Sertularella coronata Choong, 2015, sp. nov.

Sertularella coronata sp. nov.

(Figure 4)

Sertularella tenella — Fraser, 1937:158, pl. 36, fig. 190 [not Sertularella tenella Alder, 1856] Material. Holotype: CANADA: British Columbia. Off Clayoquot Sound. 16. v.1934, short hydrocauli on worm tube, hydroid hydrocaulus fragment, hydrocauli with gonothecae, ROMIZ B4056. Paratypes: CANADA: British Columbia. Tow Hill locality, north-east of Graham Island, 54˚05’00”N, 131˚48’00”W, 10. vii.1960, 45.7 meters, coll. D.B. Quayle, short hydrocaulus on hydroid stem and part of stoloniferous colony, without gonothecae, ROMIZ B4057; CANADA: British Columbia. 54˚12’18”N, 131˚27’36”W, 26.iv.1961, 21.9 meters, coll. D.B. Quayle, erect colonies developing from stolon, epizoic on Abietinaria thuiarioides (Clark, 1877) stem, without gonothecae, ROMIZ B4058. Other material: CANADA: British Columbia. West of Flores Island, 49˚19’45”N, 126˚21’45”W, 16. v.1934, 50 meters, sections of hydrocauli, without gonothecae, ROMIZ B4059. CANADA: British Columbia. West of Estevan Point, 49˚22’09”N, 126˚54’15”W, 12. vii.1934, 75–90 meters stoloniferous colony with pedicellate hydrothecae and erect hydrocaulus on worm tube, without gonothecae, ROMIZ B4060. CANADA: British Columbia. Tow Hill locality, North-east of Graham Island, 54˚05’00”N, 131˚48’00”W, 10. vii.1960, 45.7 meters, coll. D.B. Quayle, on Symplectoscyphus turgidus (Trask, 1857), without gonothecae, ROMIZ B4061. CANADA: British Columbia. Tow Hill locality, North-east of Graham Island, 54˚05’00”N, 131˚48’00”W, 10. vii.1960, 45.7 meters, coll. D.B. Quayle, short hydrocauli on hydroid hydrocaulus, without gonothecae, ROMIZ B4062. CANADA: British Columbia. 54˚06’54”N, 132˚57’00”W, 0 4. v.1961, 23.8 meters, coll. D.B. Quayle, stoloniferous colony and erect hydrocauli on Bryozoa (Bugula sp), without gonothecae, ROMIZ B3937. CANADA: British Columbia. 54˚07’00”N, 132˚06’42”W, 0 4. v.1961, 18.3 meters, coll. D.B. Quayle, part of stoloniferous colony and single polyp, pedicellate form, without gonothecae, ROMIZ B3936. CANADA: British Columbia. 48˚43’00”N, 123˚26’30”W, 13. v.1961, 51.2 meters, coll. D.B. Quayle, section of hydrocaulus, without gonothecae, ROMIZ B4063.

Reported distribution. Pacific coast of North America off Vancouver Island as Sertularella tenella (Fraser 1937).

Description. Colony dense, monosiphonic, creeping tubiform stolon, hydrocauli moderately to strongly geniculate, flexuose, irregularly branched, up to 25 mm. Reptant on worm tube or other hydroid stems. Internodes oblique and opposite, length variable; long and short internodes in same colony. Perisarc thickened throughout. Hydrothecae alternate, distant, one per internode, distal on internode, less than ¼ adnate, basal portion asymmetrically swollen on abcauline side, free adcauline side almost straight or slightly curved outwards towards abcauline side; narrowing distally towards aperture. Hydrothecal walls with 3–4 strong annulations; annulations complete, occasionally creased, giving appearance of folds, distal portion of hydrotheca smooth. Hydrothecal rim 4-cusped; cusps very well-developed, sinus deep, four triangular opercular flaps forming peak extending past opening. Reduplication of margin present. Intrathecal cusps not present.

Gonothecae large, ovate-elongate, widest basally before tapering towards aperture, arising directly from internode, one per internode, 4–5 medium to large cusps, blunt, some folded inward. No neck. Gonothecal body distally strongly annulated; annulations rounded to cresting, annulations cover almost entire body, widening towards bottom, basally may appear smooth.

Differential diagnosis. Sertularella coronata sp. nov. resembles the specimens recorded by Fraser (1937) as Sertularella tenella, which show the marked narrowing of the hydrothecae towards the aperture, along with the distinctive curve of the distal part of the abcauline wall resulting in a forward bend. However, the hydrothecae of S.tenella Alder 1856 are barrel-shaped and lack the characteristic abcauline bend present in S. coronata. Furthermore, the marked thickening of the perisarc in the specimens examined in this study is seldom present in S. tenella, although perisarc can be moderately thick basally, thin distally (Calder & Vervoort 1998). Another character distinguishing S. coronata from S. tenella is the internode length. While there is some overlap in internode length between the two species, there is considerable variation within a single S. coronata colony; internode length can be both shorter and longer than in S. tenella. The hydrocauli with shorter internodes can resemble those of S. rugosa (Linnaeus, 1758) as the hydrothecae are more closely bunched together. The hydrothecae occasionally approach the S. rugosa shape, but with deeper sinuses. Characters distinguishing S. coronata from its congeners are also apparent in its gonothecae, which are up to twice the length of those belonging to S. robusta and three times the length of the gonothecae of S. tenella. The gonothecal cusps of S. coronata are larger and more prominent than those of either S. tenella or S. robusta. Table 2 summarizes the morphological differences between S. coronata and its congeners.

Remarks. Biogeographic separation also supports the exclusion of Sertularella coronata from its congeners. Both Sertularella tenella and S. robusta are typically boreal species (Calder 2012). Although S. tenella is considered nearly cosmopolitan, it is predominantly found in the northern hemisphere (Schuchert 2001; Vervoort 1993). It has been reported from the Atlantic Ocean along European coasts (Calder 2012; Cornelius 1995; Schuchert 2001); Barents Sea, Bering Sea, Sea of Okhotsk (Naumov 1969). Naumov (1969) recorded it for the first time in Russian Far Eastern seas, but did not regard it as being common. Calder (1970) reported it from Hudson Bay, but it was not widespread in the Canadian Arctic (D. R. Calder, Royal Ontario Museum, Toronto, Ontario, Canada, pers. comm., July 2014). Fraser (1944) reported the species from Atlantic coast of North America extending to the Gulf of Mexico. In the western Pacific region, S. tenella has been recorded from Japan (Hirohito 1995; Yamada 1959). However, the occurrence of S. tenella off the west coast of North America requires further confirmation. Cornelius (1979) included a putative specimen of S. tenella from Dodd Narrows, Vancouver Island, Canada, but restricted the distribution of S. tenella to the northern hemisphere.

Etymology. The species name is derived from the Latin corona (crown), referring to the appearance of the prominent cusps and four triangular opercular flaps extending past the opercular opening.

*Material examined: ROMIZ B3881; **From Vervoort (1946); ***From Schuchert (2001); ****From Cornelius (1979)