Halopteris schucherti, Galea, 2006

Galea, Horia R., 2006, On two new species of Halopteris Allman, 1877 (Cnidaria: Hydrozoa) from Chile, Zootaxa 1165 (1), pp. 57-68 : 63-68

Halopteris schucherti sp. nov.

( Figs. 6–12 ; Tables 3–4)

Type material

Holotype: MHNG INVE 35930 , several cormoids from a single colony, 3–7.5 cm high, with many gonothecae. Chile, fjord Comau , Punta Huinay, 42°22’47.0’’S, 72°25’68.4’’W, depth 26.5 m, 9 March 2004.

Description

Colony comprising many delicate plumes up to 7.5 cm high, arising from reticular hydrorhiza. Hydrocauli upright, monosiphonic, unbranched, straight basally, slightly flexuose distally, composed of basal part formed by variable number of segments (up to three) separated by transverse nodes, with scattered frontal nematothecae, separated by the remainder of stem by oblique node; basal part of caulus devoid of hydrothecae and hydrocladia; caulus above basal part homomerously segmented into repeats by oblique nodes. Each segment with one hydrotheca, a lateral apophysis, and 10–11 nematothecae. Apophysis alternately directed left and right, supporting hydrocladia, without nematothecae. Hydrothecae on proximal part of each segment, not strictly collinear, but slightly displaced towards corresponding hydrocladial apophysis. Hydrothecae cupshaped, rim circular, straight. Abcauline and adcauline walls rather straight in side view, almost parallel, slightly converging downwards. Adcauline wall adnate for about half its length. Angle of opening with cauline axis 40 to 45°. Cauline nematothecae: one median inferior, two laterals and 6–8 above hydrotheca. Median inferior nematotheca situated far below hydrotheca, attached to frontal side of caulus. Nematotheca short, conical, wall of upper chamber much lower on adcauline side. Lateral nematothecae not reaching hydrothecal rim, placed on opposite side of caulus on small apophyses adnate to hydrotheca. Nematotheca conical in shape, wall of upper chamber straight, rim lower on adaxial side down to half height. One nematotheca behind adcauline wall of hydrotheca, distal to axil and projecting above hydrothecal rim. Distal to this are 6–7 nematothecae similar in shape, either in median axis of caulus or displaced laterally, singly or in pairs. Nematothecae conical, rim scooped on adcauline side, basal chamber longer than distal one. All cauline nematothecae bithalamic and movable with exception of median inferior one. Hydrocladia thin, alternate, up to 29 per side of plume. Branching of hydrocladia present in some colonies, branches arising from internode beside hydrotheca. Some cladia with up to eight first order lateral branches, alternating in opposite directions. Branches similar in structure to cladia. The most proximal cladia may be paired and therefore opposite; in some cormoids, up to five of the lowest cladial pairs may be opposite. First hydrocladial segment short, rectangular, both ends delimited by transverse nodes; one nematotheca on upper side. Next segment much longer, with 4 frontal nematothecae in one row, ending in oblique node. Remaining part of hydrocladium homomerously segmented by oblique nodes; with up to 12 hydrothecae per cladium. In some parts of the hydrocladia, there are transverse nodes which subdivide repeatedly (1–2 transverse nodes per repeat); their position is inconstant. Hydrocladial segments with one hydrotheca and 7–8 nematothecae. Hydrothecae borne in proximal part of cladial segments; cup­shaped, abcauline wall rather straight in side view, aperture circular, rim smooth, non­everted. Adcauline wall adnate for about half its length and with slight concavity in upper half. Angle of opening with hydrocladial axis 30 to 40°. Hydrocladial nematothecae: one median inferior, two laterals, and 4–5 above hydrotheca. Median inferior nematotheca strongly attached to internode, not reaching hydrothecal base; cone­shaped, adaxial wall deeply scooped to bottom of superior chamber. Lateral nematothecae placed on distinct apophyses adnate to hydrotheca, not overtopping hydrothecal rim; conical in shape, walls straight, distal chamber with scooped wall facing hydrotheca. Similarly to caulus, there is one nematotheca behind the adcauline wall of hydrotheca, distal to axil, overtopping the hydrothecal rim. Distal to this, 3–4 (exceptionally five) similar nematothecae, in one row, on upper side of hydrocladia; all these nematothecae conical, basal chamber longer than distal one, rim of superior chamber lower on adcauline side to half height. All cladial nematothecae bithalamic and movable with exception of median inferior nematotheca. Morphometric data of H. schucherti are given in table 3.

Colonies dioecious; both male and female gonothecae on caulus and cladia, most frequently in middle and upper parts of cormoid. Gonothecae arising laterally below hydrothecae. There may be up to two opposite gonothecae associated to one hydrotheca. Female gonotheca ovate, longitudinal axis S­shaped. Distal end truncated transversely and provided with circular operculum; proximal end tapering towards base. An internal septum in lower part, with thickened lateral walls. Pedicel of two short quadrangular segments, a hinge joint between gonothecal base and pedicel; gonotheca movable. Below septum, two nematothecae on curved basal part; all nematothecae two­chambered, movable, with scooped wall on adaxial side of upper chamber. Gonotheca containing one or two planulae. Male gonotheca ovate in shape, tapering toward base. With internal septum in lower part, two nematothecae similar to those of female gonotheca below this, and a pedicel of two short quadrangular segments.

Nematocysts: microbasic heteronemes in nematophores, size 14 × 5 µm. Smaller capsules in tentacles, size 5.5 × 3 µm.

Remarks

Halopteris schucherti sp. nov. resembles some species of the “ Halopteris polymorpha group” (see Schuchert 1997). It was therefore compared with microslide material of the following species: H. polymorpha ( Billard, 1913) [MHNG INVE 36253, Madagascar; 37494, Seychelles; and 37495, Brazil], H. liechtensternii (Marktanner­Turneretscher, 1890) [MHNG INVE 29751, Mediterranean], and H. minuta (Trebilcock, 1928) [MHNG INVE 25073, New Zealand].

All four species have nematothecae behind the hydrotheca, but in H. polymorpha and H. liechtensternii they are always axillar. In both H. schucherti and H. minuta there is one non­axillary nematotheca behind the hydrotheca. In H. schucherti this nematotheca is present on the caulus as well as on the hydrocladia, while in H. minuta it is only present on the stem. Moreover, in the last species, its presence is variable even among the segments of a single stem.

The number of nematothecae on the hydrocladial intersegments is also significantly higher in H. schucherti (up to four) than in the three other species (up to two nematothecae per intersegment).

Furthermore, the female gonothecae of H. polymorpha and H. liechtensternii are different as their axes are quite straight. The female gonothecae of H. schucherti closely resemble those of H. minuta : they are ovate, with the longitudinal axis S­shaped, they have a pedicel composed of two short quadrangular segments, and are provided with two conical nematothecae below the basal transverse septum. However, the long axis of the gonotheca of the latter species seems to have a more pronounced S­shape, as the gonothecal aperture is nearly parallel to this axis, while in H. schucherti it forms an angle of about 60–70°. Male gonothecae of H. minuta are present in sample MHNG INVE 25073; they are similar in shape with those of H. schucherti , but their end is more obtuse and they have a length of 0.7–0.8 mm; they are almost twice as large as those of H. schucherti .

The height of the hydrocaulus, in contrast, is much smaller in H. minuta than in H. schucherti (5–9 mm versus up to 75 mm). Halopteris schucherti additionally differs from all species mentioned above by having some branched hydrocladia. The distinguishing characters of the four species are listed in table 4.

Etymology

It is a great pleasure for me to name this species in honor of Dr. Peter Schuchert of the MHNG, to acknowledge his outstanding activity in hydrozoan taxonomy.

Distribution Known only from the type locality.

Figures

FIGURE 6–12. Halopteris schucherti, sp. nov. 6, colony, frontal view. Scale bar 1.5 cm; 7, part of stem with two successive hydrocladia, frontal view. Scale bar 1.2 mm; 8, part of cladium, lateral view. Scale bar 0.4 mm; 9, hydrotheca, lateral view. Scale bar 0.2 mm; 10, female gonotheca, lateral view. Scale bar 0.3 mm; 11, male gonotheca, frontal view. Same scale as in figure 10; 12, nematothecae. A–C: cauline nematothecae, A’–C’: cladial nematothecae. A, A’—nematothecae from intersegments; B, B’—lateral nematothecae; C, C’—median inferior nematothecae; D— nematotheca of male gonotheca; D’—nematotheca of female gonotheca. Scale bar 100 µm.