Pegantha polystriata Peter 2021, new comb.
Creators: name: Schuchert, Peter
name: Collins, Richard
Publisher: name: Zenodo
Year: 2021
Subjects: Biodiversity
Taxonomy
Animalia
Cnidaria
Hydrozoa
Narcomedusae
Solmarisidae
Pegantha
Pegantha polystriata

description: Pegantha polystriata (Xu & Zhang, 1978) new comb.
Fig. 54 A-G
Otoporpa polystriata Xu & Zhang, 1978: 50, pl. 12 figs 65-67.
Examined material: BFL4450; 1 specimen; 08-JUN- 2020; size 5 mm; preserved in alcohol for DNA extraction; 16S sequence MW528728. – 02-SEP- 2020; 1 specimen photographed, not collected, 2 mm. – Photos of two specimens kindly provided by Linda Ianniello, taken 21-MAR-2020 and 15-SEP-2020 during the same series of dives as for the other medusae of this study.
Observations: Bell diameter 5 mm, solid jelly, thickened aborally, margin subdivided in 8 to 9 U-shaped lappets (Fig. 54A, E), at margin of lappets 3 to 5 statocysts from which originate otoporpae (tracks of thickened epidermis with nematocysts, Fig. 54B, G) that extend almost to bell apex (Fig. 54B), otoporpae sometimes irregular, branching, or not straight. Exumbrella apart of the nematocyst tracks smooth, without radiating keels or furrows. Velum broad (Fig. 54A). Stomach large, circular; near its periphery and positioned interradially 8 to 9 diverticula for the gonads (Fig. 54 A-F), originating from stomach floor, in younger animals shallow, in older ones hanging into subumbrella (Fig. 54E); diverticula with thickened walls, dense tissue, sometimes yellow-green tint. Lappets of bell margin apparently with broad peripheral canal, difficult to see and observed only in one animal (Fig. 54E). Eight or nine thick, tapering tentacles originating in about middle of bell height in the bays between adjacent lappets (peronia), tentacles continued at right angles into the jelly as a pointed tentacle-root, tentacles held mostly in oral direction. Statocysts pendant, club shaped, with 2 to 5, usually 3, statoliths in a row, these increasing in size distally. Exumbrellar nematocysts: spherical isorhizas, ca. 10 µm (Fig. 54G).
16S data: The single sequence obtained clustered in a clade comprising other Pegantha as well as Cunina and Pseudaegina species, but without resolved internal relationships (Fig. 48).
Distribution: South China Sea, Taiwan Strait (Xu et al., 2014), Florida (this study). Type locality: Southern end of Taiwan Strait, 22.5°N, 118.5°E.
Remarks: Our medusae, especially the younger ones (Fig. 54 C-D), appear indistinguishable from figures of Otoporpa polystriata given in Xu & Zhang (1978) and we are convinced that they are the same, despite this species is so far only known from the South China Sea. However, we think that this species was not classified in the correct family. The genus Otoporpa Xu & Zhang, 1978 was originally placed in the family Aeginidae (sensu Bouillon et al., 2006) because it had apparently interradial manubrial pouches. The pouches of Otoporpa are atypical for Aeginidae as they are rather shallow and most importantly they are not sub-divided by a medium septum (see Fig. 51C, G). Likewise unusual for genera of the former Aeginidae (sensu Bouillon et al., 2006), Otoporpa has otoporpae (thickenings clasping the bell margin and usually continued as nematocyst tracks on the exumbrella, comp. Figs 50 C-D, 53B, D). We think that Xu & Zhang (1978) misinterpreted the developing gonad diverticula typical of the genus Pegantha as manubrial pouches. This is understandable as younger stages of these diverticula resemble indeed interradial manubrial pouches (Fig. 54 C-D, F).
It is possible that some of the Brazilian specimens described by Tosetto et al. (2018) as Pegantha triloba Haeckel, 1879 belong to the present species. Tosetto’s material lacked the diagnostic radial exumbrellar keels and furrows as shown in Bigelow (1909), it had 8 to 9 lappets and tentacles instead of 12 to 16 (Kramp, 1959a), and the otoporpae continued as nematocyst tracks to almost the top of the umbrella. The otoporpae in P. triloba are usually much shorter, but Kramp (1957) found also very long ones like in the present species in young P. triloba.
description: Published as part of Schuchert, Peter & Collins, Richard, 2021, Hydromedusae observed during night dives in the Gulf Stream, pp. 237-356 in Revue suisse de Zoologie 128 (2) on pages 324-326, DOI: 10.35929/RSZ.0049, http://zenodo.org/record/5639938