Sertularella oblonga Galea, Häussermann & Försterra, sp. nov.

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, Revue suisse de Zoologie 124 (2), pp. 255-321: 294

publication ID 10.5281/zenodo.893519

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Sertularella oblonga Galea, Häussermann & Försterra, sp. nov.

sp. nov.

Sertularella oblonga Galea, Häussermann & Försterra, sp. nov. 

Fig. 14View Fig. 14 M-P

Holotype material: MHNG-INVE-97916; Chile, Región de Magallanes y de la Antártica Chilena, Isla Desolación, Cabo Pilar, -52.71578° -74.68245°, 10 m, coll. HSFS, HF26, lot #221; 21.09.2015; female colony composed of multiple, highly ramified stems, up to 2.8 cm high.

Diagnosis: Colonies with indistinct stems, divided subdichotomously several times. Internodes moderatelylong, slender, geniculate. Hydrothecae adnate for 2/5th, almost tubular, tapering towards aperture, indistinctly swollen adaxially, abaxial cusp produced, two lateroadaxial, internal, submarginal cusps. Gonotheca elongated-ovoid, transversely wrinkled, aperture distal, surrounded by 4 pointed cusps.

Etymology: From the Latin oblongus, -a, -um, meaning elongated, making reference to the distinctive shape of its hydrothecae.

Description: Colony bushy, composed of a bunch of stems, up to 2.8 cm high, arising from creeping stolon. Basal part of stems of varied length, provided with a number of twists above origin from stolon; remainder divided into regular internodes by means of oblique nodes sloping in alternate directions. Internodes relatively short, decidedly geniculate, with smooth, rather thin perisarc, each bearing distally a hydrotheca. Branching subdichotomous, starting among the proximal most internodes, thus making the main stems indistinct; side branches originate from below the bases of stem hydrothecae, either laterally or decidedly shifted to one side of the stem; 1-6 hydrothecae between successive side branches; occasionally, aberrant side branches are given off from within some basal stem hydrothecae; up to 5th or 6th order branching observed; tips of branchlets from various planes often form tendrils, creating anastomoses with neighboring branches; structure of branches identical to that of stem, except for the first internode that may be longer than the subsequent ones. Hydrothecae biseriate, alternately directed left and right, coplanar or nearly so; adnate for about 2/5th their length to the corresponding internode; flask shaped, slightly swollen basally, more conspicuously on adaxial side; free adcauline wall slightly sigmoid, abcauline wall nearly straight; hydrothecal margin with four unequally developed cusps: abaxial one the longest, adaxial one the shortest and conspicuously flaring, and the two laterals of intermediate length; rim not thickened; two latero-adaxial, internal, submarginal cusps; operculum composed of four triangular flaps with concentric striae. Gonothecae (only female known) arising laterally from below the hydrothecal bases; broadly ovoid, surface provided with 5-7 more or less developed wrinkles; aperture mounted on short distal collar, and surrounded by six rather short spines; embryo development in acrocysts.

Dimensions: Ordinary internodes 515-930 μm long, first internodes of side branches 715-1200 μm long; all 170-210 μm wide at nodes. Hydrothecal free adaxial length 320-345 μm, adnate adaxial length 220-230 μm, abaxial length 545-595 μm, maximum width 275- 295 μm, diameter at aperture 230-270 μm. Female gonotheca 1690-1925 μm long and 790-910 μm wide.

Remarks: The mode of branching, giving rise to three-dimensional, bushy colonies is distinctive. Its hydrothecae recall those of S. ellisii ( Deshayes & Milne-Edwards, 1836)  and S. mediterranea Hartlaub, 1901  , but the branching pattern is different in these species with otherwise much larger hydrothecae ( Ramil et al., 1992).

Distribution: Only known from Chile – Región de Magallanes y de Antártica Chilena [Isla Desolación (present study)].