Anthoathecata, Cornelius, 1992

Galea, Horia R. & Maggioni, Davide, 2024, On some tropical hydroids (Cnidaria: Hydrozoa), with descriptions of four new species, Zootaxa 5428 (1), pp. 1-57 : 37

Anthoathecata : Aplanulata: Corymorphidae

Three individual polyps of Corymorpha balssi Stechow, 1932 from the same crab host (designated as A, B and C in Fig. 23A ) were sequenced. The multi-locus (16S, 18S, and 28S rRNA) phylogenetic hypothesis ( Fig. 23A ) shows that all cluster together with maximal node supports (BPP = 1, MLBS = 100), and the species forms a sister-group relationship with a clade composed of C. bigelowi ( Maas, 1905) from Japan and C. tropica Galea, 2023 from Indonesia. Interestingly, the three polyps show a slight intra-specific genetic distance in the 16S rRNA region (0.7 ± 0.3%), suggesting that at least some of the polyps from the same host are not clonally-produced and may have settled independently on it.

A phylogenetic hypothesis based on the COI gene was also produced to assess the phylogenetic affinities of the recently-described C. tropica , given the presence of multiple COI sequences in GenBank, and its sister-group relationship with C. bigelowi was confirmed ( Fig. 23B ). Notably, sequences obtained from Chinese samples identified as C. bigelowi and C. verrucosa ( Bouillon, 1978) , respectively, clustered together, showing minimal genetic distance (intra-group distance: 0.7 ± 0.2%), indicating that they likely belong to the same species, viz. C. verrucosa .

As noted by Galea (2023: 457), the present concept of C. bigelowi likely comprises a species complex. The Japanese material from which the sequences EU448099 (16S), EU272618 (18S), EU272563 (28 S) and JX121581 (COI), used to build the trees illustrated in Fig. 23 herein, bears the catalogue number KUNHM2829 of the Kansas University Biodiversity Institute and Natural History Museum, and is illustrated under that species in the World Hydrozoa Database.

Figures

FIGURE 23. Phylogenetic hypotheses of the genus Corymorpha based on the combined 16S, 18S and 28S rRNA dataset (A), and on the COI region (B). Numbers at nodes represent BPP and MLBS, respectively.