Το Ημερολόγιο του Blue Community (s Afr)

Global genomics of the man-o’-war (Physalia) reveals biodiversity at the ocean surface
SH. Church, RB. Abedon & others doi: https://doi.org/10.1101/2024.07.10.602499

Abstract:
The open ocean is a vast, highly connected environment, and the organisms found there have been hypothesized to represent massive, well-mixed populations. Of these, the Portuguese man-o’-war (Physalia) is uniquely suited to dispersal, sailing the ocean surface with a muscular crest. We tested the hypothesis of a single, panmictic Physalia population by sequencing 133 genomes, and found five distinct lineages, with multiple lines of evidence showing strong reproductive isolation despite range overlap. We then scored thousands of citizen-science photos and identified four recognizable morphologies linked to these lineages. Within lineages, we detected regionally endemic subpopulations, connected by winds and currents, and identified individual long-distance dispersal events. We find that, even in these sailing species, genetic variation is highly partitioned geographically across the open ocean.

Summary:
We combined these data with an independent dataset of thousands of images of Physalia uploaded to the citizen-science website inaturalist.org, which we scored for morphological characters including sail size, tentacle arrangement, and color. From these images, we identified four recognizable morphologies, described their geographical distribution, and linked them to four of the lineages identified with genomic data. We conclude there are at least four species, three of which correspond to species proposed by scientists in the 18th and 19th centuries: P. physalis, P utriculus, and P. megalista, along with one as yet unnamed species Physalia sp. from the Tasman Sea. Within each species, we observe significant population structure, with evidence of persistent subpopulations at a regional scale, as well as evidence for individual long-distance dispersal events. Our findings indicate that, instead of one well-mixed, cosmopolitan species, there are in fact multiple Physalia species with distinct but overlapping ranges, each made up of regionally endemic subpopulations that are connected by major ocean currents and wind patterns.

Out in the greater Pelagic zone - in fact, on the interface between atmosphere and marine - is a floating community that taps the food from below, and lives off one another.

(New Zealand examples here: https://www.inaturalist.org/projects/blue-fleet-monitoring-nz)

A feature of this community is their exposure to predation from above and below: to this end they are predominantly blue in colour - from whence they get their name.

They either float - on floats, bubble rafts, or flotsam - or live suspended in the surface tension of the interface. Blown about by winds, they often end up in masses along the shoreline. Here Bluebottles in their death throws and beyond, encounter humans and earn their reputation as stinging hell. But the majority of species are small and not easily noticed, and after a day or two on the beach, shrivel up, die, bleach and blow away, or are eaten by whelks and other predators.

Poorly known: this page is devoted to making the Blue Community better known.

The primary component of the community is the Portuguese-Man-O-War (or Bluebottle), which is a Cnidarian, a highly developed "social Anemone" - a community - with different animals forming a float (filled with Carbon dioxide), stinging tentacles (for defense and catching prey: these may be 10-50m long, and have contractile cells to reel in any catch), feeding polyps (which surround and digest food) and reproductive zooids. The tentacles have stinging cells that produce toxins that kill prey: to humans they can be extremely painful and may blister skin.

Feeding on these are small creatures: another Cnidarian (of course), a Seaslug, a Snail, a Crab. I did say that it was a small community: it is not very diverse, although different species may occur in different oceans. All are small and blue.

Associated with them are some fish that live among the tentacles. These are immune or do not trigger the stingers in the PMOW and thus seek safety among the tentacles. Most prominent of these is the Man-O-War-Fish or Shepherd Fish, which nibbles on the smaller tentacles.

And they are joined by Goose Barnacles, when here is enough flotsam.

And dont forget the Argonaut: the Sailing or Flying Octopus, or Paper Nautilis, which constructs a sail of calcite and travels the high seas. The shell is a retreat, egg case, sail and bubble trap, the female living inside it (males are small and merely living penises, leaving their hectocotylus with sperm in the female, after which they break off and die) and sailing the seven seas. They live off seaslugs, snails, crabs, jellyfish and salps. They can change colour, produce ink as a smoke-screen, and flash silver to confuse predators. Still they are eaten by many larger fish and dolphins.

There are other members of this community, but most appear to be rare or only join occasionally. Hopefully we will find more, and find out more.

There is no reason why the Blue Community should remain obscure.