Proboscidactyla ornata ( McCrady, 1859 )

Schuchert, Peter & Collins, Richard, 2021, Hydromedusae observed during night dives in the Gulf Stream, Revue suisse de Zoologie 128 (2), pp. 237-356 : 261

Proboscidactyla ornata ( McCrady, 1859)

Fig. 14 A-G

Willsia ornata McCrady, 1859: 149 , pl. 9 figs 9-11.

Proboscidactyla ornata . – Mayer, 1910: 189, pl. 20 figs 1-10, text fig. 100.

Material examined: BFLA4349 ; 1 specimen; 11-MAR-2020; size 4 mm, 17 tentacles, presumably a mature male; preserved in alcohol for DNA extraction; 16S sequence MW528709 . – BFLA4354 ; 1 specimen; 11-MAR-2020; size 4 mm, 18 tentacles, with green subumbrella; preserved in alcohol for DNA extraction; 16S sequence MW528710 . – BFLA4356 ; 1 specimen; 13-MAR-2020; size 4 mm, 21 tentacles, mature male; preserved in alcohol for DNA extraction; 16S sequence MW528711 . – BFLA4357 ; 1 specimen; 13-MAR-2020; size 5 mm, 21 tentacles, mature female; preserved in alcohol for DNA extraction; 16S sequence MW528712 – BFLA4454 ; 1 specimen; 11-JUN-2020; size 5 mm, 19 tentacles; preserved in formalin and deposited as FU-014065 . – BFLA4455 ; 1 specimen; 11-JUN-2020; size 6 mm, 18 tentacles, mature male; preserved in formalin and deposited as FU-014066 . – 13-MAR-2020; 1 specimen photographed, not collected; 4 mm, 16 tentacles.

Observations: Medusae with the characteristics of the genus, bell as wide as high, 4-6 mm, apical jelly about 1/3 of total height. Exumbrella with more or less linear arrays of nematocyst patches of variable length, starting from bell margin and alternating with tentacles, some reaching beyond mid part of bell, patches with up to 10 nematocysts, patches often lost in preserved animals. Manubrium rather broad, cruciform base giving impression of four (rarely 5) peradial basal pouches, gonads covering entire interradial wall of stomach, separated perradially, smooth surface; mouth rim much folded but not clearly with four lips, rim with nematocysts. Four (rarely 5) thin radial canals originate from basal manubrium pouches, branching dichotomously so that 4 to 5 ends reach circular canal (= solid strand). Tentacles only at ends of radial canals, 16-21 in mature animals, oviform basal bulb, tapering in much extensible tentacles; abaxial side of bulb gastrodermis with a dark pigment, lost in formalin preserved animals.

16S Data: See Table 1 and Fig. 16 . The sequences of this study were quite divergent from P. ornata sequences from other regions, showing p-distances of up 7.5% and separating into distinct mitochondrial lineages. The lineage of Florida Proboscidactyla ornata without medusa buds is also clearly different from those here identified as P. gemmifera (see below).

Distribution: Reportedly circumglobal in tropical and temperate waters, but in view of the genetic data presented below, the known distribution must be restricted to the coastal waters of the NE Atlantic. Type locality: USA, South Carolina, Charleston Harbor.

Remarks: The present material ( Fig. 14 ) agreed well with the descriptions given in McCrady (1859) and Mayer (1910) who had material from the same biogeographic region (warm temperate and tropical northwestern Atlantic; Spalding et al., 2007). The observed differences concerned the tentacle numbers which were 16 to 21, thus more variable than the 16 given in Mayer (1910). Our material observed in situ also had more nematocyst patches on the exumbrella, however, these are apparently lost rapidly in preserved material (likely also in net caught material). The maximum likelihood tree ( Fig. 16 ) strongly suggests that our current concept of P. ornata comprises several mitochondrial lineages, viz. most likely species. This is also the reason why we separated the morphotype with medusa buds into a separate species (see below). Our medusae P. ornata were all rather fully grown, at least some with developed gonads. Because vegetative medusa budding might only occur in immature specimens, we cannot exclude that also P. ornata can have such a medusa budding. In this context, an observation noted by Mayer (1910) is interesting. He states that the budding variety of P. ornata is confined to the region south of South Carolina, while the nonbudding form occurs from Florida up north to New England. Agassiz (1865, Buzzards Bay), Fewkes (1882a, Tortugas), and Calder (1970, Virginia) raised the medusa and did not report vegetative budding. This can be interpreted as two species with differing distributions being present. The northern limit of the budding form must be corrected to at least North Carolina as the type specimen of P. gemmifera ( Fewkes, 1882) came from Beaufort Inlet.

Figures

Fig. 14. Proboscidactyla ornata. Note that the usage of a flash brightens very much the exumbrellar nematocysts. (A-C) BFLA4357, bell size 5 mm, mature female, note that there are five radial canals leaving the manubrium. (D) BFLA4349, bell size 4 mm, subadult (?). (E) BFLA4356, bell size 4 mm, male. (F) Medusa photographed 13-MAR-2020, not collected, bell size 4 mm, note regular arrangement of exumbrellar nematocysts patches. (G) BFLA4354, bell size 4 mm, a layer of unidentified green particles is covering the subumbrella.

Fig. 16. 16S maximum likelihood phylogenetic tree of Proboscidactylidae and related taxa obtained with PhyML (GTR+G model) and based on about 600 bp positions of the mitochondrial 16S gene. Node-support values are bootstrap values of 100 pseudoreplicates (shown only if> 70%).All sequence labels start with the GenBank numbers permitting the retrieval of more information. Red labels are new sequences from this study. All samples are based on medusae.