Sertularella contorta Kirchenpauer, 1884

Peña Cantero, Álvaro L., 2022, On a few benthic hydroids (Cnidaria, Hydrozoa) from the Kerguelen Islands (southern Indian Ocean), including the description of a new species, Zootaxa 5165 (2), pp. 274-286 : 282-285

Sertularella contorta Kirchenpauer, 1884

( Fig. 4E–H )

Sertularella contorta .— Galea et al. 2017: 268–271 , figs 1E–G, 6, 7A–H.

? Sertularella lagena Allman, 1876: 114 ; 1879: 283, text-fig.— Stechow, 1925: 475, fig. 34.

Sertularella polyzonias .— Vanhöffen, 1910: 322 (in part).

Material examined. PROTEKER 2: Baie Accessible, two masses of stems, with gonothecae ( MNHN IK –2012– 10429). PROTEKER 3: Ile Suhn, several stems up to 80 mm high, with gonothecae, on Macrocystis ( MNHN IK –2012–10424) and many stems, up to 30 mm high, with gonothecae, densely growing on Macrocystis ( MNHN IK –2012–10425).

Description. Stems monosiphonic with up to five basal annulations following the short stolonal apophyses. First annulation roughly transverse, the remaining rings distally ever more oblique.

Branching generally alternate with no defined pattern. Branches up to third order observed. Branches usually originating frontally below a hydrotheca.

Stem divided into short internodes arranged in a zigzag pattern. First branch internode of similar development. Internodes with a conspicuous basal swelling or “bourrelet” on hydrothecal side.

Basal part of branches with an annulation formed by the apophysis giving rise to the branch, the basal swelling of the first hydrothecal internode and a ring (occasionally a few more) in between.

Hydrothecae alternately arranged in two planes, usually making a very open angle, but sometimes either almost making a right angle or placed in the same plane.

Hydrotheca adnate over one third of its adcauline length ( Fig. 4E–H ).Abcauline wall straight or slightly convex for most of its length, but curving outwards near the opening, making it concave ( Fig. 4E–H ). Free adcauline wall sigmoid, convex for most of its length, then concave below the aperture ( Fig. 4E–H ). Concave portion below the aperture of both adcauline and abcauline walls giving the appearance of a kind of neck. Rim with thickened perisarc, forming a sort of collar ( Fig. 4E, H ). Hydrothecal aperture with four cusps, abcauline one distinctly longer ( Fig. 4E, G ).

Some polyps with a kind of short tentacles on their basal abcauline part ( Fig. 4H ).

Gonothecae with two to four distal blunt cusps. Wall undulated at distal 1/2–2/3.

Measurements (in µm). MNHN IK–2012–10429. Internodes: length 940–1100, diameter at hydrothecal base 420–440. Hydrothecae: length of abcauline wall 730–760, length free part of adcauline wall 490–500, length adnate part of adcauline wall 220–300, length adcauline wall 720–790, diameter at aperture 300–320. Gonothecae: length 1700, maximum diameter 900. Cnidome: microbasic mastigophores, range 5.8–6.5 x 1.7–2.0.

MNHN IK-2012-10424. Internodes: length 970–1600, diameter at hydrothecal base 460–490. Hydrothecae: length of abcauline wall 690–780, length free part of adcauline wall 510–600, length adnate part of adcauline wall 290–300, length adcauline wall 810, diameter at aperture 280–320, maximum diameter 360–410. Gonothecae: length 2200–2260, maximum diameter 1000–1300. Cnidome: microbasic mastigophores, range 6.5–7.0 x 2.0.

MNHN IK-2012-10425. Internodes: length 900–1200, diameter at hydrothecal base 500–530. Hydrothecae: length of abcauline wall 610, length free part of adcauline wall 500, length adnate part of adcauline wall 250, length adcauline wall 750, diameter at aperture 340, maximum diameter 440. Gonothecae: length 2200, maximum diameter 1000–1200. Cnidome: microbasic mastigophores, range 6.0–6.5 x 1.5–1.7.

Remarks. Several species of Sertularella have been reported from Kerguelen. Allman (1876) poorly described three new species from the area, Sertularella kerguelensis Allman, 1876 , Sertularella unilateralis Allman, 1876 and Sertularella lagena Allman, 1876 , the first two found again by Studer (1879). Allman (1888) described another new species from this region, Sertularella secunda ( Allman, 1888) . Posteriorly, Vanhöffen (1910) reported Sertularella polyzonias ( Linnaeus, 1758) , Stechow (1925) S. lagena, Naumov & Stepanjants (1962) S. polyzonias and Millard (1977) Sertularella picta ( Meyen, 1834) . Galea et al. (2017), in their revision of the genus from southern South America and the sub-Antarctic, considered those records belonging to Sertularella allmani Hartlaub, 1901 , Sertularella antarctica Hartlaub, 1901 , Sertularella contorta Kirchenpauer, 1884 or Sertularella gaudichaudi ( Lamouroux, 1824) ( S. kerguelensis and S. lagena were considered nomina dubia).

I have assigned the present material to Sertularella contorta with which it agrees the most, following the concept of the species by Galea et al. (2017), although it should be noted that they were unable to find, and therefore examine, type material of this species.

The material studied here shares with Sertularella contorta the shape and size of the hydrothecae and internodes. According to Galea et al. (2017), the hydrothecae expand below the rim on both ab- and adcauline sides, which is also characteristic of the present material. In some material (MNHN IK–2012–10425) there are stout hydrothecae ( Fig. 4F ), as also depicted by Galea et al. (2017: fig. 6I), together with typical ones.

Even when the general branching is alternate, there are numerous exceptions, much more so in the lower-order branches. As an example of branching, a stem (MNHN IK–2012–10429) with an alternate pattern was unbranched until its 10 th and 11 th internodes, with branches arranged alternately in two planes, making an acute angle. The stem alternately branches again at its 18 th, 21 st and 24 th internodes and successively at its 27 th, 28 th, 29 th and 30 th, but with exceptions (i.e. two branches on the same side). The primary branches also give rise to secondary branches alternately, starting at their 5 th or 6 th internode, but apparently without following a clear pattern (sometimes there are two hydrothecae in between, sometimes none).

In another stem (MNHN IK–2012–10425), branching is alternate at the 2 nd, 3 rd and 4 th internodes, then on the same side (that of the 4 th internode) at the 6 th, and then on the opposite side at the 8 th, 10 th and 12 th (i.e. there is a hydrotheca in between). Subsequently, it changes again to the opposite side at its 13 th and 15 th internodes.

In other material (MNHN IK–2012–10424) the profuse branching is best considered as irregular in several planes. The tendency to form two planes increases distally and the third-order branches are usually those forming an acute angle. In some places, subopposite pairs in more or less two planes are found; in others, branches are directed to the same side with one hydrotheca in between.

The branching in the present material, as shown in the examples above, has nothing to do with the apparently more or less regular pinnate pattern described by Galea et al. (2017: 268), “with generally every two consecutive apophysis-bearing internodes separated by a couple of internodes not supporting side branches”. These authors, however, also described exceptions.

The other noticeable difference is the absence of the three internal hydrothecal cusps that characterised the species according to Galea et al. (2017). Nonetheless, these authors also indicated that they may be absent.

Even when Galea et al. (2017) indicated that the lateral cusps of the hydrothecal aperture are asymmetrical, I believe they are not. It is just a question of perspective. When observed from a perfect side view it is evident that they are equally developed.

Ecology and distribution. Sertularella contorta was collected at depths between 14 and 48 m off Suhm Island and from Accessible Bay, on Macrocystis ; gonothecae in December.

Figures

FIGURE 4. Campanularia sp.: A–B, hydrothecae; C, hydrothecal distal part showing cusps; D, distal part of pedicel, basal spherule and hydrothecal basal part. Sertularella contorta Kirchenpauer, 1884: E–F, hydrothecae; G, hydrotheca and basal part of branch; H, hydrotheca showing polyp and location of basal ‘tentacles’ (close-up showing tentacles). Scale bar: 200 µm (A, B, E–H), 100 µm (C, D).