Sertularella tubulosa, 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 : 40

Sertularella tubulosa sp. nov.

urn:lsid:zoobank.org:act:8D56454C-7B2C-451C-BFB2-9C42603F3005

Fig. 9 U–X; Table 6

Diagnosis

Sertularella with lightly polysiphonic, irregularly and sparsely ramified stems; internodes moderately long, geniculate; hydrothecae exceedingly long, tubular, isodiametric throughout, walls entirely smooth; four small marginal cusps, and four submarginal, intrathecal projections of perisarc. Gonothecae unknown.

Etymology

The specific name is derived from the Latin tŭbŭlus, -i, meaning tube, and describes the shape of the hydrotheca.

Material examined

Holotype

BATHUS 3: Stn. DW 810, single, sterile, branched stem, 2.6 cm high, lightly fascicled basally, but devoid of hydrorhiza (MNHN-IK-2012-16591).

Description

The colony, devoid of hydrorhiza, is composed of a single stem, 2.6 cm high, giving rise to a side branch towards its middle. Perisarc thick basally, thinning out gradually towards tip of colony. Basal part of stem ahydrothecate, overgrown by a few accessory tubes; upper and longest part divided into regular internodes by oblique constrictions of the perisarc slanting in alternate directions. Internodes moderately long, geniculate, widening distally so as to accommodate a hydrotheca. The single side branch originates laterally from below a stem hydrotheca; first internode comparatively longer than subsequent ones; the latter with same structure as the stem. Hydrothecae angled at 40–45° with the stem; long, tubular, isodiametric throughout, adnate for about ¼ their length; free adaxial wall nearly straight and smooth; abaxial wall basally convex, becoming rapidly straight for most of its length; basal foramen wide; aperture squared in frontal view, with four inconspicuous marginal cusps separated by shallow embayments; four intrathecal, submarginal cusps: two latero-adaxial and two latero-abaxial; margin often renovated in damaged hydrothecae. Gonothecae unknown.

Remarks

The characteristic tubular shape of the hydrothecae of this species is diagnostic. Tubular, smooth-walled hydrothecae are only encountered in a few congeners that can be distinguished from the new species on the following accounts: 1) the hydrothecae of S. billardi Vervoort, 1993 have a comparatively lower length/width ratio of the hydrothecae ( Vervoort 1993); 2) S. exilis Fraser, 1938 has typically curved hydrothecae ( Fraser 1938), and the species is minute ( Calder et al. 2009); 3) S. vervoorti El Beshbeeshy, 2011 possesses huge hydrothecae, whose length/width ratio is lower than in S. tubulosa sp. nov. ( El Beshbeeshy 2011); 4) in S. whitei the hydrothecae originate at a more acute angle with the axis of internode, are smaller, curve slightly outwards, and the stem internodes are longer and more slender than in the present species ( Rees & Vervoort 1987).

Geographical distribution

New Caledonia.