Halecium halecinum ( Linnaeus, 1758 )

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 : 31-32

Halecium halecinum ( Linnaeus, 1758)

Fig. 30

Sertularia halecina Linnaeus, 1758: 809 [the specific name halecina Linnaeus, 1758 conserved and placed on Official List of Specific Names in Zoology, Opinion 1220 (ICZN 1982)].

Halecium halecinum .— Segerstedt, 1889: 15, 26.— Jäderholm, 1909: 57, pl. 4, figs. 13, 14.— Rees & Rowe, 1969: 12.— Jägerskiöld, 1971: 62.

Halecium cf. halecinum .— Gislén, 1930: 329.

Type locality. England: Kent, Whitstable ( Cornelius 1975b: 394) .

Museum material. Kosterhavet, 58°52.567’N, 11°06.313’E, 6–30 m, 07.ix.2010, SCUBA , three colonies with fragments, up to 7 cm high, two colonies with female gonophores and one with male gonophores, coll. B.E. Picton, ROMIZ B3897 .

Remarks. Halecium halecinum ( Linnaeus, 1758) is one of the most distinctive species of the genus in the typical shape of its trophosome. With a regularly pinnate colony form and moderately short, relatively straight branches, it resembles a herring skeleton. As noted by Cornelius (1995a), this hydroid was aptly called the “herring-bone coralline” by Ellis (1755).

Schuchert (2005) noted that there are variations from this well-known form of the species. Identifications are best made from examination of female gonothecae, if present, which are oblong and have an aperture at the end of a terminal, asymmetrically placed collar. In the sympatric H. beanii ( Johnston, 1838) and H. sessile Norman, 1867 , and in the circumpolar H. scutum ( Clark, 1877) , such gonothecae are mitten-shaped, with the aperture occurring laterally. Several other characters distinguishing H. halecinum from H. beanii were noted by Medel & Vervoort (2000): (1) hydrocladia usually arise from the front or back of hydrothecae instead of laterally, (2) the first internode of a hydrocladium is usually thecate rather than athecate, (3) secondary hydrophores are longer.

Characters of hydranths of H. halecinum have been studied by Cornelius (1998), and by Gravier-Bonnet (2007), who described a new type of hydranth in the species termed an “extensible polyp.” Such polyps were capa- ble of great extension and contraction, and were thought to have defensive, excretory, and possibly sensory functions. They were scattered irregularly over the colony.

Contemporary taxonomic accounts of H. halecinum include those of Cornelius (1975a, 1995b), Medel et al. (1998), Medel & Vervoort (2000), and Schuchert (2005). An extensive synonymy was listed by Medel & Vervoort (2000), together with detailed distribution records of the species worldwide.

According to Rees & Rowe (1969), this is the most abundant species of the genus Halecium Oken, 1815 on the west coast of Sweden. Records by Jägerskiöld (1971) support that conclusion (see Checklist). It is also the most common species of Halecium in waters around Denmark ( Kramp 1935b), and it occurs up the Oslofjord of Norway as far as Steilene ( Christiansen 1972).

Reported distribution. West coast of Sweden.—From Säcken to southern Kattegat, 9–200 m ( Jägerskiöld 1971).

Elsewhere.—Atlantic Ocean from Spitzbergen and northern seas of the Russian Federation to South Africa in the east ( Cornelius 1995a), and from the Strait of Belle Isle to Chesapeake Bay ( Calder 2004) in the west, with questionable records from the Caribbean Sea and Gulf of Mexico ( Flórez González 1983; Bandel & Wedler 1987; Reyes & Campos 1992; Calder & Cairns 2009). It has also been reported from the western and eastern Pacific, and from the Indian Ocean ( Medel & Vervoort 2000).