Sertularella juanfernandezensis Horia R. Galea & Dirk Schories & Verena Häussermann & Günter Försterra 2017, sp. nov.
Creators: name: Horia R. Galea
name: Dirk Schories
name: Verena Häussermann
name: Günter Försterra
Publisher: name: Zenodo
Year: 2017
Subjects: Biodiversity
Taxonomy
Animalia
Cnidaria
Hydrozoa
Leptothecata
Sertulariidae
Sertularella
Sertularella juanfernandezensis

description: Sertularella juanfernandezensis Galea, sp. nov.
Figs 12C, 13E, F, H, I; Table 14
Sertularella polyzonias. – p.p. Jäderholm, 1910: 4. – p.p. Hartlaub, 1905: 655 [non Sertularella polyzonias (Linnaeus, 1758)].
Holotype material: SMNH 123883; Chile, Juan Fernández archipelago, 35 m, Swedish Magellanic Expedition 1907-1909, coll. C. Skottsberg; 24.08.1908; microslide (Fig. 12C) with three colony fragments 7-20 mm long, the largest bearing 4 gonothecae, the smallest unbranched, and the remaining two provided with two side branches each [material identified by Jäderholm (1910) as S. polyzonias (Linnaeus, 1758)].
Paratype material: ZMB Cni4421; Chile, Juan Fernández archipelago; coll. Plate, det. Hartlaub (1905, as S. polyzonias); a 3.8 cm high colony represented by a single, ramified, sterile stem.
Comparison material: HRG-0550; France, Brittany, depth unrecorded, coll. F. Ziemski; (day and month unavailable) 2011; numerous sterile, unbranched or sparingly-branched stems and fragments, up to 4.5 cm high, of S. polyzonias.
Diagnosis: Erect, coplanar colonies with monosiphonic, irregularly pinnate stems; internodes moderatelylong, slightly geniculate; hydrothecae flask-shaped, decidedly facing outwards, adnate for half their length, free adaxial wall convex; gonothecae broadly ovoid, transversely wrinkled, aperture mounted on constricted neck region, surrounded by 4 blunt spines.
Etymology: Named after its (presently known) area of occurrence.
Description: Colonies erect (though flaccid when out of liquid), up to 3.8 cm high, arising from creeping, branching stolon. Stems monosiphonic, unbranched; basal part of varied length (ca. 1.5 cm long in paratype) and ahydrothecate; above, divided into moderatelylong, slightly geniculate internodes by means of oblique constrictions of the perisarc slanting in alternate directions; one hydrotheca confined to the distal end of each internode; side branches arising generally singly (occasionally in pairs) immediately below the base of a hydrotheca, either laterally or slightly shifted on to the front of stem, giving the colony a globally planar appearance; there are no distinct apophyses supporting the branches; 1-4 hydrothecae between successive side branches; branches not strictly alternate, several successive ones may be given off on same side of the stem; up to 2nd order branches observed; first internode comparatively longer than subsequent ones; remainder with structure similar to that of stem. Hydrothecae biseriate, alternate, flask-shaped, smooth-walled, adnate for half their length to the corresponding internode, with distinct outward bend; free adaxial wall convex for most of its length, slightly upturned distally; abaxial wall concave for 3/4th its length, and distinctly convex below aperture; rim tilted away from stem/branches, and provided with 4 pointed, triangular cusps separated by moderately-deep embayments; a four-flapped operculum; three conspicuous internal, submarginal, lamellar projections of the perisarc, one abaxial and two latero-adaxial, the latter could be absent in distalmost, hence youngest, hydrothecae. Gonothecae arising laterally from the internodes, a short distance below the hydrothecal bases; broadly ovoid, transversely wrinkled (up to 6 distinct ridges in upper 2/3rd), tapering below into short, indistinct pedicel, distally bearing a constricted neck region on the top of which is found the aperture surrounded by 4 short, blunt spines; sex could not be ascertained, although a single, ovoid, central mass is carried on by the blastostyle.
Dimensions: See Table 14.
Remarks: This species has been incorrectly assigned to Sertularella polyzonias (Linnaeus, 1758) by both Hartlaub (1905) and Jäderholm (1910). Its morphological differences with the Linnean species are easily noted by comparing Fig. 13E, F and 13G, and Fig. 13H, I and 13J, respectively.
The hydrothecae of S. juanfernandezensis are very similar to those of a number of congeners, notably: 1) S. arbuscula (Lamouroux, 1816), but this species possesses very short internodes (Millard, 1957), and its gonothecae are fusiform and, most often, smoothwalled (Millard 1975); 2) S. crassiuscula Bale, 1924, but this species has comparatively smaller hydrothecae, its internodes are very short, and its gonothecae are large and devoid of the distinctly constricted neck region met with in the present species (Bale, 1924; Ralph, 1961); 3) S. falsa Millard, 1957, but this species has relatively short internodes, there are 4 submarginal, intrathecal projections of the perisarc alternating with the hydrothecal cusps, and its gonothecae are spindle-shaped (Millard, 1957).
Distribution: Only known from Chile – Juan Fernandez archipelago (Hartlaub, 1905; Jäderholm, 1910).
description: Published as part of Horia R. Galea, Dirk Schories, Verena Häussermann & Günter Försterra, 2017, Taxonomic revision of the genus Sertularella (Cnidaria: Hydrozoa) from southern South America and the subantarctic, with descriptions of five new species, pp. 255-321 in Revue suisse de Zoologie 124 (2) on pages 285-288, DOI: 10.5281/zenodo.893519