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

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.

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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.

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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

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MAKE FRIENDS WITH ANEMONE (2): SPECTACULAR REEF LIFE


Corkscrew Anenome = Peterson Cleaner Shrimps ©Melinda Riger @G B Scuba copy

Corkscrew Anemone with Peterson Cleaner Shrimps

MAKE FRIENDS WITH ANEMONE (2):  SPECTACULAR REEF LIFE

Going snorkelling? Planning a scuba day on the reef? You’ll see wonderful fish and amazing coral for sure. But sometimes the beauty of other life on the reef can be overlooked. Check out the anemone in the header image, with the camouflaged cleaner shrimps playing around it. You wouldn’t want to miss a sight like that. The many and varied forms and colours of anemone on the reefs of the Bahamas make up a vital component of a spectacular underwater world.

Giant Anenome ©Melinda Riger @ G B Scuba copyGiant Anemone ©Melinda Riger @ G B Scuba copy 4Anemone Melinda Riger @ G B ScubaAnemone on Rope ©Melinda Riger @ G B ScubaAnemone ©Melinda Riger @ Grand Bahama ScubaAnemone (Giant) ©Melinda Riger @GBS copyAnemone ©Melinda Riger @ GB Scuba

ADDED NOV 2016 Capt. Rick Guest adds this interesting material (& thanks for correcting my erroneous reference to anemones as ‘plants’. My bad. They are of course animals!):

“Anemones are living animals of the invertebrate type. Basically living corals without skeletons. All have stinging cells of several varieties to sting or entangle their prey such as small fish, or various invertebrates. A few can even, painfully, penetrate human dermal layers. Most host varieties of cleaner shrimps,and snapping shrimps that can stun their own prey. Some Dromidia crabs even pull some species of anemone off the reef, and attach them to their carapace (their back) apparently for camouflage, and perhaps protection”.

All photos: Melinda Riger of Grand Bahama Scuba, with thanks

BAHAMAS REEF CORAL: A COLOURFUL GALLERY


Orange Cup Coral ©Melinda Riger @ G B Scuba copy

BAHAMAS REEF CORAL:  A COLOURFUL GALLERY

The reefs of the northern Bahamas, as elsewhere in the world, are affected by two significant factors: climate change and pollution. Stepping carefully over the sharp pointy rocks of controversy, I’ve avoided the term ‘global warming’ and any associated implication that humans (oh, and methane from cows) are largely to blame for the first factor; but on any view, ocean pollution is the responsibility of mankind (and not even the cows). 

That said, an exploration of the reefs of Abaco or Grand Bahama will reveal not just the astounding variety of mobile marine life but also the plentiful and colourful static marine life – for example the beautiful and Christmassy orange cup coral in the header image. Here are some more corals from the reefs, with a mix of sponges added in. 

Giant Star Coral & Rope Sponge ©Melinda Riger @ GB Scuba copyCorals ©Melinda Riger @ G B Scuba copy 2Corals ©Melinda Riger @ GB Scuba copySea Fans & other corals ©Melinda Riger @ Grand Bahama Scuba copy

This rather intriguing photo shows a hermit crab’s conch home that presumably the occupant grew out of and left behind in the delicate coral branches as it went search of a more spacious shell dwelling.Coral & conch ex crab home 1380179_645156602172399_300806994_n copy

Credits: All these wonderful photos are by Melinda Riger of Grand Bahama Scuba; tendentious reef health observations are mine own…

HAWKSBILL TURTLES: WONDERFUL… & CRITICALLY ENDANGERED


Hawksbill Turtle ©Virginia Cooper @ G B Scuba

HAWKSBILL TURTLES: WONDERFUL… & CRITICALLY ENDANGERED

Hawksbill Turtle ©Melinda Riger @ G B Scuba copy 3

Hawksbill turtles are found throughout the tropical waters of the Atlantic, Pacific, and Indian Oceans. They avoid deep waters, preferring coastlines where sponges are abundant and sandy nesting sites are within reach. They are normally found near reefs rich in the sponges they like to feed on. Hawksbills are omnivorous and will also eat molluscs, marine algae, crustaceans, sea urchins, fish, and jellyfish. 

Hawksbill Turtle Range (Nat Geo)map-hawksbill-turtle-160-cb1447865323

Turtle with Gray Angelfish ©Melinda Riger @ G B Scuba

WHY ARE HAWKSBILLS CRITICALLY ENDANGERED?

  1. Despite the protection of their shells, turtles are predated on by large fish, sharks, octopuses, and (unlawfully) humans.
  2. Hawksbills are slow breeders, mating only every 2 or 3 years, which is the first drawback to species survival.
  3. Having laid the resulting eggs on a beach, the female returns to the sea. The eggs hatch after a couple of months. Unless, of course, some creature – and that includes humans – has got to them first…
  4. Hatchlings are hugely vulnerable as they make their way from the nest site to the sea. However fast they scurry along, crabs and in particular flocks of gulls are faster. Also, they may have to negotiate impossible obstacles washed up onto the beach  (see below). The attrition rate of  tiny turtles at this stage is very considerable.

Hawksbill Turtle ©Melinda Riger @ GB Scuba copy

SO, HUMANS ARE BASICALLY IN THE CLEAR, RIGHT?

Humans can take most of the credit for the turtles plight leading to their IUCN ‘critically endangered’ listing, in these mostly illegal ways:

  • Killing adult turtles for food or…
  • …for their beautiful shells
  • Digging up turtle nesting sites to take the eggs as food
  • Catching turtles in fishing nets as unintended but often inevitable BYCATCH
  • Providing a rich stew of plastic, styrofoam & other dietary or physical hazards in the ocean
  • Degrading or destroying the nesting sites, & indeed the reefs on which turtles depend

A hatchling tries to clamber over beach rubbish to get to the seaTurtle traps - Melissa Maura copy

A straw is extracted from a turtle’s nostril (small pics on purpose – I spared you the long video)Turtle & straw 1 (Nathan Robinson : Chris Figgener) Turtle & straw 2 (Nathan Robinson : Chris Figgener) Turtle & straw 3 (Nathan Robinson : Chris Figgener)

This poor creature was found just in timeHawkbill Turtle Plastic breathecostarica copy

Assorted plastic effects (the turtle trapped in the beach chair was off Man-o-War Cay) Sea Turtle tied up in balloon string (Blair Witherington : NOAA) copyphoto copy 7 This turtle, which was found floating in North Man-O-War Channel, died as a direct result of being entangled in human trash(in this case, a lawn chair) copy IMG_1346 copy

PLEASE CAN WE GO BACK TO HAPPY PICTURES?

Healthy hawksbills happily living the northern Bahamas reef lifeHawksbill Turtle (m) (Melinda Riger @ G B Scuba) Hawksbill Turtle (flipper damage) ©Melinda Riger @ GB Scuba

RELATED POSTS

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SEA TURTLE THREATS

BABY TURTLES WITH PHIL LANOUE

Hawksbill Turtle & photo ©Melinda Riger @ G B Scuba

Credits: Melinda Riger & Virginia Cooper of Grand Bahama Scuba for the main photos; Melissa Maura, Nathan Robinson, Friends of the Environment and other FB sharers for the small images; National Geographic for range chart and information

MAKE FRIENDS WITH ANEMONE: BAHAMAS REEF LIFE


Anemone (Giant) ©Melinda Riger @GBS copy

MAKE FRIENDS WITH ANEMONE: BAHAMAS REEF LIFE

The giant anemone is found in the shallow reefs and lagoons of the Caribbean and western Atlantic. These are, of course, animals and not plants, with many tentacles that surround their mouth. They attach themselves to rock or in rock crevices, mooring themselves securely against the swell of the waves.  

Giant anemone with ‘Speckles’, a spotted moray eelGiant Anemone & Speckles ©Melinda Riger @ G B Scuba copy

ARE THEY USEFUL?

One important feature of a healthy anemone population is the shelter they give to certain small fish and cleaner shrimp species. They act as bases for FISH CLEANING activities, a vital role in the undersea community.

Giant Anemone ©Melinda Riger @ G B Scuba copy

HOW DO THEY HAVE… ERM… SEX?

The sex lives of anemones seems particularly complicated (as they would doubtless think about humans). Cutting to the chase, reproduction involves the synchronous spawning of eggs and sperm, with fertilisation occurring in the surrounding water. The fertilised eggs become larval and spread in the water column, which increases their chances of survival. They settle on the BENTHOS, where they develop a “pedal leg” (rather in the manner of a gastropod) which in due course they will use to move from A to… A plus a very short distance.

Giant Anemone ©Melinda Riger @ G B Scuba copy 4

These anemones come in many colours. The tentacles often have tips of various hues, and are the only free-floating part of the animal. The body is safely attached to the rock. 

The giant anemone has primitive defensive mechanisms. It needs them, because it crawls so slowly that successful escape by moving is unlikely. Instead they reduce their size by drawing their tentacles into, or as close as possible to, their gastric cavity. They make room for this by forcing most of the water out. This reduces their overall size and of course removes – or at least diminishes – the ”50 colourful tentacles waving around” predator-magnet problem. But also…
Giant Anemone ©Melinda Riger @ G B Scuba copy 7
…they have a trump card. The tips of the giant anemones’ tentacles are packed with cells that contain a toxin. When stimulated, the cells (‘nemocysts’) “explode out of the capsule, impaling the attacker”. The toxin is then discharged, causing extreme pain and paralysis. How cool is that? It’s the superpower we’d all like to have! Or is that just me?
This is also how an anemone feeds, by quickly paralyzing its prey with the ‘toxic tentacles of doom’. The prey is moved to the mouth and swallowed whole…
Giant Anemone ©Melinda Riger @ G B Scuba copy 6
Credits: Melinda Riger of Grand Bahama Scuba, with thanks as always