BRITTLE STARS: PRIMITIVE YET INCREDIBLY COMPLEX STARFISH


Brittle Star around a Tube Sponge ©Melinda Riger @ GB Scuba

BRITTLE STARS: PRIMITIVE YET INCREDIBLY COMPLEX STARFISH

BRITTLE STARS are closely related to starfish, and in particular to Basket Stars. They are commonly known as “serpent stars”, having 5 long, thin arms that may grow as long as 2 feet long. There are lots of different types of brittle star – at least 2000 – and they are found in every ocean on earth from the poles to the tropics. In Bahamian waters they a commonly found living on reefs.

Although these creatures look primitive, their structure, nervous systems, respiratory systems, digestive systems, sex lives and transportation methods are incredibly complex. Take it from me – I’ve just read about it all. So I’ve decided to pick a few aspects of these creatures to highlight rather than discuss the minutiae of their ossicles (tiny bones), madroporites (a sort of water filter / pressure balancer) and viscera.

You are most likely to see Brittle Stars clinging to coral or spongesSponge & Brittle Star ©Melinda Riger @GB Scuba

A DOZEN BRITTLE STAR FACTS TO PLAY WITH

  • The star has no eyes and no sense organs as we know them, but can detect light chemically; and (why would they need this?) sense smell through their ‘feet’… [Not a superpower I would prize, but still]
  • The mouth is on the underside of the central disc (‘body’) of 5 segments, each with a toothed jaw
  • The mouth is used both for ingestion and, putting it delicately, egestion. [Nor that superpower]
  • Stars eat tiny organisms suspended in the water or mini-worms, gathering them with their arms
  • If I have understood this, they breathe through their armpits, and can excrete from here also
  • The arms fit the main part with ball and socket joints, and are flexible in all directions
  • The genitals seem to be located in or between the armpits (lucky we are not descended from stars)
  • Stars readily regenerate lost arms until they lose the 5th – then they are in real trouble
  • This enables them to shed an arm in a predator attack, like a lizard its tail
  • Trials indicate that a jettisoned arm cannot regenerate from itself
  • They use only 4 arms to move along, with the fifth ‘steering’ out in front or trailing behind
  • Brittle Stars are inedible but non-toxic

Brittle Star on Green Rope Sponge ©Melinda Riger @ GB Scuba

Often, brittle stars will cling on inside a spongeBrittle Stars in sponge ©Melinda Riger @ GB Scuba

I quite liked this infographic from a source new to me, ‘Weird ‘n’ Wild Creatures Wikia’Brittle_Stars_front

Here is a great video from Neptune Canada of a brittle star fight on the ocean floor over the remains of a shrimp. If you watch the ones joining the fight, you will clearly see the locomotion method described above, with one limb pathfinding and the other four ‘walking’.

I’m not renowned for extreme sensitivity, so I feel no shame in showing mating brittle stars, courtesy of Channel Banks. It’s not exactly Lady Chatterley and Mellors, but the entwined arms are rather romantic, no?

Credits: all wonderful photos by Melinda Riger of Grand Bahama Scuba; BS infographic and viddys as credited

GRACE WITH ATTITUDE: SOUTHERN STINGRAYS IN THE BAHAMAS


Southern Stingray 2 ©Melinda Riger @ G B Scuba copy

GRACE WITH ATTITUDE: SOUTHERN STINGRAYS IN THE BAHAMAS

Southern Stingrays are often seen in Abaco waters. In the bay of Rolling Harbour at Delphi, we sometimes watch them admiringly from the balcony or beach as they lazily cruise along the shoreline in the turquoise water. If someone is in the water, they will make a leisurely detour round them – unfrightened in their own element, but unthreatening and disinclined to investigate human intrusion. Diving with them is a wonderful experience (though I have never got very close). Melinda Riger – a scuba expert with great camera skills – takes the most beautiful photos of the stingrays she encounters. Here are a few that I haven’t yet featured.  Notice the little striped CLEANING GOBIES going about their business. 

Stingray, Southern with cleaning gobies ©Melinda Riger @ G B Scuba copyStingray, Southern at cleaning station ©Melinda Riger @ G B Scuba  copySouthern Stingray © Melinda Riger @GB Scuba copy

Southern Stingrays are often encountered when one is bonefishing in the low waters of the Marls. I took the photos below while we were fishing in a channel between areas of mangrove. As the skiff was poled very slowly forward, I saw the stingray coming straight towards us. I wondered how it would react. Very elegantly, was the answer. It turned effortlessly and unperturbed to one side, then resumed its original course leaving a clump of mangrove between it and the skiff. 

Southern Stingray, Abaco Marls (Keith Salvesen 1)Southern Stingray, Abaco Marls (Keith Salvesen 2)Southern Stingray, Abaco Marls (Keith Salvesen 3)Southern Stingray, Abaco Marls (Keith Salvesen 4)

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SOUTHERN STINGRAYS

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Credits: Melinda Riger, Grand Bahama Scuba; RH

RED HIND GROUPER: BAHAMAS REEF FISH (25)


Red Hind Grouper Melinda Riger @ G B Scuba copy

RED HIND GROUPER: BAHAMAS REEF FISH (25)

The Red Hind is one of several grouper species commonly found in  Bahamas waters. Commonly for now, anyway. There is less information available about this species compared with other groupers, but sources seem agreed that it is (a) abundant and (b) IUCN listed ‘least concern’ but (c) heavily fished and (d) delicious.

Red Hind, attended by Cleaner FishRed Hind Grouper ©Melinda Riger @ G B Scuba copy 2

Red Hind Grouper ©Melinda Riger GB Scuba copy

One problem arises from the fact that Red Hinds form spawning aggregations in particular areas, making them vulnerable to fishing exploitation in those locations, and consequent population decline. Already, some of their spawning areas are protected.

Another threat comes from the degradation of coastal habitats coupled with increasing commercial and recreational fishing.  Red Hinds are targeted with speargun, hook and line, fish traps and nets. They may also be by-catch of other fishing operations. Fortunately Marine Protected Areas such as the ones in Abaco waters provide localised protection but these are not found throughout the Red Hind’s range. Closed seasons have been imposed in a few areas, another conservation method that has recently been introduced in the Bahamas for the Nassau grouper. 

Female spawning Red Hind Grouper (Univ of Puerto Rico:NOAA)

Getting the right balance between traditional fishing for food, and stock conservation is inevitably a tricky calculation. For the Red Hind, the factors that may result in the population decline of a plentiful species are in plain sight and will continue to be monitored by the various scientific research organisations involved…

OTHER GROUPERS YOU MAY ENJOY…

NASSAU GROUPER

TIGER GROUPER

BLACK GROUPER

Red Hind Grouper ©Melinda Riger @ G B Scuba copy 3

Credits: All images Melinda Riger at Grand Bahama Scuba except (4) NOAA / Puerto Rico Univ; research from several sources, tip of the hat to SCRFA

THE OCTOPUS: THERE’S NOTHING QUITE LIKE IT…


THE OCTOPUS: THERE’S NOTHING QUITE LIKE IT…

I’ve posted about the octopus a couple of times before. The first time was to explore the correct plural of the word ‘and related cephalopod mysteries’. You can see that HERE. More recently there was ‘Marine Bagpipes filled with Ink’, which you can see HERE. Both posts were really a way to show some of Melinda Riger’s stunning underwater photography, with an octopoidal theme. Now I have some more images for you, so I present some new photos of Octopi… erm, Octopodes… erm, Octopuses… Octopus ©Melinda Riger @G B Scuba Octopus 1:15 ©Melinda Riger @ G B Scuba Octopus 4

This octopus is having a sleep, disguised as a rockOctopus Sleeping ©Melinda Riger @ GB Scuba

Credits: All images courtesy of Melinda Riger of Grand Bahama Scuba

CHERUBFISH (PYGMY ANGELFISH): BAHAMAS REEF FISH (23)


Cherubfish (Pygmy Angelfish) © Melinda Riger @ G B Scuba

 CHERUBFISH (PYGMY ANGELFISH): BAHAMAS REEF FISH (23)

Time for a bright little denizen of the not-so-deep. The Cherubfish Centropyge argi or pygmy angelfish is a very small (8cm) and distinctively coloured angelfish species. These fish are native to the Caribbean and Gulf of Mexico, and flicker round the coral reefs happily feeding as they go (see the video below to see how busily they forage). Or maybe they are just having a good time…

Cherubfish (rare) ©Melinda Riger @ G B Scuba

The Cherubfish is unsurprisingly a popular aquarium species. Don’t rush straight out and buy some though: a typical warning says “like other angel fish, they are not completely 100% reef-safe. Results vary among individual fish and tank qualities (size, feeding, tankmates, etc.), so caution is recommended when adding this fish to a coral tank“. You can read the whys and the wherefores HERE – sadly I lack the vibrant interest in aquaria to go into it myself…

Cherubfish Melinda Riger @ G B Scuba

Looking beyond Melinda’s lovely images of the species, I have found that these creatures will often show more yellow at the nose end. Here’s an example of a more two-tone Cherubfish in case you come across one. Cherubfish Centropyge argi  (Brian Gratwicke)

I mentioned that Cherubfish flicker around the reefs instead of proceeding serenely and in an orderly fashion.  Have a look at this short video to see what active little fish they are.

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Credits: all images Melinda Riger of Grand Bahama Scuba except the last, Brian Glanville

BAHAMAS REEF FISH (22): BLACK GROUPER


Black Grouper ed ©Virginia Cooper @ G B Scuba 2

BAHAMAS REEF FISH (22): BLACK GROUPER

The Black Grouper is a large fish of the reefs found in the western Atlantic, particularly in the waters of Florida, Bahamas, Caribbean and the Gulf of Mexico. It is a solitary species that mostly prefers the shallow waters around coral reefs.

Black Grouper ©Virginia Cooper @ G B Scuba

Formerly plentiful, these groupers (like other grouper species) have moved from an IUCN listing of ‘Least Concern’ to ‘Near-Threatened’. They have the twin disadvantages of being fished for sport and fished for food. As demand for grouper on the menu rises, so does its vulnerability. The species is described as a ‘slow breeder’, so a depleting population has less chance of sustaining numbers. 

Black Grouper ©Melinda Riger @ G B Scuba copy

An adult black grouper’s diet consists of small fish and squid. Juveniles feed primarily on crustaceans. However, certain tiny reef fish are important to the species as ‘cleaners’. You can read about their significance by clicking CLEANING STATIONS Here are examples of two black groupers receiving attention at the same cleaning station. Both also seem to be giving a ride to REMORAS.

Grouper at cleaning station ©Melinda Riger @ G B Scuba copy

Note that this fish has an embedded hook and is trailing a line – one that ‘got away’Grouper, Black, at cleaning station (+ hook) ©Melinda Riger @ GB Scuba copy

Despite the name, black groupers are not all black. They have many shades from dark to olive-coloured to pale. I believe the two photos below are of a grouper known as Arthur, a favourite with divers and definitely off the menu… Black Grouper  ©Melinda Riger @ G B ScubaBlack Grouper 2 ©Melinda Riger @ G B Scuba

The tiny bright blue fish in the photo above are Blue Chromis, a regular accompaniment on any snorkel or dive on a reef. I like the colourful little Fairy Basslet in the next photoBlack Grouper © Melinda Riger @ G B Scuba copy

Now that the NASSAU GROUPER has been awarded a closed season to help maintain numbers, it will be interesting to see if the winter fishing ban is extended to the Black Grouper…

Black Grouper (Arthur) ©Virginia Cooper @ G B Scuba

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Credits: all photos Virginia Cooper and Melinda Riger of Grand Bahama Scuba 

PEACOCK FLOUNDER: BAHAMAS REEF FISH (21)


  Peacock Flounder ©Melinda Riger @ GB Scuba

PEACOCK FLOUNDER: BAHAMAS REEF FISH (21)

PEACOCK FLOUNDER or PLATE FISH Bothus lunatus

I have briefly featured this fish before in the context of its extraordinary camouflage abilities; and also its interesting ocular arrangements. Time to give it another swim around, I think, with some additional photos that I have collected.

Peacock Flounder

Bothus lunatus is the Atlantic / Caribbean version of a species also found in the Pacific and Indian oceans. Adults may grow up to 18 inches long. The species is a ‘lefteye’ flounder, with both eyes on its left (top) side & its right side underneath.  However a baby flounder looks & swims like normal fish, with bilateral eyes. As it grows, the right eye gradually ‘moves’ round to the topside, and it becomes a flatfish.

Peacock Flounder

A flounder’s eyes can move independently of each other. One may look forwards, the other backwardsPeacock Flounder Eye ©Melinda Riger @ G B Scuba

‘NOW YOU SEE IT…’ CAMO-FISH

The Peacock Flounder has extraordinary  colour-changing powers, and can rapidly vary its background colour to make it closely resemble that of its surroundings. This enables it camouflage itself as it lies on the seabed. It can change coloration completely in between two to eight seconds.  

Four frames of the same fish taken a few minutes apart showing the ability of flounders to change colors to match the surroundings (Wiki)Peacock Flounder Brocken Inaglory

Check out these imitative patterns in Bahamas waters…Peacock Flounder (f) ©Melinda Riger @ Grand Bahama Scuba

Flower_flounder_in_Kona_wiki

There are two advantages to the ability to camouflage (‘cryptic coloration). One is obviously to avoid detection by predators. The other is to enable the flounder to ambush its meals. They feed primarily on small fishes, crabs and shrimps, lying concealed on the seabed and grabbing any unwary prey that ventures too close. They will even partially bury themselves in the sand, leaving just their eye-stalks keeping watch…Peacock Flounder ©Melinda Riger @ Grand Bahama Scuba

HOW CAN THEY POSSIBLY CHANGE COLOUR SO QUICKLY?

Scientists are still puzzling this out. In a conch shell, it seems the flounder can coordinate its amazing all-round vision with its hormones, instantly releasing certain pigments to its skin cells and suppressing other pigments to make the colour match. Not convinced? Then watch this short video and prepare to be impressed. 

Fred Riger of Grand Bahama Scuba, who kindly keeps a benign eye on my reef fish posts (he’s the expert), adds a third excellent reason for coloration changes: sex… “the male peacock flounder can, and does greatly intensify his colors, presumably to declare territory and attract females to his person. When doing this the males will also signal with the left pectoral fin, sticking it straight up and waving it around.” Maybe that is what is going on in the photo below – intensified, non-camouflage colours, and a raised fin…Peacock Flounder ©Melinda Riger@ G B Scuba

Peacock Flounder on a plate – Kim Rody Art983829_10154948988290716_6633206689277673329_n

Credits: Melinda Riger of Grand Bahama Scuba for almost all photos; wiki for 2 illustrative images