"A phylum is a broad division in taxonomy: all vertebrates, for example, from fish to humans, are in the chordate phylum. In 1995, Peter Funch and Reinhardt Mobjerg Kristensen, both then at the University of Copenhagen, Denmark, discovered an animal so unlike any other that a new phylum – Cycliophora – had to be created just for it.
Symbion pandora, as they called the new creature, is a tiny animal with a complex body and a bizarre life cycle. They live on the hairy mouthparts of Norway lobsters, with tens or even hundreds per lobster. They feed on bits of leftover food and seem to be harmless to their hosts.
Things start to get complicated when you consider their life cycle. Let's start with a feeding animal living on a lobster's mouthparts: this individual – it's hard to assign a sex – can then produce one of three kinds of offspring: a "Pandora" larva, a "Prometheus" larva or a female.
The Pandora larva develops into another feeding adult – a straightforward case of asexual reproduction. By contrast, the female remains inside the adult and awaits a male – but, attentive readers will be crying, what male?
The answer lies in the Prometheus larva. This attaches itself to another feeding adult, then produces two or three males from within itself. These dwarf males, which are even more internally complex than the other stages, seek out the females and fertilise them – though the details are unknown.
Once the female has been fertilised, she leaves the adult's body and hunkers down in a sheltered region of the lobster's mouthparts. Her body, no longer needed, turns into a hard cyst. Inside this, a fertilised egg develops into yet another stage: the chordoid larva.
In due course this larva hatches and swims off to colonise another lobster. Once it has attached itself to one, it develops into another adult and the cycle begins again."
So if reproduction can be so different here - how mindblowing different could it be many a lightyear or parsec away? Fascinating.
Link: NewScientist
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