URCHIN RESEARCHIN’: SEA HEDGEHOGS OF THE REEF


Long-spined sea urchin Diadema antillarum (Melinda Rodgers / Dive Abaco)

URCHIN RESEARCHIN’: SEA HEDGEHOGS OF THE REEF

The long-spined sea urchin Diadema antillarum featured in this post is one of those creatures that handily offers its USP in its name, so you know what you are dealing with. Something prickly, for a start. These are creatures of the reef, and many places in the Caribbean and in the western Atlantic generally sustain healthy populations.

Long-spined sea urchin Diadema antillarum (Melinda Rodgers / Dive Abaco)

These animals are essentially herbivores, and their value to vulnerable coral reefs cannot be overstated. Where there is a healthy population of these urchins, the reef will be kept clean from smothering algae by their methodical grazing. They also eat sea grass.

Long-spined sea urchin Diadema antillarum (Melinda Rodgers / Dive Abaco)

HOW DO THE SPINES OF DIFFERENT KINDS OF URCHIN COMPARE?

Small sea urchins species have spines a few cms long at most. The long-spine variety exceed 10 cms, and the largest may have spines up to 30 cms (= 1 foot) long. The length, as shown here, means that when the creatures are safely lodged in crevices near their algae supply, their spines remain very visible.
Long-spined sea urchin Diadema antillarum (Melinda Riger / G B Scuba)
Anatomy of a long-spined sea urchin. You may possess a few of these organs yourself…

Long-spined sea urchin Diadema antillarum anatomy diagram (wiki)

Long-spined sea urchin Diadema antillarum (Melinda Rodgers / Dive Abaco)

CAN YOU GIVE US A TEST, PLEASE?

As with SAND DOLLARS and similar creatures, the skeleton of a sea urchin is known as a ‘test’. Urchin tests are remarkably beautiful, especially seen in sunlight. Here are 2 examples I photographed a while ago. You’ll immediately notice the delicate colours and the amazing complexity of the pattern and symmetry. The top one is (or is most like) a long-spined urchin test.
Long-spined sea urchin Test / Skeleton Diadema antillarum (Keith Salvesen / Rolling Harbour) Long-spined sea urchin Test / Skeleton Diadema antillarum (Keith Salvesen / Rolling Harbour)

A BIT ABOUT SYMMETRY

Sea urchins are born with bilateral symmetry – in effect, you could fold one in half. As they grow to adulthood, they retain symmetry but develop so-called ‘fivefold symmetry’, rather as if an orange contained 5 equal-sized segments. The graphic above gives a good idea of how the interior is arranged inside the segments.

Long-spined sea urchin Diadema antillarum (Melinda Rodgers / Dive Abaco)

A FEW FACTS TO HAND DOWN TO YOUR CHILDREN

  • Urchin fossil records date the species back to the Ordivician period, c 40m years ago
  • In the ’90s the population was decimated and still has not recovered fully
  • Urchins feel stress: a bad sign that the spines here are white rather than black
  • Urchins are not only warm water creatures: some kinds live in polar regions
  • Urchins are of particular use in scientific research, including genome studies
  • Some urchins end up in aquariums / aquaria, where I doubt the algae is so tasty
  • Kindest not to prod or tread on them
  • Their nearest relative (surprisingly) is said to be the Sea Cucumber 

Sea Cucumber (Melinda Riger / G B Scuba)

ARE THEY EDIBLE?

Apparently they are eaten in some parts of the world; their gonads and roe are considered a delicacy. As far as I know, they are not generally on the menu in the Bahamas. Correction invited. Personally, I could leave them or leave them.

CREDITS: Melinda Rodgers / Dive Abaco (1, 2, 3, 6, 9) taken Abaco; Melinda Riger / G B Scuba (4, 10, 11) taken Grand Bahama; Keith Salvesen / Rolling Harbour (7, 8) taken Abaco; Wiki graphic (5) taken from internet. RESEARCH Fred Riger for detailed  information; otherwise the usual magpie pickings…

Long-spined sea urchin Diadema antillarum (Melinda Riger / G B Scuba)

BLUE CHROMIS: A FLASH OF COLOUR ON THE REEF


BLUE CHROMIS: A FLASH OF COLOUR ON THE REEF

I’ve gone pictorial for today because I have only got my phone with me while we are away. Composition is slow, close to decomposition – and the comms connection is close to disconnection

Blue chromis (Chromis cyaneus) belong to the same group of fishes as damselfishes. These unmistakeable, bright reef denizens are very visible despite their tiny size. These fish are shoalers, so out on the reef you can enjoy them flickering around you as you swim along or hang in the water to admire the corals.

Like many a pretty and easily captured small fish that can be monetised once removed from its natural home environment, the blue chromis is popular for aquariums, and for humans to keep in their own home environments, unselfishly feeding them concocted food.

Blue chromis are adaptable and sociable, and will happily swim with other small reef fishes (as above). My own favourite combo is chromis mixed in with sergeant majors. But a shoal of them (mostly) alone is pretty special too….

I cynically mentioned ‘concocted’ food earlier. Here is one online care instruction for looking after them: “They are omnivores, meaning that they eat both meaty and plant based foods. They are not difficult to feed and will eat a variety of regular aquarium fare, frozen, live, and sometimes even dry food. Feeding them a variety of foods will help them retain their color in captivity. They sometimes feed on the algae in the tank”. 

If you are tempted to rescue some from their reef habitat, rest assured that: They have been known to spawn in captivity. Blue chromis can usually be obtained for about $10-15. And don’t hold back on the frozen food (though maybe warm it up a bit before feeding time).

Credits: Melinda Rodgers / Dive Abaco; Melinda Riger / G B Scuba

INTERNATIONAL SHARK WEEK? IT’S SO OVER… EXCEPT HERE


Sharks in Bahamas - Melinda Riger / Grand Bahama Scuba

INTERNATIONAL SHARK WEEK? IT’S SO OVER… EXCEPT HERE

There’s never a day without a ‘Day’, nor a week without a ‘Week’. Almost all creatures under the sun are celebrated in some regular calendar-based time-frame. With the exception of No-see-ums: I’ve checked – there is no national or international Ceratopogonidae Day in any online calendar. 

Sharks in Bahamas - Melinda Riger / Grand Bahama Scuba

By a mere 2 days, I have missed Shark Week, a happening tied in with the Discovery Channel, and heralded by an amusing trailer that features no actual sharks… So, belatedly, here are some cool shark photos to enjoy, in case you didn’t get enough of them last week, or (like me) had other fish to fry.

Sharks in Bahamas - Melinda Riger / Grand Bahama Scuba“I’m so glad we agreed to watch each other’s backs…”

Sharks in Bahamas - Melinda Riger / Grand Bahama Scuba

 Meet Nurse Betty, as she is known to diversSharks in Bahamas - Melinda Riger / Grand Bahama Scuba

MANGROVES: THE SHARK NURSERY

As all children are taught and some adults know, the mangroves that grow in the shallow waters around the islands of the Bahamas are of enormous ecological significance. This isn’t the place to expand on that now, but it is worth mentioning that the mangrove swamps are the nurseries of young sharks (‘pups’) until, as juveniles, they are old enough to leave the safely of their home for deeper waters. Check out the short video below.

Sharks in Bimini Bahamas - biminis-marine-protected-areaSharks in Bimini Bahamas - biminis-marine-protected-area

Spot the REMORA hitching a ride on this shark’s backSharks in Bahamas - Melinda Riger / Grand Bahama Scuba

Nurse shark – note the twin barbels (cf recent Goatfish article)Sharks in Bahamas - Melinda Riger / Grand Bahama Scuba

Sharks in Bahamas - Melinda Riger / Grand Bahama Scuba

HAMMERHEADS FROM BIMINI Sharks in Bimini Bahamas - Grant Johnson / 60 Pound Bullet   Sharks in Bimini Bahamas - Grant Johnson / 60 Pound Bullet

These wonderful photos were all taken in Bahamian waters. Melinda Riger of Grand Bahama Scuba is, as ever, the star snap-getter of sharks (and indeed all other marine creatures). Special thanks are also due to Grant Johnson / 60poundbullet and Neal Watson / Bimini Scuba Center for occasional use permission of photos – especially of hammerheads – that are, well, eye-popping. Video from ‘ZeroEye’

Sharks in Bimini Bahamas - Grant Johnson / 60 Pound Bullet

BAHAMAS REEF FISH (53): YELLOW GOATFISH


Goatfish, Bahamas (Melinda Riger / G B Scuba)

BAHAMAS REEF FISH (53): YELLOW GOATFISH

GOATFISHES belong to the mullet family, a large group of species with a flexible membership. In other words, there is disagreement as to whether certain fish are mullet or not. For present purposes, it’s not our problem – no one doubts that the goatfish is a mullet.

Goatfish, Bahamas (Melinda Riger / G B Scuba)

SO WHY ARE THESE CALLED GOATFISH? WAS SOMEONE KIDDING?

These fish get their name for the pair of so-called ‘barbels’ below their mouths (see image below), thought to be reminiscent of a goatee beard. The name has Latin origin, ‘barbula‘, meaning a small beard. Linnaeus may have had a hand in this choice of description.

Goatfish, Bahamas (Melinda Riger / G B Scuba)

WHAT IS THE FUNCTION OF THE BARBELS?

The barbels are sensory organs which, depending on the creature, may be located on either side of the mouth, on the chin, or even extending from the nostrils. In broad terms, the barbels are where the taste buds are located. They help a fish to find food even when the water is stirred up or murky or at night, and are used to probe into sand or into holes in the reef for prey.  

Goatfish, Bahamas (Melinda Riger / G B Scuba)

WHY ARE THEY OFTEN SEEN WITH YELLOWTAIL SNAPPERS, GRUNTS & PORKFISH?

Goatfish have limited means of self-protection. They are not poisonous or venomous, they have no spines or razor-sharp teeth, nor ink to squirt. They do have an ability to change colour rapidly to blend into their surroundings – e.g. over pale sand – to make them less conspicuous to predators. Overall, however, they are docile and probably delicious to many other species. Their bright hues may have some function as aposematic colouring to warn, scare or repel potential predators, but this is possibly of limited use among the familiar reef denizens. So instead the goatfish goes in for so-called protective mimicry, as shown in the image above.

Goatfish, Bahamas (Melinda Riger / G B Scuba)

PROTECTIVE MIMICRY?

Goatfish and yellowtail snappers (in particular) are similar in size, appearance, coloration and behaviours, though the feeding patterns differ. The reason they are often found in mixed groups on the reef is for the individual protection they gain in a larger mixed school. This really amounts to taking advantage of safety in numbers (especially for the fishes in the middle). Here’s a very recent photo that shows exactly this scenario – a large mixed shoal of two almost indistinguishable fish species.

Goatfish & Yellowtail Snappers shoaling (Melinda Riger, GB Scuba)

IS THIS A ‘SPOT THE DIFFERENCE’ TEST?

If you’d like to make it so! (click on the image to enlarge it). Look out for the fish with the barbels (Goatfish); and the fish with the larger, more deeply forked tails (Snappers). A predator won’t take a great deal of notice of the finer points of difference of course, but overall this large mixed shoal gives a degree of protection to individual fish in the unit as a whole

Goatfish, Bahamas (Melinda Riger / G B Scuba)

ARE GOATFISH EDIBLE?

Goatfish are eaten in many ares of the world, though I can’t recall seeing it on a Bahamian menu. The Romans ate the local mullet / goatfish species, but then they ate many things that we do not now consider as permissible food – dormice in honey for example. Rather revoltingly, the goatfish were served live so that guests could watch them die and see the amazing change of colours in the process. Barbaric? But don’t we cook live… well, never mind that.

Goatfish, Bahamas (Melinda Riger / G B Scuba)

Photos: all great photos from Melinda Riger / Grand Bahama Scuba; magpie research pickings inc. the abstract of a scientific paper with about 23 authors; tip ‘o the hat to Wiki, no seriously

Goatfish, Bahamas (Melinda Riger / G B Scuba)

PEACOCK FLOUNDERS REVISITED: NOW YOU SEE THEM…


Peacock Flounder (Melinda Riger / G B Scuba)

        PEACOCK FLOUNDERS (Part Deux)

MASTERS OF SUBAQUATIC CAMOUFLAGE

I featured the extraordinary, colour-transforming PEACOCK FLOUNDER Bothus lunatus about 3 years ago in the Bahamas Reef Fish series (No. 21 I think). These really are remarkable creatures, and I am pleased to be able to show some more wonderful illustrative photos. 

Peacock Flounder (Melinda Riger / G B Scuba)

ROVING EYES

In the fish shown here, you’ll see that – surprisingly – both eyes are on the upperside of the fish, above the rather grumpy mouth, whereas the head is horizontal to the ocean floor. Oddest of all, juveniles are constructed conventionally with bilateral eyes, and look like ‘normal’ fish rather than flatfish.

Peacock Flounder (Melinda Rogers / Dive Abaco)

As the fish matures, in some magic way the mechanics of which I can only guess at**, the right eye grows round to the topside and the flounder transforms from a ‘vertical’ fish to a flatfish. For this reason, the PF is known as a ‘lefteye’ flounder. Maybe in other flounder species in the world – the southern hemisphere maybe? – the eye that moves round to the upperside is the left eye.

Peacock Flounder (Virginia Cooper / G B Scuba)

The eyes of this fish have another special trick up their sleeves (so to speak). They operate completely independently. Thus the creature can look left and right, or forwards and backwards, simultaneously. It’s an excellent system for detecting predators coming from any angle. It’s a superpower we might all benefit from.

Peacock Flounder (Melinda Rogers / Dive Abaco)

DO THEY HAVE ANY OTHER TRICKS WE SHOULD KNOW ABOUT?

Yes they do indeed. If you have been admiring the fish shown so far, you’ll have noticed that the colour of each one differs from the others. In addition to the predator-protection that the eyes provide, the peacock flounder can make itself (near) invisible. They can rapidly change colour to match their surroundings. There are 3 reasons for this: to avoid / confuse predators; to conceal themselves on the sea-floor to catch passing prey; and, as dive expert Fred Riger has pointed out, “the male peacock flounder can, and does greatly intensify his colours to declare territory and attract females. When doing this the males will also signal with the left pectoral fin, sticking it straight up and waving it around.” 

The same fish, photographed over several minutes as it moves over the ocean floorPeacock Flounder (Wiki)

Matching the background happens as the fish swims, and in a few seconds. When they rest on the sea-floor, the camouflage may even become total. In #4 above you can just about make out the eyes. The whole effect is known as ‘cryptic coloration’ or CRYPSIS. In contrast, the image below shows just how adaptable the transformation can be. Note how the fish can even mimic the pinkish tinge of the sand perfectly. If threatened, the fish will bury itself in the sand, with just its eyes showing.

Peacock Flounder (Melinda Rogers / Dive Abaco)

HOW DO THEY MANAGE TO CHANGE COLOUR IN SECONDS?

It’s complicated! A simple answer is: a mix of hormones, pigment-cells and vision, all coordinating rapidly. The colour change works in two ways: pigments are selectively released to the skin cells; and other pignments can be selectively suppressed. An analogy might be image manipulation using variations in brightness, saturation etc. Not convinced? Then watch this short video and prepare to be impressed. Astonished, even.

WHAT IF A FLOUNDER CAN’T SEE CLEARLY FOR SOME REASON?

As with many (all?) superpowers, there is usually some kryptonite-style flaw. A flounder with a damaged eye, or one temporarily covered (by sand, for example) will have difficulty in changing colour – possibly at all, or at any rate with the swiftness it needs to have. 

Peacock Flounder (Melinda Riger / G B Scuba)

THESE SIDEWAYS FISH – HOW DO THEY… YOU KNOW…?

Take a look at the fish above with its top fin raised. It’s a ‘ready’ signal in a harem. Male flounders have a defined and defended territory within which live up to 6 females – a so-called ‘harem.’ I can do no better than borrow the description of the rituals from an article derived from scientific papers by Konstantinou, 1994Miller, et al., 1991 in the website animaldiversity.org/…ounts/Bothus_lunatus To which I can only add, ’15 seconds, eh?’

Peacock Flounder (Melinda Riger / G B Scuba)

“Mating activities usually begin just before dusk. At this time, a male and a female approach each other with the ocular pectoral fin erect. The two fish arch their backs and touch snouts. After this interaction the female swims away, and the male sometimes follows, approaching the female again from the left side. At this point the male pectoral fin is erect and the female pectoral fin moves up and down, possibly signalling willingness to mate. The male then positions himself underneath the female and mating begins. This process consists of a mating rise, during which the female and male rise in the water column together. On average, these rises last about 15 seconds. At the highest point of this rise, usually around 2 m above the substrate, gametes from both fish are simultaneously released, producing a cloud of sperm and eggs. Once the couple returns from the rise, the male “checks” to make sure mating was successful, and the pair separates quickly, swimming away from each other in opposite directions. Not all mating rises are successful, and the process of “checking” is thus important. The exact purpose of the mating rise in these flounders unknown; possible reasons for rising include better dispersal of gametes and predator avoidance.” 

Peacock Flounder – Kim Rody ArtPeacock Flounder (Kim Rody Art))

**This may in fact be through sheer laziness

Credits: Melinda Riger & Virginia Cooper / Grand Bahama Scuba; Melinda Rogers / Dive Abaco; Adam Rees / Scuba Works; Kim Rody; animaldiversity.org; magpie pickings and other credits in the text

Peacock Flounder (Melinda Riger / G B Scuba)

BABY SPERM WHALE IN BAHAMAS WATERS: AMAZING FOOTAGE


Sperm Whale baby (neonate) Abaco Bahamas (Charlotte Dunn / BMMRO)

BABY SPERM WHALE IN BAHAMAS WATERS: AMAZING FOOTAGE

Over several years I have had the privilege of being able to feature wonderful photographs and video footage in this blog. Birds, course, and also reef fish, sharks, seahorses, coral and anemones and a whole lot more. I have also been involved throughout with the wonderful work of the Bahamas Marine Mammal Research Organisation (BMMRO), and have been a part of team since 2017. Abaco is lucky enough to have the HQ at Sandy Point, but we must keep in mind that the organisation’s remit extends throughout the entire Bahamas archipelago, and has firm links with research and conservation organisations on the other islands.

Sperm Whale baby (neonate) Abaco Bahamas (Charlotte Dunn / BMMRO)

The clear turquoise waters around the islands and their cays are well-known to, and appreciated by, all. This is the playground of the smaller marine mammals – the dolphins, smaller whales and the (now a significant presence) manatees.

   

Less well known are the denizens of the deeper waters and the immense depths of the GREAT BAHAMA CANYON of the northern Bahamas. This is the realm of the large marine animals, from the mysterious speciality beaked whales right up to massive sperm whales. 

Sperm Whale baby (neonate) Abaco Bahamas (Charlotte Dunn / BMMRO)

About 3 weeks ago, the BMMRO research team encountered something truly wondrous off the south Abaco coastline – something to quicken the pulse and gladden the heart – a newborn sperm whale investigating the underwater world it has just been born into. Hopefully it will flourish and live for decades. The hope is sadly tempered by the overwhelming – and increasing – evidence of the terrible effect that humans have caused in just one generation by the pollution of air, land and sea. 

Charlotte Dunn posted the footage of 2 separate sightings. Her first caption reads:

“Close encounter with a curious newborn (‘neonate’) sperm whale yesterday – reminding us of the importance of our Shared Waters project about the effects of ship traffic on resident sperm whales, http://www.bahamaswhales.org/research.aspx. The young individuals like this one will be the most impacted if we don’t make serious conservation changes. As this young whale matures, the policy changes we make in the Bahamas now will affect its survival”.

“While their mothers are feeding at depth (knocking sound in the background) this newborn is being cared for by a slightly older calf until the adults return.”

After the second encounter, Charlotte wrote: “Here’s another amazing short clip of the neonate sperm whale we videoed off south Abaco two weeks ago – thank you to the BEP Foundation and the Devereux Ocean Foundation for funding some of our important work with sperm whales in the Bahamas”.

Sperm Whale baby (neonate) Abaco Bahamas (Charlotte Dunn / BMMRO)

On Charlotte’s conservation points above, over the last 3 months or so I have been checking daily for posts and articles specifically related to stranded, dead, and killed whales, and their stomach contents as revealed by necropsies. I have collected images from around the world. I won’t wreck this marvellous find in Abaco waters by including any of these. This casual research reveals a horrifying attrition rate for marine mammals. Most animals were full of plastics, from micro through flip-flops all the way up to very large chunks. Some of this junk clearly was the actual cause of death rather than a contributing factor. A whale may take several weeks to die in this way. All of it is entirely the responsibility of mankind – and pretty much caused in the last 50 years.

So let’s enjoy this little sperm whale, and hope it grows to an adulthood that will have seen a radical change for the better in its birth environment – the one that should never have been considered ours to destroy.

Sperm Whale baby (neonate) Abaco Bahamas (Charlotte Dunn / BMMRO)

CREDITS: Brilliant close-up footage plus the clips I have taken from it – Charlotte Dunn / Diane Claridge / BMMRO.  

DONATE: If you are touched by the magic of this little Bahamas sperm whale, may I invite you to consider making a donation to BMMRO for its research and conservation work – a scientific commitment that reaches far beyond the waters of the Bahamas. The system is set up to process donations from just $10 upwards, and every cent is used to further the work of BMMRO. Please click the logo below to reach the right page directly.

Sperm Whale baby (neonate) Abaco Bahamas (Charlotte Dunn / BMMRO)

Baby sperm whale off south Abaco, Bahamas ©BMMRO

DOLPHINS IN THE SEA OF ABACO: PLAYTIME


Dolphins, Sea of Abaco Bahamas (BMMRO / Charlotte Dunn / Keith Salvesen)

DOLPHINS IN THE SEA OF ABACO: PLAYTIME

Earlier this year, the team at Friends of the Environment in Marsh Harbour Abaco, in conjunction with BMMRO (Bahamas Marine Mammal Research Organisation), arranged a fundraising trip to look for whales and dolphins. On both counts, the guests’ hopes and expectations were amply fulfilled – in fact, almost certainly exceeded.

Dolphins, Sea of Abaco Bahamas (BMMRO / Charlotte Dunn / Keith Salvesen)

Where there is a single dolphin, there will almost invariably be others – and so it proved. The group of bottlenose dolphins turned out to be in a very playful mode, living up to their reputation as delightful, inquisitive, entertainers.

Dolphins, Sea of Abaco Bahamas (BMMRO / Charlotte Dunn / Keith Salvesen)

One of the dolphins turned out to be a young 3rd generation animal from the same family, recently weaned. The BMMRO has a large photographic library of dolphins and whales, collected over many years. In the photo above, you’ll see that the dorsal fin of the nearest one is ragged, especially near the top. This is the primary method by which individual animals are recorded to assist with subsequent identification in the field (= water) or back at base in Sandy Point by means of the photo archive.

Dolphins, Sea of Abaco Bahamas (BMMRO / Charlotte Dunn / Keith Salvesen)

The trip was perfected when a young female sperm whale came close to the boat… and then rolled onto her side, flipper up, to get a good look at the boat and its human contents. A wonderful experience for all those on board.

Dolphins, Sea of Abaco Bahamas (BMMRO / Charlotte Dunn / Keith Salvesen)

Credits: BMMRO / Charlotte Dunn; Friends of the Environment

Dolphins, Sea of Abaco Bahamas (BMMRO / Charlotte Dunn / Keith Salvesen)