PREHENSILE TALES FROM THE REEF (3): SEAHORSING AROUND


Seahorse (Adam Rees / .Scuba Works)

PREHENSILE TALES FROM THE REEF (3): SEAHORSING AROUND

It’s Friday at last. It’s springtime. A spirit of benign goodwill is evident in the vicinity of Rolling Harbour. Seahorses are irresistible. Don’t even try to pretend they don’t make you smile. Hippocampophobia is an affliction that, as yet, has never been diagnosed in a human being – for whom fear of beards, clowns and the number 5 (quintaphobia) are known medical conditions. Immerse yourself with these little creatures – and then have a good weekend.

Seahorse (Adam Rees / Scuba Works)Seahorse (Adam Rees / Scuba Works)Seahorse (Adam Rees / Scuba Works)Seahorse (Adam Rees / Scuba Works)Seahorse (Adam Rees / Scuba Works)Seahorse (Adam Rees / Scuba Works)

All fantastic hippocampi photos: Adam Rees / Scuba Works

DUSKY DAMSELFISH: BAHAMAS REEF FISH (34)


Dusky Damselfish, Bahamas (Melinda Riger)

DUSKY DAMSELFISH: BAHAMAS REEF FISH (34)

The dusky damselfish Stegastes fuscus is one of a number of damselfish species found in Bahamian waters. These small reef fish, in adult form, are dark coloured as their name suggests. Their appearance is brightened by having distinctive blue edges to their fins.

Dusky Damselfish, Bahamas (Melinda Riger)

These fish feed mainly on algae, with a preference for red. They top up their diet with small invertebrates. Their value to the reef is that their feeding patterns help to prevent coarser seaweeds from becoming dominant in areas where these are prevalent. 

Dusky Damselfish, Bahamas (Melinda Riger)

Like many damselfish, the dusky is a territorial species, guarding its chosen area of seabed and the food sources within it by repelling intruders – often seeing off far larger algae-grazing fishes such as parrotfish and wrasse. Yet besides their aggressive traits, they are also rather cute, as photo #2 shows!

Dusky damselfish, Bahamas (Melinda Riger)

All photos: Melinda Riger / Grand Bahama Scuba

BLUEHEAD WRASSE: PRIVATE LIFE LAID BARE


bluehead_wrasse_thallasoma_bifasciatum_oregonstate-edu-pinterest

BLUEHEAD WRASSE: PRIVATE LIFE LAID BARE

The bluehead wrasse (or blue-headed wrasse) Thalassoma bifasciatum is a denizen of the coral reefs of the tropical waters of the western Atlantic Ocean. This bright little 4-inch fish is… a wrasse with a blue head. No more and no less. Unless it’s a juvenile. Then it is mainly bright yellow. It’s similar to BLUE TANG (aka ‘the Disney Dory’), which starts life bright yellow and grows up to be blue.

blue-head-wrasse-melinda-riger-g-b-scuba-copy

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. 

thalassoma_bifasciatum_bluehead_wrasse_san_salvador_island_bahamas-james-st-john-wiki

Having said that, blueheads are of course fair game as a snack for species that aren’t in the market for their cleaning services. And, unfairly, some species that are content to let cleaner gobies runtle around their gills and mouths are not so considerate of the wrasse. Some types of grouper and moray eel, for example.

bluehead_wrasse

TELL US EXACTLY SEVEN BLUEHEAD WRASSE FACTS

  • Juveniles can alter the intensity of their colour, stripes & bars
  • The bluehead wrasse is a ‘protogynous sequential hermaphrodite’
  • All are born female**. Some change sex to male during maturation (see below)
  • Food includes zooplankton, small molluscs and small crustaceans…
  • …and parasites / other juicy bits (fungal growths, anyone?) from bigger fish
  • The main threat to the species is coral reef degradation or destruction
  • The bright colours invite aquarium use, but the trade is not a significant one

** Some sources suggest some are born male and remain male. I’m not sure which is right

A juvenile bluehead (with feather-duster worms) – mostly yellow, with a pale underside
Bluehead Wrasse juvenile (wiki)

THE REMARKABLE SEX LIFE OF THE BLUEHEAD WRASSE

This is an unavoidable topic, I’m afraid. The bluehead’s sex life is the most interesting thing about them, and this is no time to be prudish. It is the subject of extensive scientific research, not all of which I have read since I decided to write about the species last night. Like many human relationships, “it’s complicated”, but in a conch shell it boils down to this:

  • To recap, BWs are born female and as they mature, some become male.
  • Males reach an ‘initial phase’ when they can breed in groups with females
  • Some males grow even larger & reach full colouration. This is the ‘terminal phase’
  • These large males aggressively chase away smaller ones & seek females to pair with
  • Their state of readiness (as it were) is signalled by colour changes
  • This behaviour is similar to that seen in many city centres in a Saturday night
  • The smaller fish have one bonus – their sperm count is higher than a dominant male
  • Prozac tests have shown that the drug reduces a dominant male’s aggression

blue-headed_wrasse_det (wiki)

As the excellent organisation OCEANA puts it: Bluehead Wrasses may reproduce in four different ways throughout their lifetime:  1) as a female in a group spawning event; 2) as a female in a pair spawning event within the territory of a large male; 3) as a small male in a group spawning event; and 4) as a dominant, terminal male in a pair spawning event within its own territory.

A cropped still from a video I took at Fowl Cay marine reserve. I’ve looked at dozens of images online and not found one that was all blue with a yellow end to its tail fin. Maybe it’s not a BW at all. Or it’s a different type of fish completely. Or perhaps it is just an all-blue alpha male.bluehead-wrasse-fowl-cay-mr-abaco

Credits & Sources: Melinda Riger; Adam Rees; James St John; Oregon State edu / Pinterest; Wiki images; self; Oceana; IUCN; magpie pickings

A bluehead wrasse passes the time of day with a gruntbluehead-wrasse-grunt-adam-rees

ABSORBING SPONGES ON THE BAHAMAS REEFS…


sponge-melinda-riger-gb-scuba

ABSORBING SPONGES ON THE BAHAMAS REEFS…

A while back I showed a collection of colourful sponges – one that you might come across with minimum equipment. Snorkel, mask, flippers. Oh, and a coral reef, if you happen to have one handy. I suspect that to quite a few people the word ‘sponge’ means soggy yellow thing, as found in the proximity of a bath. Or a scratchy nylon-based equivalent. Well, here are a few more sponges to enjoy. Some I can give you the names of, some I don’t know and am too idle busy to look up… Sorry.

sponges-melinda-riger-g-b-scuba

Candelabra Songe (with brittle stars attached)candelabra-sponge-melinda-riger-g-b-scubasponge-melinda-riger-g-b-scuba

Black Ball Spongesblack-ball-sponge-melinda-riger-g-b-scuba-copy

One for Valentine’s Dayheart-shaped-sponge-melinda-riger-gb-scuba

Vase Spongesvase-sponge- pink-melinda-riger-gb-scubavase-sponge-melinda-riger-g-b-scuba

sponges-and-coral-on-the-reef

Spawning Brown Encrusting Spongebrown-encrusting-sponge-spawning-melinda-riger-g-b-scuba

All photos: Melinda Riger, Grand Bahama Scuba

CHRISTMAS TREE WORMS: FABULOUSLY FESTIVE


christmas-tree-worms-adam-rees-scuba-works-copy

CHRISTMAS TREE WORMS: FABULOUSLY FESTIVE

music-notes-clip-art-png-music“Deck the Reefs with Worms Like Christmas Trees… Fal-La-La-etc-etc ” is a traditional Carol familiar to all. Well, most. Ok, some, then. Oh right – maybe with different words. Anyway, now is as good time as any to take a look at these remarkable plants creatures and subsurface symbols of good cheer.

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-worms-melinda-riger-g-b-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…

spirobranchus_giganteus_orange_christmas_tree_worm-nick-hobgood-wiki

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

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

christmas_tree_worm-nick-hobgood-wiki

LOOK, YOU DON’T REALLY UNDERSTAND THESE CREATURES, DO YOU?

I won’t lie. I found it hard to work out how the CTWs function in practice. There are plenty of resources showing them in their full glory, but that only takes one so far. Then I came across a short video that shows it all brilliantly simply (except for the reproduction part). So maybe I should have just posted this first and saved you (and me) some trouble…

The worm, invisible in its coral burrow, hoists its pair of trees. You can easily see small particles – possibly zooplankton – drifting in the water, and the radioles swaying to catch potential food. Bingo. It all makes sense! Next: the New Year Worm

Credits: Melinda Riger (G B Scuba); Adam Rees (Scuba Works); Nick Hobgood; Betty Wills; Absolutely Wild Visuals; MarineBio; Wikibits & Magpie Pickings

blue_christmas_tree_worm-betty-wills-wiki

WTF? (WHAT’S THAT FISH?) 12: THE TRUMPETFISH


trumpetfishmelinda-riger-gb-scuba

WTF? (WHAT’S THAT FISH?) 12: THE TRUMPETFISH

It’s been a while since the previous post in the WTF? series, dedicated to the unusual or downright weird marine creatures that, when you see them swim into in the frame of your mask, prompt the involuntary exclamation “WTF?” (What’s That Fish?). Now, in all its glory meet… The Trumpetfish. These long piscine pipes are in no way related to the President-Elect and his tank of pet fish, but perhaps more explicably to seahorses and seadragons.

trumpetfish-melinda-riger-g-b-scuba

Trumpetfishes Aulostomus maculatus are as happy to swim upright as more conventionally, which helps them to blend in with vertical corals and sponges on the reefs in the tropical waters of the western Atlantic. Adults may grow to 3 foot long or more. These creatures come in a variety of colours – shades of red, orange, brown, green and yellow.

trumpetfish-adam-rees-scuba-works_

At the end of the fish’s long snout – see how far back the eyes are set – is a small mouth. Here’s how a trumpetfish goes about catching its prey (mostly small fishes):

  • Slowly swimming or drifting to a target from behind, and sucking it into its mouth
  • Staying suspended in the water, motionless, and waiting like a malevolent stick for a passing wrasse or similar to get too close
  • Swimming alongside larger fishes, which camouflages its presence and enables it to ambush small fish as they pass 
  • More generally, the trumpetfish has some ability to change its colour to blend with its surroundings – both a defensive as well as an attacking advantage

Trumpetfish (Adam Rees / Scuba Works)

The very excellent Peppermint Narwhal recently produced a series of posters in appreciation of particular species – and trumpetfishes and their kin in the Order syngnathidae were honoured. The PN’s cheerful website is well worth checking out for the sheer diversity of their ideas.

14991470_1159096584183417_5198894741175308852_o

MUSICAL NOTES

We are beginning to collect the makings of a decent orchestra here. The trumpetfish has a relative, the cornetfish, elsewhere in the world. The remarkable GUITARFISH has already featured in the WTF? series, as has a species of BASS, the Harlequin. And – hey! – what about the spotted DRUMFISH to lay down the beat? Maybe I need to compose a little jingle featuring these one day…

Credits: Melinda Riger (Grand Bahama Scuba); Adam Rees (Scuba Works)

FLORAL CORAL: BEAUTIFUL BAHAMIAN REEF LIFE


coral-soft-corals-melinda-riger-g-b-scuba

FLORAL CORAL: BEAUTIFUL BAHAMIAN REEF LIFE

This post needs no commentary from me, nor my larky intrusions. These wonderful images from Melinda Riger speak for themselves. You’ll see a wide variety of soft and hard corals in the images below (prize** for the full list). If these superb photos don’t want to make you want to grab a snorkel, mask and flippers, then… well, that would be a very great shame.

coral-melinda-riger-g-b-scubacoral-melinda-riger-gb-scubacoral-reef-2-melinda-riger-g-b-scubafire-coral-melinda-riger-gb-scubapillar-coral-melinda-riger-gb-scubablushing-star-coralpurple-sea-fan-melinda-riger-g-b-scubapurple-sea-fan-melinda-riger-g-b-scuba-copy

**the prize is the usual legendary bottle of Kalik. Or do I mean mythical?

All wonderful photos by Melinda Riger, Grand Bahama Scuba. All corals also available in a wide range of colours in Abaco waters. See them there on the third largest barrier reef in the world (and in rather better nick that the greatest, by all accounts).