CRITTER CONFIDENTIAL What ’ s the link ? Angler fish – Lophius piscatorius Eckstrom ’ s topknot – Zeugopterus regius
If you ’ re wondering why Paul Naylor is featuring two unrelated fish in the same column , all is about to be revealed ...
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’ ll start with a few basics about the two species . The angler fish , sometimes known by anglers and in a gastronomic context as a ‘ monkfish ’, is a superbly adapted bottom-living predator with a very unusual and rather squashed appearance . It has a massive , broad and flattened head with a relatively slim body and small tail . The angler ’ s camouflage is excellent , with a blotchy seabed-colour pattern enhanced by intricately lacy flaps of skin that help to break up its outline . There are stories of divers virtually landing on large anglers – they can reach 2 metres in length – before spotting them !
I have only ever seen two but I wonder how many others I ’ ve swam over without realising . The ‘ angler ’
Angler fish on a wreck near Sunderland
Eckstrom ’ s topknot among soft corals on a rock face , clearly showing its elongated first dorsal fin ray name comes from their ‘ fishing rod ’, the forwardmost dorsal fin ray , which is greatly elongated with a fleshy tip that can be moved around to act as a lure . When oblivious victims are enticed fatally close to the angler ’ s large mouth , the combination of inwardcurving teeth and the rush of water as it opens its jaw seal the victim fate . Prey includes all sorts of fish and even diving birds .
Eckstrom ’ s topknot is also a specialist seabed dweller but has followed a very different evolutionary path . Like other flatfish , it is flattened from side-toside , the opposite way to the angler fish , and lies on its side when it reaches adulthood . Unlike flatfish such as plaice and sole , which lie with their rightside uppermost , topknots lie left-side up . While the normal topknot ( Zeugopterus punctatus ) is a very common sight for those of us who spend a lot of time watching the inhabitants of rocky reefs and their crevices , Eckstrom ’ s topknot is a much rarer beast . It is distinguished by different markings , spines on its scales that make it look slightly hairy and ( on some individuals ) a greatly elongated front dorsal fin ray that extends in front of the fish ’ s mouth .
Writing about the two species now , the link seems obvious , but it only occurred to me after one particular dive . We were in Loch Carron , exploring the beautiful site called ‘ Conservation Bay ’ where there is an impressive rock wall covered in soft corals and other life in abundance . In among the dead men ’ s fingers on the wall , we spotted two Eckstrom ’ s topknots and settled down to watch , particularly to see if there was to be any courtship . They are such an unusual find that I was excited simply by the sighting , but the real intrigue came from processing my video long after the dive .
The video was far from brilliant , with much of the action shaded from my lights by the corals , but we could make out one of the Eckstrom ’ s topknots approaching a small prawn . It appeared to ‘ waggle ’ its elongated fin ray at the prawn , just before shooting out its highly extendable and almost telescopic mouth . As is often the case with the lighting fast interactions of predator and prey , we couldn ’ t tell if the prawn was captured on this occasion . We did see enough , however , to be enthralled by the thought that Eckstrom ’ s topknot may have developed a similar angling technique to the angler fish ! Is this what ’ s called ‘ convergent evolution ’ in action ? �
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