Aequorea spec. 1

Schuchert, Peter & Collins, Richard, 2021, Hydromedusae observed during night dives in the Gulf Stream, Revue suisse de Zoologie 128 (2), pp. 237-356 : 301-303

Aequorea spec. 1

Fig. 40 A-K

Material examined: BFLA3781 ; 1 specimen; 18-SEP- 2018; size 9 mm, gonads developing; preserved in alcohol for DNA extraction; 16S sequence identical to MW528631 . – BFLA3788 ; 1 specimen; 24-SEP-2018; no size data, no gonads; preserved in alcohol for DNA extraction; 16S sequence MW528637 . – BFLA3790 ; 1 specimen; 24-SEP-2018; no size data, gonads developing; preserved in alcohol for DNA extraction; 16S sequence identical to MW528631 – BFLA3796 ; 1 specimen; 13-OCT-2018; size 6 mm, no gonads; preserved in alcohol for DNA extraction; 16S sequence identical to MW528631 . – BFLA3809 ; 1 specimen; 19-OCT-2018; size 10 mm, no gonads; preserved in alcohol for DNA extraction; 16S sequence identical to MW528631 . – BFLA3814 ; 1 specimen; 20-OCT- 2018; size 12 mm, gonads developing; preserved in alcohol for DNA extraction; 16S sequence identical to MW528631 – BFLA3815 ; 1 specimen; 20-OCT-2018; size 10 mm, no gonads; preserved in alcohol for DNA extraction; 16S sequence identical to MW528631 . – BFLA3817 ; 1 specimen; 20-OCT-2018; size 12 mm, no gonads; preserved in alcohol for DNA extraction; 16S sequence identical to MW528631 . – BFLA3818 ; 1 specimen; 24-OCT-2018; size 8 mm, no gonads; preserved in alcohol for DNA extraction; 16S sequence identical to MW528631 . – BFLA3830 ; 1 specimen; 15-NOV-2018; size 7 mm, no gonads; preserved in alcohol for DNA extraction; 16S sequence MW528638 . – BFLA4001 ; 1 specimen; 20-NOV-2018; size 13 mm, gonads developing; preserved in alcohol for DNA extraction; 16S sequence MW528631 . – BFLA4002 ; 1 specimen; 20-NOV-2018; size 17 mm, gonads developing; preserved in alcohol for DNA extraction; 16S sequence identical to MW528631 . – BFLA4163 ; 1 specimen; 06-AUG-2019; fragments 4 and 6 mm, gonads developing; part preserved in formalin and deposited as FU-013813, part preserved in alcohol for DNA extraction; 16S sequence MW528681 . – BFLA4164 ; 1 specimen; 06-AUG-2019; size 8 mm, no gonads; part preserved in formalin and deposited as FU-013814 , part preserved in alcohol for DNA extraction; 16S sequence MW528682 . – BFLA4167 ; 1 specimen; 06-AUG-2019; size 6 mm, no gonads; part preserved in formalin and deposited as FU-013815 , part preserved in alcohol for DNA extraction; 16S sequence identical to MW528638 . – BFLA4168 ; 1 specimen; 06-AUG-2019; size 6 mm, no gonads; part preserved in formalin and deposited as FU-013816 , part preserved in alcohol for DNA extraction; 16S sequence identical to MW528681 . – BFLA4205 ; 1 specimen; 23-AUG-2019; size 4 mm, gonads developing; preserved in alcohol for DNA extraction; 16S sequence identical to MW528631 . – BFLA4244 ; 1 specimen; 11-NOV-2019; size 10 mm, no gonads; preserved in alcohol for DNA extraction; 16S sequence identical to MW528631 – BFLA4443 ; 1 specimen; 07-JUN-2020; size 10 mm, no gonads; part preserved in formalin and deposited as FA-014058 , part preserved in alcohol for DNA extraction; 16S sequence identical to MW528631 . – BFLA4464 ; 1 specimen; 13-JUN-2020; size 9 mm, no gonads; preserved in alcohol for DNA extraction; 16S sequence identical MW528681 . – BFLA4476 ; 1 specimen; 18-JUN-2020; size 5 mm, no gonads; preserved in alcohol for DNA extraction; 16S sequence identical to MW528631 .

Observations: Small Aequorea medusae with bell diameters reaching 17 mm, only some with beginning gonad development ( Fig. 40 A-B), gonad development starts at about 9 mm size. Bell in smaller animals nearly hemispherical, larger ones more flattened. Stomach small, in the larger individual diameter ~1/4 to 4/5 of bell diameter. Mouth rim with many broad fimbriae ( Fig. 40C ). Radial canals thin, up to 46 seen, often also developing centrifugal canals. Gonads developing in some of the radial canals ( Fig. 40A ), but apparently not fully developed. Up to 25 fully developed tentacles, additionally 1-5 very small tentacles or small bulbs without tentacles. Ratio of radial canals to tentacles 1.3 to 1.8 in individuals with visible gonads, thus always more radial canals than tentacles. Tentacles in life with a distinct, short, conical basal bulb ( Fig. 40 A-B, D-E), with faint abaxial keel, emphasized or feigned by a whitish line on median of abaxial side (visible in life only), abaxial side of bulb usually continued onto exumbrella as a short abaxial spur ( Fig. 40E ). Conspicuous excretory papilla on adaxial side of tentacle bulbs ( Fig. 40I ), pointing into subumbrella. One to two statocysts between tentacles or small bulbs, statocysts with two statoliths.

16S data: The five haplotypes had a range of divergences of below 1.0 % ( Table 1 , intrapopulation variation). A maximum likelihood tree of the partial 16S sequence ( Fig. 37 ) found no significant relationship to other congeners.

Remarks: This species was delimited by the 16S sequences. Were it not for the 16S data, we would have considered the specimens as juveniles or a smaller form of A. neocyanea , this notably for their resembling tentacle bulbs (comp. Figs 38E and 40E ). However, the 16S sequence data ( Fig. 37 ) separated them into two unrelated clades. The base pair differences between sequences of the two clades were>8.2%. The two sample sets cannot well be compared morphologically as they represent different developmental stages. None of the specimens of the present species had fully developed gonads. One difference we noted was the presence of a large excretory papilla in a majority of specimens of the present species.

We were initially tempted to identify this lineage as Aequorea floridana (L. Agassiz, 1862) , a species also reported to be common along the cost of Florida and the Bahamas by Mayer (1900) [for descriptions see Mayer (1910) and Bigelow (1913, 1938)]. Mature Aequorea floridana have 16 to 24 radial canals and up to 80-100 tentacles ( Mayer, 1910). Sixteen is the prevalent number of radial canals. Our specimens with gonads had 14 to 46 radial canals and consistently fewer tentacles than radial canals. It was mainly the low tentacle number which influenced our decision to reject an identity with A. floridana . The lack of fully developed animals and the lack of distinctive features made it advisable not to introduce a new species name. This is an unsatisfactory situation, but 16S data of fully-grown animals and also of typical A. floridana morphotypes are needed to solve the problem and to put a name on this lineage.

Figures

Fig. 40. Aequorea spec. 1. (A-B) BFLA4163, size> 10 mm. (C) BFLA4163, manubrium. (D) BFLA3814, close up of bell margin. (E) BFLA4163, close up of bell margin. (F) BFLA3814, size 12 mm. (G) BFLA3788, size not recorded. (H) BFLA4002, size 17 mm. (I) BFLA4002, bell margin from oral side, arrow points to excretory papilla. (J) BFLA3781, size 9 mm. (K) BFLA4476, size 5 mm, youngest observed stage with 6 complete radial canals, a large prey item is in the stomach.

Fig. 37. 16S maximum likelihood phylogenetic tree of the genus Aequorea and related genera obtained with PhyML (GTR+G+I model) using 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. Red labels are new sequences from this study, for the taxa in bold either a voucher specimen or photos of it have been examined. Notes: *1) Unpublished, L. Leclère, pers. comm. *2) See Material & Methods. *3) Could be a misidentification. *4) Unpublished, A. Hosia & L. Martell, pers. comm., see Fig. 39A.

Fig. 38. Aequorea neocyanea new name. (A-C) BFLA4085, bell diameter 60 mm. (A) Oblique view from below. (B) Aboral view. (C) Bell margin with tentacles and their bulbs. (D) BFLA4083, bell diameter 42 mm, young animal with beginning gonad development. (E) BFLA4043, bell margin. (F) BFLA4236, bell margin, the green dots are not a pigment but likely due interference effects. (G) BFLA4236, mouth region with short fimbria. (H) BFLA3783, bell margin. (I) BFLA3783, tentacles after fixation in formalin.