Plumularia setacea ( Linnaeus, 1758 )

Calder, Dale R., 2013, Some shallow-water hydroids (Cnidaria: Hydrozoa) from the central east coast of Florida, USA, Zootaxa 3648 (1), pp. 1-72 : 37-38

Plumularia setacea ( Linnaeus, 1758)

Fig. 10e

Sertularia setacea Linnaeus, 1758: 813 .

Plumularia setacea .— Deevey, 1950: 347, fig. 6.

Type locality. UK: Brighton (“Brighthelmstone”) and Whitstable ( Ellis 1755: 19, as Corallina setacea ). Linnaeus (1758) gave the binomen Sertularia setacea to the species described by Ellis, listing its locality only as “Habitat in Oceano.”

Voucher material. Off Vero Beach , 27°41.2’N, 80°14.5’W, 17 m, 13.ii.1974, small biological dredge, R/ V Gosnold Station 220/226, several colony fragments, up to 2.4 cm high, without gonophores, ROMIZ B1077 .— Fort Pierce Inlet , north jetty, north side, 27°28’24.2’N, 80°17’20.3”W, low water, on polychaete tubes, 15.ii.1991, 20° C, collected manually, six colony fragments, up to 2.1 cm high, with gonophores, coll. D.R. Calder, ROMIZ B1111 .

Remarks. Plumularia setacea ( Linnaeus, 1758) and P. strictocarpa Pictet, 1893 are generally said to be indistinguishable morphologically in the absence of reproductive structures. Part of the material examined here (ROMIZ B1111) bore gonophores protected by fusiform gonothecae, typical of P. setacea . Specimens from shelf waters off Vero Beach (ROMIZ B1077), although sterile, were assigned to the same species based on the size of the colonies, larger than normally found in P. strictocarpa , and their identical appearance to colonies from Fort Pierce Inlet (ROMIZ B1111) having gonophores.

Also somewhat resembling Plumularia setacea are three less well known species originally described from the Straits of Florida region, P. filicula Allman, 1877 , P. attenuata Allman, 1877 , and P. megalocephala Allman, 1877 . As noted earlier ( Calder 1997), all appear to differ from the present species in having hydrocladial apophyses with pronounced cylindrical extensions distal to the mamelon, and in bearing a nematotheca on the proximalmost (ahydrothecate) internode of each hydrocladium. Moreover, gonothecae of P. filicula , as described and illustrated by Allman (1877), have a wide, oblique aperture rather than a small circular one at the end of a narrow neck as in P. setacea . In P. attenuata , all hydrocladial internodes beyond the proximalmost one are hydrothecate instead of being alternately hydrothecate and athecate. Hydrocauli of P. megalocephala were described by Allman as being irregularly branched, whereas those of P. setacea are usually unbranched or only sparingly branched. In some respects these hydroids resemble species of Nemertesia Lamouroux, 1812 , but further study is needed to confirm their generic affinities.

Thorough taxonomic accounts of Plumularia setacea are given by Ansín Agís et al. (2001) and Schuchert (2013).

Reported distribution. Atlantic coast of Florida. Central east coast of Florida ( Deevey 1950, distribution map).

Western Atlantic. Marthas Vineyard ( Fraser 1944) to Argentina (Oliveira et al. submitted), including Bermuda ( Calder 1997), the Gulf of Mexico ( Calder & Cairns 2009), and the Caribbean Sea ( Galea 2010).

Elsewhere. Cosmopolitan except for polar regions ( Ansín Agís et al. 2001; Schuchert 2013).

Figures

FIGURE 10. a, Dentitheca dendritica: part of hydrocladium with two hydrothecae, ROMIZ B1130, scale equals 0.10 mm. b, Nemertesia simplex: apophysis and basal part of hydrocladium, ROMIZ B1121, scale equals 0.20 mm. c, Nemertesia simplex: part of hydrocladium with hydrotheca, ROMIZ B1121, scale equals 0.10 mm. d, Plumularia floridana: part of hydrocaulus with basal parts of two hydrocladia, and three hydrothecae, ROMIZ B1080, scale equals 0.25 mm. e, Plumularia setacea: part of hydrocaulus with basal parts of two hydrocladia, a female gonotheca, and a hydrotheca, ROMIZ B1111, scale equals 0.20 mm. f, Plumularia strictocarpa: part of hydrocaulus with basal parts of two hydrocladia, and three hydrothecae, ROMIZ B3971, scale equals 0.20 mm.