Aequorea taiwanensis

16 S data: The three haplotypes had a range of base pair divergences of 0.2 to 0.5 % (Table 1). The maximum likelihood tree of the partial 16 S sequences (Fig. 37) identified them as very closely related to A. taiwanensis (p-distances 0.2 - 0.64 %).

Fig. 41 A-G

Observations: Subadult Aequorea medusae with bell diameters 30 to 50 mm, gonad development starts at about 30 mm size. Bell relatively high, apical jelly about 1 / 2 of bell height. Stomach wide, 7 / 10 of bell diameter. Mouth rim with numerous, long, thin fimbriae (Fig. 41 B). Radial canals thin, 100 to 240, often also with 15 to 100 developing centrifugal canals. 14 to 25 fully developed tentacles, between pairs of tentacles 3 - 5 small bulbs without tentacles. Ratio of radial canals to tentacles 7.5 to 10, thus always many more radial canals than tentacles. Tentacles in life either with a distinct conical basal bulb with a slight depression of upper side (Fig. 41 D) or widened laterally to give a T-shape (Fig. 41 C, G). Abaxial spurs absent. Small, abaxial excretory papillae can be present, only seen in preserved material. Tentacle bases in preserved material usually also with lateral expansions (Fig. 41 F), but some simply conical (Fig. 41 E). Statocysts about as numerous as radial canals but not in phase with them, two statoliths per statocyst.

Remarks: This material resembles very much Aequorea pensilis (Haeckel, 1879), only the lateral expansions of the bulbs are shorter and sometimes absent in preserved material, and small excretory papillae can be present. Our identification of the present material as A. taiwanensis was based on the strong similarity of the 16 S sequences (Table 1). The haplotype divergences to the published sequences from Taiwan Strait were only 0.2 to 0.64 %, while within the Florida population we found a maximal value of 0.5 %, thus intra- and interpopulation divergences are in the same range. In the ML tree (Fig. 37) the distance of the two population appears higher than the values obtained by pairwise comparisons. This is due to the fact that another substitution model was used for the distance calculation and more importantly, the sequences from the Taiwan Strait specimens were 112 bases shorter at the 3 ’ end, leading to a bias in the ML analysis. While the similarity of our sequences with A. taiwanensis almost certainly implies that our material is conspecific, it must be noted that so far no Aequorea pensilis 16 S sequences are available. It might turn out that A. taiwanensis is in fact a synonym of Aequorea pensilis. Aequorea taiwanensis, according to the description in Zehng et al. (2009), resembles A. pensilis but lacks the diagnostic long lateral expansions of the tentacle base and it has excretory papillae (comp. Browne, 1905; Maas, 1905; Kramp, 1968: Fig. 268). In our material, the lateral expansions were present, but also not as wide as usually shown for A. pensilis. Our material is thus intermediate between A. pensilis and A. taiwanensis. The specimens of Zheng et al. (2009) measured only 25 mm, were thus likely younger than ours, which reached up to 50 mm diameter. Pacific Aequorea pensilis reach 100 mm in diameter (Kramp, 1968). The Atlantic occurrence of a rare Aequorea medusa of the Western Pacific Ocean is surprising, but not unparalleled. Pruski & Miglietta (2019) recently found Aequorea australis in the Gulf of Mexico, a species formerly only known from the Indo-Pacific Ocean. The presence of A. taiwanensis in the Atlantic Ocean must not be interpreted as a possible recent introduction. While we found three different haplotypes, the four samples from Taiwan Strait (Zheng et al., 2014) represented only a single one. The higher haplotype diversity in the Altantic argues against a recent introduction from the Pacific. The species has likely a wide distribution.

Distribution: Taiwan strait, Florida (this study). Type locality: Taiwan Strait.

Material examined: BFLA 4105; 1 specimen; 27 - MAY- 2019; size 27 mm, beginning gonad development; part preserved in formalin and deposited as UF- 013793, part preserved in alcohol for DNA extraction; 16 S sequence MW 528674. – BFLA 4173; 1 specimen; 09 - AUG- 2019; size 30 mm; part preserved in formalin and deposited as UF- 013820, part preserved in alcohol for DNA extraction; 16 S sequence MW 528685. – BFLA 4308; 1 specimen; 16 - JAN- 2020; size 31 mm, gonads visible; part preserved in formalin and deposited as UF- 013846, part preserved in alcohol for DNA extraction; 16 S sequence MW 528705. – BFLA 4332; 1 specimen; 31 - JAN- 2020; size 40 mm, gonads visible; part preserved in formalin and deposited as UF- 013890, part preserved in alcohol for DNA extraction; 16 S sequence identical MW 528705. – BFLA 4425; 1 specimen; 28 - MAY- 2020; size 50 mm, gonads visible; part preserved in formalin and deposited as UF- 014051, part preserved in alcohol for DNA extraction; 16 S sequence identical MW 528705. – 1 specimen photographed 07 - FEB- 2020, not collected; size 30 mm. The formalin samples are mostly strongly fragmented and damaged.