Sertularella asymmetra 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 : 31-32

Sertularella asymmetra Galea & Schories , sp. nov.

(Figs 6A, B; 7A; Table 6 )

Material examined. Corral, Chaihuin/Huiro, lat. -39.95000, long. -73.61667, 17.x.2011, 10 m, sample 28: a sterile colony (paratype: MHNG-INVE-86232); 03.x.2011, 10 m, sample 26: a 2.5 cm high, male colony on sponge (paratype: MHNG-INVE-86231); 27.x.2011, 10 m, sample 05: a 4.0 cm high female colony on bryozoan (holotype: MHNG-INVE-86230).

Description. Colony arising from creeping, branching, anastomosing hydrorhiza. Stems erect, up to 4 cm high, monosiphonic, spirally twisted at origin from stolon, then divided into internodes by oblique, conspicuous constrictions of the perisarc. Internodes geniculate, each bearing a latero-distal hydrotheca; length varied, though generally short, the adaxial cusp of a hydrotheca reaching or slightly surpassing the base of following hydrotheca (Fig. 6A). Side branches arising irregularly from below the base of stem hydrothecae, either laterally or slightly displaced towards the front or the rear side of the colony. Branches with the same structure as the stem, delimited from the latter by a constriction of the perisarc. Hydrothecae fusiform, adnate for about one third their adaxial length; free adaxial wall with 2–3 weak transverse ridges; abcauline wall with margin tilted conspicuously (Fig. 6B1); aperture facing upwards, composed of four triangular cusps separated by shallow embayments; operculum of four flaps; there are two latero-adaxial and one abaxial internal, submarginal cusps (Fig. 6B2). Gonothecae ovoid, walls more or less transversely ridged; male similar to female, though more slender and longer; aperture surrounded by 3–4 perisarc projections in males (Fig. 7A2), and 5 in females (Fig. 7A1); the latter producing 12–18 rounded oocytes.

Remarks. The present species is immediately distinguished through its asymmetric hydrothecae, each with a well-developed abaxial cusp, making the plane of aperture to change from perpendicular to the long axis of the theca, to oblique. Only a few congeners exhibit such a character, viz. S. africana Stechow, 1919 , S. antarctica Hartlaub, 1901b , S. fuegonensis El Beshbeeshy, 2011 , S. gaudichaudi ( Lamouroux, 1824) , S. mediterranea Hartlaub, 1901b , and S. uruguayensis Mañé-Garzón & Milstein, 1973 . Comparative measurements of all these species are given in Table 6 .

Sertularella africana appears as the closest to S. asymmetra , in having short, unbranched or sparingly branched stems and hydrothecae with “weak transverse annulations on free part of adcauline wall” ( Millard 1975). However, there are no submarginal, intrathecal perisarc projections in the hydrotheca and its gonothecae are provided with a different number of spines around the aperture. Sertularella antarctica is not only a larger species, with a characteristic habit ( Galea & Schories 2012a), but its conspicuously thickened hydrothecae are typically shifted on to the anterior side of the colonies ( Galea et al. 2009). Sertularella fuegonensis is also a much larger species, with coplanar, profusely ramified colonies, divided into moderately long internodes, each carrying a hydrotheca that is distinctly swollen adaxially, the perisarc there being devoid of corrugations (Galea 2007). Sertularella gaudichaudi builds rather tall, much and irregularly branched colonies, its internodes are long and slender, and its thin-walled hydrothecae are all shifted on to one side ( Galea & Schories 2012b). Comparison of S. asymmetra with specimens of Sertularella mediterranea from southern France showed that the latter have wider stems, as well as larger hydro- and gonothecae. Finally, a reliable comparison with S. uruguayensis is difficult to establish, due major inconsistencies between the size shown on the figure and the measurements given in the original description.

Etymology. From the Latin asymmeter (-tra, -trum), meaning asymmetric, with reference to hydrothecal aperture conspicuously tilted abaxially.

Distribution in Chile. Only known from Corral (present study).

World records. Not recorded from elsewhere.

Tables

TABLE 6. Comparative measurements (in µm) of several species morphologically related to Sertularella asymmetra sp. nov. Dimensions of hydrothecae of S. uruguayensis were recalculated from Figs 2 & 3 in Mañé-Garzón & Milstein (1973) and are given in brackets.

	Sertularella asymmetra sp. nov.	S. africana Millard, 1957	S. antarctica Hartlaub, 1901	S. fuegonensis El Beshbeeshy, 2011	S. gaudichaudi (Lamouroux, 1824)	S. mediterranea Hartlaub, 1901	S. uruguayensis Mañé-Garzón & Milstein, 1973
Reference	Present study	Millard (1957)	Galea et al. (2009)	Galea (2007)	Galea & Schories (2012b)	Ramil et al. (1992)	Mañé-Garzón & Milstein (1973)
Internodes
- length	560–730	290–790	340–640	449–646	730–1335	504–561	450–640
- diameter at node	140–230	130–200	125–205	208–230	325–350	160–230	–
Hydrotheca
- free adaxial wall	285–355	250–370	335–390	421–478	470–570	375–432	280–400 [360–385]
- adnate adaxial wall	230–280	240–320	135–245	225–309	320–375	317–360	170–270 [295–305]
- abaxial wall	535–590	470–630	390–540	506–601	705–770	590–662	450–650 [555–585]
- maximum width	250–285	250–330	275–360	309–348	–	–	270–300 [280–305]
- diameter at aperture	230–240	220–270	205–295	240–263	255–295	260–288	200–240 [210–225]
Gonotheca
- length	ca. 1695 (♀) ca. 1890 (♂)	1930–2360 (♀) ca. 1860 (♂)	1805–2205	Unknown	2500–2950 (♀)	1390–1780	Unreliable data
- width	ca. 795 (♀) ca. 710 (♂)	810–1030 (♀) ca. 830 (♂)	995–1120	Unknown	950–1180 (♀)	680–870	Unreliable data