Gonaxia cf. errans 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 : 13-14

Gonaxia cf. errans Vervoort, 1993

Fig. 4 E–F

Gonaxia errans Vervoort, 1993: 154 , figs 23a–d, 24a–c.

Material examined

BATHUS 2: Stn. CP737, two stem fragments, 13 and 9 mm high, the former corresponding to the middle part of a colony, while the latter is likely the distalmost end of (another?) colony; both are sterile; several broken cladia are also present (MNHN-IK-2012-16534).

Remarks

The pattern of cladial arrangement on the stem in this scarce material seems to follow a rather peculiar sequence: each equivalent of internode (the nodes are inconspicuous) has a proximal apophysis with its associated axillar hydrotheca, two alternate hydrothecae above, as well as a second, distal apophysis (on the side opposite to the former) with its associated axillar hydrotheca; the same sequence is repeated on the following “internode” but, there, it is the opposite image of the preceding one. In the distalmost part of one of the available colony fragments, two successive cladia occur on the same side, and are separated on the opposite side by a single stem hydrotheca. According to Vervoort (1993), the cladial arrangement is varied, with “zero to three hydrothecae between two successive apophyses”, which is apparently the case in the present material.

The shape of the hydrothecae also fits the original description of G. errans , though they are comparatively shorter in the material in hand (free adaxial side 335–365 µm, adnate adaxial side 280–300 µm, abaxial side 490–510 µm), but seem to have almost the same width (maximum width 205–220 µm, diameter at aperture 165–175 µm) as in Vervoort’s samples. Consequently, the present material is provisionally assigned to G. errans .

Geographical distribution

New Caledonia (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.