Aequorea Peron & Lesueur, 1810

Mizrahi, Gur A., Shemesh, Eli, van Ofwegen, Leen & Tchernov, Dan, 2015, First record of Aequoreamacrodactyla (Cnidaria, Hydrozoa) from the Israeli coast of the eastern Mediterranean Sea, an alien species indicating invasive pathways, NeoBiota 26, pp. 55-70 : 58

Genus Aequorea Peron & Lesueur, 1810 Fig. 1A

Aequorea macrodactyla (Brandt, 1835)

Morphological description.

The freshly collected jellyfish were observed carefully in the lab by using: Nikon SMZ100 Binocular, Nikon AZ100 Binocular with DS-Ri1 camera, and Zeiss Imager microscope M2. All specimens have a biconvex lens umbrella (central disc is lens-shaped) of around 20 mm thick and 65 mm to 80 mm in diameter. The stomach is shallow with a diameter of a little less than half of the umbrella, around 30 mm to 38 mm (Fig. 1A). There is an average of 32 straight radial canals (Fig. 1B) and the gonads are linear on both sides of each radial canal (Fig. 1C). The jellyfish have between 10-20 broad marginal tentacle bulbs (Fig. 1A) each with abaxial keel (Fig. 1D). The identification of Aequorea spp. can be confusing mainly due to their considerable variability, and misidentification has occurred in the past ( Kramp 1965). The amount of radial canals and tentacles, and the shape of the bases of the marginal tentacles are of great importance and the key to distinguish morphologically between other similar jellyfish belonging to the genus Aequorea , for example Aequorea pensilis and Aequorea macrodactyla that bear a close resemblance one to another. The marginal bulb should be determined in order to distinguish between similar species of Aequorea ( Mayer 1910; Kramp 1956; Kramp 1965; Russell 1970; Bouillon et al. 2006; Gul and Gravili 2013). In our findings we can see clearly (Fig. 1C) the cross-shaped bases of the marginal tentacles that continue the radial canal. Also it is evident (Fig. 1C) that some radial canals end as marginal bulbs but did not develop tentacles and should be considered as non-tentacular marginal bulbs or rudimentary bulbs (Fig. 1D), which is a characteristic phenomenon of the Aequorea macrodactyla . In Figure 1C we can see the position of the gonads surrounding the radial canal. The color of the radial canal, the endoderm of the lips and the tentacle bulbs present a milky color as other parts are mostly transparent.