Dynamena pourtalesi ( Nutting, 1904 ) Calder, 2019

Calder, Dale R., 2019, On a collection of hydroids (Cnidaria, Hydrozoa) from the southwest coast of Florida, USA, Zootaxa 4689 (1), pp. 1-141 : 83-85

Dynamena pourtalesi ( Nutting, 1904) , comb. nov.

Fig. 21d

Sertularia distans Allman, 1877: 25 , pl. 16, figs. 9, 10.— Clarke, 1879: 246.— Nutting, 1895: 179 [junior primary homonym of Sertularia distans Lamouroux, 1816 ].

Sertularia pourtalesi Nutting, 1904: 59 , pl. 5, fig. 5 [nomen novum for Sertularia distans Allman, 1877 ].

Type locality. USA: Florida, Tennessee Reef , 21 ftm (38 m) ( Allman 1877: 25, as Sertularia distans ) .

Material examined. Southwest Florida Shelf, middle shelf west of Gasparilla Island, 26°45.86’N, 83°21.44’W, 50 m, 18 July 1981, triangle dredge, four colony fragments, up to 6.4 cm high, without gonophores, coll. Continental Shelf Associates, ROMIZ B306.— Southwest Florida Shelf , middle shelf west of North Naples, 26°16.83’N, 83°23.81’W, 59.5 m, 19 July 1981, triangle dredge, eight colony fragments, up to 3.4 cm high, without gonophores, coll. Continental Shelf Associates, ROMIZ B1965 .

Remarks. This species was originally described as Sertularia distans by Allman (1877) from the Tennessee Reef off Long Key, Florida. Nutting (1895: footnote, p. 179) recognized that the binomen was a junior primary homonym of Sertularia distans Lamouroux, 1816 , and later ( Nutting 1904) proposed S. pourtalesi as a replacement name for it. No new records of this species have been reported since Nutting’s monograph.

Allman’s species has been regarded as a synonym of Amphisbetia distans ( Lamouroux, 1816) in some works ( Cornelius 1979, as Sertularia distans ; Garcia et al. 1980, as S. distans ; Calder 1983, as S. distans ), and of Dynamena disticha ( Bosc, 1802) in others (Calder 1990 [1991]; Medel & Vervoort 1998). Its colonies are much more robust than the exceptionally fine ones of T. distans , its hydrothecae are larger and more tubular, and its hydrothecal pairs are more adnate. Conspecificity of the two is considered improbable. In this work, S. pourtalesi is also held to be distinct from D. disticha , a smaller species in which hydrothecae are more cylindrical and only 2/3 as large, and hydrothecal pairs that are much closer together given the significantly shorter length of the internodes. In being a species of the continental shelf, it also appears to occur in deeper waters than D. disticha , a species most often found within a few metres of the surface. Dynamena dalmasi ( Versluys, 1899) is somewhat similar in general colony form, but its hydrothecal walls are much more constricted distally and its hydrothecal pairs tend to be less adnate.

In lacking an abcauline diverticulum, S. pourtalesi is combined here with Dynamena Lamouroux, 1812 instead of Sertularia Linnaeus, 1758 or Tridentata Stechow, 1920 . Marktanner-Turneretscher (1890) had earlier included the species in the same genus, although under the binomen Dynamena distans (not D. distans Lamouroux, 1816 ) and on the basis of a misidentification, as noted below. Also in accord with the diagnosis of Dynamena , the hydrothecal margin of D. pourtalesi is tridentate, with two large lateral cusps and a smaller median adcauline one. Nutting (1904) and Fraser (1944) were mistaken in describing the margin as having only two cusps.

Two distribution records of Dynamena pourtalesi have been discounted here. Nutting (1904, as Sertularia pourtalesi ) reported it from 45°35’N, 55°01’W, 67 ftm (123 m), a location in cold waters south of Placentia Bay, Newfoundland, and an unlikely environment for this warm-temperate to tropical species. In addition, Marktanner- Turneretscher (1890: 239, as D. distans ) recorded it on algae from the Sargasso Sea. After examining his description and illustrations of the species, that account is taken to be a misidentification of the similar D. disticha , a common species on pelagic Sargassum .

Dynamena pourtalesi is a rarely reported species with a known distribution largely restricted to the shelf waters of southwest Florida. The only other records of it are those of Fewkes (1881, as Sertularia distans ) from the Caribbean island of St. Vincent and Wells et al. (1964) from Core Banks, North Carolina. Its gonosome remains unknown.

Reported distribution. Gulf coast of Florida. Tennessee Reef, 21 ftm (38 m) ( Allman 1877: 25, as Sertularia distans ).—WNW of the Dry Tortugas, 24°46’N, 83°16’W, 36 ftm (66 m) ( Clarke 1879: 246, as Sertularia distans ).—Pourtalès Plateau ( Nutting 1895: 179, as Sertularia distans ).—Off Cape San Blas, 29°16’30”N, 85°32’W, 26 ftm (48 m) ( Nutting 1904: 59, as Sertularia pourtalesi ).—S of Key West, 24°26’N, 81°48’15”W, 37 ftm (68 m) ( Nutting 1904: 59, as Sertularia pourtalesi ).—W of Venice, 27°04’N, 83°21’15”W, 26 ftm (48 m) ( Nutting 1904: 59, as Sertularia pourtalesi ).

Elsewhere in western North Atlantic. St. Vincent, 114 ftm (208 m) ( Fewkes 1881a: 128, as Sertularia distans ) .— USA: North Carolina, Core Banks , on Aequipecten gibbus , 17–20 ftm (31–37 m) ( Wells et al. 1964: 566) .

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.