Sertularella gigantea Hincks, 1874

Choong, Henry H. C., 2015, Hydroids of the genus Sertularella (Cnidaria: Hydrozoa: Sertulariidae) from the Pacific coast of Canada in the collection of the Royal Ontario Museum, with descriptions of four new species, Zootaxa 3925 (3), pp. 387-408 : 396-399

Sertularella gigantea Hincks, 1874

( Figure 5)

Sertularella polyzonias — Fraser, 1937: 156, pl. 35, fig. 187 [not Sertularella polyzonias ( Hincks, 1861] Sertularella polyzonias , var. gigantea Hincks, 1874: 151 , pl. 7, figs. 11–12.

Sertularella gigantea — Mereschkowsky, 1878b: 339, pl.14, figs. 6–7.

Material. CANADA: British Columbia. Queen Charlotte Land District. Masset Harbor, 14. ix.1935, part of multilevel epizoic complex, without gonothecae, ROMIZ B4036. CANADA: British Columbia. Queen Charlotte Land District. Masset Harbor, 14. ix.1935, epizoic on Bryozoa ( Bugula sp), without gonothecae, ROMIZ B4037.

CANADA: British Columbia. Queen Charlotte Land District. Masset Harbor, 14. ix.1935, epizoic on Bugula sp, without gonothecae, ROMIZ B4038. CANADA: British Columbia. Queen Charlotte Land District. Masset Harbor, 14. ix.1935, epizoic on stolon of Plumularia lagenifer a Allman, 1885, without gonothecae, ROMIZ B4039. CANADA: British Columbia. Queen Charlotte Land District. Masset Harbor, 14. ix.1935, epizoic on Abietinaria filicula ( Ellis & Solander, 1786) , without gonothecae, ROMIZ B4040. CANADA: British Columbia. Queen Charlotte Land District. Masset Harbor, 14. ix.1935, without gonothecae, ROMIZ B4041. CANADA: British Columbia. Masset Harbor, 14. ix.1935, short hydrocauli, without gonothecae, ROMIZ B4042. CANADA: British Columbia. Queen Charlotte Land District. Masset Harbor, 14. ix.1935, on Symplectoscyphus turgidus ( Trask, 1857) , without gonothecae, ROMIZ B4043. CANADA: British Columbia. Queen Charlotte Land District. Masset Harbor, 14. ix.1935, on Symplectoscyphus tricuspidatus ( Alder, 1856) , without gonothecae, ROMIZ B4044. CANADA: British Columbia. Queen Charlotte Land District. Masset Harbor, 14. ix.1935, on Sertularia sp. without gonothecae, ROMIZ B4045. CANADA: British Columbia. 54˚12’48”N, 133˚07’24”W, 29. iv.1961, two hydrocauli, without gonothecae, 82.2 meters, coll D.B. Quayle, ROMIZ B4046. CANADA: British Columbia. 49˚13’00”N, 125˚57’00”W, 12. v.1961, 20.1 meters, hydrocauli, without gonothecae, coll. D.B. Quayle, ROMIZ B4047. CANADA: British Columbia. 48˚43’00”N, 123˚26’30”W, 13. v.1961, 51.2 meters, hydrocauli, without gonothecae, coll. D.B. Quayle, ROMIZ B4048. Other material: CANADA: British Columbia. 48˚43’00”N, 123˚26’30”W, 13. v.1961, 51.2 meters, coll. D.B. Quayle, sections of hydrocauli, without gonothecae, CMNI 1982- 1383. CANADA: British Columbia. 48˚43' 0.0012", 123˚26' 30.0006", 13. v.1961, 51.2 meters, coll. D.B. Quayle, hydrocauli, without gonothecae, CMNI 1982-1384. CANADA: British Columbia. 54˚13’00”N, 132˚09’00”W, 29.iv.1961, 98.8 meters, coll. D.B. Quayle, hydrocauli, without gonothecae, CMNI 1982-1391. CANADA: British Columbia. 54˚12’48”N, 133˚07’24”W, 29. iv.1961, stolonal colony, without gonothecae, coll D.B. Quayle, CMNI 1982-1403.

Reported distribution. Greenland ( Hincks 1874, as Sertularella polyzonias , var. gigantea ). All Russian and Far Eastern Seas (except Chukchi Sea), Norwegian and Greenland seas, Davis Strait (Naumov 1969). Kamchatka ( Kirchenpauer 1884). Okhotsk Sea, Sea of Japan, some Arctic regions ( Linko 1912). North Atlantic, Nova Scotia to Nantucket and Vineyard Sound ( Fraser 1944).

Description. Colony monosiphonic, occasionally epizoic on other hydroids. Basal part of stem connecting with hydrorhiza may show four or more annulations. Perisarc slightly thickened. Internodes short, 1230–1580 mm, hydrothecae alternating on same plane, one hydrotheca per internode. Internode directly connected to previous hydrotheca. Base of internode with 1–2 oblique annulations; distinctive notch on basalmost part of internode immediately adjacent to abcauline side of previous hydrotheca. Hydrotheca tubular, narrowing distally, almost straight or slight abcauline tilt; a slight constriction, if present, proximal to hydrothecal aperture; walls smooth or slightly undulated. Hydrothecae 2000–2380 mm long, 1270–1410 mm at widest point. Hydrotheca almost free, length of adnate part 1620–2000 mm. Sinus moderate to deep with pointed denticles, four triangular flaps forming a peak at midpoint and extending slightly past hydrothecal aperture margin. Hydrothecal aperture margin may be reduplicated. Hydrothecal aperture usually at right angles to hydrothecal axis. Gonothecae not found.

Remarks. Sertularella gigantea is widely distributed over the circumboreal region of the Pacific and the Atlantic ( Yamada 1957). However, this species has not hitherto been reported from the Pacific coast of Canada; in part due to confusion with S. polyzonias . This is the first reported occurrence of S. gigantea from the North American west coast. Sertularella gigantea , with hydrothecae measuring more than 1000 mm in depth (length of the abcauline side), has been regarded as a larger form of S. polyzonias ( Linnaeus, 1758) (e.g. Broch 1918; Calder 1970). Smaller forms with hydrothecae measuring less than 1000 in depth are considered to be the typical form ( Schuchert 2001). Broch (1918) reported the occurrence of intermediate forms along the west coast of Greenland, differing only in size, but these are comparatively few. Schuchert (2001) observed striking morphological differences in the two forms, although he was equivocal about whether the two forms are conspecific. Furthermore, recent molecular work by Moura et al. (2011) using 16S rRNA sequences indicates that haplotypes of S. polyzonias are somewhat divergent (up to 1.9% of sequence divergence). I follow Mereschkowsky (1878), Nutting (1904) and Naumov (1969) in regarding S. gigantea to be a valid separate species. Observed differences in the hydrothecae and gonothecae are given in Table 3 . Fraser’s (1937) description of S. polyzonias from Alaska and the Pacific coast of Canada largely corresponds to S. gigantea .

*Material examined: ROMIZB1039, ROMIZ B3886 **Material examined: ROMIZ B4064

Tables

TABLE 3. Characters used to distinguish Sertularella gigantea from S. polyzonias.

Character	* Sertularella polyzonias (Linnaeus, 1758)	Sertularella gigantea Hincks, 1874
Hydrotheca undulated	Smooth or very slightly	Smooth or very slightly
Hydrotheca with ridges	Occasionally	No
Hydrothecae length (non-adnate side)	≤1100 µm	2200–2380 µm
Hydrotheca, adnate part	1/3–1/2	0–1/3
Hydrotheca shape	Flask-shaped with wide base	Tubular or slightly wide basally
Sinus	Deep	Moderate to deep
Stem flexuous	Yes	No
Base of internode with 1–2 oblique annulations	No	Yes
Distinctive notch on basalmost part of internode immediately adjacent to abcauline side of previous hydrotheca	No	Yes, usually
Gonothecal cusps	3–4, small to medium	**4, large
Gonothecal shape and annulations	Elongated-ovoid, 8 or more annulations on distal half to two-thirds; rounded	Ovoid, 8 or more annulations over entire surface, crested
Gonotheca, maximal length	2950–3240 µm	2680–2840 µm
Gonotheca, maximal width	1540–1620 µm	2000–2260 µm