Gonaxia elegans Vervoort, 1993

Galea, Horia R., 2016, Notes on some sertulariid hydroids (Cnidaria: Hydrozoa) from the tropical western Pacific, with descriptions of nine new species, European Journal of Taxonomy 218, pp. 1-52 : 13

Gonaxia elegans Vervoort, 1993

Fig. 4 B–D

Gonaxia elegans Vervoort, 1993: 153 , figs 19c, 21b–c, 22.

Material examined

BATHUS 3: Stn. DW809, a 4.4 cm high colony devoid of hydrorhiza and bearing female gonothecae, as well as an originally 5.4 cm high colony (now broken into two parts) bearing male gonothecae and several broken cladia originating from both colonies (MNHN-IK- 2012 -16533).

Remarks

This species is immediately recognizable through the characteristic position and shape of its hydrothecae. The 5.4 cm high colony is evidently male when compared to the smaller one, which bears gonothecae possessing much wider apertures. Only the female gonothecae were described by Vervoort (1993) but, upon a careful inspection of the present material, it should be stated that they do not arise from the accessory tubes on the hydrocaulus, but from the main tube itself, as this is indisputably seen in the monosiphonic part of the stem. In addition, in this colony at least, nearly all accessory tubes are found on the “dorsal” aspect of the stem, while the row of gonothecae is situated on its “front”.

The male gonothecae, observed here for the first time, are similar in shape to the female ones, and also arise from the main tube of the stem, but in both the frontal and dorsal aspects of the colony. They are given off closely and in a single row ( Fig. 4D ), are about half adnate, and their free parts are shifted alternately left and right; their bases are obscured by the numerous accessory tubes running up the stem. They are long (1.5–2 mm), tubular (480–520 µm wide), with small, circular apertures (100–120 µm wide) mounted on the summit of a conical, distal neck region.

Geographical distribution

New Caledonia ( Vervoort 1993; present study), Norfolk Ridge ( Vervoort 1993).

Figures

Fig. 4. ― A. Gonaxia crassicaulis Vervoort, 1993 (MUSORSTOM 4, Stn. DW205), portion of cladium. ― B–D. Gonaxia elegans Vervoort, 1993 (BATHUS 3, Stn. DW809). B. Portion of stem and basal part of a cladium. C. Two consecutive internodes with their hydrothecae. D. Portion of stem with male gonothecae. ― E–F. Gonaxia cf. errans Vervoort, 1993 (BATHUS 2, Stn. CP737). E. Distalmost portion of stem with basal parts of four hydrocladia. F. Two consecutive cladial internodes with their hydrothecae. ― G–J. Gonaxia plumularioides sp. nov. (BIOCAL, Stn. CP34). G. Distalmost part of a stem, showing the structure of internodes. H. Two consecutive cladial internodes with their hydrothecae. I. Stem hydrotheca. J. Axillar hydrotheca. Scale bars: A–B, D–E, G = 1 mm; C, F, H–J = 300 µm.