Gonaxia crusgalli Vervoort, 1993

Galea, Horia R. & Maggioni, Davide, 2021, An integrative study of some species of Gonaxia Vervoort, 1993 from off New Caledonia, with the establishment of Gonaxiidae as a new family of thecate hydroids (Cnidaria: Hydrozoa), Zootaxa 5004 (3), pp. 401-429 : 410

Gonaxia crusgalli Vervoort, 1993

Figs 1C , 6F–G , 15 , 16 ; Table 3

Gonaxia crusgalli Vervoort, 1993: 149 , figs 18E, 20, 21A.

Material examined. KANACONO, Stn. DW4744, MNHN-IK-2015-2678: a 2.8 cm high, sterile colony; GenBank: MZ 099695 (16S).

Remarks. The present material, without gonothecae, is immediately recognizable as being G. crusgalli , due to the pair of fronto-dorsal spurs on its hydrothecae ( Fig. 6F, G ), a character not met with in any of its congeners. As with Vervoort (1993), the presence of a basal foramen communicating with the hydrothecal lumen could be noted (their distal tips are always closed in the available specimen), but no traces of coenosarc investing their own lumina could be observed, making their role uncertain.

Although no reports of branched cladia are available ( Vervoort 1993), aberrant branches were seen in the material at hand: 1) in one instance, a short branch is given off from within the proximal most hydrotheca; 2) in another case, an equally short branch takes the place of one of the lateral spurs of a proximal hydrotheca on the original cladium.

For a thorough description of this species, refer to Vervoort (1993).

Bathymetric distribution. Between 255–310 m ( Vervoort 1993; present study).

Figures

FIGURE 1. Species of Gonaxia dealt with in this study: G. bulbifera Vervoort, 1993 (A), G. crassicaulis Vervoort, 1993 (B), G. crusgalli Vervoort, 1993 (C), G. elegans Vervoort, 1993 (D), G. errans Vervoort, 1993 (E, unbranched form), G. incisa Galea, sp. nov. (F), G. cf. intermedia Vervoort, 1993 (G), G. perplexa Vervoort, 1993 (H), G. sinuosa Vervoort, 1993 (I), G. solenoscyphoides Galea, sp. nov. (J). Scale bar: 1 cm.

FIGURE 6. A–E. Gonaxia crassicaulis Vervoort, 1993 (continued). A. Hydrotheca seen laterally. B. Opercular apparatus in frontal view. C. Cross section of a hydrotheca seen frontally, to show lateral diverticula. D. Cross section through a cladial internode at the level of the hydrothecal floor, showing the hydropore. E. Cross section through the middle part of a cladial internode to show the unilateral gutter of perisarc to which the coenosarc is confined. F, G. Gonaxia crusgalli Vervoort, 1993. Hydrotheca in lateral (F) and frontal (G) aspects. From samples MNHN-IK-2019-2088 (A–E) and MNHN-IK-2019-2678 (F, G). Scale bar: A–G = 300 µm.

FIGURE 15. Phylogenetic hypothesis for Gonaxia species based on a 16S dataset. Numbers at nodes show maximum likelihood bootstrap values, Bayesian posterior probabilities, and maximum parsimony bootstrap values, respectively.

FIGURE 16. Phylogenetic hypothesis for the position of the Gonaxiidae Maggioni, fam. nov. within Macrocolonia, based on a multi-locus dataset. Numbers at nodes show maximum likelihood bootstrap values, Bayesian posterior probabilities, and maximum parsimony bootstrap values, respectively, and are shown only when at least two analyses demonstrated high support (> 0.9 for Bayesian posterior probabilities and> 75 for bootstrap values).