WTF? (WHAT’S THAT FISH?) 14: ARROW CRABS


Arrow Crab (Melinda Riger / Grand Bahama Scuba)

WTF? (WHAT’S THAT FISH?) 14: ARROW CRABS

It’s been a while since the last in the WTF? series, which is dedicated to the wilder, less conventionally fish-shaped side of reef life – those creatures that you may come across, blink into your face-mask,  and silently mouth the words ‘What’s That Fish?’ (that’s what it looks like you are saying, anyway).

Arrow Crab (Adam Rees)

Let’s meet some Arrow Crabs Stenorhynchus seticornis, one of the very few creatures surely to have a triangular body plus a huge pointy nose (rostrum), supported on long skinny legs. To which add, they wear tiny blue gloves on their two front claws.

Arrow Crab (Melinda Riger / Grand Bahama Scuba)

These crabs are coral reef dwellers and mostly stay concealed during the day. Their body is protected by a carapace, and the rostrum has serrated edges like a tiny rasp or file. I haven’t found a definitive reason for this gadget, but I suspect it is more for probing than for piercing or fighting.

Arrow Crab (Melinda Riger / Grand Bahama Scuba)

There’s a considerable colour variation among these crabs, as these images show. The body may even have blue iridescent lines (#2, above). And those claws may be any of 50 shades of blue…

Arrow Crab (Melinda Riger / Grand Bahama Scuba)

Arrow crabs are most active at night. They eat feather-duster worms (illus.) and similar invertebrates such as bristle worms.

Feather-duster worm (Melinda Riger / G B Scuba)

Arrow Crab Meal

Like certain types of shrimp, they also have a symbiotic relationship with anemones, whereby they make use of an anemone to benefit from the food it captures – and possibly for cover too. They are protected from anemone stings, whereas some of their predators are not.

This was the place where I was going to tell you about the arrow crab’s private life, but, well… “it’s complicated”. Briefly it is: male passes sperm-filled capsule to female; she uses it in some way whereby it fertilises her eggs; she then ‘broods’ the eggs in one of her ‘swimming legs’; the eggs hatch into larvae and swim off to eat plankton; each one then grows & moults, repeating the process until it has reached adult form. On balance, humans have arguably perfected a preferable method.

Arrow Crab (Nick Hobgood / Wiki)

Arrow Crabs are apparently popular aquarium creatures, although they sound to me rather a disagreeable challenge. They can move quickly on those long legs, and it seems as if they inclined to be aggressive to other inhabitants of the tank. As far as I can make out, it’s best not to put 2 of them together: they certainly won’t be doing the sperm capsule thing described earlier… 

Arrow Crab (Adam Rees)

Master of Disguise

Photo credits: Melinda Riger / G B Scuba (1, 3, 4, 5, 6); Adam Rees / Scuba Works (2, 8, 9); Nick Hopgood,Wiki (7); Chuck Elliot – video

Arrow Crab (Adam Rees)

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

‘RAISE AWARENESS’: SPOTTED EAGLE RAYS


Spotted Eagle Rays, Abaco, Bahamas (Gabrielle Manni)

Spotted Eagle Rays – Abaco, Bahamas

‘RAISE AWARENESS’: SPOTTED EAGLE RAYS

Mention of rays may conjure up thoughts of the familiar southern stingrays that populate the bright shallows and colourful reefs of the Bahamas. But there are other ray species out there gracefully patrolling the coral reefs – and one of these species is the spotted eagle ray (Aetobatus narinari).

Spotted Eagle Rays, Abaco, Bahamas (Catherine / Tara Pyfrom)

These fish (for that is what they are) are not uncommon. In fact they are found in tropical oceans worldwide (though there is a taxonomic distinction between the Atlantic version and the Pacific / Indo-Pacific ones). Note the concentration in the Caribbean sea.

Spotted Eagle Rays, Grand Bahama, Bahamas (Melinda Riger / GB Scuba)

Spotted eagle rays obviously have spots, but they are not notably eagle-like to look at. In fact, their snouts resemble a duck’s bill, and in some place they are less glamorously known as the duckbill ray. The ‘eagle’ part relates to the way in which they use their wings and appear to be soaring as they glide effortlessly through the water (see videos below).

Spotted Eagle Rays (Lazlo-photos Wiki)

Despite their global presence, these rays are categorised as ‘near-threatened’ on the IUCN Red List. Aside from vulnerability to predators including many types of shark, the rays may be caught as bycatch. In some areas they suffer entanglement in shark nets. And unsurprisingly there is a trade for them for large commercial aquariums. For the Atlantic species, Florida has taken a lead by banning fishing for, landing, buying or trading in spotted eagle rays. 

Spotted Eagle Rays, Abaco, Bahamas (Gabrielle Manni)

10 ESSENTIAL FACTS ABOUT SPOTTED EAGLE RAYS

  • They have 2 – 6 venomous barbed spines at the base of the tail
  • Adults are among the largest rays, with a 10 ft wingspan
  • They can leap clear of the water, and may do this more than once at a time
  • Occasionally they land in boats, to the consternation of all concerned
  • Their main diet is small fish and crustaceans, & sometimes octopuses
  • Their broad snouts are used to dig food out of the seabed as they forage
  • The rays are basically shy but may be curious of divers & snorkellers
  • They suffer from parasites, both externally and in their gills
  • Ray sex is quite physical, yet actual mating is brief (up to 90 secs…)
  • The female hatches her eggs internally, then her ‘pups’ are born live a year later

SPOTTED EAGLE RAY PUP

                          

Spotted Eagle Ray (John Norton Wiki)

 VIDEO SHOWCASE
These 3 short videos demonstrate the grace and beauty of spotted eagle rays as they glide elegantly around the reefs. The first (50s) was taken off Grand Bahama by Fred Riger (Melinda’s husband, for those who follow the underwater forays hereabouts); then one by Stephen Dickey (2:12) ; and finally one from Wildscreen Arkive (2:00).

WEIRD CREATURE CORNER

I have a lot of time for these cards produced by ‘Weird ‘n’ Wild Creatures’. In their unique style they are simple, educative and often give information nuggets not found elsewhere. The link is to their 4th series, Monsters of the Deep.

 

Photo credits: Gabrielle Manni (1), (5); Catherine & Tara Pyfrom (2); Melinda Riger / Grand Bahama Scuba (3); Lazlo-photos Wiki (4); Wiki (baby ray thumbnails); John Norton Wiki (6); Jacob Robertson Wiki (7); Weird ‘n’ Wild Creatures – card images. Videos as credited in text.

Spotted Eagle Ray, TCI (Jacob Robertson, Wiki)

HAWKSBILL TURTLES + ANGELS = REEF HEAVEN


Hawksbill Turtle & Angelfish (Melinda Riger / Grand Bahama Scuba)

HAWKSBILL TURTLES + ANGELS = REEF HEAVEN

Hawksbills on their own, nosing around the colourful coral reefs of the Bahamas, are a beautiful sight. I don’t want to overdo the religious tendency of the title, but they are indeed wonderful to behold. Add FRENCH ANGELFISH and a QUEEN ANGELFISH and it’s as close to perfection as a reef scene gets. Click on the links above for more pictures and details about the two angelfish species seen here with the turtle. As ever, Melinda Riger was ready with her camera to capture these great images.

Hawksbill Turtle & Angelfish (Melinda Riger / Grand Bahama Scuba) Hawksbill Turtle & Angelfish (Melinda Riger / Grand Bahama Scuba) Hawksbill Turtle & Angelfish (Melinda Riger / Grand Bahama Scuba) Hawksbill Turtle & Angelfish (Melinda Riger / Grand Bahama Scuba)

This astonishing photo was of course achieved by carefully balancing a GoPro on the turtle’s back, wrapping duct tape around it, and pressing ‘go’ (camera and turtle simultaneously). **

Hawksbill Turtle & Angelfish (Melinda Riger / Grand Bahama Scuba)

** This is not true. It’s just a cleverly shot turtle’s-eye view as it forages on the reef

This short video shot by Melinda’s husband Fred of a turtle ‘loving’ the camera is one of those wildlife events that cannot be predicted… but when it happens, it’s frankly a bit of a scoop.

OPTIONAL MUSICAL DIGRESSION

As I was writing this, an earworm started up and grew insidiously in both ears and then inside my head… the dread words “Elenore, gee I think you’re swell”. Followed by “so happy together…”. And then “she’d rather be with me…” Yes, I’ve now got TURTLES in my head, the (?long-and-hitherto-forgotten) band from the second half of the 60’s, with their cheery anodyne soppy-poppy love songs. And dammit, they’ve stuck… Here’s a reminder for those whose memory I have jogged. For anyone under, say, 75, step away from this area. Nothing to hear here.

Hawksbill Turtle & Angelfish (Melinda Riger / Grand Bahama Scuba)

Credits: Grand Bahama Scuba: all photos – Melinda Riger & video – Fred Riger; Turtle music – someone else’s music collection, not mine, honestly… (oh dear another lie I am afraid – cred gone)

ONE GOOD INTERN DESERVES ANOTHER (Part 1)


Coral reef research, Australia (Oscar Ward)

ONE GOOD INTERN DESERVES ANOTHER (Part 1)

Four years ago a young English friend of ours, Oscar Ward, was lucky enough to be offered an internship with the Bahamas Marine Mammal Research Organisation (BMMRO). At the time, he was post-school, and waiting to start a degree course in marine biology at university. He had no practical experience at all, so he had to progress from the menial tasks (scraping barnacles off the bottom of the research boat) to the more adventurous (whale poop-scooping) to the scholarly (collection and analysis of samples and data, including audio file matching of whale calls for identification). The need for hard work, concentration and accuracy were made clear from the outset… and as you will see, Oscar’s short internship has stood him in very good stead during his university course.

Oscar weekending at Gilpin Point – self-sufficientBMMRO Internship - weekend off (Oscar Ward)

From a promising start on Abaco, and with 2 year’s study behind him, Oscar is currently spending the 3rd year of his 4-year course in Australia, working with The Australian Institute of Marine Science. He has been involved in a number of complex projects focussed on corals and reef life – as we all know, a matter of huge concern – and the projections for the future of the reef systems in a time of warming seas and raised acid levels. Oscar also assists PhD students, for example examining the damaging effects of parasitic worms on coral; and the effect of changing light conditions on corals.

Nurse Sharks, Great Barrier Reef (Oscar Ward)

Much of Oscar’s time has been spent doing fieldwork. Often he is at sea, monitoring and collecting samples in the Southern Great Barrier Reef, diving two or three times a day. This work is often carried out in restricted or preservation zones, and with ever-present manta rays, sharks and sea turtles around him.

Manta Ray, Great Barrier Reef (Oscar Ward)

Right now Oscar is involved with the investigations into the recent bleaching events, work that is at the forefront of serious concern for the GBR and far beyond. I have recently corresponded with him – he has definitely not forgotten that his grounding for the fieldwork and studies that he is engaged in – and very likely his career – came from his time on Abaco and the lessons he learned during his time with the BMMRO at Sandy Point.  (In part 2: another good intern, currently at Sandy Point)

Coral reef research, Australia (Oscar Ward)

All photos: Oscar Ward (the header image is taken from a research vessel – no idea how, maybe a drone with fish-eye lens?)

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

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).