Being ‘on-island’ right now, I don’t get so much time to write stuff. To everyone’s relief, I guess (including mine). So for a while I’ll post some individual pics that particularly appeal to me. Elvis the squirrelfish (featured in a previous post) has now upgraded to a more spacious and frankly rather posher address. And in he goes…
FORAYS WITH MORAYS (4): EXPRESSIVE FEATURES
Time to return to those extremely expressive characters of the coral reefs, moray eels. Specifically, some green morays. One hesitates to anthropomorphise or ‘project’ human emotions onto creatures but with some species it’s hard not to do so. Following Mr Grumpy (or perhaps Mr Sad) in the header image, here are some close-ups of morays appearing to express their emotions, from happy to downright furious… Eels featured here include Judy and Wasabi, and I remind myself that the human habit of naming familiar wild creatures is itself a (perfectly harmless) form of benign animism. Exactly as with the regular banded piping plovers featured elsewhere in this blog that overwinter on Abaco’s beaches, such as Harry Potter, Bahama Mama and the delightfully-named Felicia Fancybottom…
THE NEXT POST WILL BE FROM ABACO HQ NEXT WEEK
Credits: All morayvellous photos, Melinda Riger / Grand Bahama Scuba except 6, Virginia Cooper / Grand Bahama Scuba
BLUEHEAD WRASSE: PRIVATE LIFE LAID BARE
The bluehead wrasse (or blue-headed wrasse) Thalassoma bifasciatum is a denizen of the coral reefs of the tropical waters of the western Atlantic Ocean. This bright little 4-inch fish is… a wrasse with a blue head. No more and no less. Unless it’s a juvenile. Then it is mainly bright yellow. It’s similar to BLUE TANG (aka ‘the Disney Dory’), which starts life bright yellow and grows up to be blue.
The species may be found singly, in pairs or small groups, or in schools. They have an important role to play in the life of the reef. They are CLEANER FISH, vital to the health and wellbeing of the larger species they attend to, and thus of the reef itself. This is ‘cleaning symbiosis’, a relationship of mutual benefit. The big fish get cleaned; the little fish have a useful function and – importantly for them – therefore don’t get eaten.
Having said that, blueheads are of course fair game as a snack for species that aren’t in the market for their cleaning services. And, unfairly, some species that are content to let cleaner gobies runtle around their gills and mouths are not so considerate of the wrasse. Some types of grouper and moray eel, for example.
TELL US EXACTLY SEVEN BLUEHEAD WRASSE FACTS
- Juveniles can alter the intensity of their colour, stripes & bars
- The bluehead wrasse is a ‘protogynous sequential hermaphrodite’
- All are born female**. Some change sex to male during maturation (see below)
- Food includes zooplankton, small molluscs and small crustaceans…
- …and parasites / other juicy bits (fungal growths, anyone?) from bigger fish
- The main threat to the species is coral reef degradation or destruction
- The bright colours invite aquarium use, but the trade is not a significant one
** Some sources suggest some are born male and remain male. I’m not sure which is right
THE REMARKABLE SEX LIFE OF THE BLUEHEAD WRASSE
This is an unavoidable topic, I’m afraid. The bluehead’s sex life is the most interesting thing about them, and this is no time to be prudish. It is the subject of extensive scientific research, not all of which I have read since I decided to write about the species last night. Like many human relationships, “it’s complicated”, but in a conch shell it boils down to this:
- To recap, BWs are born female and as they mature, some become male.
- Males reach an ‘initial phase’ when they can breed in groups with females
- Some males grow even larger & reach full colouration. This is the ‘terminal phase’
- These large males aggressively chase away smaller ones & seek females to pair with
- Their state of readiness (as it were) is signalled by colour changes
- This behaviour is similar to that seen in many city centres in a Saturday night
- The smaller fish have one bonus – their sperm count is higher than a dominant male
- Prozac tests have shown that the drug reduces a dominant male’s aggression
As the excellent organisation OCEANA puts it: Bluehead Wrasses may reproduce in four different ways throughout their lifetime: 1) as a female in a group spawning event; 2) as a female in a pair spawning event within the territory of a large male; 3) as a small male in a group spawning event; and 4) as a dominant, terminal male in a pair spawning event within its own territory.
A cropped still from a video I took at Fowl Cay marine reserve. I’ve looked at dozens of images online and not found one that was all blue with a yellow end to its tail fin. Maybe it’s not a BW at all. Or it’s a different type of fish completely. Or perhaps it is just an all-blue alpha male.
Credits & Sources: Melinda Riger; Adam Rees; James St John; Oregon State edu / Pinterest; Wiki images; self; Oceana; IUCN; magpie pickings
WONDERS OF THE DEEP: FROM SUBLIME TO… THE OTHER THING
It’s a statistically proven fact (and not, in any way, a ‘post-truth’ proposition) that no one has ever had a bad thing to say about seahorses. Indeed, some love them too much and consume them – see HERE for threats to seahorse populations in some areas of the world.
Sometimes they are easy to see. The header image shows an orange seahorse curling its tail round green weed on pink coral – hard to miss. Yet sometimes it may be quite difficult to see the little creatures against their chosen background.
These guys are, I think, for their size among the most sublime of all underwater creatures. I use the word in the strict historical sense “of very great excellence or beauty, exalted, awe-inspiring, majestic, magnificent, glorious.” Not just to mean “nice”.
In contrast, there are some undersea creatures that inspire… not awe exactly, but maybe an amused respect that so wonderful and bizarre a creature can exist in our oceans, in some cases only a few feet below the surface. Here are two examples of what I mean.
This is a BATFISH. It was an early shoo-in for my “WTF? (What’s that Fish?)” series, and you can read all about them and their ways HERE. Of all the creatures I have featured on this blog, this is by some distance the oddest…
…except for its companion in oddness, the FROGFISH. This was next in the WTF? series, and the creature is, if anything, even stranger. You can read all about these critters HERE, where you will learn inter alia about their superpowers – any one of which you might like to have yourself. There are plenty of photos, and videos too.
- Invisibility Cloak
- Irresistible (and, to their prey, Fatal) Attraction
- Buoyancy Control
I do not court controversy, recognising that people following this site, or maybe stumbling across it by mistake and lingering, reach their views on natural history from different directions. But these strange and fascinating species exist and thrive in their own particular and ingenious ways – it doesn’t really matter how or why they are as they are. The bats and the frogs are high in the list of the least conventional of undersea creatures, and if they are not exactly sublime in a seahorse sense, can we just agree that they are awesome?
WATCHING NURSE SHARKS: BE PATIENT…
I last took a look at nurse sharks nearly 3 years ago HERE. Time to revisit these creatures. Indeed, time for a close-up look. If you want to know more about this fascinating species, just click the link above.
Admire the extraordinary texture of the the skin; and the tiny evil eye. Click or – better – double click on the image and you will see that the skin is in fact tessellated, made up of a mosaic of tiny squares and near-squares**
Head, mouth, jaws and teeth
SO, THEY ARE SHARKS – ARE THESE GUYS DANGEROUS?
Not really, no. They aren’t looking to pick a fight; and they are not as territorially aggressive as the ‘bitey’ sharks are (or can be). These slow-moving bottom-dwellers are generally harmless to humans. However, they can be huge—up to 4 metres —and have very strong jaws filled with thousands of tiny, serrated teeth. They will bite defensively if stepped on or bothered by divers who assume they’re docile. [As I said previously, “there are recorded instances of injuries caused to divers who have tried to pull nurse sharks by the tail. And serve them right, I say. Treat them with patience and respect!”]
M.C. ESCHER (the inspiration for Mr Hammer) was the master of tessellation in art. Click the link to explore the dedicated website. Maybe, sensationally, one day a shark will be found with skin like this… (Alert reader: “Actually, I think it most unlikely…”)
Credits: field photos by Melinda Riger, Grand Bahama Scuba; Wiki for the 4 mouth images & the Escher
CHRISTMAS TREE WORMS: FABULOUSLY FESTIVE
“Deck the Reefs with Worms Like Christmas Trees… Fal-La-La-etc-etc ” is a traditional Carol familiar to all. Well, most. Ok, some, then. Oh right – maybe with different words. Anyway, now is as good time as any to take a look at these remarkable
plants creatures and subsurface symbols of good cheer.
10 CHRISTMAS TREE WORM FACTS TO PONDER
- The 2 colourful spirals are not the worm, but complex structures for feeding & respiration
- The spirals act as specialised mouth extensions for ‘filter-feeding’
- Prey is trapped by the feathery tentacles & guided by cilia (microscopic hairs) to the mouth
- The tentacle things are radioles and act as gills for breathing as well as prey traps
- It is not believed that prey slide down the spiral to their doom, like on a helter-skelter
- The actual worm lives in a sort of segmented tube, with extremely limited mobility skills
- It contains digestive, circulatory & nervous systems – and a brain in the middle of it all
- The worm also has a tiny drainage tube (I think I have this right) for excretion etc
- They embed themselves into heads of coral such as brain coral. And stay there
- And yes, the Christmas trees are retractable…
HOW DO THE WORMS… YOU KNOW… ER… REPRODUCE?
This is a delicate area. They don’t tend to talk about it much, but as far as I can make out they eject gametes from their what-I-said-above. There are mummy and daddy CTWs, and their respective gametes (eggs and spermatozoa) drift in the current and presumably into each other to complete the union. The fertilised eggs develop into larvae, which settle onto coral and burrow into it, build their protective tubes and the process begins again.
LOOK, YOU DON’T REALLY UNDERSTAND THESE CREATURES, DO YOU?
I won’t lie. I found it hard to work out how the CTWs function in practice. There are plenty of resources showing them in their full glory, but that only takes one so far. Then I came across a short video that shows it all brilliantly simply (except for the reproduction part). So maybe I should have just posted this first and saved you (and me) some trouble…
The worm, invisible in its coral burrow, hoists its pair of trees. You can easily see small particles – possibly zooplankton – drifting in the water, and the radioles swaying to catch potential food. Bingo. It all makes sense! Next: the New Year Worm
Credits: Melinda Riger (G B Scuba); Adam Rees (Scuba Works); Nick Hobgood; Betty Wills; Absolutely Wild Visuals; MarineBio; Wikibits & Magpie Pickings
WTF? (WHAT’S THAT FISH?) 12: THE TRUMPETFISH
It’s been a while since the previous post in the WTF? series, dedicated to the unusual or downright weird marine creatures that, when you see them swim into in the frame of your mask, prompt the involuntary exclamation “WTF?” (What’s That Fish?). Now, in all its glory meet… The Trumpetfish. These long piscine pipes are in no way related to the President-Elect and his tank of pet fish, but perhaps more explicably to seahorses and seadragons.
Trumpetfishes Aulostomus maculatus are as happy to swim upright as more conventionally, which helps them to blend in with vertical corals and sponges on the reefs in the tropical waters of the western Atlantic. Adults may grow to 3 foot long or more. These creatures come in a variety of colours – shades of red, orange, brown, green and yellow.
At the end of the fish’s long snout – see how far back the eyes are set – is a small mouth. Here’s how a trumpetfish goes about catching its prey (mostly small fishes):
- Slowly swimming or drifting to a target from behind, and sucking it into its mouth
- Staying suspended in the water, motionless, and waiting like a malevolent stick for a passing wrasse or similar to get too close
- Swimming alongside larger fishes, which camouflages its presence and enables it to ambush small fish as they pass
- More generally, the trumpetfish has some ability to change its colour to blend with its surroundings – both a defensive as well as an attacking advantage
The very excellent Peppermint Narwhal recently produced a series of posters in appreciation of particular species – and trumpetfishes and their kin in the Order syngnathidae were honoured. The PN’s cheerful website is well worth checking out for the sheer diversity of their ideas.
We are beginning to collect the makings of a decent orchestra here. The trumpetfish has a relative, the cornetfish, elsewhere in the world. The remarkable GUITARFISH has already featured in the WTF? series, as has a species of BASS, the Harlequin. And – hey! – what about the spotted DRUMFISH to lay down the beat? Maybe I need to compose a little jingle featuring these one day…
Credits: Melinda Riger (Grand Bahama Scuba); Adam Rees (Scuba Works)