Gonaxia aff. similis 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 : 20

Gonaxia aff. similis Vervoort, 1993

Figs 5H , 6 S–X

Gonaxia similis Vervoort, 1993: 174 , figs 33e–f, 34, 36a, 39a.

Material examined

MUSORSTOM 6: Stn. DW423, a 2.7 cm high, sterile colony (MNHN-IK-2012-16545).

Remarks

The present specimen is likely part of the material in RMNH-Coel. 25839 (also from MUSORSTOM 6, Stn. DW423) studied by Vervoort (1993).

According to Vervoort, his material had gonothecae adnate to the stem (p. 174, fig. 34c), not arranged perpendicularly to it, as in the majority of samples assigned by him to G. similis . Consequently, the material in hand may belong to a separate species.

One hydrocladium in the present specimen is branched, and the secondary cladium is borne on a short, quadrangular apophysis originating from below the hydrothecal base of the first internode of a cladium.

Not mentioned by Vervoort in his sample RMNH-Coel. 25839 is the constant presence of well-developed antero-posterior diverticuli within the hydrothecae ( Figs 5H , 6 S–V). Such variably developed diverticuli also occur in other congeners discussed herein, viz. G. amphorifera ( Fig. 3A ), G. ampullacea ( Fig. 3C ), and G. scalariformis ( Fig. 5F ). In the present material, their development is considerable, and extends well on each lateral side of the hydrotheca. A frontal view of the free adaxial wall of the hydrotheca ( Fig. 6W), and a frontal view of the aperture ( Fig. 6X) show two empty lateral “pockets” which narrow considerably the hydrothecal lumen; the foramen for the passage of the hydranth within the hydrotheca is minute and horseshoe-shaped.

Geographical distribution

New Caledonia ( Vervoort 1993; present study).

Figures

Fig. 5. ― A–B. Gonaxia nova sp. nov. (MUSORSTOM 8, Stn. CP1083). A. Distalmost, monosiphonic part of a colony. B. Portion of stem with basal part of a cladium. ― C–G. Gonaxia scalariformis Vervoort, 1993, portions of stems and basal parts of cladia from BIOCAL, Stn. DW46 (C = colony #1; D = colony #2; E = colony #3), Stn. DW66 (F), and NORFOLK 1, Stn. DW1699 (G), showing discrete differences in shape and size. ― H. Gonaxia aff. similis Vervoort, 1993 (MUSORSTOM 6, Stn. DW423), portion of stem with cladium. Scale bars: A = 1 mm; B–H = 500 µm.

Fig. 3. ― A–B. Gonaxia amphorifera Vervoort, 1993 (SMIB6, Stn. DW127). A. Two successive cladial internodes with their hydrothecae. B. Portion of stem with male gonothecae. ― C–D. Gonaxia ampullacea Vervoort, 1993 (BATHUS 4, Stn. DW914). C. Two successive cladial internodes with their hydrothecae. D. Portion of stem with male gonothecae. ― E–F. Gonaxia compacta Vervoort, 1993 (BATHUS 4, Stn. DW923). E. Two successive cladial internodes with their hydrothecae. F. Abortive gonotheca (of undetermined sex) originating from within a hydrotheca. ― G–K. Gonaxia intermedia Vervoort, 1993 (BATHUS 4). G. Two successive cladial internodes with their hydrothecae (Stn. CP906). H. Portion of stem with male gonothecae (Stn. CP906). I. Portion of stem with female gonothecae (Stn. CP906). J–K. Abortive gonothecae arising from hydrothecal lumina (Stn. DW902). ― L–N. Gonaxia sinuosa Vervoort, 1993 (SMIB 4, DW40). L. Two successive cladial internodes with their hydrothecae. M–N. Two female gonothecae. Scale bars: A, C, E, G, L = 300 µm; B, D, F, H–K, M–N = 1 mm.