Chrysaora caliparea

Morphological and biometric approach Within the current study, adult jellyfish with a bell diameter between 15 and 22 cm have been analyzed morphologically on the same day of bloom spotting and sampling at Khor Al-Adaid (Figure 2). The scyphomedusa is characterized by a hemispherical umbrella with 4 rounded marginal lappets per octant without canals. Adults have 3 tentacles per octant and 24 tentacles in total. The exumbrella surface is granulated with a milky-white coloration associated with small brown spots and a radial pattern of 16 brown triangles shaped like elongated V’s on the bell surface of more or less intense coloring depending on the individuals (Figure 3). The mouth followed by the stomach shows a tetramerous symmetry and is extended by 4 long festooned oral arms reaching sometimes 2 meters in extension. The W-shaped gonads characteristics described previously (Daly Yahia et al. 2023) within the gastrovascular cavity are also confirmed on all adult specimens analyzed morphologically within this population. The biometric analysis of Chrysaora cf caliparea population had shown that for the bell diameter length versus individual dry weight relationship there is a low positive allometric growth (b = 1.21). Nevertheless, for the oral arm length versus individual dry weight the allometric growth is negative (b = 0.40) showing a lower growth rate compared to the scyphomedusae body weight growth rate (Figure 4). Molecular analyses For the nuclear 28 S gene, the approximate 1100 bp fragment was successfully amplified and unambiguously sequenced (Accession number: PP 393039). We aligned our sequence with available reference sequences from the different Chrysaora clades deposited in GenBank. Hence, the dataset comprised 27 sequences with Cyanea capillata (HM 194873.1) used as outgroup to root the phylogenetic trees over 811 bp. The Qatari specimen is observed grouping on a distinct lineage (100 %) that contains the Malaysian Chrysaora chinensis and a Chrysaora specimen found within Gulf of Oman (KY 655779). Despite the clustering, the position of the Qatari Chrysaora may suggest its differentiation from Chrysaora chinensis, however it is with weak support of less than 60 % bootstrap value (Figure 5). The analysis of the intraspecies and interspecies genetic distance 28 S for C. cf caliparea and C. chinensis (Supplementary Table 1) revealed no distance metric if compared pair by pair with all the C. chinensis (KY 610954 vs MF 141629; KY 610954 vs MF 141630; MF 141629 vs MF 141630) resulting in “ 0 ” Mean Intraspecies Distance. However, the distance of C. cf caliparea vs all C. chinensis isolates was 0,003 7037 individually generating the same Mean Interspecies Distance of 0,003 7037. Despite the small distance disparity, the results of 28 S suggest genetic distinction between Chrysaora cf. caliparea and C. chinensis. On the other hand, the generated corrected sequence for the mitochondrial 16 S of 649 bp fragment length (Accession number: PP 393040) was initially compared online to the GenBank database by BLAST-N approach. The highly similar sequences were retrieved and included within the 16 S dataset comprising in total 35 sequences with Cyanea capillata (KY 610739.1) used as outgroup covering a length of 542 bp. The phylogenetic analysis confirmed the clustering observed previously with the nuclear marker showing clustering of our specimen within the Chrysaora chinensis clade. It is noteworthy that the clade is revealed to be not restricted to the Malaysian specimens but includes also unidentified Chrysaora specimens found within Thailand waters (KT 982701, KT 982706, KT 982709, KT 982711). Despite such clustering, the Qatari specimen stands distinguished on a separate branch of the phylogenetic tree suggesting once again that the species reported within this work is a different Chrysaora species not genetically reported previously (Figure 6). These results are supported again by the intraspecies and interspecies genetic distance for C. cf caliparea and C. chinensis (Supplementary Table 2) with Mean Intraspecies Distance within C. chinensis isolates around 0.0021756 whereas the Mean Interspecies Distance C. cf. caliparea vs. each C. chinensis is around 0.0247222. This shows a clear barcode gap — the interspecies distances are much higher than intraspecies, which supports that Chrysaora cf. caliparea and Chrysaora chinensis are genetically distinct. Targeting the polymorphic COX gene, unambiguous sequence of 611 bp was generated (Supplementary Figure S 1) and subjected to BLAST-N revealing highest similarity of 93.14 % with Chrysaora sp. Chr _ Ch 1 isolate (KY 655792) identified within Chabahar, Gulf of Iran. Both specimens were then included in phylogenetic analysis alongside 41 reference sequences with Cyanea capillata (MF 141607.1) used as outgroup covering a length of 298 bp in order to include all the available sequences of Chrysaora chinensis. The topology of the phylogenetic tree agrees with the previously generated ones: the Qatari Chrysaora cf. caliparea forms a monophyletic grouping within the same clade as Chrysaora chinensis isolates yet remains genetically distinct and does not constitute conspecificity with C. chinensis (Figure 7). Distances calculation aligns with such observations with mean Intraspecies equals 0.01726 whereas mean Interspecies equals 0.05255 (Supplementary Table 3). Along the three genes used in this study, interspecies distances are consistently higher than intraspecies distances, which advance species separation, hence Chrysaora cf. caliparea and Chrysaora chinensis are distinct species.