Sertularella polyzonias ( 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 : 36-37

Sertularella polyzonias ( Linnaeus, 1758)

Fig. 36

Sertularia polyzonias Linnaeus, 1758: 813 .

Sertularella polyzonias .— Segerstedt, 1889: 16, 26.— Jäderholm, 1909: 100, pl. 11, fig. 12.— Rees & Rowe, 1969: 18.— Jägerskiöld, 1971: 64.— Cornelius, 1979: 288.

Type locality. England: Kent, north coast ( Cornelius 1979: 288) .

Museum material. Kosterhavet, 58°52.424’N, 11°06.178’E, 35– 11 m, 06.ix.2010, biological dredge, R / V Nereus , several colonies and colony fragments, up to 2.3 cm high, on bryozoans and algae, without gonothecae, ROMIZ B3886 .

Remarks. Sertularella polyzonias ( Linnaeus, 1758) can be somewhat difficult to distinguish from S. gayi ( Lamouroux, 1821) , which also occurs in northwestern Europe. According to Ramil & Vervoort (1992) and Ramil et al. (1992), S. polyzonias differs from S. gayi in: (1) the form of the hydrocaulus, which is indistinct and monosiphonic instead of distinct and strongly polysiphonic; (2) the type of branching, which is irregular instead of regularly pinnate and in one plane; (3) the shape of the adcauline hydrothecal wall, which is smooth or minimally undulated instead of being more distinctly wavy; (4) the number of cusps flanking the aperture of the gonotheca, with four instead of two. Cornelius (1995b) noted that variations have been noted in these characters, but he retained both species as valid. In addition to morphology, molecular differences have been noted in specimens assigned to the two species ( Moura et al. 2008, 2011).

FIGURE 37. Sertularella rugosa : part of hydrocaulus with three hydrothecae, ROMIZ B3910. Scale equals 0.5 mm.

Also similar to S. polyzonias in the northeastern North Atlantic is Sertularella ellisii ( Deshayes & Milne Edwards, 1836) , a species differing from S. polyzonias in having three intrathecal cusps within its hydrothecae. These two have recently been shown to be genetically distinct ( Moura et al. 2011). Ramil et al. (1992) and Medel & Vervoort (1998) noted that S. ellisii has sometimes been misidentified in European waters as S. gaudichaudi ( Lamouroux, 1824) , a species from the southwestern South Atlantic.

Sertularella polyzonias is abundant at shallow depths in western Sweden, but it becomes scarcer in deeper water ( Rees & Rowe 1969). It is also present in Danish waters ( Kramp 1935b) and in the Oslofjord, Norway ( Christiansen 1972). An extensive synonymy of the species is given by Medel & Vervoort (1998).

Reported distribution. West coast of Sweden.—From Säcken Reef in the Kosterfjord to southern Kattegat ( Rees & Rowe 1969; Jägerskiöld 1971).

Elsewhere.—Often described as “cosmopolitan.” From Spitzbergen and the northern seas of the Russian Federation at least to Morocco in the eastern North Atlantic ( Naumov 1960; Cornelius 1995b; Ramil & Vervoort 1992), and from Foxe Basin in the Canadian Arctic and west Greenland to Long Island Sound in the west ( Broch 1918; Calder 2004); from the northeastern seas of the Russian Federation to Japan ( Hirohito 1995) in the western North Pacific, and from Alaska to Washington state ( Fraser 1937) in the east.

Figures

FIGURE 36. Sertularella polyzonias: part of branch with two hydrothecae, ROMIZ B3886. Scale equals 0.5 mm.