‘TERN, TERN, TERN’: THE UN-NOTORIOUS BIRD COUSINS

June 26, 2024 by Rolling Harbour

‘TERN, TERN, TERN’: THE UN-NOTORIOUS BIRD COUSINS

There are twelve species of tern – ‘swallows of the sea’ – that to a greater or lesser extent may be found on Abaco. Whether they will actually be visible at any given time is less certain, though. For a start, the only resident species is the lovely Royal Tern, available at many locations on Abaco and the cays throughout the year. The rest are migratory or just passing through.

PERMANENT RESIDENTS

ROYAL TERNS Thalasseus maximus PR1

MIGRATORY TERNS: SUMMER

In the slightly less commonly-found category are the summer migrant terns that, by definition, are only in residence for around half the year. Four of these are fairly common in certain areas, and actually breed on Abaco; these include arguably the prettiest of all, the bridled tern. The other two tern species (gull-billed and sandwich) are more rare and as far as I can make out do not breed locally; or perhaps only rarely.

LEAST TERN Sternula antillarum SR B 1

BRIDLED TERN Onychoprion anaethetus SR B 2

ROSEATE TERN Sterna Dougallii SR B 2

SOOTY TERN Onychoprion anaethetus SR B 2

GULL-BILLED TERN Gelochelidon nilotica SR 3

SANDWICH TERN Thalasseus sandvicensis SR 4

MIGRATORY TERNS: WINTER

There is one very rare winter resident migratory tern species, with few records of sightings for Bahamas and until early 2019, no photographic record for Abaco until Sally Chisholm saw one at Treasure Cay and managed to capture it for posterity.

FORSTER’S TERN Sterna forsteri WR 4

OCCASIONAL & RARE VISITORS

A further four tern species are very much occasionals that drop by. Three of them pass over the Bahamas on their longer migration, but may make a pit-stop around Abaco to take on fuel. Likelihood of sighting one? Slender but not impossible… the Caspian tern below was photographed on Abaco. The fourth, the Arctic Tern, is a very rare vagrant, a bird well away from its usual home or migration route as the result of storms or faulty satnav or sheer happenstance. Don’t travel to the Bahamas intent on seeing one.

CASPIAN TERN Hydroprogne caspia TR 4

The remaining species are the transient black tern and common tern; and the vanishingly rare vagrant Arctic tern. No photos of any of these I’m afraid. Here’s a handy checklist of all the tern species.

ELECTIVE MUSICAL DIGRESSION

Written by Pete Seeger, Turn x 3 was released in 1965, the title track on the second album by The Byrds. At a rather febrile time in US history (Vietnam, draft riots, civil rightists v cops and so on), this unusually palliative and thoughtful song with its religious connotations to some extent stood for peace and hope in a time of turmoil.

PS the somewhat laboured title of this post shoehorns in the name of another Byrds album, ‘The Notorious Byrd Brothers’

Photo credits: Keith Salvesen (1, 2, 3, 5, 18); Tony Hepburn (4); Alex Hughes (10, 11); Bruce Hallett (6, 7, 12); Woody Bracey (8, 13, 16); Duncan Wright (9); Dick Daniels (14); Sally Chisholm (15); Keith Kemp (17)

WTF? (WHAT’S THAT FISH?): THE FROGFISH

June 11, 2024 by Rolling Harbour

WTF? (WHAT’S THAT FISH?): THE FROGFISH

The ‘WTF?’ series started with relatively conventional species eg REMORAS and became progressively more bizarre. In due course, having covered the excellently strange BATFISH it was time to ramp up the stakes: with many thanks to scuba expert Adam Rees for use permission for his terrific photos, I present… the FROGFISH.

The frogfish is a kind of anglerfish found in almost all tropical and subtropical oceans and seas. There are about 50 different species worldwide, covering an astonishing range of strange appearances. They generally live on the sea floor around coral or rock reefs. In size they vary from tiny to about 15 inches long – although ‘long’ is a flexible concept because they are to an extent shape-changers in height and width.

FROGFISH SUPERPOWERS YOU MAY WISH TO HAVE

INVISIBILITY CLOAK . Frogfish are masters of disguise and camouflage. This enables them to catch their prey with minimal effort and also to avoid predators. Their camouflage methods – broadly known as ‘aggressive mimicry’ – include
- Ability to change colour for days or even weeks to mimic their surroundings
- Getting covered in algae and other organic matter that matches their habitat or
- Looking inherently like a plump rock or in some cases, plant

Fear for the life of the spider crab…

IRRESISTIBLE ATTRACTION
- A sort of frontal dorsal fin called an illicium to which is attached a
- Lure called an esca which may mimic a worm, shrimp or small fish etc and which is
- Retractable in many species and
- Regenerates if it gets mislaid

The ‘dollop of cream’ thing is the esca. Note the characteristic large mouth

BUOYANCY CONTROL & SHAPE-SHIFTING
- Most frogfish have a ‘gas bladder’ to control their buoyancy.
- Some species can change shape or even inflate themselves by sucking in quantities of water in a so-called defensive ‘threat display’.

frogfish-black

HOW DO FROGFISH REPRODUCE?

Although not conventionally attractive creatures, frogfish clearly manage to reproduce. Little is known about the techniques in the wild, but one is probably ‘with care’, especially for a male frogfish who may not survive for long if he hangs around after fertilisation has taken place. It has been noted that females tend to select far smaller males to fertilise their huge numbers of eggs, perhaps for that very reason.

Spot the esca… 1280px-Antennarius_striatus2

FROGFISH FEEDING SKILLS – GOOD OR BAD?

When deploying the lure, potential prey that comes too close to that wide mouth stands no chance. A frogfish will strike in a fraction of a second. Frogfishes have voracious appetites for crustaceans, other fish, and even each other. I can do no better than borrow this vivid description of a feeding frogfish:

“When potential prey is first spotted, the frogfish follows it with its eyes. Then, when it approaches within roughly seven body-lengths, the frogfish begins to move its illicium in such a way that the esca mimics the motions of the animal it resembles. As the prey approaches, the frogfish slowly moves to prepare for its attack; sometimes this involves approaching the prey or “stalking” while sometimes it is simply adjusting its mouth angle. The catch itself is made by the sudden opening of the jaws, which enlarges the volume of the mouth cavity up to twelve-fold, pulling the prey into the mouth along with water. The attack can be as fast as 6 milliseconds. The water flows out through the gills, while the prey is swallowed and the oesophagus closed with a special muscle to keep the victim from escaping. In addition to expanding their mouths, frogfish can also expand their stomachs to swallow animals up to twice their size.“

HOW DO FROGFISHES GET AROUND? SWIM? WALK? CRAWL?

Frogfishes do not in fact move around a great deal. Using their camo advantages, they prefer to lie on the sea floor and wait for prey to come to them. As mentioned in the quote above, they may slowly approach prey using their pectoral and pelvic fins to “walk” along the sea bottom. They can swim using their tail fin (or in some species by simple ‘jet propulsion’ by forcing water out of their gills) but rarely do so – they don’t feed on the move, and they are adapted to the sea floor environment where they food is readily available. However their “walking” ability is limited to short distances.

DO FROGFISH HAVE OTHER COLOUR SCHEMES?

Indeed they do. In stark contrast to the camo species, some frogfishes are hi-lighter bright. Here are two of my favourite photos by Adam that show this clearly. I’ve no idea if these are a male and female. I suspect they are different species. I think the brown one is a striated frogfish and the other is… a yellow frogfish. Some people keep these creatures in aquaria, but apparently it is impossible to sex them, and they have to be kept on their own for everyone’s peace of mind…

FROGFISH INFOGRAPHICS

FROGFISH VIDEOS

These two videos, from Lester Knutsen and Daan Van Wijk respectively, show some of the characteristics I have written about above. Both are short and both are fascinating.

Credits: All main photos, Adam Rees of Scuba Works with many thanks; wiki for ‘spot the esca’, red quote & basic info; videos Lester Knutsen & Daan Van Wijk; Jens Petersen /wiki; Teresa Zubi for website & gifs; infographics, authors u/k

CARIBBEAN REEF SQUID: SUPERPOWERS & SQUID SEX

April 27, 2024 by Rolling Harbour

CARIBBEAN REEF SQUID: SUPERPOWERS & SQUID SEX

The Caribbean reef squid Sepioteuthis sepioidea is a small squid species of (mainly) the Caribbean Sea and the Floridian coast, and the most common in its range. These squid tend to form small shoals in and around reefs. From now on, and through the summer, would be a good time to investigate.

Caribbean Reef Squid, Bahamas (Melinda Riger / G B Scuba)

Squid are voracious eaters, dragging their prey to their mouths with some or all of their 10 limbs and using their beak to cut it up. The target species are small fish, molluscs and crustaceans. The squid have a ‘raspy tongue’ known as a radula which further breaks up the food for easy consumption.

REEF SQUID SUPERPOWERS (SUPERCOOL)

Squid are capable of brief flight out of the water (a fairly recent discovery)
They can also hide from / confuse predators by ejecting a cloud of black ink
Squid can change colour, texture and shape, and can even match their surroundings
This enviable power is used defensively as camouflage or to appear larger if threatened
It is also used in courtship rituals (something that humans might find disconcerting)
Colour patterns are also used for routine squid-to-squid communication AND GET THIS:
A squid can send a message to another on one side, & a different message to a squid on its other side

SQUID SEX (1) “ROMANCING THE SQUID”

A male will gently stroke a female with his tentacles
The female will (most likely) flash an ‘alarm’ pattern. She’s playing hard to get.
The male soothes her (don’t try this at home, guys) by blowing and jetting water at her
If this doesn’t go well, he’ll move off, then repeat the routine until she sees his good points
However this on / off courtship can last for hours until at last he succeeds and then…
… he attaches a sticky packet of sperm onto the female’s body (romance is not dead on the reef)
She then reaches for it and moves it to her seminal receptacle
Meanwhile he stays close, emitting a pulsing pattern, as well he might after all that palaver
She then finds a safe place to lay her eggs. Job done. **

SQUID SEX (2) IT ALL ENDS BADLY. VERY BADLY.

As soon the female squid has laid her eggs, she usually dies soon after
Male squid live a bit longer and – erm – may have other packets to stick on other lady squid
But then in the end he dies too
It’s all horribly reminiscent of Romeo and Juliet. The lovers tragically die in the end (but there’s no romantic balcony scene first)

THE CORRECT PLURAL OF SQUID

I had an unwise look online, always a hotbed of conflicting opinions. Inserting an algorithm into the interstices of the internet proves conclusively that the plural of squid is… squid. One squid, ten squid, a group of squid, a plate of squid. Unless, that is, you are talking about more than one of the many squid species, when you could possibly say ‘I collect both reef and giant squids’. “Squidses” sounds fun but is sadly not permitted.

RELATED POST (from the past): THE PLURAL OF OCTOPUS

** For an excellent article about squid including the intricate details of courtship and reproduction (and an image of a squid penis) check out SQUID WIKI

Credits: Fabulous underwater pics – Melinda Riger of Grand Bahama Scuba; research sources include MarineBio; Animal Diversity Web (Michigan Uni); and Wiki, which comes into its own in some fields of natural history where experts write the entry)

PURPLE VASE SPONGES: BAHAMAS REEF ORNAMENTS

April 19, 2024 by Rolling Harbour

PURPLE VASE SPONGES: BAHAMAS REEF ORNAMENTS

The Purple Vase is an unmistakeable sponge, a colourful reef creature (for they are animals, of course) that stands even out amongst the bright corals that surround it. And like corals, sponges are vulnerable to all the usual threats (mainly human-generated).

Catch them while you can in the clear waters of the Bahamas while stocks last. I say this because as study after study concludes, the prospects of reef-mageddon get closer each year. When the corals die off, so in all probability will the sponges and anemones…

After such a depressing intro, let’s move on to take a positive look at the purple vase sponge. As with all sponges, once a newborn sponge is wafted by the current to a place on the reef, it takes root there throughout its life. There, these attractive sponges exist by filtering the water that surrounds them, separating out plankton to feed on. Static filter-feeders, if you will.

You’ll notice that in some of the photographs, the sponges have guests. These are BRITTLE STARS, and they are often found on – and indeed in – purple vases. This is a form of symbiotic relationship known as commensalism, in which one species benefits and the other is neither benefitted nor harmed. The brittle star gains a shelter and a safe base for feeding; the vase gets a harmless companion. Small fishes benefit from the vases in a similar way.

Besides the impact of damaging human interventions (which may be permanent), extreme weather events also affect reef life and the static inhabitants adversely. Storms and hurricanes can cause localised havoc, but the damage is not necessarily permanent. The reef can in time repopulate naturally and flourish again. Humans can even promote this recovery. The photograph above shows a purple vase sponge that was detached from the reef by Hurricane Matthew in October 2016. Melinda Riger in effect replanted it on the reef and it reattached itself and grew. In due course it even acquired its brittle star occupant.

*JIMI AND ‘PURPLE VASE’ – A VOLUNTARY MUSICAL DIGRESSION

In an interview with NME Hendrix is reported to have said that Purple Haze “was about a dream I had that I was walking under the sea.” Originally the song was intended to be ‘Purple Vase’, and reflect the psychedelic experience of life on a coral reef. Realising he was getting bogged down by sub-aquatic imagery (he was a non-swimmer), he toked for a while and then ‘Purple Haze’ emerged almost fully formed. Jimi was always far happier kissing the sky than wandering about under water. Most covers of the song are pale imitations of the original, but here’s a rather unusual take that succeeds by trying a different approach.

Credits: Melinda Riger / Grand Bahama Scuba for all great photos; magpie pickings for bits and pieces, with a shout-out to ‘Critter Squad’ for its informative site aimed at kids. And amateur grown-ups can benefit too… commensalism in humans; Friend ‘n’ Fellow audio

WTF? (WHAT’S THAT FISH?) . YELLOWHEAD JAWFISH

March 31, 2024 by Rolling Harbour

WTF? (WHAT’S THAT FISH?) . YELLOWHEAD JAWFISH

The WTF series is designed to bring some of the more outlandish reef denizens under close scrutiny. Jawfishes (Opistognathidae) come into this category, not least because of their interesting ways with their eggs. Also, they tend to stick upright out of the substrate, which is not especially fishy behaviour.

More than 50 species of jawfish are found around the world. In the Bahamas, you are most likely to encounter the Yellowhead (or Yellow-headed) variety. And if you think they look slightly… primitive, that’s because they are. In fact, their forebears (forefishes?) originated in prehistoric times, specifically the Miocene era (a lot of million years ago, I didn’t count exactly).

These rather extraordinary little fish superficially resemble certain types of BLENNY. Their modus operandi is to burrow down into sandy, gravelly or other loose substrate. They do so by cramming their mouths with sand and spitting it out to one side. By this means they form a tunnel of sorts in which they can live, and from which they can emerge, or half-emerge and take a look around them. As they do so, they hoover up passing food, mostly plankton and suchlike.

If something looks threatening while they are feeding or having a look around, they can simply duck down into their burrow for safety. They guard their patch against rivals, and behave ‘territorially’ in the jawfish community. One method is to ingest and then eject sand or gravel at a would-be intruder.

YES, BUT WHERE IS THE REAL ‘WTF?’ FACTOR HERE?

Good question. With a good and original answer. These little creatures are so-called ‘MOUTHBROODERS‘, meaning that they carry their eggs in their mouths. Depending on the species, females, males or even both parents (don’t try this at home) will do this at or after fertilisation. In effect the eggs are safely incubated until they hatch as fry. Then they are on their own.

ARE THERE ANY DRAWBACKS TO THIS UNUSUAL GESTATION METHOD?

Apart from accidentally swallowing the occasional potential junior, the eggs need aeration from time to time. This is achieved by expelling the eggs from the mouth, and quickly sucking them back in again. Try this very short video to see this rather improbable behaviour in action. It’s only 8 seconds – blink and you’ll miss the action. The eggs hatch into fry in 8 – 10 days, after which both parents can relax. Until the next time.

Yellowhead Jawfish (Melinda Riger / Grand Bahama Scuba)

Photo Credits: all images from Melinda Riger / Grand Bahama Scuba except (4) Virginia Cooper / GBS; (5) Michael Wolf / Wikimedia; video, Alan Keller. Research: magpie picking, not excluding yet not limited to Wiki…

WTF? (WHAT’S THAT FISH?): SCORPIONFISH

February 12, 2024 by Rolling Harbour

WTF? (WHAT’S THAT FISH?) 15: SCORPIONFISH

The WTF? series is aimed at shedding light on fishes that are unusual. Or very unusual. Or puzzling, dangerous and maybe less than elegant in appearance. The scorpionfish is one such. It belongs to a large family, the Scorpaenidae, and many types are found throughout the world, especially in the Pacific and Indian oceans. LIONFISH, the newcomers to the western Atlantic, are a species of scorpionfish.

Just another rock on the seabed… Caribbean Scorpionfish, Bahamas (Melinda Riger / G B Scuba)

WHY ‘SCORPIONFISH’? THEY LOOK SCARY. ARE THEY DANGEROUS?

One feature common to many scorpionfish species is that they are highly venomous. As the name suggests, a sting is involved. Or several stings. These come from the creature’s sharp spines, which are coated with mucus, and are to be avoided. If you want to pet one, the dorsal, anal and pelvic fins are the ones to steer clear of – these all have venom glands at the base. The spines act like injection needles. Scorpionfish aren’t naturally aggressive (except to prey), but they know how to defend themselves if need be. If you get ‘got’, you are in for “extreme pain and burning sensation”.

DO THEY HAVE ANY OTHER TRICKS TO WATCH OUT FOR?

As many have written, scorpionfish are ‘Masters of Camouflage’. They are able to disguise themselves very effectively. Their appearance is a remarkably adapted to their surroundings, as if covered in a raggle-taggle of colourful algae. They can change colour to aid concealment. They can flick sand over themselves as they settle on the seabed. These ploys enable them to lie motionless on a coral reef or on the seabed, ready to ambush their prey. This consists mainly of small fishes and crustaceans, but really anything edible that will fit in their mouths is fair game.

Concealed against coral

HOW DO THEY FEED?

The large mouth of scorpionfishes has a particular function. They don’t have teeth because they have no need. A scorpionfish can open its mouth and its gills simultaneously, thereby creating an instant vacuum that will suck in its prey in a flash. I have seen this described as “a nearly imperceptible split-second movement (15 milliseconds)”…

THESE SCARY MONSTERS MUST BE HUGE, RIGHT? I’M KEEPING OUT OF THE WATER

Not so fast. When all is said and done – and in my view, most disappointingly – adult Caribbean Scorpionfish grow in the range of… erm… 7 – 14 inches. So now you are reassured, here’s a great short video from Ocean Frontiers Dive Shop, who kindly shared it on YT. I’ve used a couple of illustrative stills from it too.

ANYTHING ELSE WE NEED TO KNOW?

I can do no better than to turn to Card 81 to the excellent ‘Monsters of the Deep‘ series of trading cards (the link is to my MotD page). I do realise that this is a rather unscientific approach. On the other hand these guys pack memorable information into a very short space, and do it well. Note that you can get a reflex sting from a scorpionfish for up to a week after it has died. Eat dust, earthbound scorpions.

Credits: Melinda Riger / Grand Bahama Scuba (1, 2, 3, 4,); Ocean Frontiers Dive Shop (video from YT, 2 stills); Wierd (sic) Creatures / Monsters of the Deep (O/S)

OCTOPUS’S GARDEN (TAKE 9) IN THE BAHAMAS

January 18, 2024 by Rolling Harbour

OCTOPUS’S GARDEN (TAKE 9) IN THE BAHAMAS

We are back again under the sea, warm below the storm, with an eight-limbed companion in its little hideaway beneath the waves.

It’s impossible to imagine anyone failing to engage with these extraordinary, intelligent creatures as they move around the reef. Except for octopodophobes, I suppose. I’ve written about octopuses quite a lot, yet each time I get to look at a new batch of images, I feel strangely elated that such a intricate, complex animal can exist.

While examining the photo above, I took a closer look bottom left at the small dark shape. Yes my friends, it is (as you feared) a squished-looking seahorse,

The kind of image a Scottish bagpiper should avoid seeing Octopus (Melinda Riger - Grand Bahama Scuba) n

OPTIONAL MUSICAL DIGRESSION

With octopus posts I sometimes (rather cornily, I know) feature the Beatles’ great tribute to the species, as voiced with a delicacy and tunefulness that only Ringo was capable of. There’s some fun to be had from the multi-bonus-track retreads currently so popular. These ‘extra features’ include alternative mixes, live versions and – most egregious of all except for the most committed – ‘Takes’. These are the musical equivalent of a Picasso drawing that he botched or spilt his wine over and chucked in the bin, from which his agent faithfully rescued it (it’s now in MOMA…)

You might enjoy OG Take 9, though, for the chit chat and Ringo’s endearingly off-key moments.

All fabulous photos by Melinda Riger, Grand Bahama Scuba taken a few days ago

CHRISTMAS TREE WORMS: SEASONAL SPIROBRANCHES

December 17, 2023 by Rolling Harbour

CHRISTMAS TREE WORMS: SEASONAL SPIROBRANCHES

“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 the perfect time to take a look at these remarkable subsurface symbols of seasonal good cheer (nb they are wonderful animals not gorgeous plants).

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
There is little evidence that prey slide down the spiral to their doom, like on a helter-skelter

Christmas Tree Worm (Melinda Riger / Grand Bahama Scuba)

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… (see below for some action)

HOW DO THE WORMS… YOU KNOW… ERM… REPRODUCE?

This is a delicate area. They are very discreet, but as far as I can make out they eject gametes from their what-I-said-above. There are mummy and daddy worms, and their respective gametes (eggs and spermatozoa) drift in the current and into each other to complete the union. The fertilised eggs develop into larvae, which settle onto coral and burrow into it as their parents did, build their protective tubes, and the process begins again.

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).

The worms, in their coral burrows, hoist their pairs of ‘trees’. You can easily see small particles – zooplankton – drifting in the water, and the radioles swaying to catch potential food. Suddenly it all makes sense (except the repro bit – I haven’t found footage of that). Next: the New Year Worm (there is no Easter worm).

A WHOLE FESTIVAL OF CHRISTMAS TREE WORMS

Credits: Melinda Riger (Grand Bahama Scuba); Nick Hobgood; Betty Wills; Video by ‘Super Sea Monkey’; Reef Collage by RH; MarineBio; Wikibits & Magpie Pickings

Happy Christmas to all those who put up with RH with such fortitude over many years

LETTUCE SEA SLUGS: SOLAR POWERED ‘CRISPY BLISSFUL HEAVEN’

December 4, 2023 by Rolling Harbour

LETTUCE SEA SLUGS: SOLAR POWERED ‘CRISPY BLISSFUL HEAVEN’

The Lettuce Sea Slug Elysia crispata (transl. ‘Crispy Blissful Heaven’) was No.3 in the ‘WTF’ ‘What’s That Fish’ series (despite not actually being a fish at all). It is not by any means the weirdest creature featured so far but it is nonetheless an animal whose appearance excites curiosity. Unless you see one moving, it could easily be mistaken for a plant. Maybe even lettuce. It is in fact a SACOGLOSSAN.

The name ‘sacoglossan’ literally means ‘sap-sucker’. This group (or ‘clade’) comprises small gastropod mollusks that ingest the cellular content of algae (which isn’t really sap).

WHY WOULD THEY DO THAT?

Because they are… SOLAR POWERED slugs

WHAAAAA…..?

As I mentioned when I last visited these remarkable creatures, this isn’t a technical forum and too much science hurts my head. This species primarily lives off algae. May I give you the word KLEPTOPLASTY to drop lightly into your conversation? In a couple of sentences, algae / algal content is eaten but only partially digested. Certain elements are stored to produce photosynthesis by which light is converted to energy (cf plants) and the slug can in effect live and move around without food. You could entertain your neighbour at dinner (or maybe on public transport, why not?) by summarising the process as “chloroplast symbiosis”. Meanwhile, I’m fetching a beer. Two beers.

HOW DO THEY REPRODUCE?

This topic doesn’t seem to have excited much investigative interest, and there’s not much specific information about it. What there is sounds unnecessarily complicated, so I am just going to say authoritatively ‘they do it like many other slug species’ and hope that covers it. The pair shown below may be exploring the possibilities, or at least trying to work out which end is which. Time to make our excuses and leave…

Elysia_crispata_(Lettuce_Sea_Slug_pair) Nick Hobgood

HOW FAST, EXACTLY, DOES A LETTUCE SEA SLUG MOVE?

This rather beautiful video from ‘CORAL MORPHOLOGIC STUDIO’ will reveal all. You’ll soon see that progress is very slow. I recommend watching the first 30 seconds and you’ll get the idea. If you choose to persist, you will see the slug sort of turn and move off to the left.

DO SAY: What an intriguing creature. It’s a true wonder of marine nature.

DON’T SAY: Any good in a mixed salad?

Credits: Melinda @ Grand Bahama Scuba, Nick Hobgood, Coral Morphologic Studio, Laszlo Ilyes wiki

URCHIN RESEARCHIN’: SEA HEDGEHOGS OF THE REEF

October 30, 2023 by Rolling Harbour

URCHIN RESEARCHIN’: SEA HEDGEHOGS OF THE REEF

The long-spined sea urchin Diadema antillarum featured in this post is one of those creatures that handily offers its USP in its name, so you know what you are dealing with. Something prickly, for a start. These are creatures of the reef, and many places in the Caribbean and in the western Atlantic generally sustain healthy populations.

These animals are essentially herbivores, and their value to vulnerable coral reefs cannot be overstated. Where there is a healthy population of these urchins, the reef will be kept clean from smothering algae by their methodical grazing. They also eat sea grass.

Long-spined sea urchin Diadema antillarum (Melinda Rodgers / Dive Abaco)

HOW DO THE SPINES OF DIFFERENT KINDS OF URCHIN COMPARE?

Small sea urchin species have spines a few cms long at most. The long-spine variety can exceed 10 cms, and the largest may have spines up to 30 cms (= 1 foot) long. The length, as shown here, means that when the creatures are safely lodged in crevices near their algae supply, their spines remain very visible.

Long-spined sea urchin Diadema antillarum (Melinda Riger / G B Scuba)

Anatomy of a long-spined sea urchin. You may possess a few of these organs yourself…

CAN YOU GIVE US A TEST, PLEASE?

As with SAND DOLLARS and similar creatures, the skeleton of a sea urchin is known as a ‘test’. Urchin tests are remarkably beautiful, especially seen in sunlight. Here are 2 examples I photographed a while ago. You’ll immediately notice the delicate colours and the amazing complexity of the pattern and symmetry. The top one is (or is most like) a long-spined urchin test.

Long-spined sea urchin Test / Skeleton Diadema antillarum (Keith Salvesen / Rolling Harbour)

A BIT ABOUT SYMMETRY

Sea urchins are born with bilateral symmetry – in effect, you could fold one in half. If you wear gloves. As they grow to adulthood, they retain symmetry but develop so-called ‘fivefold symmetry’, rather as if an orange contained 5 equal-sized segments. The graphic above gives a good idea of how the interior is arranged inside the segments.

A FEW FACTS TO HAND DOWN TO YOUR CHILDREN

Urchin fossil records date the species back to the Ordivician period c 40m years ago
In the ’90s the population was decimated and still has not recovered fully
Urchins feel stress: a bad sign that the spines here are white rather than black
Urchins are not only warm water creatures: some kinds live in polar regions
Urchins are of particular use in scientific research, including genome studies
Some urchins end up in aquariums / aquaria, where I doubt the algae is so tasty
Kindest not to prod or tread on them
Their nearest relative (surprisingly) is said to be the Sea Cucumber

ARE THEY EDIBLE?

They are eaten in some parts of the world, but only where the gonads and roe are considered a delicacy. Personally, I could leave them or leave them.

CREDITS: Melinda Rogers / Dive Abaco (1, 2, 3, 6, 9) taken Abaco; Melinda Riger / G B Scuba (4, 10, 11) taken Grand Bahama; Keith Salvesen / Rolling Harbour (7, 8) taken Abaco; Wiki graphic (5) CC . RESEARCH Fred Riger for detailed information; otherwise magpie pickings… This is an archive post

SOUTHERN STINGRAYS: BAHAMAS REEF FISH

October 12, 2023 by Rolling Harbour

SOUTHERN STINGRAYS: BAHAMAS REEF FISH (41)

Anyone who has scuba-dived or snorkelled around the bright coral reefs of the Bahamas, or hunted bonefish out on the Abaco Marls will have come across Southern Stingrays Dasyatis americana. And there are certain places (eg Manjack Cay) where you can actually feed them – and not come to any harm…

FEED THEM? AREN’T THESE GUYS LETHALLY DANGEROUS CREATURES?

The name that always comes to mind in connection with stingrays is poor Steve Irwin, the charismatic Australian wildlife expert who was tragically ‘stung’ over his heart as he swam close over a ray while filming underwater. But this was, it would appear, a dreadful combination of circumstances with a terrible outcome.

The ray’s stinger is in fact an erectile venomous barbed spine near the base of the tail and not on the end of it (as one might expect). But these creatures are not out to harm you – though of course when you are in their environment you should accord them the respect that they merit.

If you are walking / wading in the water, avoid the risk of accidentally treading on a ray. Best to shuffle your feet forward in the sand; if there’s a half-concealed ray feeding or resting on the bottom nearby, it will swim away peacefully. I took the photo below while bonefishing on the Marls; the ray directly ahead slowly makes off as the skiff drifts closer. The next one is of a ray with its young – completely aware of us as we glide past to one side, but not especially bothered.

If you are swimming, snorkelling or diving, don’t get too close – especially by swimming directly over a ray (apparently Steve Irwin’s mistake, so that he was struck right in the chest by the stinger when the ray reacted).

Enough of the potential dangers. The southern stingray is a magnificent creature, as Melinda’s wonderful photographs show. She spends half her life underwater and I’m not aware that she has had a problem with a ray.

Like many larger sea creatures, stingrays need help with their personal care – the removal of parasites, dead skin and so forth. And so they make use of the services offered by small fish like gobies, wrasses and shrimps at a CLEANING STATION. Here are 2 photos of rays doing just that. You can see the tiny fish by the reef, going about their work. There’s a mutual benefit in this symbiotic relationship, in which it is understood that the cleaners are unharmed. Indeed, they will often enter the mouths and gills of a fish to clean… including the teeth. So there’s dental hygiene on offer too…

RELATED POSTS

YELLOW STINGRAY

GRACE WITH ATTITUDE

TAKEN TO THE CLEANERS

Photo Credits: Melinda Riger / Grand Bahama Scuba, except for the feeding photo (cheers, Samantha Regan), the ‘specimen’ from Tomas Willems (Wiki) and my two noted above

BRAIN WAVES: UNDERSEA CORAL MAZES & LABYRINTHS

October 4, 2023 by Rolling Harbour

BRAIN WAVES: UNDERSEA CORAL MAZES & LABYRINTHS

The most apposite description of brain coral Diploria labyrinthiformisis is essentially a no-brainer. How could you not call the creatures on this page anything else**. These corals come in wide varieties of shape and colour, and 4 types are found in Caribbean waters. They date from the Jurassic period.

Each ‘brain’ is in fact a complex colony consisting of genetically similar polyps. These secrete CALCIUM CARBONATE which forms a hard carapace. This chemical compound is found in minerals, the shells of sea creatures, eggs, and even pearls. In human terms it has many industrial applications and widespread medicinal use, most familiarly in the treatment of gastric problems.

The hardness of this type of coral makes it an important component of reefs throughout warm water zones world-wide. The dense protection also guarantees (or did until our generation began systematically to dismantle the earth) – extraordinary longevity. The largest brain corals develop to a height of almost 2 meters, and are believed to be several hundred years old.

HOW ON EARTH DO THEY LIVE?

If you look closely at the cropped image below and other images on this page, you will see thousands of tiny tentacles nestled in the trenches on the surface. These corals feed at night, deploying their tentacles to catch food. Their diet consists of tiny creatures and their algal contents. During the day, the tentacles retract into the sinuous grooves. Some brain corals have developed tentacles with defensive stings.

THE TRACKS LOOKS LIKE MAZES OR DO I MEAN LABYRINTHS?

The difference between mazes and labyrinths is that labyrinths have a single continuous path which leads to the centre. As long as you keep going forward, you will get there eventually. You can’t get lost. Mazes have multiple paths which branch off and will not necessarily lead to the centre. There are dead ends. Therefore, you can get lost. Or never get to the centre at all.

** On the corals shown here, you will get lost in blind alleys almost at once. Therefore in human terms these are mazes. The taxonomic labyrinthiformisis is Latin derived from Greek, and applied generally to this kind of structure, whether in actual fact a labyrinth or a maze.

CREDIT: all amazing underwater brain-work thanks to Melinda Rogers / Dive Abaco; Lucca Labyrinth, Keith Salvesen / Rolling Harbour

Here is a beautiful inscribed labyrinth dating from c12 or c13 from the porch of St Martin’s Cathedral in Lucca, Italy. Very beautiful but not such a challenge.

WTF? (WHAT’S THAT FISH): ‘GUITARFISH ROCK’

September 24, 2023 by Rolling Harbour

WTF? (WHAT’S THAT FISH): ‘GUITARFISH ROCK’

A spectacular entry in my WTF? series came courtesy of Adam Rees and a night dive in Florida waters: the guitarfish, (Gr: rhinos – nose; batis – ray) . Until I saw Adam’s photos, this creature was unknown to me. It sounded so improbable, and conjured up some nightmare piscine-based modification of a Stratocaster, an instrument whose classic looks should not be meddled with without consequent loss of liberty.

Guitarfish, Florida (Adam Rees)

The guitarfish belongs to a family of rays, Rhinobatidae, of which there are many species worldwide. In some ways the fish looks like a crossover with a shark. Although they have a ‘ray face’ and small wings, there is also a sharklike appearance with its fins and a sharklike swimming action (see video, below). If you think there is a primitive or prehistoric look to the guitarfish, you’d be right. According to the temporal range chart they date from the late Jurassic era.

Guitarfish Temporal Range

I have been trying to nail the exact model of Adam’s finny Strat-ray. I am putting my money on the Atlantic guitarfish Rhinobatos lentiginosus, which may (or may not) be the same as the spotted or freckled; and is similar to the more widely photographed shovelnose guitarfish with its cute face. Not that I am very bothered: it’s the overall unusualness of Adam’s creature that really counts.

Shovelnose Guitarfish (ventral view) (Greg Hume wiki)

The strange thing is that although the guitarfish is a denizen of, for example, floridian, caribbean and mexican gulf waters, it is said to be unrecorded for the Bahamas. These bottom-feeding creatures inhabit shallower waters near coastlines and estuaries. They eat crabs, shellfish and worms – all in plentiful supply in Bahamas waters – so I can’t see a reason why they should not be found there. Perhaps they are seen but unreported. I have in mind the recent reports of SAWFISH and BATFISH. So kudos awaits the person who reports – with photo – the ‘first’ Bahamas guitarfish. Maybe there’s scope for a song about it!

GUITARFISH ‘LIVE’

Usually caught by mistake by anglers, or as bycatch by fishing vessels
Inedible (unless someone knows better…)
Non-aggressive and harmless to humans despite having a mouthful of small teeth
Swims like a shark – the tail has no spinal structure
Has a cute face (unlike a a shark)
Adults are about 30 inches long
They may bury themselves in sand or mud to ambush prey
They are viviparous, giving birth to live young that are born fully developed

As a postscript, it’s worth mentioning that on the same night dive, Adam also came across the uncommon batfish, a seriously prickly-looking starfish, and a spotted eagle ray. Worth losing sleep for.

A similar kind of guitarfish, showing the very sharklike movements in the water

Credits: Adam Rees, with many thanks; Greg Hume; Johan Fredriksson wiki; magpie pickings, in particular Florida Museum of Natural History / Taylor Sullivan and the truthful parts of various Wiki articles

Guitarfish, Florida (Adam Rees)

WTF? (WHAT’S THAT FISH?): ARROW CRABS

July 14, 2023 by Rolling Harbour

WTF? (WHAT’S THAT FISH?): ARROW CRABS

The WTF? series is dedicated to the wilder, less conventionally fish-shaped side of reef life – those creatures that you may come across, blink into your face-mask, and silently mouth the words ‘What’s That Fish?’ (that’s what it looks like you are saying, anyway).

Let’s meet some Arrow Crabs Stenorhynchus seticornis, one of the very few creatures surely to have a triangular body plus a huge pointy nose (rostrum), supported on long skinny legs. To which add, they wear tiny blue gloves on their two front claws.

These crabs are coral reef dwellers and mostly stay concealed during the day. Their body is protected by a carapace, and the rostrum has serrated edges like a tiny rasp or file. I haven’t found a definitive reason for this gadget, but I suspect it is more for probing than for piercing or fighting.

There’s a considerable colour variation among these crabs, as these images show. The body may even have blue iridescent lines (#2, above). And those claws may be any of 50 shades of blue…

Arrow crabs are most active at night. They eat feather-duster worms (illus.) and similar invertebrates such as bristle worms.

Like certain types of shrimp, they also have a symbiotic relationship with anemones, whereby they make use of an anemone to benefit from the food it captures – and possibly for cover too. They are protected from anemone stings, whereas some of their predators are not.

This was the place where I was going to tell you about the arrow crab’s private life, but, well… “it’s complicated”. Briefly it is: male passes sperm-filled capsule to female; she uses it in some way whereby it fertilises her eggs; she then ‘broods’ the eggs in one of her ‘swimming legs’; the eggs hatch into larvae and swim off to eat plankton; each one then grows & moults, repeating the process until it has reached adult form. On balance, humans have arguably perfected a preferable method.

Arrow Crabs are apparently popular aquarium creatures, although they sound to me rather a disagreeable challenge. They can move quickly on those long legs, and it seems as if they inclined to be aggressive to other inhabitants of the tank. As far as I can make out, it’s best not to put 2 of them together: they certainly won’t be doing the sperm capsule thing described earlier…

Master of Disguise

Photo credits: Melinda Riger / G B Scuba (1, 3, 4, 5, 6); Adam Rees / Scuba Works (2, 8, 9); Nick Hopgood,Wiki (7); Chuck Elliot – video

FRIGATEBIRDS aka MAN-O-WAR BIRDS: TRULY MAGNIFICENT

June 13, 2023 by Rolling Harbour

FRIGATEBIRDS aka MAN-O-WAR BIRDS: TRULY MAGNIFICENT

This is a male frigatebird (Fregata magnificens) in the breeding season, with his extraordinary inflatable GULAR POUCH fully blown up. He is at his most chest-burstingly dashing, at least to female frigatebirds, and this great capture by photographer Athena Alexander from the excellent blog of JET ELIOT, shows one of the wonders of the bird world. A glimpse of his mate can be seen just behind his head, but frankly he has made the story his own! And just look at the size of his wings. If a bird can steal limelight, he has effortlessly done so.

COURTSHIP DISPLAY

The image below shows the male enacting his courtship display. Jet Eliot describes it thus: “During courtship display this balloon-like sac takes about 20 minutes to fully inflate. It is featherless, scarlet red, and tight as a drum. It’s so big it distorts him. When he’s ready and has a suitable audience of females flying overhead, he points his face skyward and rapidly beats his wings against the balloon, creating a low, booming sound”. The male’s pouch is not entirely inflated. A female is nestled under the his protective wing. Presumably she has been won over and mating will soon occur once the performance ends. Or maybe she’s bored with the whole routine – she looks rather as though she has seen it all before… frigatebird-displaying

magnificent-frigatebird

NESTING

Even on the nest, males are keen to be in the picture. Not for them the ‘absentee father’ role, out fishing the entire day. Instead, they share chick-care duties, looking after the single enormous, fluffy chick. An adult pair stays together for the year, forsaking all other. Chick care takes a long time from egg to fledging and beyond – so much so that frigatebirds only breed every other year, and always produce a single egg. For this reason, habitat destruction of breeding grounds has a far greater effect on population numbers than for birds that breed annually. Magnificent Frigatebird (m) and chick on nest - Athena Alexander / Jet Eliot

magnificent-frigatebird

10 MAGNIFICENT FACTS ABOUT FRIGATEBIRDS

Magnificent Frigatebirds are the largest of several frigatebird species around the world
They are found in tropical and subtropical waters
Females have white fronts that make them easily distinguishable in flight
An adult’s wingspan is 7+ feet, with the largest wing-area / bodyweight ratio of any bird
Frigatebirds can remain in flight and far out to sea for many days
They are KLEPTOPARASITES and will rob other seabirds of their food
Their diet is mainly fish & squid snatched from the water’s surface; also seabird chicks
They nest in colonies, producing a single egg every other season
They don’t actually land on water, as they don’t float; and they are feeble at walking on land
One of the earliest depictions of a frigatebird is by Eleazar Albin in 1737. He was a naturalist contemporary of MARK CATESBY and pre-dated AUDUBON

Frigatebird_Eleazar_Albin_1737

magnificent-frigatebird

NAMING THE FRIGATEBIRD: A POTTED HISTORY

Columbus encountered them on his first voyage in 1492, but knew them by their Spanish name rabiforçado or ‘fork-tail’.
The use of the name ‘frigatebird’ was first recorded in 1667 and referenced the frigate warship, a powerful sea-vessel
‘Man-o-War Bird’ was the name given to the bird by English mariners in the Caribbean, being the colloquial name given by sailors to a frigate.

magnificent-frigatebird

A MAN-O-WAR GALLERY

A female frigatebird hunts for food among the mangroves on Abaco Magnificent Frigatebird.Abaco Bahamas.2.12.Tom Sheley 2

A female frigatebird soars high over Marsh Harbour Magnificent Frigatebird, Marsh Harbour, Abaco - Tom Reed

This male has taken off before his gular pouch has had time to deflate fully Frigatebirds (m) 2 Michael Vaughn

An osprey escorts a female frigatebird from his territory to a different bit of sky… Frigatebird & Osprey Michael Vaughn

Juvenile frigatebird Frigatebird (juv) Michael Vaughn

A fully-inflated male with a droopy one who needs to get started quick if he’s going to get a mate Frigatebirds (m) 1 Michael Vaughn

ARE FRIGATEBIRDS ANY USE TO MAN OR BEAST?

Yes, emphatically so, to man anyway. Mariners through the ages have used frigatebirds as indicators of nearby land – not necessarily visible, but within sailing distance. And fishermen through the ditto have used them as reliable indicators of where fish are to be found. As an example from personal experience on Abaco, going fishing out of Casuarina into the deep waters of the open sea, the sight of high-flying frigatebirds signals ‘get ready to fish’. They are scouting around for fish, and so are you. But they know where the fish are. Follow them and you ~~will~~ may be rewarded. Because where there are fish for seabird predators, there are fish for the large fish predators – mahi mahi, tuna and wahoo, for example. This is not my main type of fishing, but each time we have been out in those waters – with the Delphi Club often a still-visible speck on the horizon – the frigatebirds have led us to good catches of mahi mahi (= dorado or ‘dolphin’). Last year, under the watchful gaze of the frigatebirds, in a heart-stopping moment I jumped a wahoo. If that sounds slightly rude, it isn’t – and I didn’t catch it anyway. It just leapt vertically right out of the water without taking the goodies…

STOP PRESS Cheryl Wile Ferguson sent me a great photo of a female MF being sociable with humans in the Galapagos. She hitched a ride for 2 hours during a sea crossing… Magnificent Frigatebird (f) hitching a boat ride (Cheryl Wile Ferguson)

Audubon’s Magnificent Frigatebird Audubon Frigatebird

Credits: first and foremost to Athena Alexander and Jet Eliot for use permission for images 1 – 3 (taken on Galapagos) and much invaluable info; as ever to Tom Sheley (4), Tom Reed (5) and Michael Vaughn (6,7,8,9) for their photos; Cartoon from Birdorable; other images open source; magpie pickings for facts and figures; and some limited personal experience (regrettably but unsurprisingly all my photos of frigatebirds flying, diving, triumphantly catching fish etc are too crap to use)

WTF? (WHAT’S THAT FISH): FLYING GURNARD

May 24, 2023 by Rolling Harbour

WTF? (WHAT’S THAT FISH) 10: FLYING GURNARD

Imagine that you are swimming along resplendent in your snorkelling gear (me) – or in scuba gear for the advanced swimmer (you). There, below you, camouflaged against the sea bottom is a fish. A strange-shaped brown sort of creature with odd side fins. As it progresses over the gravelly sand, your immediate reaction is ‘what the…?’ Its fins seem to be turning into… wings. Like this:

Flying Gurnard (Adam Rees / Scuba Works)

Yes, it’s a flying gurnard. Unlike flying fish, it can’t actually fly through the air. But once its wings are fully spread, it certainly looks as though it could.

Flying Gurnard (Adam Rees / Scuba Works)

WHAT’S THE POINT OF THE WINGS IF THE THING CAN’T FLY?

This gurnard species usually gets around using its ventral fins as ‘legs’, with the pectoral fins (‘wings’) close to the body. There seem to be several possible reasons for possessing the ‘sudden-deployment-of-flashy-wings’ superpower.

It surprises and deters predators by movement, turning prospective prey into an apparently different creature
Bright or lurid colouring may be a deterrent warning of a foul-tasting or poisonous species (APOSEMATISM)
A creature may actually be harmless and even tasty (as here) but may appear to be unpalateable or poisonous (BATESIAN MIMICRY)
In any event, the wings enable the fish to take off from the sea bottom and travel faster by ‘flying’ thought the water to escape a predator

Dactylopterus_volitans Flying Gurnard (cralize wiki)

I had a quick look to see how scientists in history had depicted this extraordinary fish. The earliest illustration I could find was taken from “Allgemeine Naturgeschichte der Fische (General natural history of fishes),” a 12-volume encyclopedia by author/illustrator Marcus Elieser Bloch (1723-1799), which described all fish species then known to science (and 267 previously unknown) (© AMNHD. Finnin) sourced from ‘Hyperallergic’
Flying Gurnard

Here’s a short video of a flying gurnard on the move, from ‘Sia Big Fish’

Credits: All main images Adam Rees / Scuba Works with many thanks, except final one ‘cralize wiki’; Hyperallergic for the historic image; Sia Big Fish for the video

Rolling Harbour / Keith Salvesen

ROCK BEAUTY: BAHAMAS REEF FISH

April 7, 2023 by Rolling Harbour

ROCK BEAUTY . Holacanthus tricolor . BAHAMAS REEF FISH

These creatures are a small species of angelfish. Seen swimming around the reefs they are unmistakeable, not least because of their bright yellow hi-viz jackets, remarkable blue eyeliner and blue-black lipstick.

Rock Beauties look like prime candidates for anyone’s aquarium, but they have picky dietary requirements and a tendency for aggression that make them unsuitable (fortunately for them).

They are highly specialised feeders, needing marine sponges in their daily diet. They are also prone to chase tank-mates and nip them. On balance, they look more fetching nosing about the coral anyway.

WHAT DO JUVENILES LOOK LIKE?

Juvenile rock beauties are cute mini-versions of the adults, only even more yellow and with yellow lips.

In development stages, they may have a vivid blue and black circle in front of the tail fin…

… or a large dark patch on their sides

NOT A TRUE ‘ROCK BEAUTY’ (no offence, Lita)

A TRUE ROCK BEAUTY

Credits: Melinda Riger, Grand Bahama Scuba; WP

WTF? (WHAT’S THAT FISH): ‘GUITARFISH ROCK’

March 14, 2023 by Rolling Harbour

WTF? (WHAT’S THAT FISH): ‘GUITARFISH ROCK’

A spectacular entry in my WTF? series came courtesy of Adam Rees and a night dive in Florida waters: the guitarfish, (Gr: rhinos – nose; batis – ray) . Until I saw Adam’s photos, this creature was unknown to me. It sounded so improbable, and conjured up some nightmare piscine-based modification of a Strat, an instrument whose classic looks should not be meddled with without consequent loss of liberty.

Guitarfish, Florida (Adam Rees)

Guitarfish Temporal Range

Shovelnose Guitarfish (ventral view) (Greg Hume wiki)

GUITARFISH ‘LIVE’

Usually caught by mistake by anglers, or as bycatch by fishing vessels
Inedible (unless someone knows better…)
Non-aggressive and harmless to humans despite having a mouthful of small teeth
Swims like a shark – the tail has no spinal structure
Has a cute face (unlike a a shark)
Adults are about 30 inches long
They may bury themselves in sand or mud to ambush prey
They are viviparous, giving birth to live young that are born fully developed

. .

A similar kind of guitarfish, showing the very sharklike movements in the water

Guitarfish, Florida (Adam Rees)

BLUEHEAD WRASSE: PRIVATE LIFE LAID BARE

January 23, 2023 by Rolling Harbour

BLUEHEAD WRASSE: PRIVATE LIFE LAID BARE

The bluehead wrasse (or blue-headed wrasse) Thalassoma bifasciatum is a denizen of the coral reefs in 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. Rather unfairly, some species that are quite content to let cleaner gobies pick 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
Main threats to the species are coral reef degradation / destruction and pollution
The bright colours invite aquarium use, but the trade in this species is not critical.

** Some sources suggest some are born male and remain male.

A juvenile bluehead – mostly yellow, with a pale underside

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 has been the subject of extensive scientific research. As with 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 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 is signalled by colour changes BUT the females know…
…that the smaller males have a sperm count higher than dominant males.

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. 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

FLAMINGO TONGUE SNAILS: DECORATIVE CORAL-DWELLERS

January 9, 2023 by Rolling Harbour

FLAMINGO TONGUE SNAILS: DECORATIVE CORAL-DWELLERS

FLAMINGO TONGUE SNAILS Cyphoma gibbous are small marine gastropod molluscs related to cowries. The living animal is brightly coloured and strikingly patterned, but that colour only exists in the ‘live’ parts – the so-called ‘mantle’. The shell itself is usually pale, and characterised by a thick ridge round the middle. Whether alive or as shells, they are gratifyingly easy to identify. These snails live in the tropical waters of the Caribbean and the wider western Atlantic.

Flamingo Tongue Snails (Melinda Rogers, Dive Abaco, Bahamas)

THE IMPORTANCE OF CORAL

Flamingo tongue snails feed by browsing on soft corals. Often, they will leave tracks behind them on the coral stems as they forage (see image below). But corals are not only food – they provide the ideal sites for the creature’s breeding cycle.

Adult females attach eggs to coral which they have recently fed upon. About 10 days later, the larvae hatch. They eventually settle onto other gorgonian corals such as Sea Fans. Juveniles tend to live protectively on the underside of coral branches, while adults are far more visible and mobile. Where the snail leaves a feeding scar, the corals can regrow the polyps, and therefore the snail’s feeding preference is generally not harmful to the coral.

The principal purpose of the patterned mantle of tissue over the shell is to act as the creature’s breathing apparatus. The tissue absorbs oxygen and releases carbon dioxide. As it has been (unkindly?) described, the mantle is “basically their lungs, stretched out over their rather boring-looking shell”. There’s more to them than that!

THREATS AND DEFENCE

The species, once common, is becoming rarer. The natural predators include hogfish, pufferfish and spiny lobsters, though the spotted mantle provides some defence by being (a) startling in appearance and (b) on closer inspection by a predator, rather unpalatable. Gorgonian corals contain natural toxins, and instead of secreting these after feeding, the snail stores them. This supplements the defence provided by its APOSEMATIC COLORATION, the vivid colour and /or pattern warning sign to predators found in many animal species.

MANKIND’S CONTRIBUTION

It comes as little surprise to learn that man is considered to be the greatest menace to these little creatures, and the reason for their significant decline in numbers. The threat comes from snorkelers and divers who mistakenly / ignorantly think that the colour of the mantle is the actual shell of the animal, collect up a whole bunch from the reef, and in due course are left with… dead snails and their allegedly dull shells Don’t be a collector; be a protector…

The photos below are of nude flamingo tongue shells. Until I read the ‘boring-looking shell’ comment, I believed everyone thought they were rather lovely… I did, anyway. I still do. You decide!