Tridentata distans ( Lamouroux, 1816 )

Calder, Dale R., 2013, Some shallow-water hydroids (Cnidaria: Hydrozoa) from the central east coast of Florida, USA, Zootaxa 3648 (1), pp. 1-72: 30-31

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Tridentata distans ( Lamouroux, 1816 )


Tridentata distans ( Lamouroux, 1816)  

Fig. 9c View FIGURE 9

Dynamena distans Lamouroux, 1816: 180   , pl. 5, figs. 1a, B.

Sertularia stookeyi   .— Fraser, 1943: 93.

Sertularia gracilis   .— Jones, 2002: 215.

Type locality. Atlantic Ocean, on Fucus natans   (= Sargassum natans   ) and other flotsam ( Lamouroux 1816: 180).

Voucher material. Fort Pierce Inlet , north jetty, north side, 27°28’24.1”N, 80°17’21.2”W, intertidal zone, on stem of Thyroscyphus ramosus   , 14.vii.2012, 28° C, 35‰, collected manually, one colony, 5 mm high, without gonothecae, coll. D.R. Calder, ROMIZ B3968 GoogleMaps   .

Remarks. Billard (1906) noted that the original description of Tridentata distans   by Lamouroux (1816, as Dynamena distans   ) was inadequate, and he justifiably described illustrations of the species in that initial account as “gross.” Nevertheless, he was able to confirm the identity of the species after examining Lamouroux’s type at l’Institut Botanique de Caen. That identification, upheld in a subsequent review of Lamouroux’s types ( Billard 1909), is the foundation of the current concept of the species.

Recently, the possible existence of cryptic species in T. distans   has been raised on the basis of molecular studies ( Moura et al. 2011, as Sertularia distans   ). Moreover, the generic affinity of the species needs clarification. Moura et al. showed that the species was genetically closer to Sertularia operculata Linnaeus, 1958   , type species of Amphisbetia L. Agassiz, 1862   , than to Sertularia perpusilla Stechow, 1919   , type species of Tridentata Stechow, 1920   . Differences in morphology support such a possibility. For example, gonothecal walls in T. distans   are ovate and smooth rather than barrel-shaped with transverse ribs as in S. perpusilla   .

Tridentata distans   is a eurytopic hydroid with a wide latitudinal range, occurring from temperate regions to the tropics. In the southeastern United States it is frequent both inshore ( Calder 1983, as Sertularia distans   ) and on hard bottoms of the continental shelf ( Wenner 1984, as S. distans   ). Live colonies were found in estuaries of South Carolina at salinities of 20–34‰ (Calder 1976, as S. stookeyi Nutting, 1904   ) and temperatures of 8–32° C ( Calder 1990, as S. distans   ). It is also a component of the pelagic Sargassum   fauna (e.g., Lamouroux 1816, as Dynamena distans   ; Fraser 1944, as S. stookeyi   ; Calder 1991a).

This species is noteworthy for the minuteness of its hydrothecae.

Reported distribution. Atlantic coast of Florida. Between Biscayne and Duck Keys ( Fraser 1943, as Sertularia stookeyi   ); Biscayne Bay ( Jones 2002, as S. gracilis Hassall, 1848   ).

Western Atlantic. Massachusetts ( Fraser 1912a, as S. stookeyi   ) to Brazil (Oliveira et al. submitted, as S. distans   ), including Bermuda ( Calder 1991a), the Gulf of Mexico ( Calder & Cairns 2009), and the Caribbean Sea ( Fraser 1943, as S. stookeyi   ).

Elsewhere. Circumglobal in tropical, subtropical, and temperate waters ( Vervoort & Watson 2003, as S. distans   ).














Tridentata distans ( Lamouroux, 1816 )

Calder, Dale R. 2013

Sertularia gracilis

Jones, T. 2002: 215

Sertularia stookeyi

Fraser, C. M. 1943: 93

Dynamena distans

Lamouroux, J. V. F. 1816: 180