Leptomedusa sp. B (Cosmetirella simplex sp. inc.)

Verhaegen, Gerlien, Cimoli, Emiliano & Lindsay, Dhugal, 2021, Life beneath the ice: jellyfish and ctenophores from the Ross Sea, Antarctica, with an image-based training set for machine learning, Biodiversity Data Journal 9, pp. 69374-69374 : 69374

Leptomedusa sp. B (Cosmetirella simplex sp. inc.)

Materials

Type status: Other material. Occurrence : individualID: MCMEC2019_ Leptomedusa _sp_B_a; lifeStage: adult; associatedMedia: https://youtu.be/hrufuPQ7F8U; Taxon : kingdom: Animalia ; phylum: Cnidaria ; class: Hydrozoa ; order: Leptomedusae ; Location: continent: Antarctica; waterBody: McMurdo Sound; maximumDepthInMeters: 1; decimalLatitude: -77.637; decimalLongitude: 166.401; Identification: identifiedBy: Dhugal Lindsay; Event: samplingProtocol: Sony Alpha 7 III camera equipped with a FE 90mm F2.8 Macro G OSS lens; eventDate: 2019-11-22; Record Level: type: StillImage, Video; language: en; rightsHolder: Emiliano Cimoli

Notes

Description of and comments on observed material: N = 1 in 2019 (Fig. 6 ). This medusa showed the typical characteristics of the order Leptomedusae : flattened umbrella and gonads confined to the radial canals ( Bouillon et al. 2006). The following families were excluded, based on the following observed diagnostic characters: only one manubrium ( Sugiuridae ), presence of statocysts or cordyli ( Orchistomidae , Melicertidae and Dipleurosomatidae ), gonads not extending on manubrium ( Tiarannidae ). Transparent medusa, four radial canals; 28 tentacles, short and white, with the inside of tentacle bulb light orange; sometimes one rudimentary tentacle bulb between each pair of tentacles; gonads very thin and linear located on the lateral canals, ca. one third of the radial canals away from the bell margin and length ca. one fifth of the length of the radial canal. Diagnostic characters that could not be definitively verified for further classification of the medusa: distinction and structure of statocyst or cordyli, gastric peduncle and manubrium connection to sub-umbrella. It resembles Cosmetirella simplex Browne, 1910, which was described with 32 tentacles or more and which is currently regarded as synonymous with Cosmetirella davisii (Browne, 1902) [basionym Tiaropsis davisii Browne, 1902], which was described by Browne (1902) with about 80 tentacles around a 11 mm wide umbrella. When Kramp (1930) synonymised the species, he recognised a smaller growth form from the Antarctic with fewer (28-48) tentacles (i.e. C. simplex ) and a larger form from the sub-Antarctic with more (56-150) tentacles ( C. davisii + C. kerguelensis ). Until these forms can be definitively assigned to the same species using molecular techniques, we tentatively assign the present individual to C. simplex , noting that, although cirri apparently are not present, we were unable to count the number or observe the type of statocysts for a definitive species identification.

Figures

Figure 6. Leptomedusa species B (specimen MCMEC 2019 _ Leptomedusa _ sp _ B _ a) observed on 22 / 11 / 2019: oral view (A-B) and oral view when contracted (C). Abbreviation: g, gonad. Photos courtesy: E. Cimoli.