: 1133).— Cuba: Ciudad de La Habana province, Cojimar, on Sargassum ( Ortiz 2001a: 64, as Dynamena cornicina ).— Costa Rica: Limón, Isla Uvita, 09°59’40”N, 83°00’50”W ( Kelmo & Vargas 2002: 607).— Panama: Colón, Isla Margareta, Fort Randolph, shore, 09°23’15”N, 79°53’11”W, 0-1 m + Bocas del Toro area, Hospital Point, 09°20’01.9”N, 82°13’07.7”W, 2-13 m + 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, Crawl Cay, 09°15.261’N, 82°07.787’W, 2-4 m + Bocas del Toro area, near Laguna Bocatorito, 2-4 m + Bocas del Toro area, Bastimentos (front), 09°20.898’N, 82°09.959’W, 1-4 m + Bocas del Toro area, Boca del Drago, 0-3 m + Bocas del Toro area, “Emelio’s Beach,” 09°22.027’N, 82°14.336’W + Bocas del Toro area, Drago 2, 2- 4 m ( Calder & Kirkendale 2005: 485).—French Lesser Antilles: Guadeloupe, Grande-Terre, E of Saint François, 16°15’18.00”N, 61°14’37.00”W, seagrass meadows, on Thalassia + Basse-Terre, N of Malendure, 16°10’25.00”N, 61°46’58.00”W, rocky shore, on sponge, algae, rock + Basse-Terre, Petite Anse, 16°05’47.00”N, 61°46’17.00”W, rocky shore, on algae, concretions + Basse-Terre, Anse à la Barque, 16°05’21”N, 61°46’00”W, rocky shore, dock, pil- ings, on ascidian ( Galea 2008: 30, 31).—French Lesser Antilles: Les Saintes, Terre-de-Haut, Pompierre Bay, 15°52’25”N, 61°34’15”W, large rocks in seagrass meadows, on Halimeda , Thalassia + Terre-de-Haut, Pain de Sucre, 15°51’45”N, 61°35’60”W, rocky shore, on algae, sponge, concretions, bivalve shell ( Galea 2008: 31).— Cuba (Castellanos et al. 2009: 99, as Dynamena cornicina ).—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 ( Galea 2010: 3, 4).—French Lesser Antilles: Les Saintes, Terre-de-Haut, Pointe Morel, 15°53.050’N, 61°34.410’W, 6–11 m ( Galea 2010: 5).— USA: Florida: Fort Pierce Inlet State Park, 27°28’29.5”N, 80°17’25.8”W, on stranded Sargassum ( Calder 2013: 27) .—French Lesser Antilles: Martinique ( Galea 2013: 50).—Caribbean Sea ( Wedler 2017b: 125, figs. 125, 126A, B).— Mexico:Alacranes Reef, on algae, seagrass, corals, artificial reefs ( Mendoza-Becerril et al. 2018b: 130).— Cuba: Havana, coral reef system west of the city (Castellanos et al. 2018: Supplementary Table S2).— Panama: Bocas del Toro area, Crawl Cay ( Miglietta et al. 2018b: 108).

Figures

FIGURE 21. a, Amphisbetia distans: part of hydrocaulus with two hydrothecal pairs, Sanibel Island, ROMIZ B4387. Scale equals 0.1 mm. b, Amphisbetia distans: gonotheca, Sanibel Island, ROMIZ B4386. Scale equals 0.1 mm. c, Dynamena disticha: part of hydrocaulus with two hydrothecal pairs, Sanibel Island, ROMIZ B4410. Scale equals 0.1 mm. d, Dynamena pourtalesi: part of hydrocaulus with two hydrothecal pairs, Southwest Florida Shelf, ROMIZ B306. Scale equals 0.2 mm. e, Idiellana pristis: base of hydrocaulus with a branch, Sanibel Island, ROMIZ B4390. Scale equals 0.2 mm. f, Idiellana pristis: part of branch with hydrothecae, Sanibel Island, ROMIZ B4390. Scale equals 0.1 mm. g, Tridentata turbinata: part of hydrocaulus with two hydrothecal pairs, Sanibel Island, ROMIZ B4393. Scale equals 0.2 mm. h, Sertularella areyi: part of colony with two hydrothecae, Southwest Florida Shelf, ROMIZ B1978. Scale equals 0.2 mm. i, Sertularella diaphana: part of colony with three hydrothecae, Southwest Florida Shelf, ROMIZ B4392. Scale equals 0.2 mm. j, Sertularella unituba: part of colony with two hydrothecae, Southwest Florida Shelf, ROMIZ B2001. Scale equals 0.2 mm.