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

BRAIN WAVES: UNDERSEA CORAL MAZES & LABYRINTHS

April 27, 2022 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.

ELKHORN CORAL – REEF LIFE . ABACO . BAHAMAS

March 21, 2022 by Rolling Harbour

ELKHORN CORAL (Acropora palmata) is a widespread reef coral, an unmistakeable species with large branches that resemble elk antlers. The dense growths create an ideal shady habitat for many reef creatures. These include reef fishes of all shapes and sizes, lobsters, shrimps and many more besides. Elkhorn and similar larger corals are essential for the wellbeing both of the reef itself and also its denizens. These creatures in turn benefit the corals and help keep them in a healthy state.

Examples of fish species vital for healthy corals include several types of PARROTFISH, the colourful and voracious herbivores that spend much of their time eating algae off the coral reefs using their beak-like teeth. This algal diet is digested, and the remains excreted as sand. Tread with care on your favourite beach; in part at least, it will consist of parrotfish poop.

Other vital reef species living in the shelter of elkhorn and other corals are the CLEANERS, little fish and shrimps that cater for the wellbeing and grooming of large and even predatory fishes. Gobies, wrasse, Pedersen shrimps and many others pick dead skin and parasites from the ‘client’ fish including their gills, and even from between the teeth of predators. This service is an excellent example of MUTUALISM, a symbiotic relationship in which both parties benefit: close grooming in return for rich pickings of food.

VULNERABILITY TO CLIMATE CRISIS

Formally abundant, over the course of just a couple of decades elkhorn coral (along with all reef life) has been massively affected by climate change. We can all pinpoint the species responsible for much of the habitat decline and destruction, and the primary factors involved. In addition, global changes in weather patterns result in major storms that are rapidly increasing in both frequency and intensity worldwide.

Physical damage to corals may seriously impact on reproductive success: elkhorn coral is no exception. The effects of a reduction of reef fertility are compounded by the fact that natural recovery is in any case inevitably a slow process. The worse the problem gets, the harder it becomes even to survive, let alone recover, let alone increase.

HOW DOES ELKHORN CORAL REPRODUCE?

There are two types of reproduction, which one might call asexual and sexual:

Elkhorn coral reproduction occurs when a branch breaks off and attaches to the substrate, forming a the start of a new colony. This process is known as Fragmentation and accounts for roughly half of coral spread. Considerable success is being achieved now with many coral species by in effect farming fragments and cloning colonies (see Reef Rescue Network’s coral nurseries)
Sexual reproduction occurs once a year in August or September, when coral colonies release millions of gametes by Broadcast Spawning

All photos: Melinda Rogers, with thanks as ever for use permission

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

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

Dolphin Research . Sea of Abaco . Bahamas . BMMRO – all photos © BMMRO

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

CHRISTMAS TREE WORMS: SEASONAL SPIROBRANCHES

December 21, 2020 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
It is not believed 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 the years

ENDANGERED SPECIES, ABACO (3): NASSAU GROUPER

May 28, 2020 by Rolling Harbour

ENDANGERED SPECIES, ABACO (3): NASSAU GROUPER

The Nassau grouper Epinephelus striatus is one of a number of grouper species found in Bahamian waters. Of these, only the Nassau grouper is on the IUCN Red List, as Critically Endangered. When I last wrote about them they were in the lesser category ‘Threatened’.

In order to sustain a viable population, it is vital to maintain numbers and preferably to increase them year on year. Once it became clear that year-round commercial overfishing was a prime component of the steep decline in the population, a 3-month closed season during the breeding period was imposed. This has ensured that at the most critical time in the lifecycle of the species, the groupers are left alone to breed in peace and to perpetuate their species.

The closed season operates from December to February to maximise the chances of breeding success. As with some other fish species, reproduction occurs around the full moon. The fish gather at spawning sites and the process is at its height around sunset.

10 CONVENIENTLY COLLECTED NASSAU GROUPER FACTS

An adult can grow to more than a metre long, and weigh 25 kg
They tend to be solitary daytime feeders, eating small fish & crustaceans
Their large mouths are use to ‘inhale’ or suck in prey
The colouring of an individual can vary from red to brown
These fish have little black spots around the eyes (I’ve no idea why).
Their habitat is in the vicinity of coral reefs, from shallows to 100 m deep
Spawning mainly occurs in Dec & Jan during a full moon
Large numbers gather in a single location to mate in a mass spawning
These groupers are slow breeders, which compounds the overfishing problem
They are easy mass targets at spawning time; hence the need for a closed season

A Nassau Grouper glumly contemplates the possibility of extinction

RELATED POSTS

Credits: Melinda Riger / Grand Bahamas Scuba (1, 2, 3, 5, 6); Melinda Rogers / Dive Abaco (4, 7)

SPERM WHALE BONES & RESEARCH: LIFE AFTER DEATH

March 31, 2020 by Rolling Harbour

SPERM WHALE BONES & RESEARCH: LIFE AFTER DEATH

I made this short video last year at BMMRO HQ, Sandy Point, Abaco. A sperm whale had stranded earlier in the year, and after the necropsy some of the bones were taken from the beach for research. In order to clean them, the bones were sunk and anchored to the seabed offshore in quite shallow water. Strandings are always sad, of course, but it is good to know that even after death the creature makes an important contribution to scientific research. In a sense, it has life after death.

BMMRO / Rolling Harbour Abaco / Keith Salvesen

MANATEES: PICTURE PERFECT ON ABACO (4)

March 25, 2020 by Rolling Harbour

MANATEES: PICTURE PERECT ON ABACO (4)

MANATEE APPRECIATION DAY 2020

Mrs RH and I are sticking to self-isolation right now (we are fine, but thank you for asking). However I am already breaking my current self-imposed ‘single-picture-and-not-much-writing’ regime with today’s creature feature. The excuse? It is of course the last Wednesday in March and as everyone must know it is Manatee Appreciation Day.

Anyone can (and indeed should) appreciate manatees anywhere at any time, and their contemplation is a way to lift the spirits. They were first found in Abaco waters about a dozen years ago. BMMRO reported their movements and the ongoing research. Later, Bahamian locals enthusiastically followed the lives of Gina, Rita, Georgie, Randy & co; and the calves such as JJ and Sayle (winning name in a public competition). Citizen scientist reports were invaluable to the research. Unsurprisingly, since Hurricane Dorian reports have greatly reduced. Manatees may well still be around but even now, 6 months later, trichechi sightings are sporadic. There are other concerns, after all.

Manatees love the camera and, Madonna-like, are often pleased to ‘strike the pose’. Of a sort.

Today the Marine Conservation Society (MCS) showed their appreciation for manatees with a superb image and an excellent set of Manatee Facts that I recommend to anyone who has read this far. For example, recent broadcasts and news articles have featured the importance of seagrass. You will see that it is the primary diet of manatees.

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Happy #ManateeAppreciationDay! ☺️ We have a great photo-feature of these amazing animals in the Spring issue of our magazine coming to all members in the next few days but whilst you wait, here are some fun facts about them: ⠀ ⠀ 💙The manatee, also known as a 'sea cow', is a large marine mammal with an egg-shaped head, flippers and a flat tail. ⠀ 💙Manatees range in size from 8 to 13 feet (2.4 to 4 meters) and can weigh 440 to 1,300 lbs. (200 to 590 kilograms). ⠀ 💙Although they may seem like cumbersome creatures, manatees can swim quickly and gracefully.They have strong tails that power their swimming and usually swim about 5 mph but they can swim up to 15 mph (24 km/h) in short bursts ⠀ 💙There are three species of manatee: the Amazonian manatee, the West Indian/American manatee and the African manatee. ⠀ 💙Manatees often swim alone or in pairs. If manatees are seen in a group (called an aggregation), it is either a mating herd or an informal meeting of the species simply sharing a warm area that has a large food supply. ⠀ 💙Manatees are herbivores. At sea, they tend to prefer sea grasses. When they live in rivers, they consume freshwater vegetation. Manatees also eat algae. It's reported that a manatee can eat a tenth of its own weight in 24 hours! ⠀ 💙The IUCN's Red List of Threatened Species lists all manatees as vulnerable or endangered and facing a high risk of extinction. ⠀ Manatees are thought to have evolved from four-legged land mammals more than 60 million years ago. Except for the Amazonian manatee, their paddlelike flippers have vestigial toenails — a remnant of the claws they had when they lived on land. ⠀ 💙Manatees' eyes are small, but their eyesight is good. They have a special membrane that can be drawn across the eyeball for protection. ⠀ 💙Manatees don't always need to breathe. As they swim, they poke their nose up above the water's surface to catch a few breaths every few minutes. If they are simply resting, they can stay under the water for 15 minutes without taking a breath ⠀ ⠀ #marinemammal #marineconservation #marnebiology #marinelife #oceanlife #oceanindoors #manatee ⠀ ⠀

A post shared by Marine Conservation Society (@mcs_uk) on Mar 25, 2020 at 7:44am PDT

Credits: Photos #1 – #4 Charlotte Dunn / Bahamas Marine Mammal Research Organisation (BMMRO) and #5 Caine Delacy / BMMRO; MCS UK

MCS links: https://www.mcsuk.org; https://www.facebook.com/mcsuk/

Gina with her calf Sayle

OCTOPUS’S GARDEN (TAKE 9) IN THE BAHAMAS

February 10, 2020 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)

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 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

BABY SPERM WHALE, ABACO, BAHAMAS: HOPE FOR A NEW DECADE

January 6, 2020 by Rolling Harbour

BABY SPERM WHALE, ABACO, BAHAMAS

HOPE FOR A NEW DECADE

Looking back at 2019, one of the most enjoyable posts to put together featured an adult sperm whale with a neonate calf. The wonderful photos were obtained last summer during 2 research trips in the deeper water off the south coast of Abaco by the Bahamas Marine Mammal Research Organisation (BMMRO) It seems fitting to greet the new decade with a revised version of my original post. There’s optimism in these images, and more generally in the recovery in some areas of the savagely depleted whale populations of past decades. I’d like to think that a smiling baby whale holds out hope for the 2020s.

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

These are just some of the BMMRO research team’s images and footage of the baby sperm whale investigating the underwater world it has just been born into. Hopefully it will flourish and live for decades. If it does not, the overwhelmingly likely cause will be mankind, either directly or indirectly.

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

BRAIN WAVES: UNDERSEA CORAL MAZES & LABYRINTHS

December 19, 2019 by Rolling Harbour

BRAIN WAVES: UNDERSEA CORAL MAZES & LABYRINTHS

The name ‘brain coral’ is essentially a no-brainer. How could you not call the creatures on this page anything else. These corals come in wide varieties of colour, shape and – well, braininess – and are divided into two main families worldwide.

The hardness of this type of coral makes it a 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 hundreds of little tentacles nestled in the trenches on the surface. These corals feed at night, deploying their tentacles to catch food. This consists of tiny creatures and their algal contents. During the day, the tentacles are retracted into the sinuous grooves. Some brain corals have developed tentacles with defensive stings.

THE TRACKS LOOKS LIKE MAZES OR DO I MEAN LABYRINTHS?

Mazes, I think. 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. Check out which type of puzzle occurs on brain coral. Answer below…**

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

** On the coral I got lost straight away in blind alleys. Therefore these are mazes. Here is a beautiful inscribed labyrinth dating from c12 or c13 from the porch of St Martin Cathedral in Lucca, Italy. Very beautiful but not such a challenge.

‘DEEP DIVERS IN DIVERS DEEPS’: CUVIER’S BEAKED WHALES

December 13, 2019 by Rolling Harbour

‘DEEP DIVERS IN DIVERS DEEPS’: CUVIER’S BEAKED WHALES

JOURNEY TO THE WORLD’S MIDNIGHT ZONE

Please join me in a dive down from the sparkling surface of the turquoise sea to the twilight zone at 200 meters. You’ll pass plenty of sea-life on the way: manatees grazing on seagrass just below the surface; reef fish, barracudas, reef sharks, mahi-mahi, maybe an orca at 100 meters. Other familiar creatures that are found even lower include a few reef fish, some shark species and green sea turtles. You are now running out of clear light.

As you descend from 200 meters the waters become murky, then inky. The variety of inhabitants and their numbers are gradually decreasing. There are eels, some sharks, squid, stranger deep-water creatures. You may be surprised to see familiar bottlenose dolphins, recorded as diving nearly 300 meters. At 332 meters you will equal the deepest point any human being has ever scuba-dived (Ahmed Gabr 2014). There is little light, but you still have a long way to go to reach your goal.

Descending still deeper, species and numbers continue to thin out. Around the world the limits of larger recognisable species is being reached – more shark species, tuna, chinook salmon, emperor penguins, swordfish, the few corals that can survive the depth. As the light fades to black, giant creatures and strange fish abound. Huge crabs. Sunfish. The (no-longer-extinct) Coelocanth. Massive octopuses.

Deeper down, nearing 1000 meters now, there are still some familiar species. Leatherback turtles; Baird’s beaked whales (nb not in the Atlantic); and at 920 meters, the deepest recorded sperm whale dive. It’s pitch dark: you have reached the level that sunlight never penetrates. You are in the Midnight Zone.

DEEP OCEAN DWELLERS

In black depths below 1000 meters, creatures have adpated to create their own light sources – so-called bioluminescence. This is the realm of the self-lit anglerfish, the blobfish and the goblin shark. It’s the Attenborough world of deep sea exploration. The geology is changing: there are hypervents, volcanic rocks, heavy metals. Below are the deep ocean-floor trenches. Yet there are still recognisable species down here, diving astonishingly deep to 1800 meters to feed – not least the narwhal which makes this trip several times a day to feed.

We need to quicken up the descent now – we have to get down nearly twice as far as this to reach our destination…

We pass large squid and isopods, the deepest diving shark – the Greenland, the 10 meter-long 700 kilo colossal squid – yet amazingly there are marine mammals yet to be encountered: at 2400 meters we drift past a huge elephant seal. There are evil-looking creatures down here with names to match – devilfish, viperfish, black swallowers that can eat a larger fish whole, vampire squid and zombie worms.

At 3000 feet, we finally end our quest. We have reached the depth to which the world’s deepest diving mammal has been recorded: the Cuvier’s beaked whale Ziphius cavirostris

Cuvier’s beaked whales, or “goose-beaked whales,” are not rare. For a start, unlike many beaked whale species, they inhabit most oceans and seas in the world and have the most extensive range. Unsurprisingly therefore, they are one of the most often sighted beaked whale species and one of the best studied.

FIN FACT

You may be wondering about the pressure exerted on a creature at a depth of 3000 meters. The answer is, an astounding 300 atm (atmospheres), enough to crush all but the hardiest and best adapted of species. The question how these whales manage to survive at such a depth is one for the future…

The Cuvier’s is one of the 3 beaked whale species found in Bahamas waters. Like the rarer Blainville’s and Gervais’s beaked whales, the Cuvier’s is the subject of ongoing research by the BAHAMAS MARINE MAMMAL RESEARCH ORGANISATION BMMRO.

The research into marine mammal populations in the Bahamas and far beyond is focussed on the massive increase in single and mass strandings, including recently in a remote area of Scotland (Hebrides) where more than 40 Cuvier’s were washed ashore.

One significant area of research examines the effect on marine mammals of man-made noise. There is plenty of it in the world’s oceans caused by noise pollution in and around shipping channels that traverse marine mammal migration, feeding and breeding grounds; naval surface and submarine exercises; seismic surveys, sonar waves and undersea resource investigations. The evidence of sound / acoustic damage as an additional hazard for marine mammals is starting to look very clear.

DEEP WATER INFOGRAPHIC

Do not miss this wonderful work by Neal Agarwal. This article is based around it and includes facts and images derived from his incredibly complex structure that has resulted in a remarkably simple resource for layman and ocean-lover alike (I realise these categories may overlap). To see the entire masterpiece, double click of the box below – “it will be worth it”.

CREDITS: Neal Agarwal; BMMRO / Charlotte Dunn; M.Rosso GIMA – IUCN; NOAA Fisheries; BW – Getty – Times; Pierangelo Pirak / BBC Earth (depth infographic), general sources – BMMRO, IUCN, NOAA, WDC

As ever, the Bahamas Philatelic Bureau has produced a wonderful stamp special issue

EEL-SPOTTING: FORAYS WITH MORAYS (7)

December 9, 2019 by Rolling Harbour

EEL-SPOTTING: FORAYS WITH MORAYS (7)

MORAY EELS are plentiful around the reefs of the Bahamas. Some species, anyway. The ones you are most likely to encounter are green morays, and the spotted morays shown here. Less common are chain and golden-tail morays and, rarer still I suspect (because I have only one image in the archive…) is the ‘purple-mouth’.

Despite their moderately intimidating appearance – an adult may grow to 1.5 meters or more, with sharp teeth at the front end – these eels are not especially aggressive unless provoked. Best to assume that all humans will behave respectfully around them and remember that people are the intruders in the eels’ domain.

Morays tend to be loners of the reefs, but they do gather in groups from time to time. And as shown below, they will also hunt with other species, for example this tiger grouper.