CHRISTMAS TREE WORMS: SEASONAL SPIROBRANCHES


Christmas Tree Worm (Melinda Riger / Grand Bahama Scuba)

CHRISTMAS TREE WORMS: SEASONAL SPIROBRANCHES

music-notes-clip-art-png-musicDeck 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 another look at these remarkable subsurface symbols of seasonal good cheer (nb they are animals not plants).

christmas-tree-worm-melinda-riger-g-b-scuba

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 (Neil Hobgood Wiki)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)

spirobranchus_giganteus_orange_christmas_tree_worm-nick-hobgood-wiki

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

This is a delicate area. They don’t tend to talk about it much, but as far as I can make out they eject gametes from their what-I-said-above. There are mummy and daddy worms, and their respective gametes (eggs and spermatozoa) drift in the current and presumably into each other to complete the union. The fertilised eggs develop into larvae, which settle onto coral and burrow into it, build their protective tubes and the process begins again.

christmas_tree_worm-nick-hobgood-wiki

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 – possibly 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 WORMSChristmas Tree Worms (Neil Hobgood Wiki)

Credits: Melinda Riger (G B 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
blue_christmas_tree_worm-betty-wills-wiki

SPERM WHALES – BMMRO FIELD TRIP, BAHAMAS


Sperm Whales, Bahamas (BMMRO)

SPERM WHALES – BMMRO FIELD TRIP, BAHAMAS

I can never quite get my head around the fact that the waters around Abaco are home to the twin leviathans, sperm whales and humpback whales. And before anyone points it out, I realise they can’t actually be twins: sperms whales (cachelots) are TOOTHED WHALES whereas humpback whales are BALEEN WHALES

Sperm Whales, Bahamas (BMMRO)

During November, the Bahamas Marine Mammal Research Organisation (BMMRO) undertook a rather special field trip. Using sophisticated devices, the scientists first located a group of sperm whales, and then tracked them through the night using the communications between the creatures – ‘vocalisations’ – to follow them. Later analysis of the recordings will have made it possible to identify the individuals through their unique vocal patterns – and so to recognise them again. 

Sperm Whale, Bahamas (BMMRO)

The hydrophonic equipment used is extremely sensitive, and can pick up the sounds made by whales and dolphins over a great distance. The box of tricks looks deceptively modest – I took these photos on a previous trip when we were looking for beaked whales and dolphins. Charlotte Dunn holds the microphone submerged on a cable and underwater sounds are amplified so that the slightest chirrup of a dolphin can be heard by everyone on the vessel. The sounds are recorded and locations carefully logged.

Besides the sperm whales, the BMMRO team also had sightings of spotted dolphins, bottlenose dolphins and beaked whales during the field trip. These bonus sightings will also have been logged for future reference. It all adds to the detailed research data that assists the conservation of the prolific marine mammal life in Bahamian waters.

Atlantic Spotted DolphinsAtlantic Spotted Dolphins, Bahamas (BMMRO)

By the time one of the whales decided to breach, it was some distance away, so I’m afraid I can’t bring you a dramatic close-up from the trip. But just to see this view at all is breathtaking.

All photos BMMRO except the 2 hydrophone ones on the research boat (Keith Salvesen)

BAHAMAS REEF FISH (39): YELLOWTAIL DAMSELFISH


Yellowtail Damselfish (©Melinda Riger / Grand Bahama Scuba)

BAHAMAS REEF FISH (39): YELLOWTAIL DAMSELFISH

Yellowtails are just one of several damselfish species in Bahamas waters. These small fish are conspicuous not just for the bright tails that give them their name. More striking if anything – especially if seen underwater in sunlight against the coral – are the electric blue spots visible in both adults and juveniles.

Yellowtail Damselfish (©Melinda Riger / Grand Bahama Scuba)

The body of adults is dark blue to brownish to almost black 

The body of juveniles is blue

Yellowtails are a common and widespread variety of damselfish. They have a limited ability to change colour according to their surroundings, but with their bright tails and luminous blue flecks, it’s hard to see how they can look, to a predator, anything other than a tasty snack.

I have enjoyed seeing these little fish at Fowl Cay Marine Preserve, Abaco. The reef there makes for easy and rewarding snorkelling, with a wide variety of small and medium-size reef fishes to be seen. It’s an expedition I would definitely recommend to anyone wanting to see a healthy and active reef in a completely natural protected area.

I found that a video I took with a tiny camera was sadly of use only to myself. No one else would be able to make anything out due to the marked camera shake. Novices, huh? You are spared that: here’s a brief example of yellowtails swimming instead, showing the difference between juveniles and adults.

Credits: all photos, Melinda Riger / Grand Bahama Scuba; video from Desert Diving

BLAINVILLE’S BEAKED WHALES IN ABACO WATERS


Blainville's Beaked Whale, Abaco (BMMRO)

BLAINVILLE’S BEAKED WHALES IN ABACO WATERS

It’s hard to believe that the seas around Abaco and its cays are home to a number of whale species, from huge sperm and humpback whales down to so-called dwarf or pygmy species. In the middle of this range come the beaked whales, the most common being the Blainville’s Beaked Whale. I say ‘most common’, but in fact they are rare in the world, being found in only two other main locations on earth. 

Blainville's Beaked Whale, Abaco (BMMRO)

These whales are carefully monitored by the Bahamas Marine Mammal Research Organisation (BMMRO), and there is a tagging program to keep track of them. As with dolphins, individuals are identified by markings on the dorsal fin, which vary for each whale. The one above has distinctive scarring at the tip. There are also striations on the body, and conspicuous circular marks that are healed wounds caused by cookie-cutter sharks.

Blainville's Beaked Whale, Abaco (BMMRO)

To the untrained eye, there are no noticeable marks on the dorsal fin of the whale above. However, the whale’s back has a prominent pattern of scarring and healed cookie-cutter wounds. The whale below really looks as though it has been in the wars, with long deep healed wounds behind the head.

Blainville's Beaked Whale, Abaco (BMMRO)

I can’t tell without seeing the head, but I wonder if it is a male and the scars have been caused in a fight with another male – adult males have prominent tusks with which they do battle. Here is an photo that I took from the research boat on a different occasion. The tusks protrude upwards from the lower jaw, and are often covered in barnacles. They are capable of causing serious injury.

Blainville's Beaked Whale male, Abaco (Keith Salvesen)

Blainville’s beaked whales are amongst the deepest divers of all whales. But that and other whale topics will have to wait for another day… My computer malware / virus has been removed professionally with no data loss, and I have some catching up to do. Cost in terms of panic and stress: huge. Cost in real terms: $90.

Blainville's Beaked Whale, Abaco (BMMRO)

All photos BMMRO except the tusked male, Keith Salvesen

AN ‘EXHILARATION’ OF ABACO DOLPHINS


Bottlenose Dolphins, Abaco Bahamas (BMMRO)

AN ‘EXHILARATION’ OF ABACO DOLPHINS

Bottlenose dolphins! Tursiops truncatus! These engagingly playful show-offs of the inshore waters round Abaco are 99.99% adorable**. It’s been a harrowing few weeks in the western Atlantic, and everyone is hoping that the 2017 hurricane season has had enough of causing death and destruction over vast swathes of vulnerable islands and on the US mainland. Some cheer is needed.

Bottlenose Dolphins, Abaco Bahamas (BMMRO)

Dolphins are good for the soul. And if you are out on a boat watching them – and especially tracking them for a whole day – every encounter reinforces the impression that all the leaping, bow-wave riding, boat under-swimming, and general sociability and interaction is often as much for sheer enjoyment as anything else. 

Bottlenose Dolphins, Abaco Bahamas (BMMRO)

Abaco is fortunate in having the HQ of the Bahamas Mammals Research Organisation (BMMRO) based at Sandy Point. That just happens to be an excellent area for bottlenose dolphin spotting in the turquoise shallows. Many sightings are made within clear sight of land. Further south, where the bright blue gives way to darker and deeper water, live the equally frolicsome Atlantic spotted dolphins. The 3 photos above were all taken on the margins of where the colour of the sea changes from light to dark.

Bottlenose Dolphins, Abaco Bahamas (BMMRO)

I’m a bit of a collector of collective nouns. For dolphins, apart from the matter-of-fact ‘group’ or ‘pod’, there is no exotic word to describe a number of them when they are having fun. No equivalent of ‘exaltation’ (larks), ‘charm’ (goldfinches) or ‘parliament’ (owls). So I’m nominating an ‘exhilaration’ as a candidate to fill the gap…

The photo above shows clearly how individual dolphins can be identified by researchers. All tend to have scars or tears to their dorsal fins that enable them to be distinguished. The closest has distinctive scars near the tip. The furthest has a W-shaped nick at the back. In fact, it could even be Rocky, a well-known dolphin on Abaco that has been sighted over many years. There are regular reports annually. I saw him myself once, in 2012, playing about in Hopetown harbour. 

STOP PRESS To demonstrate how the ID methods work, I’ve now cross-checked with the BMMRO photo ID archive. Here is Rocky’s original dorsal fin ID image (“Tt15”) from October 2010. There’s a W-shaped nick, sure, but my speculation above was wrong because overall the two fins are clearly different…

Rocky the Dolphin Tt15, from BMMRO ID photo archive

** The 0.01%? Dolphins may, rarely, be alarming for divers in circumstances I won’t repeat here (hint: to do with over-friendliness, ok? Yes, the thing that dogs do)

Credits: all photos BMMRO – and taken in the last 2 months

EYES ON STALKS: CONCH WATCH ON ABACO


Conch Man-o-War Cay, Abaco, Bahamas (Charmaine Albury)

EYES ON STALKS: CONCH WATCH ON ABACO

This is not so much about you looking at, and admiring (without salivating too much, I trust) conchs in their natural element. More about them watching you watching them – and focusing on their rather remarkable stalk-based eyes. Take a look at these examples of the ‘watcher in the shallows‘ (to misquote a well-known book title).

Conch and their eyes, Bahamas (Melinda Riger)Conch and their eyes, Bahamas (Melinda Riger)

HALF A DOZEN CONCH EYE FACTS TO PONDER

  • The eyestalks are attached to an extendable ‘snout’
  • The two eyestalks (ommatophores) are retractable within the shell
  • Their purpose is to provide a wider field of vision around the shell
  • The eyes at the tip of each eyestalk have ‘proper’ lenses, pupils and irises 
  • Amazingly, amputated eyes normally regenerate completely
  • The small projection below the eye is a ‘sensory tentacle’ or feeler

Conch and their eyes, Bahamas (Melinda Riger)Conch and their eyes, Bahamas (Melinda Riger)

CAUTIONARY WARNING

For a rather depressing view of the current state of conch populations, check out this recent article in the MIAMI HERALD. Not a great deal to be optimistic about…

I’M WATCHING YOU…

CREDITS: All remarkable ‘conch watching’ photos by Melinda Riger / Grand Bahama Scuba – except for the wonderful header image by Charmaine Albury (contributor the The Birds of Abaco), taken on Man-o-War Cay; Cindy James Pinder for the heads-up for the Miami Herald article

DOLPHINS DISPORTING IN THE BAHAMAS


Atlantic Spotted Dolphin, Bahamas (BMMRO)

DOLPHINS DISPORTING IN THE BAHAMAS

‘Disporting’. Not a word I’ve used very often. Or possibly ever. It looks a bit like ‘unsporting’, which is emphatically what dolphins are not. Basically, it just describes what dolphins are doing when you see them on the surface: amusing themselves, frolicking around in the waves, and simply enjoying themselves.Bottlenose Dolphin, Bahamas (BMMRO)

True, they are probably keeping an eye out for food… But when you have a group sociably following alongside the boat your are in, moving in front, dropping behind, diving under, and generally playing around, it’s quite hard to believe that these are completely wild creatures. They seem to be performing just for you, simply because they want to. You don’t even have to throw fish at them to earn this free display.

Atlantic Spotted Dolphin, Bahamas (BMMRO)Atlantic Spotted Dolphin, Bahamas (BMMRO) Atlantic Spotted Dolphin, Bahamas (BMMRO)

As is well-known, the BAHAMAS MARINE MAMMAL RESEARCH ORGANISATION (BMMRO) is the custodian for the welfare of these beautiful creatures for the entire Bahamas. However, being based on Abaco and carrying out the majority of the research from the HQ at Sandy Point means that many of the great images that get taken are from Abaco waters. Indeed some are taken within swimming distance (not mine) of the shore.  Bottlenose Dolphin, Bahamas (BMMRO)Bottlenose Dolphin, Bahamas (BMMRO)Bottlenose Dolphin, Bahamas (BMMRO)Bottlenose Dolphin, Bahamas (BMMRO)

The photographs featured here were taken during the last few weeks. Some are of the familiar bottlenose dolphins. The others – with speckled undersides clearly visible in the header image & below – are of Atlantic spotted dolphins. There’s even one of my own taken from the research vessel. Atlantic Spotted Dolphin, Abaco Bahamas (Keith Salvesen)Atlantic Spotted Dolphin, Bahamas (BMMRO)

For the researchers, the most important part of an individual dolphin is its dorsal fin. Unique patterns of cuts and scars mean that each dolphin sighted can be logged and their profiles built up. Some have been found in the same area for many years. They are not usually given jocular names – ‘Davy Jones’, ‘Finny Phil’ or whatever. The first time we went out on the research vessel we were slightly surprised by the practical, scientific calls during a sighting of a dolphin group: “there’s B4 again” and “over there – D5 is back”. All said fondly however – many of the dolphins are old friends.

This dolphin has a notable notch on the dorsal fin with a nick below, & a scar line – with a prominent white scar on the lower front edge Bottlenose Dolphin, Bahamas - Dorsal Fin Damage (BMMRO)

Notice how these 3 dolphins all have quite different fin profiles.  The nearest one’s fin looks unblemished, but has a paler tip. Powerful binoculars and a serious camera can pick out small  differences at a distance that the eye could notBottlenose Dolphin, Bahamas - Dorsal Fin Damage (BMMRO)

Coming soon: Manatees & Man in the Bahamas

All photos (bar one by me) BMMRO, with thanks to Diane & Charlotte, and a tip of the hat to the current interns involved in the research projects (Hi, UK Thomas!)