Gonaxia crassicaulis 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 : 11-13

Gonaxia crassicaulis Vervoort, 1993

Fig. 4A

Gonaxia crassicaulis Vervoort, 1993: 145 , figs 18c–d, 19a–b.

Material examined

MUSORSTOM 4: Stn. DW205, a cladium, 2.5 cm long (MNHN-IK- 2012 -16531).

NORFOLK 1: Stn. DW 1712, an infertile colony, 3.8 cm high (MNHN-IK- 2012 -16532).

Remarks

According to Vervoort (1993), G. crassicaulis is easily recognizable through the characteristic development of the perisarc, forming thick, internal, longitudinal ridges, connecting the adnate adaxial walls of the hydrothecae in each row ( Fig. 4A ).

Also characteristic is the presence of large, internal, semi-circular “thickenings” of the perisarc ( Fig. 4A ), arching over the basal foramina, when the hydrothecae are seen laterally. These structures, one situated in the “frontal” aspect of the hydrothecae, the other on their “dorsal” side, correspond in fact to the attachment points of the hydrothecal bases to the lateral walls of the thecae which, in this species, are raised above the level of the foramina. When the hydrothecae are seen facing their apertures, the hydrothecal bases appear U-shaped, the foramina being situated at the bottom of this concavity.

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.