Halecium maximum 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 : 20-22

Halecium maximum Galea & Schories , sp. nov.

(Plate 2B; Figs 2 G, H; 3E, F; 4D; Table 4 )

Material examined. Corral, Chaihuin/Huiro, lat. -39.95000, long. -73.61667, 09.xi.2011, 10 m, sample 05: a 8 cm high, female colony (holotype: MHNG-INVE-86218); 16.xi.2011, 8‒ 10 m, sample 18: a 5.7 cm high, female colony (paratype: MHNG-INVE-86220); 30.xi.2011, 8‒ 10 m, sample 20: a 4 cm high male colony and several fragments (paratype: MHNG-INVE-86221); 30.xi.2011, 8‒ 10 m, sample 56: a 9 cm high, male colony (paratype: MHNG-INVE-86219).

Description. Colonies arising from a mass of loosely aggregated, creeping, branching stolonal fibers. Stems rather tall, up to 9 cm high (Pl. 2B), mostly monosiphonic, except for a short, basal portion invested by a reduced number of auxiliary tubes. Internodes geniculate, of moderate length, delimited by oblique nodes; there are slight bulges at both ends of each internode, as well as a well-developed, latero-distal hydrophore, greatly surpassing the level of distal node, and provided with a conspicuous pseudodiaphragm on its adaxial side ( Fig. 2 G). Hydrothecae very deep, with everted margins; renovations present ( Fig. 2 H). Branches arising singly from the primary hydrophores ( Fig. 2 G). Largest branches given off irregularly and in all directions, while comparatively shorter branchlets, of no more than 3–5 internodes, are given off from every single hydrophore, and appear arranged on all sides of the stem and branches. Gonothecae large, lenticular, tapering abruptly basally into short pedicels; male (Fig. 3F) similar to female (Fig. 3E), both provided with an aperture, the latter notched in female (Fig. 3E1, 3, 4). Cnidome ( Fig. 4D ): small (ca. 4.6 × 1.7 µm) and large (ca. 8.3 × 2.9 µm) heteronemes (none seen discharged), as well as microbasic mastigophores (ca. 6.0 × 1.7 µm).

Remarks. This species superficially resembles the following one, and their differences are listed under the latter.

Female gonothecae with a similar shape were found previously in specimens from Tristan da Cunha examined by one of us (see Galea 2010b, Halecium ? delicatulum Coughtrey, 1876 , morphotype 2). Consequently, a comparison between the two sets of collection materials, as well as with the other species of Halecium discussed herein, was found necessary. The Tristan da Cunha specimens are mainly characterized by their nearly straight stems and side branches, with almost collinear internodes, and by their unusual, exceedingly long primary hydrophores. Although most of its hydranths were shed, a closer inspection of the available material (part of NHM 2009.18) revealed the remains of a couple of polyps. These were used to analyze the cnidome composition ( Fig. 4E ), which showed, besides the common spindle shaped microbasic mastigophores, the presence of a peculiar, large nematocyst [(10.9–12.3) × (5.5–5.7) µm] with a long, coiled shaft, apparently making more than a complete turn inside the capsule. The sole (partly?) discharged capsule exhibited a shaft whose length exceeded that of the capsule itself. Taken together, these differences with the related congeners prompted the first author of the present study to introduce the new name, Halecium tristaniensis 13 Galea, sp. nov., in order to distinguish this species from its relatives.

Etymology. From the Latin maximus (-a, -um), used with the meaning “the largest”, to show its size difference with the following species.

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

Figures

FIGURE 2. A, B: Halecium flexile Allman, 1888 — portion of stem (A) compared with H. balei Fraser, 1911 (C); detail of hydrophore and renovated hydrotheca (B), and comparison with H. balei (D). E, F: Halecium humeriformis sp. nov. — stem fragments (E); hydrophore and renovated hydrotheca (F). G, H: Halecium maximum sp. nov. — stem fragments (G); hydrophore and renovated hydrotheca (H). I ‒ L: Halecium modestum sp. nov. — stem fragments (I ‒ K); hydrophore with hydrotheca (L). M, N: Halecium platythecum sp. nov. — stem fragment (M); hydrophore and renovated hydrotheca (N). Scale bars: 300 µm (B, D, F, H, L, N) and 1 mm (A, C, E, G, I ‒ K, M).

FIGURE 4. A ‒ F, M: Cnidomes of some Halecium species discussed herein— H. flexile Allman, 1888 (A); H. balei (B); H. humeriformis sp. nov. (C); H. maximum sp. nov. (D); H. tristaniensis sp. nov. (E); H. modestum sp. nov. (F). G: Halecium pallens Jäderholm, 1904 — female gonotheca. H ‒ M: Halecium tehuelchum (d’Orbigny, 1842) — fragments of colonies (H), primary hydrophore and renovated hydrotheca (I); female gonotheca (J) and shape variation (K); male gonothecae (L); cnidome (M). Scale bars: 10 µm (A ‒ F, M); 300 µm (I, J, L), 500 µm (G, K), 1 mm (H).