Ectopleura L. Agassiz, 1862

Calder, Dale R., 2010, Some anthoathecate hydroids and limnopolyps (Cnidaria, Hydrozoa) from the Hawaiian archipelago 2590, Zootaxa 2590 (1), pp. 1-91 : 46-48

Genus Ectopleura L. Agassiz, 1862

Ectopleura L. Agassiz, 1862: 342 .

Type species. Tubularia dumortierii Van Beneden, 1844b [ Ectopleura dumortierii ], by subsequent designation by Mayer (1910a).

Diagnosis. Tubulariid hydroids solitary or colonial. Hydrocaulus erect, long, cylindrical, with open lumen, usually with two longitudinal V-shaped endodermal ridges, rarely with five, arising from a creeping hydrorhiza or hydrothizal mat; neck region bulbous, with perisarc groove around widest part; perisarc over neck region thin. Hydranths with oral tentacles usually filiform, rarely moniliform or capitate, in a single whorl, aboral tentacles essentially filiform.

Gonophores free medusae, eumedusoids, or sporosacs, borne on dichotomously branched or unbranched blastostyles just above aboral tentacles. Medusae when present bell-shaped, radially symmetrical; exumbrella with four pairs of meridional nematocyst tracks; marginal tentacles four perradial or two opposite, equally developed, moniliform or with abaxial nematocyst clusters; manubrium short, extending at most to velar opening; radial canals four; gonads encircling manubrium.

Remarks. The widely-used generic name Ectopleura L. Agassiz, 1862 is threatened by several older but now unused senior subjective synonyms, including Pyxidium Leuckart, 1856 , Vorticlava Alder, 1856 , Parypha L. Agassiz, 1860 , and Thamnocnidia L. Agassiz, 1860 . Of these threats to nomenclatural stability, only that represented by Pyxidium can be resolved here.

The type species of Pyxidium , P. truncatum Leuckart, 1856 (by monotypy), is of questionable identity. It was included by L. Agassiz (1862) in Parypha (see also A. Agassiz 1865: 194), a senior subjective synonym of Ectopleura . Haeckel (1879) listed it in an index of obsolete names. Reversal of Precedence (ICZN Art. 23.9) can be applied to relegate Pyxidium to the status of nomen oblitum. That name has been not been used as valid in zoology after 1899 (ICZN Art. 23.9.1.1). Meanwhile, Ectopleura has been used in over 25 works by more than 10 authors in the past 50 years (Art. 23.9.1.2) (e.g. Kramp 1961; Brinckmann-Voss 1970; Millard 1975; Bouillon 1978b; Wedler & Larson 1986; Calder 1988; Hirohito 1988; Petersen 1990; Migotto 1996; Calder & Vervoort 1998; Bouillon & Boero 2000; Faucci & Boero 2000; Marques & Migotto 2001; Cairns et al. 2002; Peña Cantero & García Carrascosa 2002; Kirkendale & Calder 2003; Schuchert 2003, 2009; Calder & Kirkendale 2005; Bouillon et al. 2006; Galea et al. 2007; Xu et al. 2007; Altuna 2008; Watson 2008; Guenther et al. 2010). Accordingly, Ectopleura is herein assigned precedence over Pyxidium whenever the two are considered congeneric.

FIGURE 29. Eudendrium sp. 1 : part of hydrocaulus with a branch; hydranths lacking, USNM 22270. Scale equals 1 mm.

FIGURE 30. Hydra sp. : polyp with two lateral buds, ROMIZ B3831. Scale equals 0.25 mm.

FIGURE 31. Hydra sp. : nematocysts, ROMIZ B3831. a, desmoneme. b–c, atrichous isorhizas. d, holotrichous isorhiza. e, small stenotele. f, large stenotele.

The identity of Vorticlava is fixed by its type species by monotypy, V. humilis Alder, 1856 , now regarded as a junior subjective synonym of Ectopleura larynx Ellis & Solander, 1786 ( Vervoort 1946; Cornelius & Garfath 1980). The threat of Vorticlava to Ectopleura cannot be removed by Reversal of Precedence because the senior name was used as valid several times during the first half of the 20 th century (ICZN Art. 23.9.1.1) (e.g. Bedot 1910, 1912, 1916, 1918, 1925; Rees 1937).

Parypha and Thamnocnidia were both initially introduced without included species. However, brief definitions of them were given (L. Agassiz, 1860: 45, 46), thereby making the names available (ICZN Art. 12.1). In a subsequent work (L. Agassiz 1862: 342), several nominal species were assigned to each one. Included under Parypha were Pyxidium truncatum Leuckart, 1856 , Tubularia cristata McCrady, 1859 , and Parypha crocea L. Agassiz, 1862 . Species referred to Thamnocnidia were Tubularia coronata Abildgaard , in Müller, 1806, T. calamaris sensu Van Beneden, 1844b (non Pallas, 1766), Thamnocnidia spectabilis L. Agassiz, 1862 , and T. tenella L. Agassiz, 1862 . No type species were designated for either genus, but all of them are referable or questionably referable to Ectopleura , as currently defined. Reversal of Precedence cannot be applied to assign priority to Ectopleura over Thamnocnidia and Parypha because both of the latter have been used as valid since 1900 (e.g. Thamnocnidia was used as a genus name by Whiteaves 1901: 20, and as a subgenus name by Fenchel 1905: 573; Parypha was employed by Allen 1900: 291). Other instances of their usage early in the 20 th century are listed in Bedot (1925).

In the interests of nomenclatural stability, a case to the International Commission on Zoological Nomenclature is needed requesting conservation of the widely used name Ectopleura in place of its essentially abandoned senior subjective synonyms Vorticlava , Parypha , and Thamnocnidia . In the meantime, existing usage is maintained here.

The diagnosis of Ectopleura given above, modified from that proposed by Petersen (1990), Bouillon et al. (2006), and Schuchert (2010), reflects the current concept of the genus. Additional characters are from a cladistic analysis of Tubulariidae Fleming, 1828 by Marques & Migotto (2001). In the classification of the family by Marques & Migotto, species earlier assigned to Ectopleura that had (1) fixed gonophores, (2) sexually dimorphic blastostyles, and (3) oral tentacles adnate to hypostome, were assigned to Pinauay Marques & Migotto, 2001 (type species Tubularia larynx Ellis & Solander, 1786 , by original designation). However, Pinauay is predated by Vorticlava , Parypha , and Thamnocnidia , and was not recognized as distinct from Ectopleura by Schuchert (2009, 2010).