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)

HAWKSBILL TURTLES: DIVERS VIEWS…


Hawksbill Turtle (Adam Rees / Scuba Works)

HAWKSBILL TURTLES: DIVERS VIEWS…

Daydream for a moment. Imagine that you had a different occupation. And your new one involved daily contact with spectacular wildlife underwater (this assumes you can swim – debatable in my case). And access to some upmarket camera equipment. And the ability to use it effectively. Oh, and use of a reliable boat. And some sea.

Hawksbill Turtle (Adam Rees / Scuba Works)

Say, for example, you joined a dive operation. Then the chances are very high that these wonderful creatures would be a part of your daily 9-to-5. 

Hawksbill Turtle (Adam Rees / Scuba Works)

You wake up with a start. Oh no! Half an hour gone, and that crucial email still half-written… Where did the time go?

Hawksbill Turtle (Adam Rees / Scuba Works)

All gorgeous turtles taken by Adam Rees of Scuba Works (slogan: “Land is so overrated”) in the course of his everyday working life. Some people, eh?

Hawksbill Turtle (Adam Rees / Scuba Works)

TURTLE BREEDING SEASON & A SMALL POEM TO PONDER


Sea Turtle - Adam Rees / Scuba Works

TURTLE BREEDING SEASON & A SMALL POEM TO PONDER

The turtle lives ‘twixt plated decks
Which practically conceal its sex.
I think it clever of the turtle 
In such a fix, to be so fertile.

Sea Turtle - Adam Rees / Scuba Works

Anyone unfamiliar with the works of OGDEN NASH (1902 – 1971) would do well the check out his inimitable poetry, in which he takes extreme liberties with both rhyme and scansion to great comic effect. The poem above is a good example of Nash’s neat way with words. It always makes me laugh, anyway. So simple, looks so easy, but a very difficult trick to pull off consistently as Nash effortlessly does.Sea Turtle - Adam Rees / Scuba Works

As the turtle breeding season moves forward, I though this would be a good time to show a few of the great turtle photos taken by Adam Rees of ‘Scuba Works’.Sea Turtle - Adam Rees / Scuba Works

Sea Turtle - Adam Rees / Scuba Works

All photos: Adam Rees / Scuba WorksSea Turtle - Adam Rees / Scuba Works

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

SAWFISH: UNIQUE LIVE BIRTH FOOTAGE ON ANDROS


sawfish-biminis-marine-pa-campaign-grant-johnson

SAWFISH: UNIQUE LIVE BIRTH FOOTAGE ON ANDROS

The word ‘awesome’ – a word of Biblical origin and medieval usage connoting an experience of wonderment with an element of dread* – lost its power once it became the common verbal currency for describing the offer of a beer, a photograph of a sulky cat, or a so-so pub band. Where to turn for something truly momentous? Oh, actually that might do nicely. Breathtaking, astounding, astonishing, awe-inspiring, staggering, extraordinary, stupendous, and spectacular are examples of synonyms that have retained at least some of their power. And perhaps ‘mind-blowing’, though it’s a bit substance-tinged. ‘Amazing’ has pretty much gone the way of awesome. Amazeballs and badass? Let’s not!

Sawfish Grand Bahama (BNT / Buzz Cox)

Ok. Having got that linguistic grump out of the way (index under ‘English Language, debasement of, modern usage in), here’s the real deal: a truly phenomenal short video of a smalltooth sawfish Pristis pectinata safely giving live birth in the wild to her 5 babies (which are called pups) on Andros during a FSU research trip. The pups emerge as small replicas of their parent, complete with their hedgetrimmer-style rostrums, ready to swim away. Fishes that carry their young and give birth to one or more developed juveniles in this way are called ovoviviparous.

Sawfish_1

The commentary is clear and informative, the research potential for this vulnerable species is considerable, and if you have a soul and a spare 3 minutes, you really should watch this!

This unique recorded event took place last December. The joint research trip to Andros by the FSU Coastal and Marine Lab and NOAA was led by Dr. Dean Grubbs. The purpose of the research was to discover evidence of any exchange between the sawfish population in the U.S. and Bahamas. You can find out more about the research and scientists at the FSUCML website. And if you want to get involved and take part in an expedition, click GET INTO THE FIELD

Sawfish_1

RELATED POSTS

RH SAWFISH PAGE – pics, facts and vids, including how the rostrum is used in feeding

GUITARFISH (WTF? 8)

* ‘Awful’ had the same meaning as awesome, historically – cf dreadful. It did not mean a bad film or a lousy restaurant.Sawfish_1This recent photograph by Adam Rees of Scuba Works was taken in Florida waters. It is one of an astonishing school of 8 smalltooth sawfish, the largest group Adam has ever encountered.sawfish-2-adam-rees-scuba-works-copy

Credits: Header, Grant Johnson @60poundbullet (Bimini), with many thanks; BNT / Buzz Cox (Grand Bahama); Adam Rees / Scuba Works

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

WONDERS OF THE DEEP: FROM SUBLIME TO… THE OTHER THING


Seahorse (Adam Rees / Scuba Works)

WONDERS OF THE DEEP: FROM SUBLIME TO… THE OTHER THING

Seahorse by Alex Konahin

It’s a statistically proven fact (and not, in any way, a ‘post-truth’ proposition) that no one has ever had a bad thing to say about seahorses. Indeed, some love them too much and consume them – see HERE for threats to seahorse populations in some areas of the world. 

Seahorse (Adam Rees / Scuba Works)

Sometimes they are easy to see. The header image shows an orange seahorse curling its tail round green weed on pink coral – hard to miss. Yet sometimes it may be quite difficult to see the little creatures against their chosen background.

Seahorse (Adam Rees / Scuba Works)

These guys are, I think, for their size among the most sublime of all underwater creatures. I use the word in the strict historical sense “of very great excellence or beauty, exalted, awe-inspiring, majestic, magnificent, glorious.” Not just to mean “nice”. 

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In contrast, there are some undersea creatures that inspire… not awe exactly, but maybe an amused respect that so wonderful and bizarre a creature can exist in our oceans, in some cases only a few feet below the surface. Here are two examples of what I mean.

Batfish (Adam Rees / Scuba Works)

This is a BATFISH. It was an early shoo-in for my “WTF? (What’s that Fish?)” series, and you can read all about them and their ways HERE. Of all the creatures I have featured on this blog, this is by some distance the oddest…

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frogfish-anglerfisch

…except for its companion in oddness, the FROGFISH. This was next in the WTF? series, and the creature is, if anything, even stranger. You can read all about these critters HERE, where you will learn inter alia about their superpowers – any one of which you might like to have yourself. There are plenty of photos, and videos too.

FROGFISH SUPERPOWERS

  • Invisibility Cloak
  • Irresistible (and, to their prey, Fatal) Attraction
  • Buoyancy Control
  • Shapeshifting

Frogfish (Adam Rees / Scuba Works) 

I do not court controversy, recognising that people following this site, or maybe stumbling across it by mistake and lingering, reach their views on natural history from different directions. But these strange and fascinating species exist and thrive in their own particular and ingenious ways – it doesn’t really matter how or why they are as they are. The bats and the frogs are high in the list of the least conventional of undersea creatures, and if they are not exactly sublime in a seahorse sense, can we just agree that they are awesome?

Frogfish (Adam Rees / Scuba Works) 

Photo Credits: Adam Rees / Scuba Works; Melinda Riger; Alex Konahin (seahorse gif)

Seahorse (Bahamas) 4 ©Melinda Riger @G B Scuba Long-nosed Batfish Wiki Frogfish Hunting (Adam Rees : Scuba Works)