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)

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

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): 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

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!

Image Credits: Melinda Rogers / Dive Abaco; Keith Salvesen / Rolling Harbour; Wiki Leopard

ABACO PARROT FOR A CHEERFUL YULETIDE & OPTIMISM FOR 2023

December 22, 2022 by Rolling Harbour

Thanks to all followers, likers, commenters, regular visitors, one-offs, local wildlife organisations, and friends of Rolling Harbour in general. This year we passed 1 million hits over the ten years of this blog. Proving that people love Abaco, the Bahamas, birds, marine mammals, manatees, reef fish, sharks, turtles, shore-life, shells, insects, plant life, bonefishing, lighthouses, local history, maps, conservation and a whole lot more; and are prepared to tolerate bad puns, haphazard presentation, and a less than rigourous scientific approach to it all.

Weirdest search term ever: How to dispose of dead bodies?

BLUE CHROMIS: A FLASH OF COLOUR ON THE REEF

October 25, 2022 by Rolling Harbour

BLUE CHROMIS: A FLASH OF COLOUR ON THE REEF

Larger reef fish tend to get more attention than the tiddlers, for obvious reasons. Yet a reef would not properly exist without the small fish that drift and wriggle round the corals. Blue chromis (Chromis cyaneus) are among the first reef fish species I ever met when snorkelling at Fowl Cays.*

Blue chromis belong to the same group as damselfishes. These unmistakeable, bright reef denizens are very visible despite their tiny size. These fish are shoalers, so out on the reef you can enjoy them flickering around you as you swim along or hang in the water to admire the corals.

Like many a pretty and easily captured small fish that can be monetised once removed from its natural home environment, the blue chromis is popular for aquariums. Humans like to keep them in their own home environments safely away from oceans and reefs, unselfishly feeding the little things concocted food to keep their little lives going till the cat gets them. [Sorry, I don’t know what came over me there]

Blue chromis are adaptable and sociable, and will happily swim with other small reef fishes (as above). My own favourite combo is chromis mixed in with sergeant majors. But a shoal of them (mostly) alone is pretty special too….

I cynically mentioned ‘concocted’ food earlier. Here is one online care instruction for looking after them: “They are omnivores, meaning that they eat both meaty and plant based foods. They are not difficult to feed and will eat a variety of regular aquarium fare, frozen, live, and sometimes even dry food. Feeding them a variety of foods will help them retain their color in captivity. They sometimes feed on the algae in the tank”. So I think it’s ok to suggest that leaving the fish out on the reef might suit them better.

If tempted to ‘rescue’ some from their reef habitat, rest assured that they have been known to spawn in captivity. Blue chromis can usually be obtained for about $10-15. And don’t hold back on the frozen food (though maybe warm it up a bit before feeding time). I rest my case.

*I say ‘snorkelling’ rather than anything more impressive because I am a pathetic swimmer and I know my limitations…

Credits: Melinda Rodgers / Dive Abaco; Melinda Riger / G B Scuba

PEACOCK FLOUNDERS: NOW YOU SEE THEM…

June 2, 2022 by Rolling Harbour

PEACOCK FLOUNDERS

MASTERS OF SUBAQUATIC CAMOUFLAGE

I featured the extraordinary, colour-transforming PEACOCK FLOUNDER Bothus lunatus a while back as part of a Bahamas Reef Fish series. These really are remarkable creatures, and I have decided to return to them mainly because of the wonderful illustrative photos I was able to incorporate. There are plenty of flounder facts too, but if you just enjoy the pictures and skip the blurb I’ll understand.

ROVING EYES

In the fish shown here, you’ll see that – surprisingly – both eyes are on the upper-side of the fish, above the rather grumpy mouth, whereas the head is horizontal to the ocean floor. Oddest of all, juveniles are constructed conventionally with bilateral eyes, and look like ‘normal’ fish rather than flatfish.

As the fish matures, in some magic way the mechanics of which I can only guess at**, the right eye grows round to the topside and the flounder transforms from a ‘vertical’ fish to a flatfish. For this reason, the PF is known as a ‘left-eye’ flounder. Maybe in other flounder species in the world – the southern hemisphere maybe? – the eye that moves round to the upper-side is the left eye.

The eyes of this fish have another special trick up their sleeves (so to speak). They operate completely independently. Thus the creature can look left and right, or forwards and backwards, simultaneously. It’s an excellent system for detecting predators coming from any angle. It’s a superpower we might all benefit from.

DO THEY HAVE ANY OTHER TRICKS WE SHOULD KNOW ABOUT?

Yes they do indeed. If you have been admiring the fish shown so far, you’ll have noticed that the colour of each one differs from the others. In addition to the predator-protection that the eyes provide, the peacock flounder can make itself (near) invisible. They can rapidly change colour to match their surroundings. There are 3 reasons for this: to avoid / confuse predators; to conceal themselves on the sea-floor to catch passing prey; and, as dive expert Fred Riger has pointed out, “the male peacock flounder can, and does greatly intensify his colours to declare territory and attract females. When doing this the males will also signal with the left pectoral fin, sticking it straight up and waving it around.”

The same fish, photographed over several minutes as it moves over the ocean floor

Matching the background happens as the fish swims, and in a few seconds. When they rest on the sea-floor, the camouflage may even become total. In #4 above you can just about make out the eyes. The whole effect is known as ‘cryptic coloration’ or CRYPSIS. In contrast, the image below shows just how adaptable the transformation can be. Note how the fish can even mimic the pinkish tinge of the sand perfectly. If threatened, the fish will bury itself in the sand, with just its eyes showing.

HOW DO THEY MANAGE TO CHANGE COLOUR IN SECONDS?

It’s complicated! A simple answer is: a mix of hormones, pigment-cells and vision, all coordinating rapidly. The colour change works in two ways: pigments are selectively released to the skin cells; and other pigments can be selectively suppressed. An analogy might be image manipulation using variations in brightness, saturation etc. Not convinced? Then watch this short video and prepare to be impressed. Astonished, even.

WHAT IF A FLOUNDER CAN’T SEE CLEARLY FOR SOME REASON?

As with many (all?) superpowers, there is usually some kryptonite-style flaw. A flounder with a damaged eye, or one temporarily covered (by sand, for example) will have difficulty in changing colour – possibly at all, or at any rate with the swiftness it needs to have.

THESE SIDEWAYS FISH – HOW DO THEY… YOU KNOW…?

Take a look at the fish above with its top fin raised. It’s a ‘ready’ signal in a harem. Male flounders have a defined and defended territory within which live up to 6 females – a so-called ‘harem.’ I can do no better than borrow the description of the rituals from an article derived from scientific papers by Konstantinou, 1994; Miller, et al., 1991 in the website animaldiversity.org/…ounts/Bothus_lunatus To which I can only add, ’15 seconds, eh?’

“Mating activities usually begin just before dusk. At this time, a male and a female approach each other with the ocular pectoral fin erect. The two fish arch their backs and touch snouts. After this interaction the female swims away, and the male sometimes follows, approaching the female again from the left side. At this point the male pectoral fin is erect and the female pectoral fin moves up and down, possibly signalling willingness to mate. The male then positions himself underneath the female and mating begins. This process consists of a mating rise, during which the female and male rise in the water column together. On average, these rises last about 15 seconds. At the highest point of this rise, usually around 2 m above the substrate, gametes from both fish are simultaneously released, producing a cloud of sperm and eggs. Once the couple returns from the rise, the male “checks” to make sure mating was successful, and the pair separates quickly, swimming away from each other in opposite directions. Not all mating rises are successful, and the process of “checking” is thus important. The exact purpose of the mating rise in these flounders unknown; possible reasons for rising include better dispersal of gametes and predator avoidance.”

Peacock Flounder – Kim Rody Art

**This may in fact have been through sheer laziness

Credits: Melinda Riger & Virginia Cooper / Grand Bahama Scuba; Melinda Rogers / Dive Abaco; Adam Rees / Scuba Works; Kim Rody; animaldiversity.org; magpie pickings and other credits in the text

BRAIN WAVES: UNDERSEA CORAL MAZES & LABYRINTHS

April 27, 2022 by Rolling Harbour

BRAIN WAVES: UNDERSEA CORAL MAZES & LABYRINTHS

HOW ON EARTH DO THEY LIVE?

THE TRACKS LOOKS LIKE MAZES OR DO I MEAN LABYRINTHS?

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.

CARIBBEAN REEF SQUID: SUPERPOWERS & SQUID SEX

April 18, 2022 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)

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 one 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… 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 die in the end (but there’s no romantic balcony scene first)

THE CORRECT PLURAL OF SQUID

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

FAIRY BASSLET (‘MIND YOUR GRAMMA’): BAHAMAS REEF FISH

April 10, 2022 by Rolling Harbour

FAIRY BASSLET (‘MIND YOUR GRAMMA’): BAHAMAS REEF FISH (33)

The Fairy Basslet is a tiny brightly-coloured fish with a pretentious alternative name. It is otherwise known as the Royal Gramma (Gramma loreto). These fish are found in the coral reefs of the (sub)tropical western Atlantic. They are also found in aquariums anywhere you like, being small, bright, placid and generally good-natured.

Conveniently, the basslet is unlikely to be confused with any other species. Its striking two-tone colour scheme of purple and yellow is hard to miss. The purple front half (which is presumably where the ‘royal’ comes from, being a regal or imperial colour) may also be violet or even blue in some fish and / or in some light conditions. Another identification pointer is a black spot on the dorsal fin.

You’ll notice that the basslet above appears to be upside down. Which is because it is – this isn’t an inadvertent photo-flip. These little fish tend to orientate themselves to be parallel with the closest surface. This leads to them happily swimming upside down, or aligning vertically. As one article I read says severely, “this behaviour is not to be mistaken for illness”.

Fairy basslets / royal grammas are also CLEANER FISH. They pick parasites and dead skin off larger fish that visit so-called cleaning stations to be attended to by tiny fish and cleaner shrimps, and in some instances to have their gills and even their teeth cleaned. The deal is that, in return, the large fish do not eat the cleaners. Even snack-sized ones rootling around inside their mouths.

WHAT ABOUT BREEDING?

I really can’t improve on this rather touching description from Wiki: “The male will build the nest among rocks using pieces of algae. The male will then lead the female to the nest, where she will deposit 20-100 eggs in the nest. During the breeding period, this behaviour is repeated almost every day for a month or longer (my italics). The eggs are equipped with small protuberances over the surface with tiny threads extending from them which hold onto the algae of the nest and keep the eggs in place. The eggs will hatch in five to seven days, normally in the evening…”

HOW COME THE NAME ‘GRAMMA LORETO’?

This official name became a brainworm with me after I started this post. I had to check it out. The ‘Gramma’ part is unrelated to the fond name for a grandmother; rather, it simple denotes a member of the genus of fishes in the family Grammatidae.

The Loreto part is more mysterious. It is an an ancient town in Italy; and the name of several British schools, including – almost too good to be true – a school called Loreto Grammar. In a nutshell, the link between the town and places of education is that the Sisters of Loreto, founded in the c17 and named for a shrine in the Italian village, are dedicated to education in their Ministry.

How that ties in with a tiny Caribbean reef fish, I have yet to find out. I probably never will… Here’s a short video to alleviate the disappointment.

I failed to be able to resist finding out whether any country of the world has a purple and yellow flag. The answer is, no. However I am delighted to be able to report that the flag of the Independent Party of Uruguay is basslet-coloured.

Credits: all fantastic photos by Melinda Riger of Grand Bahama Scuba; magpie pickings of an unacademic sort for facts and speculation

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

March 8, 2022 by Rolling Harbour

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

I have just been lightly involved in a long online thread showcasing the weirdest / most science fiction-y creatures around the world. Trust me, there are plenty. There were quite a few duplications. My own contribution was the frogfish, which no one else had nominated. They are so special – and so weird – that I am reposting my article about them. Don’t miss the last video!

This ‘WTF?’ series started with a relatively conventional species, the REMORA. It has been getting progressively more bizarre. We moved onto an omnium gatherum of WEIRDO FISHES, then the remarkable LETTUCE SEA SLUG, and most recently the BATFISH. 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

Spot the esca…

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.

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 highlighter 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.

To read more about frogfishes and for some fabulous photos I highly recommend the website FROGFISH.CH You can reach the main page(s) but the link seem to be broken so I have not been able to contact Teresa Zubi, whose site it is. She clearly has a sense of humour and uses a neat pair of gifs which I hope she won’t mind my using…

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; Teresa Zubi for website & gifs; infographics, authors u/k

SPERM WHALE CALF, ABACO, BAHAMAS: WHY WORLD WHALE DAY MATTERS

February 20, 2022 by Rolling Harbour

WORLD WHALE DAY 2022

NEONATE SPERM WHALE CALF, ABACO, BAHAMAS

After many decades of the savage depletion of the global whale population, the tide turned in their favour in the 1960s. It was fair to assume that, gradually, a new era of cetacean recovery must follow and that whales would be accorded the respect they deserve. Over time, many organisations were formed with the specific aim of protecting and conserving marine mammals, the Bahamas Marine Mammal Research Organisation (BMMRO) based on Abaco among them.

The struggle to fulfil that aim in the face of entirely man-made environmental damage has become increasingly difficult. However, there have more recently been encouraging reports of population recovery in some seas, a good reason to celebrate WORLD WHALE DAY and to consider supporting the many organisations that work to preserve marine mammals.

The photographs and the 2 very moving videos below are of an adult sperm whale and new-born calf. They were taken by BMMRO in Bahamas waters. There’s optimism in these images. I’d like to think that a smiling baby whale holds out hope for the future. Hopefully it will flourish and live for decades. If it does not, the overwhelmingly likely cause will be mankind, either directly or indirectly.

Sperm Whale baby (neonate) Abaco Bahamas (Charlotte Dunn / BMMRO)

CREDITS: Close-up footage plus the clips I have taken from it – Charlotte Dunn / Diane Claridge / BMMRO

DONATE: If you are touched by the magic of this little Bahamas sperm whale, may I invite you to consider making a donation to BMMRO for its research and conservation work – a scientific commitment that reaches far beyond the waters of the Bahamas. The system is set up to process donations from just $10 upwards, and every cent is used to further the work of BMMRO. Please click the logo below to reach the right page directly.

ABSORBING SPONGES ON THE BAHAMAS REEFS…

February 17, 2022 by Rolling Harbour

ABSORBING SPONGES ON THE BAHAMAS REEFS…

It is a rather special and indeed specialist day today: it is #spongethursday, a component of the 11th World Sponge Conference (I’d add the logo, but it closely resembles a pink Covid symbol). Poriferaphiles everywhere should be celebrating these beautiful creatures today. Here are some gorgeous examples. Now you know why sponges deserve a day of their own.

Candelabra Songe (with brittle stars attached)

Black Ball Sponges

One for Valentine’s Day

Vase Sponges

Spawning Brown Encrusting Sponge

All photos: Melinda Riger, Grand Bahama Scuba – with thanks as ever

IS THIS THE REAL LIFE? IS THIS JUST FANS AT SEA?

January 1, 2022 by Rolling Harbour

IS THIS THE REAL LIFE? IS THIS JUST FANS AT SEA?

I am re-posting this sea fan article as 2021 rolls over into 2022 with much the same disruption, anxiety, and (for many) grief that we were all facing a year ago. The converse and somewhat rhapsodic title reflects the experience of many people since Covid engulfed the world. Life has become simultaneously real and surreal. It continues in many respects as normal yet who would have guessed that as we entered a new decade in 2020, the face mask would quickly become an essential (or anyway a medically recommended) part of daily life and remain so?

This post was written at a time of sunshine, normality and optimism, before Covid and even before the violent destructive force of Dorian in autumn 2019. Here’s some cheer from sea fans on the coral reefs of the Bahamas.

GALLERY OF GORGONIANS

The waters of Abaco teem with myriads of fish that depend on the coral reefs for shelter and safety, for breeding, for growing up in, and for nourishment. Sea fans (or gorgonians, to use the technical name) are animals too. They may look like plants and stay rooted to the spot, but like anemones these ‘soft corals’ are creatures of the reef and essential indicators of its health.

The purple sea fan Gorgonia ventalina (classified by Linnaeus in 1785) is one of the most common species of sea fan, and a spectacular one at that. The main branches are linked by a lattice of smaller branches. Below the ‘skin’ is a skeleton made of calcite compounded with a form of collagen.

Sea fans are filter-feeders, and have polyps with eight tiny tentacles that catch plankton as it drifts past. They develop so that their orientation is across the prevailing current. This maximises the water passing by and consequently the supply of food as the fans gently wave in the flow.

Gorgonians have a chemical defence mechanism that protects against potential troublemakers. The main effect is to make themselves unpleasant to nibble or uproot.

One species impervious to this deterrent is the fascinating FLAMINGO TONGUE SNAIL. Other ‘safe’ species include the fireworm and BUTTERFLYFISHES.

One benefit of sea fans to mankind is that their defensive chemicals have been discovered to provide the basis for drug research and development, specifically in the field of anti-inflammatories. Another benefit, of course, is that they are very beautiful to look at. And in bad times, that can only be good .

Credits: these wonderful photos were taken by Melinda & Keith Rodgers / Dive Abaco, Marsh Harbour; and Melinda & Fred Riger / Grand Bahama Scuba. Huge thanks to them all for allowing me to freely use their skilful underwater photography in this blog for the best part of a decade.

A SPECIAL FAN FOR A HAPPY AND HOPEFUL 2022

BAHAMAS DOLPHINS: VIEW FROM A RESEARCH BOAT with BMMRO

November 18, 2021 by Rolling Harbour

Recent weather conditions have mostly been perfect for launching the new BMMRO boat and continuing with ongoing marine mammal research. The field work at the moment is one aspect of the ‘Saving Abaco’s Dolphins after Hurricane Dorian’ project.

Acoustic research involves deploying specialised recorders to monitor sub-surface noise levels such as ship-generated sound. This helps to determine the effects of underwater noise pollution on marine mammals. Areas of concern can be identified and monitored. Naturally the dolphins take a keen interest as well, and there is plenty of opportunity to enjoy their company out on the water.

More general research includes compiling intricate records of dolphins encountered, noting specific characteristics. The dorsal fin is generally the most helpful ID marker, as they are all different – especially when there is some wear and tear to go by.

BMMRO records for dolphins go back a long way, and often involve two or more generations of the same family. Amazingly, during the last few days, a dolphin was encountered whose mother was first seen as a calf in 1992…

BMMRO are hosting a meeting in Hope Town to explain recent work and its results

BMMRO intern Jaylen gets to admire dolphins at close quarters in the Sea of Abaco

FLAMINGO TONGUE SNAILS: DECORATIVE CORAL-DWELLERS

April 20, 2021 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. These snails live in the tropical waters of the Caribbean and the wider western Atlantic. Whether alive or dead, they are gratifyingly easy to identify.

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

THE IMPORTANCE OF CORAL

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 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.

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 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 now 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 “boring-looking shells” (see photos below). Don’t be a collector; be a protector…

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

Image Credits: Melinda Rogers / Dive Abaco; Keith Salvesen / Rolling Harbour