Halammohydra coronata Clausen, 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 : 464-465

Halammohydra coronata Clausen, 1967

Eight specimens of Halammohydra coronata are from the “Pier at the Youth Hostel” of Helgoland, and three are from Roscoff ( Table 3). All species delimitation tests and node values of both phylogenetic analyses support the cluster of this species well ( Figs. 1 , SI 2). The ovoid to the elongated gastric tube is 292 ± 96 µm (n = 9) long and connects to a cylindrical and slightly round aboral cone, measuring 56 ± 7 µm (n = 4) in length and 46 ± 6 µm (n = 3) in width ( Fig. 2d ). Unfortunately, most specimens adhered to the slide during the investigation, which made it impossible to observe the adhesive organ in detail. The number of statocysts is 4 or 5 .

In total, specimens have 10 to 15 tentacles, distributed unevenly in the two whorls ( Fig. 2d ). The number of aboral tentacles is lower, mostly 4, than of subaboral tentacles. When the animals were swimming, this uneven number was best visible, because the tentacles of the aboral and subaboral whorl are held in different directions ( Fig. 2d ). There is no thickening at the tentacle bases, and the tentacles are slender in both whorls. In some cases, one tentacle is about one and a half to two times longer than the others, and it has no bulb at the base. Tentacles in the subaboral whorl have an unequal length ( Fig. 2d , Table 4).

In this group, some specimens are clearly identified as H. coronata , whereas others are not, due to the lower difference in structure between the tentacles of both whorls, some damage, and the adhesion to the slides. The identification of the specimens with unclear characters is based solely on molecular analyses.

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. 2 Light microscopy images of Halammohydra species. a H. vermiformis with a 3 times longer tentacle (arrowhead) in the subaboral whorl. b Magnifi- cation of aboral cone in a show- ing a thickening at the tentacle bases of the subaboral tentacles (arrowhead). c H. octopodides with 2 times longer tentacle (arrowhead). d H. coronata with 1.5 times longer tentacle (arrowhead) in the subaboral whorl. ab, aboral tentacles; ac, aboral cone; ao, adhesive organ; gt, gastric tube; sub, subaboral tentacles