Cunina becki Bouillon, 1985

Schuchert, Peter & Collins, Richard, 2021, Hydromedusae observed during night dives in the Gulf Stream, Revue suisse de Zoologie 128 (2), pp. 237-356 : 316

Cunina becki Bouillon, 1985

Fig. 49 A-F

Cunina becki Bouillon, 1985: 263 , fig. 9.

Examined material: BFLA4022 ; 1 specimen; 15-FEB- 2019; size 14 mm; preserved in formalin and deposited as UF-013444 . – BFLA4023 ; 1 specimen; 15-FEB- 2019; size 20 mm; preserved in formalin and deposited as UF-013444 . – BFLA4025 ; 1 specimen; 15-FEB- 2019; size 20 mm; part preserved in formalin and deposited as UF-013446 , 1/4 part in alcohol for DNA extraction; 16S sequence MW528643 .

Observations: Medusae flatter than hemisphere, 14 to 20 mm in diameter, jelly very soft and fragile, margin lobed. Stomach flat, circular, about 1/3 of bell diameter, mouth opening simple, circular ( Fig. 49A ). 16 bandlike manubrial pouches radiating from stomach to the bell margin, pouches slightly widening to about 3/5 of their length, then gradually narrowing again before dividing above tentacle into two narrow peripheral canals or strands ( Fig. 49E ). The proximal 3/5 of the gastric pockets are more opaque ( Fig. 49D ) than the rest as the bottom contains the gonad tissue, in the present cases containing numerous, densely packed, small (16 µm), round cells interpreted as oogonia. Tentacles 16, between pairs of tentacles 4 to 7 otoporpae clasping bell margin ( Fig. 49E ). No peronia.

16S data: The sole 16S sequence clustered within a clade comprising Narcomedusae of different families ( Fig. 48 ).

Distribution: Papua New Guinea, Florida (this study). Type locality: West Pacific, Bismarck Sea, Hansa Bay.

Remarks: Cunina becki has so far only been recorded from its type locality in the Bismarck Sea (western Pacific Ocean). It was thus very surprising to find it in the western Atlantic Ocean. The species may have been overlooked as it has a very fragile jelly, which might not withstand usual net collecting. Cunina becki is rather unusual for its genus – or even all Narcomedusae – in that the gastric pockets are very narrow and extend to the bell margin, resembling thus radial canals of other hydromedusae. While the main diagnostic features of our medusae – long and narrow gastric pockets, otoporpae, and peripheral canal or strand – match the description given in Bouillon (1985), there are nevertheless some slight differences:

- larger diameter (20 versus 15 mm)

- 16 gastric pockets and tentacles (versus 12-15)

- 4-7 otoporpae between successive tentacles (versus 3-4)

- the gastric pockets narrow gradually distal to the gonads (versus rather abrupt).

Considering the variability of other Cunina species (see e. g. Kramp, 1959a, 1968), we think that these differences are due to intraspecific variations and mainly correlated to the somewhat larger size.

With the available material it was not possible to decide if the peripheral canal is really a canal or just a tissue strand. Histological sections are needed to answer this.

Figures

Fig. 49. Cunina becki. (A) Aboral view of whole animal, sample BFLA4022, diameter 14 mm. (B) Medusa in contraction phase, sample BFLA4025. (C) BFLA4023, side view showing optical cross-section through gastric pockets (secant plane of bell), oral side is downwards, arrows indicate the lateral margins of one gastric pocket. (D) Gastric pockets seen from above, note transition from the opaque zone with the developing gonads to clear part (arrow). (E-F) BFLA4022, bell margin showing several otoporpae per lappet (yellow arrows) and the bases of tentacles (red arrows).

Fig. 48. Maximum likelihood phylogenetic tree of Narcomedusae obtained with PhyML (GTR+G+I 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%). Sequence labels start with the GenBank numbers (except for identical haplotypes) permitting the retrieval of more information. Some proveniences were obtained from Lindsay et al. (2017) or through personal communications. Red ODEHOV DUH QHZ VHTXHQFHV IURP WKLV VWXG\. &RORXUHG ER[HV LQGLFDWH IDPLO\ DI¿OLDWLRQV DFFRUGLQJ WR WKH FXUUHQWO\ XVHG V\VWHP. (") 'HQRWHV SRVVLEOH PLVLGHQWL¿FDWLRQV.