Halammohydra adherens Swedmark & Teissier, 1967

Tödter, Lenke, Worsaae, Katrine & Schmidt-Rhaesa, Andreas, 2023, Comparative molecular and morphological species delineation of Halammohydra Remane, 1927 (Hydrozoa) - with the description of four new species, Organisms Diversity & Evolution (New York, N. Y.) 23 (3), pp. 455-476 : 465

Halammohydra adherens Swedmark & Teissier, 1967

All seven animals identified as Halammohydra adherens are from Roscoff, six of them from the station “Trezen ar Skoden” ( Table 3). Genetically, this species is closely related to H. coronata and GMYC analysis of 18S even groups these two species into one cluster ( Fig. 1 ). It is important to notice that there is only one sequence of 18S and no CO1 sequence available for H. adherens . The cluster of this group is mostly based on 16S sequences. Node support values, ABGD implies an affiliation of the specimen R93 from “Bazin Malvog” to this species, but GMYC and bPTP exclude it (SI 2). K2p values between R93 and H. adherens are 0.018 ± 0.006 and between H. adherens and H. coronata 0.090 ± 0.014 (SI 3).

Specimens of H. adherens have an ovoid body shape and are very adhesive ( Fig. 3 ). The structure of the aboral cone and adhesive organ could not be investigated due to this behavior ( Table 4). The tentacles of both whorls are not separated and are of slender shape. The number of tentacles was 11, 16, or 22 ( Fig. 3a ). One specimen even has more than 25 tentacles ( Fig. 3b ). This specimen is exceptionally large, and the amount of tentacles obscured further observation of the aboral cone or the tentacle bases. The other specimens have no special structure at the tentacle bases, and 4 or 5 statocysts are visible. All specimens of this group have elongated nematocysts, which are even observable in lower magnification ( Fig. 3c and d ). Tentacles of the largest specimen are fully packed with these nematocysts ( Fig. 3d ), whereas in the smaller ones, they are less densely concentrated ( Fig. 3c ).

Figures

Fig. 1 Phylogenetic tree of all three genes concatenated with support values of BI/ML (posterior probability/bootstrap value). Nodes with an * have a support of 100/100. Some clusters are collapsed. Sum-

Fig. 3 Light microscopy images of Halammohydra adherens. a Smaller variant with less tentacles. b Larger variant with more tentacles. c Magnifica- tion of a tentacle of a with a few elongated nematocysts (arrowheads). d Magnification of the tentacle of c filled with elongated nematocysts (arrow- heads). gt, gastric tube; mo, mouth opening