Nausithoe sp. Figs 1, 3, 4

Metagenetic species.

Solitary polyp with typical periderm tube, dark to light brown (Fig. 1C, D), conical, with transverse rings on the surface with longitudinal striations (5 rings every 0.4 mm at 2 mm above base). Polyps 5.05-20.2 mm long; basal disk 0.63-0.66 mm in diameter; diameter just above the basal disk 0.14-0.4 mm; tube diameter at 2-mm height 0.09-0.45 mm, and at 5-mm height 0.35-0.45 mm; tube aperture diameter 1.28 mm. Tubes with 3-10 whorls of internal cusps (Fig. 1C); closer to base, number of internal cusps per whorl is 16: 4 large (perradius) with additional cusps on the surface, 4 intermediate (interradius), and 8 small (adradius) (Fig. 3A). Upper whorls with only 8 cusps: 4 large (perradius) with no additional cusps, and 4 intermediate (interradius) (Fig. 3B, C). Polyps with 26-37 filiform tentacles (Fig. 1D). Polydisc strobilation, with more than 100 ephyrae at a time. Medusa (Figs 2A, B, 4) entirely translucent, with slightly flattened smooth umbrella; 16 slightly elongated lappets with rounded margins; 8 rhopalia with statocyst and red ocelli. Live specimens measuring up to: 9.5 mm total diameter; 7.74 mm diameter between opposite rhopalia; 2.83 mm coronal groove diameter; gastric cirri approximately 0.9 mm in length; and tentacle length up to half the total diameter of the medusa. Stomach with 4 gastric septa, each with 2 gastric filaments (8 in total) (Figs 2A, 4D, E). Gonads, 8, but not fully developed (Fig. 4A-C); in fact, only a single individual had them and they were malformed (Fig. 4B, C), so complete data about their morphology are lacking. Cnidome composed of only two nematocyst types: holotrichous isorhiza and heterotrichous microbasic eurytele (Fig. 5; Table 6).