Bougainvillia spec.

Schuchert, Peter & Collins, Richard, 2021, Hydromedusae observed during night dives in the Gulf Stream, Revue suisse de Zoologie 128 (2), pp. 237-356 : 241-242

Bougainvillia spec.

Fig. 1 A-B

Examined material: BFLA3826 ; 1 specimen, 14 -NOV- 2018; bell height 5 mm; photographed and then preserved in alcohol for DNA extraction; 16S sequence MW528641 .

Observations: Bell 5 mm high, higher than wide, mesoglea thick, apical mesoglea 1/4 of bell height, apex rather flat. Manubrium with cruciform base, oral region tubular, widest at base and thus like an inverted cone; four perradial oral tentacles arise well above mouth rim, trunk long, branched about 3 to 4 times, ending in spherical nematocyst knobs. Four gonads, male, interradial, encircling stomach entirely. Four radial canals and marginal bulbs, bulbs D-shaped ( Fig. 1B ), each with about eight filiform tentacles; dark, round ocelli on adaxial side of tentacle base.

16S Data: A blastn search with the partial 16S gene sequence ( MW528641 ) did not give a close match, but the best five matches were Bougainvillia species. The sequence with the highest similarity (94% identity) was EU305470 , obtained from a B. fulva collected in Japan (Kirsten Jensen, Kansas University, pers. com.). Others were B. triestina and B. carolinensis with about 92% identity. Bougainvillia muscus sequences differed even more, reaching only 87% identity.

Remarks: This Bougainvillia medusa could not be identified reliably. Morphologically, it resembles B. carolinensis ( McCrady, 1859) and B. muscus ( Allman, 1863) . It differs from B. carolinensis (see descriptions in Mayer, 1910; Kramp, 1959a; Calder, 1971) in lacking the characteristic shape of the manubrium, which is widening from the aboral end towards the mouth. The manubrium of the present medusa is widest at the aboral end ( Fig. 1A ). Bougainvillia muscus medusae (for a description see Schuchert, 2007) differ in being smaller (1-4 mm), they have less tentacles per bulb (2-6), and the oral tentacles branch less (0-2).

Also, the 16S data argue against B. carolinensis and B. muscus . There are several 16S sequences of B. muscus available in GenBank (e.g. AM183126 , AM411411 ), covering populations from Europe to New Zealand and with an intraspecific divergence of up to 1.5% base pair differences. The Bougainvillia medusa from Florida differed from B. muscus in 13% of the base pairs, and was thus far beyond the intraspecific divergence. The single available sequence from a B. carolinensis from Brazil ( MG791827 ) did also not match (90% identity only). No morphological data are available for this sample and its identification cannot be verified.

Other Bougainvillia medusae known from the region can also be excluded based on their morphology. Bougainvillia niobe Mayer, 1894 buds medusae from the manubrium. These might not always be present, especially in mature animals (compare fig. 90 in Mayer, 1910), but the gonads are reportedly adradial and not interradial ( Kramp, 1959a: 12). Bougainvillia rugosa Clarke, 1882 has medusae with unbranched oral tentacles and only 3 tentacles per bulb ( Migotto, 1996).

The observed medusa thus likely belongs to an unnamed species, or a hydroid-based nominal species for which the adult medusa is not known yet. Using the 16S sequence will certainly in the future permit the identification of the hydroid (comp. Schuchert et al., 2017; Schuchert, 2019), as well as additional growth stages and the females of the medusa, and thus give a more solid base for the description as a new species.

Figures

Fig. 1. Bougainvillia spec. of 14-NOV-2018, bell height 5 mm (A) Lateral view of whole animal. (B) Oral view.