Sertularella curta Galea & Schories

Galea, Horia R., Schories, Dirk, Försterra, Günter & Häussermann, Verena, 2014, New species and new records of hydroids (Cnidaria: Hydrozoa) from Chile, Zootaxa 3852 (1), pp. 1-50 : 34-35

Sertularella curta Galea & Schories , sp. nov.

(Figs 6D, E; 7C; Table 7 )

Sertularella geniculata ― Leloup, 1974: 28, Fig. 23.

not Sertularella geniculata Hincks, 1874: 152 , pl. 7 Figs 13, 14.

Material examined. Taltal, lat. -25.38333, long. -70.51667, 24.iv.2012, 12‒ 20 m, sample 24: 1.8 cm high, male colony on barnacle covered with bryozoan (holotype: MHNG-INVE-86236). Taltal, lat. -25.38333, long. - 70.46667, 22.iv.2012, 12‒ 20 m, sample 25: a 1.6 cm high male colony on bryozoan (paratype: MHNG-INVE- 86237).

Description. Colonies arising from creeping, branching stolon. Stems erect, monosiphonic; basal part very short and devoid of hydrothecae, perisarc smooth or with up to 4 annuli; remainder of stem slightly geniculate, divided into internodes by oblique, inconspicuous constrictions of the perisarc; internodes short, each carrying a latero-distal hydrotheca; adaxial cusp of a hydrotheca generally surpassing base of following hydrotheca. Side branches, when present (up to 3), short (composed of up to 17 hydrothecae) given off irregularly, generally from below a stem hydrotheca, either in front or the rear side of the colony (Fig. 6D); occasionally arising from within a stem hydrotheca; up to second order branching could be observed. Hydrothecae alternate, fusiform, adnate for about two thirds their adaxial length; free adaxial wall with about 3 ridges prolonged abaxially, better seen in cleaned hydrothecae (Fig. 6E1); abcauline wall slightly concave, aperture expanding below rim, and perpendicular to long axis of theca; margin with four triangular cusps separated by rounded, moderately deep embayments; operculum composed of four triangular flaps meeting centrally to form a pyramidal roof; there are three internal, submarginal projections of perisarc (2 latero-adaxial and one abaxial), occasionally less noticeable (Fig. 6E2). Gonothecae, male in present material (Fig. 7C), up to 3 per stem, ovoid-fusiform, ringed transversally (6–7 ribs), aperture provided invariably with 4 perisarc projections.

Remarks. We have no hesitation in including in the synonymy of this species the Chilean record by Leloup (1974) assigned to S. geniculata Hincks, 1874 [now recognized as a synonym of S. tenella (Alder, 1856 18), see Cornelius (1979)]. Northern records of S. tenella (e.g. Jäderholm 1909, Calder 1970, Schuchert 2001) describe and depict a species with long, more or less geniculate internodes and hydrothecal walls provided “with 3–6 annulations […] usually complete and conspicuous” ( Cornelius 1995b).

The characteristic shape of the hydrothecae of S. curta recalls those of S. catena ( Allman, 1888) , S. integra Allman, 1876 , S. jorgensis El Beshbeeshy, 2011 , S. pulchra Stechow, 1923 , and S. undulitheca Vervoort, 1959 . The comparative measurements of these species are summarized in Table 7 .

Sertularella catena builds irregularly branched colonies, with polysiphonic stems and strongly geniculate, moderately long internodes; its hydrothecae are large and tubular, with parallel walls, and their free adaxial side is provided with more numerous wrinkles; in addition, its almost smooth-walled gonothecae are provided distally with only two poorly-developed processes flanking the aperture ( Allman 1888, Nutting 1904).

Unlike S. curta , the hydrothecae of S. integra are much bigger and are provided with more numerous (4–8 vs. 2–3) and conspicuous adaxial ridges. In addition, their gonothecae may be almost twice as big as those of S. curta ( Ralph 1961, Vervoort & Watson 2003).

The small, sparingly branched colonies of S. jorgensis have characteristically long, slender internodes, and its hydrothecae have a smaller length/width ratio than those of S. curta , and are devoid of internal, submarginal cusps ( El Beshbeeshy 2011).

The hydrothecae of the new species also recall those figured by Millard (1964) for S. pulchra Stechow, 1923 , but the latter has polysiphonic stems bearing alternate hydrocladia, and its hydro- and gonothecae are much bigger.

Sertularella undulitheca has comparatively longer and wider hydrothecae, provided with 6–10 undulations on their free adaxial walls, and the gonothecae possess about 18 transverse ridges ( Vervoort 1959).

Etymology. From the Latin curtus (-a, -um), meaning short, thus characterizing the length of internodes.

Distribution in Chile. Tocopilla ( Leloup 1974), Taltal (present record).

World records. Not known from elsewhere.

Tables

TABLE 7. Measurements (in µm) of Sertularella curta sp. nov. and comparison with related species.

	Sertularella curta sp. nov.	S. integra Allman, 1876	S. jorgensis El Beshbeeshy, 2011	S. pulchra Stechow, 1923	S. undulitheca Vervoort, 1959
Reference	Present study	Vervoort & Watson (2003)	El Beshbeeshy (2011)	Millard (1964)	Vervoort (1959)
Internodes
- length	340–490	990–1405	686–1189	430–820	870–1040
- diameter at node	170–210	160–215	110–133	200–420	250–290
Hydrotheca
- free adaxial wall	345–380	605–625	295–353	360–460	700–720
- adnate adaxial wall	230–270	345–395	203–237	320–460	300–310
- abaxial wall	485–515	805–815	434–469	580–780	670–680
- maximum width	250–270	345–395	–	290–380	370–400
- diameter at aperture	210–230	230–265	203–214	210–280	240–260
Gonotheca
- length	1440–1660 (♂)	2475–3125	Unknown	2950–3420	2000
- width	575–620 (♂)	1140–1200	Unknown	990–1630	950