Sertularella pacifica, Choong, Henry H. C., 2015

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 : 399-400

Sertularella pacifica sp. nov.

( Figure 6 )

Sertularella fusiformis — Torrey, 1902: 61, pl. 6, fig. 53–54.— Fraser, 1937: 153, pl. 34, fig. 181 [not Sertularella fusiformis ( Hincks, 1861) ]

Material. Holotype: CANADA: British Columbia. Vancouver Island, Juan de Fuca Strait, Race Rocks, 48˚18’00”N, 123˚32’00”W, 0 5. iv.1986, 6–10 meters, two short hydrocauli, with gonothecae, coll. A. Brinckmann- Voss, ROMIZ B670. Paratype: CANADA: British Columbia. Queen Charlotte Land District. Masset Harbor, 14. ix.1935, without gonothecae, ROMIZ B4065. Other material: CANADA: British Columbia. Queen Charlotte Land District. Masset Harbor, 54˚03’00”N, 132˚13’00”W, 14. ix.1935, colony arising from stolon at the base of Abietinaria pulchra ( Nutting, 1904) colony, without gonothecae, ROMIZ B4066. CANADA: British Columbia. Queen Charlotte Land District. Masset Harbor, 14. ix.1935, two short hydrocauli, without gonothecae, ROMIZ B4067. CANADA: British Columbia. Queen Charlotte Land District. Masset Harbor, 14. ix.1935, colony arising from stolon at the base of Sertularia sp.colony, without gonothecae, ROMIZ B4068. CANADA: British Columbia. Queen Charlotte Land District. Masset Harbor, 54˚03’00”N, 132˚13’00”W, 14. ix.1935, hydrocauli, without gonothecae, ROMIZ B4069.

Reported distribution. California: San Francisco, as Sertularella fusiformis ( Hincks, 1861) ( Torrey, 1902) . Oregon: Three locations off Heceta Head, 0–113 meters ( Fraser, 1937).

Description. Colonies erect, hydrorhiza stolonal, occasionally anastomosing. Hydrocaulus geniculate, unbranched. Perisarc thickened throughout, up to 60 mm thick. Hydrocaulus monosiphonic, unfascicled, divided into internodes. Internodes 1003–1530 mm long, with one to three (usually two) complete annulations basally; proximal-most annulation often spirally twisted ( Fig. 3 A,B). Internode has tendency to spiral relative to main axis. Single hydrotheca distal to internode. Hydrothecae alternate, often not on same plane ( Fig. 3 A). Hydrotheca tubular, walls asymmetrical; abcauline and adcauline wall slightly swollen basally, swelling on abcauline wall more proximal. Perisarc of hydrothecae thickened, up to 60 mm thick. Distal half of hydrotheca narrowed towards aperture, greater narrowing on abcauline side. Adcauline hydrothecal wall adnate for approximately 1/4–1/2 of length. Hydrothecal margin dentate with four equally-developed cusps; one adcauline, one abcauline, and two laterals. Opercular flaps triangular, four present; when closed forms roof extending slightly beyond opercular margin. Intrathecal cusps present, three in number, occasionally missing; two small intrathecal cusps proximal to and flanking adcauline marginal cusp, one long and narrow intrathecal cusp on abcauline side ( Fig 3 A).

Gonothecae (♂) few, attached to internode or directly below base of hydrotheca; large, up to three-times longer than hydrothecae, spindle-shaped, widest medially, longer than wide, flexed or bent mid-axis. Gonothecal body strongly annulated throughout; 10–12 complete, well-developed annulations. Neck short or barely discernible, four low rounded cusps around gonothecal aperture. Occasionally, one of the four cusps may be more developed than other three.

Differential diagnosis. The records from the west coast of North America ( Torrey 1902; Fraser 1937) seem to be morphologically distinct from descriptions of S. fusiformis elsewhere as shown by the absence of four intrathecal cusps and the presence of two annulations at the base of the internodes. These descriptions correspond to the specimens examined by the author in this study. Given the variability of the species included in the S. fusiformis / S.ellisii complex, this species was most likely misidentified as S. fusiformis . Measurements of the internodes, hydrothecae, and gonothecae ( Table 4 ) show that these specimens are much larger than S. fusiformis . The intrathecal cusps are never as well-developed as in S. fusiformis . Moreover, the hydrothecae of Sertularella pacifica sp. nov. lack the considerably swollen basal portion and strongly tapered upper portion characteristic of the fusiform hydrothecal shape, and the gonothecae are distinct from those belonging to S. fusiformis in being spindle-shaped and bent around their mid-axis.

Remarks. This material agrees with the hydroids attributed to Sertularella fusiformis ( Hincks, 1861) from the west coast of North America by Torrey (1902), and subsequently included in reports by Fraser (1911, 1937). Sertularella fusiformis is well distributed in temperate and subtropical parts of the Atlantic as well as in the Mediterranean, but records of occurrences elsewhere are few and dispersed ( Ramil et al. 1992). The latter are from the Indian Ocean coast of South Africa ( Millard 1975) and from the Pacific coast of North America: Californian Pacific coast ( Fraser 1911); off Heceta Head, Oregon ( Fraser 1937). I consider the reports of Sertularella fusiformis from the Pacific coast of North America to be erroneous. Its biogeographic distribution, and the distinct morphological characteristics of Sertularella pacifica set this species apart from its congeners. Even within the Atlantic, it is probable that the nominal species Sertularella fusiformis is part of a species complex. Sertularella fusiformis , along with S. mediterranea , S. ellisii , S. ornata , and S. polyzonias are morphologically similar and so have been variously kept separate or synonymised with other taxa ( Cornelius 1979; Ramil et al. 1992; Medel & Vervoort 1998). Millard (1958) considered S. fusiformis to be a variable species, but accepted the diagnostic value of the presence of 4 intrathecal cusps that alternate with the marginal cusps in this species, a view shared by Corrales et al. (1980). Others, such as Picard (1956) considered S. fusiformis to be an extreme, Atlantic form of S. ellisii . 16S genetic data has provided evidence that nominal species of Sertularella fusiformis from Madeira and the Azores in the North Atlantic fall into distinct clades likely corresponding to different species ( Moura et al. 2011).

Etymology. The species name refers to the Pacific Ocean and emphasizes its distinctiveness from its congeners elsewhere.

Figures

FIGURE 3. Sertularella conella, ROMIZ B 4029: (A) Branch showing hydrothecae; (B) close-up of hydrothecae; (C) gonotheca; (D) detail of gonotheca cusps. Scale bars equal 1.0 mm.

FIGURE 6. Sertularella pacifica sp. nov., ROMIZ B 4065: (A) Branch showing hydrothecae; (B) close-up of hydrotheca; (C) gonothecae. Scale bars equal 1.0 mm.

Tables

TABLE 4. Measurements of Sertularella pacifica sp. nov. and Sertularella fusiformis.

Measurements (in µm)	Sertularella fusiformis (From Ramil et al. 1992)	Sertularella pacifica sp. nov.
Axial segment (internode) length	605–720	1003–1530
Axial segment (internode) diameter	130–173	390–460
Hydrotheca, adnate part adcauline wall	288–331	550–660
Hydrotheca, free part adcauline wall	360–432	880–980
Hydrotheca, abcauline wall	560–576	1350–1410
Hydrotheca, diameter at rim	216–245	470–590
Gonotheca, maximal length	1000–1300	3730–3780
Gonotheca, maximal width	520–740	1450–1670