Sertularella folliformis, Galea, 2016

Galea, Horia R., 2016, Notes on some sertulariid hydroids (Cnidaria: Hydrozoa) from the tropical western Pacific, with descriptions of nine new species, European Journal of Taxonomy 218, pp. 1-52 : 26-27

Sertularella folliformis sp. nov.

urn:lsid:zoobank.org:act:7A654AE7-6B4E-465C-9F5A-1D48528466E5

Fig. 8 A–G; Table 3

Diagnosis

Sertularella species with flabellate colonies; branching irregular; stem and branches strongly polysiphonic basally, grading to monosiphonic distally; internodes short, slightly geniculate to collinear; hydrothecae exceedingly long, tubular, curved downwards, with 8–10 broad, complete annuli and four internal, submarginal cusps. Gonothecae large, elongated-ovoid, distally truncate.

Etymology

From the Latin words follis, meaning bellows, and fōrma, meaning shape, with reference to the plicate condition of the hydrothecal wall, recalling the bellows of an accordion.

Material examined

Holotype

BATHUS 3 : Stn. DW 809, a 4.5 × 4.5 cm sterile colony and four smaller fragments, three of which bear one gonotheca, and the fourth two gonothecae (MNHN-IK-2012-16566).

Paratype

BATHUS 3: Stn. DW809, a few colonies and fragments, largest one 7.5 × 3.5 cm, all sterile (MNHN- IK-2012-16567).

Description

Colonies flabellate, attaining 7.5 cm high, arising from rhizoid stolons firmly attached to substrate. Branching irregular, with up to 3 rd order branches arranged roughly in one plane. Stems and side branches polysiphonic, main stem reaching as much as 2 mm wide basally. Both stem and branches divided into internodes by slightly-marked nodes slanting in alternate directions. Internodes short, slightly geniculate to collinear, each carrying a hydrotheca in its distal half. Side branches originate laterally below the bases of stem hydrothecae; first internode comparatively longer than subsequent ones. Hydrothecae exceedingly long, tubular, slightly curved downward, adnate for ¼ th or less their length, tapering imperceptibly towards aperture, walls provided with 8–10 broad, complete annuli; margin occasionally renovated; rim provided with four short cusps separated by shallow embayments; four submarginal, intrathecal projections of perisarc, two latero-adaxial and two latero-abaxial. Gonotheca originating from axil of hydrotheca, in front and/or backside of colony; elongated-ovoid, tapering abruptly below, distally truncate, wall smooth to slightly undulate.

Remarks

The hydrothecal shape is diagnostic in this species. There are few congeners which approach this condition, viz. S. catena ( Allman, 1888) and S. pseudocatena sp. nov. ( Fig. 9J), but both have much shorter hydrothecae, and their transverse ribs do not extend over the abaxial wall. Three other species, namely S. helenae Vervoort, 1993 ( Fig. 8H), S. paucicostata Vervoort, 1993 ( Fig. 8I), and S. pseudocostata Vervoort, 1993 , exhibit comparatively more prominent hydrothecal ridges. The eastern Pacific S. exilis Fraser, 1938 has isodiametric hydrothecae “regularly curved upward and then outward” ( Fraser 1938), but their surface is reportedly smooth. In addition, it is “an especially diminutive species” ( Calder et al. 2009). Sertularella whitei Rees & Vervoort, 1987 also has exceedingly long, outwardlycurved hydrothecae, but their surface is entirely smooth ( Rees & Vervoort 1987).

Geographical distribution

New Caledonia.