What's left in the tank? Identification of non-ascribed aquarium's coral collections with DNA barcodes as part of an integrated diagnostic approach.

The unprecedented threats to coral reef ecosystems from global climate change require an urgent response from the aquarium community, which is becoming an increasingly vital coral conservation resource. Unfortunately, many hermatypic corals in aquaria are not identified to species level, which hinders assessment of their conservation significance. Traditional methods of species identification using morphology can be challenging, especially to non-taxonomists. DNA barcoding is an option for species identification of Scleractinian corals, especially when used in concert with morphology-based assessment. This study uses DNA barcodes to try to identify aquarium specimens of the diverse reef-forming genus Acropora from 127 samples. We identified to our best current knowledge, to species name 44% of the analysed samples and provided provisional identification for 80% of them (101/127, in the form of a list of species names with associate confidence values). We highlighted a sampling bias in public nucleotide sequences repertories (e.g. GenBank) towards more charismatic and more studied species, even inside a well-studied genus like Acropora. In addition, we showed a potential "single observer" effect with over a quarter of the reference sequences used for these identifications coming from the same study. We propose the use of barcoding and query matching as an additional tool for taxonomic experts and general aquarists, as an additional tool to increase their chances of making high confidence species-level identifications. We produce a standardised and easily repeatable methodology to increase the capacity of aquariums and other facilities to assess non-ascribed species, emphasising the value of integrating this approach with morphological identification optimising usage of authoritative identification guides and expert opinion. Supplementary Information: The online version contains supplementary material available at 10.1007/s12686-021-01250-3.

The highly toxic and cryptogenic clinging jellyfish Gonionemus sp. (Hydrozoa, Limnomedusae) on the Swedish west coast.

The clinging jellyfish Gonionemus sp. is a small hydromedusa species known historically from the Swedish west coast but not reported in recent times. This species is thought to be native to the northwest Pacific where it is notorious for causing severe stings in humans and is considered invasive or cryptogenic elsewhere. This year, unlike in the past, severe stings in swimmers making contact with Gonionemus sp. medusae occurred in Swedish waters from a sheltered eelgrass bed in the inner Skagerrak archipelago. To the best of our knowledge, this is only the second sting record of Gonionemus sp. from the Northeast Atlantic-with the first record occurring off the Belgian coast in the 1970s. Stinging Gonionemus sp. medusae have also been recently reported from the northwestern Atlantic coast, where, like on the Swedish coast, stings were not reported in the past. We analyzed sea surface temperature data from the past 30 years and show that 2018 had an exceptionally cold spring followed by an exceptionally hot summer. It is suggested that the 2018 temperature anomalies contributed to the Swedish outbreak. An analysis of mitochondrial COI sequences showed that Swedish medusae belong to the same clade as those from toxic populations in the Sea of Japan and northwest Atlantic. Gonionemus sp. is particularly prone to human-mediated dispersal and we suggest that it is possible that this year's outbreak is the result of anthropogenic factors either through a climate-driven northward range shift or an introduction via shipping activity. We examined medusa growth rates and details of medusa morphology including nematocysts. Two types of penetrating nematocysts: euryteles and b-mastigophores were observed, suggesting that Gonionemus sp. medusae are able to feed on hard-bodied organisms like copepods and cladocerans. Given the now-regular occurrence and regional spread of Gonionemus sp. in the northwest Atlantic, it seems likely that outbreaks in Sweden will continue. More information on its life cycle, dispersal mechanisms, and ecology are thus desirable.

World-wide whale worms? A new species of Osedax from the shallow north Atlantic.

We describe a new species of the remarkable whalebone-eating siboglinid worm genus, Osedax, from a whale carcass in the shallow north Atlantic, west of Sweden. Previously only recorded from deep-sea (1500-3000 m) whale-falls in the northeast Pacific, this is the first species of Osedax known from a shelf-depth whale-fall, and the first from the Atlantic Ocean. The new species, Osedax mucofloris sp. n. is abundant on the bones of an experimentally implanted Minke whale carcass (Balaenoptera acutorostrata) at 125m depth in the shallow North Sea. O. mucofloris can be cultured on bones maintained in aquaria. The presence of O. mucofloris in the shallow North Sea and northeast Pacific suggests global distribution on whale-falls for the Osedax clade. Molecular evidence from mitochondrial cytochrome oxidase 1 (CO1) and 18S rRNA sequences suggests that O. mucofloris has high dispersal rates, and provides support for the idea of whale-falls acting as 'stepping-stones' for the global dispersal of siboglinid annelids over ecological and evolutionary time.