Halecium textum Kramp, 1911

Calder, Dale R., 2012, On a collection of hydroids (Cnidaria, Hydrozoa, Hydroidolina) from the west coast of Sweden, with a checklist of species from the region 3171, Zootaxa 3171 (1), pp. 1-77 : 32-33

Halecium textum Kramp, 1911

Fig. 31

Halecium textum Kramp, 1911: 368 , pl. 21, figs. 5, 6.

Halecium tenellum .— Segerstedt, 1889: 16, 26.— Jäderholm, 1909: 55, pl. 4, fig. 12 [not Halecium tenellum Hincks, 1861 ]. Halecium undulatum .— Hamond, 1957: 304.— Cornelius, 1995a: 300; 1998: 91 [Not Halecium undulatum Billard, 1922 ].

Type locality. Greenland: Maroussia , 160 –180 m ( Kramp 1911: 369) .

Museum material. Kosterhavet, 58°53.039’N, 11°05.602’E, 160 m, 09.ix.2010, biological dredge, R / V Nereus , two colony fragments, up to 1 cm high, with one on Sertularella polyzonias , without gonophores, ROMIZ B3906.

Remarks. Schuchert (2001a) concluded that several reports of H. undulatum Billard, 1922 , including at least some of those in Calder (1970), Hamond (1957), and Cornelius (1995a), were based on the little-known H. textum Kramp, 1911 . Differences between the two species appear minor, the only distinguishing character of note appearing to be the presence of a pseudodiaphragm in H. textum and its absence in H. undulatum . After examining the sterile type material of H. undulatum, Schuchert noted that it could not properly be identified but nevertheless treated it as a questionable synonym of H. textum . Schuchert (2005) continued to regard them as possible synonyms, although both are currently recognized as valid in the World Hydrozoa Database ( Schuchert 2011). Cornelius (1975b) believed that H. undulatum was based on small colonies of H. labrosum Alder, 1859 , but later maintained it as distinct ( Cornelius 1995 a, 1998). He noted that the publication date of Billard’s (1922) original account of H. undulatum , although given as 1921, appeared in 1922 ( Cornelius 1995b: 343). Material from Sweden, examined here, corresponds morphologically with accounts of H. textum by Schuchert (2001 a, 2005), including presence of a pseudodiaphragm.

Halecium textum has also been mistaken for H. tenellum Hincks, 1861 , as in Jäderholm’s (1909) records from the west coast of Sweden ( Schuchert 2001a). Jäderholm’s material included hydroids identified as H. tenellum by Segerstedt (1889). According to Schuchert, H. textum can be distinguished from H. tenellum in having: (1) larger and more profuse colonies that sometimes form tangled masses, (2) perisarc that is strongly annulated over frequent stretches of the colony, (3) frequent polytomies, with two or more side branches arising beneath a hydrotheca, (4) a pseudodiaphragm, (5) short hydrophores.

Another small species of the genus Halecium Oken, 1815 in cold North Atlantic waters having a similar colony form and flared rim is Halecium minutum Broch, 1903 . It is distinguished from H. textum in having unusually deep hydrothecae for the genus, and its pseudodiaphragm, when present, is distal to the insertion of a branch ( Schuchert 2001a). Moreover, gonothecae of H. minutum arise from the hydrorhiza, have the shape of an empty coin purse, and have distal spines. Those of H. textum occur on the branches, are oblong in shape, and lack distal spines.

Reported distribution. West coast of Sweden.—Kosterhavet (this study) to Gullmarfjord ( Cornelius 1995a).

Elsewhere.—North Atlantic from Iceland, Faroes, and Svalbard questionably to British Isles in the east ( Schuchert 2005; Ronowicz 2007; Ronowicz et al. 2008), and from Greenland and Frobisher Bay at least to Northumberland Strait ( Calder 2004, as H. undulatum ) in the west. Schuchert (2005) included Fraser’s (1944) records of H. tenellum in the synonymy of H. textum . If so, records extend to New England, with highly questionable reports from further south.

FIGURE 33. Diphasia fallax : part of branch with two subopposite pairs of hydrothecae, ROMIZ B3911. Scale equals 0.5 mm.

Figures

FIGURE 31. Halecium textum: part of colony with hydrothecae, ROMIZ B3906. Scale equals 0.5 mm.