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

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

NASSAU GROUPER: VULNERABLE, ENDANGERED… & NOW PROTECTED


Nassau Grouper ©Melinda Riger @ GB Scuba copy

NASSAU GROUPER: VULNERABLE, ENDANGERED… & NOW PROTECTED

The Nassau grouper Epinephelus striatus is one of a number of Caribbean grouper species found generally in the Northern Bahamas and specifically in Abaco waters. Others include the Black, Tiger, and Yellowfin groupers, the Red Hind,and the Graysby. The Nassau grouper is special, however, not least because (unlike the others) it is on the IUCN Red List as an Endangered Species and is also a US National Marine Fisheries Service Species of Concern. It is considered the most important of the groupers for commercial fishing in the Caribbean, and the IUCN listing data suggests that a population decline of 60% occurred over the last three generations (27-30 years), a startling rate. The current population size is estimated at >10,000 mature individuals.

Nassau Grouper ©Melinda Riger @ G B Scuba copy 2

The Nassau Grouper is a creature of the coral reefs in the Caribbean and adjacent seas, though it can also be found in deep water. It feeds in the daytime on small fish and small crustaceans such as shrimps, crabs and lobsters. It lurks in caves and recesses in the reef, sucking in the prey that passes unsuspecting by. The coloration of an individual fish may vary considerably with conditions, and it can adapt its colour to its surroundings as camouflage.  

Tiger grouper meets Nassau grouperNassau & Tiger Grouper ©Melinda Riger @ Grand Bahama Scuba  copy

Spawning takes place in December and January as the seawater cools, always at full moon, and always in the same place. In the moonlight, huge numbers of the grouper gather together to mate in a mass spawning aggregation. This may continue for several days. However, the species is slow breeder, which is why overfishing is particularly damaging to the population as the depleted stock cannot readily be replaced.

3846_aquaimages Wiki

CONSERVATION ISSUES

There are other besides factors commercial overfishing that make the Nassau grouper so vulnerable, including fishing during the breeding season; taking undersized fish; pollution and reef decline; habitat loss; and invasive species. The spawning areas are especially vulnerable to exploitation. In the Bahamas, as elsewhere,  the government has now instituted a closed fishing season for the Nassau grouper. Here is the BREEF  flyer, just circulated – and in fact the reason for this post, which reminded me that I had planned to write about this fish! 10382222_10152869346685953_7443797899832698038_o

THREATS

The Bahamas National Trust sums up the multiple threats in this uncompromising way:

Nassau grouper is eaten by barracudas, lizard fish, dolphins, sharks and other large predators of the reef community. But the predators that have the biggest impact on the grouper population are humansPeople are fishing groupers before they can grow to maturity and reproduce. Sex change may also cause a problem. In undisturbed areas there are usually equal numbers of male and females. In heavily fished areas there are often three or more times more females than males. This means many eggs will not be fertilized during spawning. Other threats include, habitat destruction, coral breakage from divers, siltation from construction, runoff from logging and agriculture, dredging, sewage, oil spills and other contaminants that harm coral reefs where Nassau Groupers live.

grouperEpinephelus_striatus_2

There’s an extent to which a country can be judged on its attitude to wildlife from the stamps it chooses to issue. It’s something to do with appreciation and promotion of the country’s natural resources. For example, North Korea rates nil in this respect, with stamps involving scary weaponry, flags, marching and eerily glowing leaders – not a single sparrow to be seen.  By fortunate contrast the Bahamas and its Postal Service score very highly in celebrating the diversity of the wildlife of the islands. The Nassau Grouper was first featured on Bahamas stamps as long ago as 1971, some 25 years before the IUCN Red Listing, and probably before the sharp decline in population numbers had even begun.

bahamas-1971-nassau-grouper-sg-363-fine-used-19448-p

In 2012 the Bahamas Postal Service released ‘a new definitive 16 stamp series’ depicting the marine life of The Bahamas. The Nassau has been promoted from 5c in 1971 to 70c in 2012. That’s inflation for you.

bahamas-marine-life-stamps2

Finally in 2013 BREEF’s 20 years of marine conservation was commemorated with a distinguished and colourful set of 8 stamps, noting in their release: ‘Two of the new stamps feature the Nassau Grouper, a now endangered species that has experienced severe population decline throughout the region… BREEF is well known as an advocate for an annual closed season for the iconic Nassau Grouper during its winter breeding period. The push for the closed season was based on scientific evidence of population collapses throughout the region due to overfishing. BREEF is calling on the government to implement a fixed closed season for the Nassau Grouper in order to protect the species and the fishing industry. The closed season traditionally runs during the spawning season from December 1st until February 28th, to allow the fish to reproduce.  BREEF is calling urgently for the announcement of this year’s Nassau Grouper closed season….’ And so it came to pass… Not only is the Nassau grouper now worth 2 x 65c; it is strictly protected for 3 months during its breeding season. Maybe philately even had a hand in getting somewhere…

BREEF_Comemorative_stamps_PastedGraphic-3

Nassau Grouper (Rick Smit wiki)

Credits: Melinda Riger, Rick Smit, Open Source, BNT, BREEF, Wikimedia, Bahamas Postal Service

FLAMINGO TONGUE SNAILS: ALL YOU NEED TO KNOW


Cyphoma_gibbosum Clark Anderson - Aquaimages

FLAMINGO TONGUE SNAILS: ALL YOU NEED TO KNOW

I wrote about FLAMINGO TONGUE SNAILS Cyphoma gibbous more than two years ago. They have not changed noticeably since then but this site has – in scope, available material and audience. So I am revisiting these small marine gastropod molluscs, which are related to cowries. The live animal is brightly coloured and strikingly patterned, but that colour only exists in the ‘live’ parts – the ‘mantle’. The shell itself is usually pale and characterised by  a thick ridge round the middle. These snails live in the tropical waters of the Caribbean and the wider western Atlantic. Whether alive or dead, they are gratifyingly easy to identify.

FLAMINGO TONGUE SNAIL ON A PURPLE ROPE SPONGEFlamingo Tongue on purple rope sponge ©Melinda Riger @ GB Scuba copy

FEEDING ON A CORAL STEM

This snail is snacking on a coral stem, leaving a feeding track behind it. The structural shell ridge is clearly visible beneath the distinctively marked live tissue of these creatures.

Flamingo Tongue LASZLO ILYES Cyphoma_gibbosum_(living)_2

The flamingo tongue feeds by browsing on soft corals. Adult females attach eggs to coral which they have recently fed upon. About 10 days later, the larvae hatch. They eventually settle onto other gorgonian corals such as Sea Fans. Juveniles tend to live on the underside of coral branches, while adults are far more visible and mobile. Where the snail leaves a feeding scar, the corals can regrow the polyps, and therefore the snail’s feeding preference is generally not harmful to the coral.

Flamingo_Tongue_Snail_on_Soft_Coral_LASZLO ILYES

The principal purpose of the mantle of  tissue over the shell is as the creature’s breathing apparatus.  The tissue absorbs oxygen and releases carbon dioxide. As I have seen it described (unkindly?) “it’s basically their lungs, stretched out over their rather boring-looking shell”. 

Flamingo Tongue, Abaco (Char Albury)

This snail species, once common, is becoming rarer. The natural predators include Hogfish, Pufferfish and Spiny Lobsters, though the spotted mantle provides some defence by being rather unpalatable. Gorgonian corals contain natural toxins and instead of secreting these, the snail stores them. This supplements the defence provided by its APOSEMATIC COLORATION, the vivid colour and /or pattern warning sign to predators found in many species.

It comes as little surprise to learn that man is now considered to be the greatest menace to these little  creatures, and the reason for their significant decline in numbers. The threat comes from snorkelers and divers who mistakenly / ignorantly think that the colour of the mantle is the shell of the animal, collect up a whole bunch from the reef, and in due course are left with… “boring-looking shells” (see photos below). Don’t be a collector; be a protector…
Flamingo Tongue, Abaco (Char Albury)

These photos are of flamingo tongue shells from the Delphi Club Collection. Until I read the ‘boring-looking shell’ comment, I believed everyone thought they were rather lovely… I did, anyway. You decide!

Flamingo Tongue Snail Shell, Keith Salvesen AbacoFlamingo Tongue Snail Shell, Keith Salvesen AbacoFlamingo Tongue Snail Shell, Keith Salvesen Abaco

Finally, a couple of videos. The first is rather charmingly titled ‘FLAMINGO TONGUES DOING…. SOMETHING’. Any (printable but amusing) suggestions via the Comment box are welcome. The second punchily summarises this post in 30 seconds. Maybe that’s all that was needed!

Image Credits: Clark Anderson, Melinda Riger, Laszlo Ilyes, Charmaine Albury, RH

Doh! Reading through this after posting I can’t remove from my mind the likeness of Homer Simpson on the snail in Melissa’s photo (2). I had to  check it out and… it’s uncanny!

Homer Simpson Flamingo Tongue copy images

‘WTF?’ IN BAHAMAS WATERS (3) : LETTUCE SEA SLUG


Lettuce Sea Slug ©Melinda Riger @ Grand Bahama Scuba copy

  ‘WTF?’ IN BAHAMAS WATERS (3): LETTUCE SEA SLUG

The ‘WTF’ series so far has covered Bahamas reef fish on the bizarre end of the unusual-to-completely-weird appearance spectrum. And it has stood, of course, for ‘What’s That Fish?’. Today, it doesn’t. The feature creature isn’t a fish at all; it looks like a plant; it is in fact a SACOGLOSSAN – specifically the Lettuce Sea Slug Elysia crispata

The head end is on the left…Lettuce Sea Slug ©Melinda Riger @ G B Scuba copy

The name ‘sacoglossan’ literally means ‘sap-sucker’ (the sapsucker bird has a different latin name, however). And the slug’s frilly edges supposedly resemble certain types of curly lettuce. I’ve no idea where the ‘crispata’ comes from, but I am sure it doesn’t relate to crisp lettuce. These are creatures of shallow, clear waters such as the sub-tropical reefs of the Bahamas.

Lettuce_Sea_Slug_LASZLO ILYES

 ‘SOLAR POWERED SLUGS’

This isn’t a technical forum and too much science hurts my head. This species primarily lives off algae. However I give you the word KLEPTOPLASTY to drop into your conversation. In a sentence, algae is eaten but only partially digested; certain elements are stored to produce photosynthesis by which light is converted to energy and the slug can live without food. But baffle your neighbour at dinner, why not, by summarising the process as “chloroplast symbiosis”. Meanwhile, I’m fetching a beer.

Lettuce Sea Slug ©Melinda Riger @ GB Scuba copy

My research suggests that very little is known about the mating behaviour of these slugs. The pair shown below may be exploring the possibilities, or at least trying to work out which end is which. One is easy to tell, but the other? Time to make our excuses and leave…

Elysia_crispata_(Lettuce_Sea_Slug_pair) Nick Hobgood

HOW FAST, EXACTLY, DOES A LETTUCE SEA SLUG MOVE?

This rather beautiful video from ‘CORAL MORPHOLOGIC’ will reveal all. You’ll soon see that progress is very slow. I recommend watching the first 30 seconds and you’ll get the idea. If you choose to persist, you will see the slug sort of turn a corner to the left.

Credits: Melinda @ Grand Bahama Scuba, Laszlo Ilyes, Nick Hobgood, Coral Morphologic, Wiki

SHELL HOMES: HERMIT CRABS IN THE BAHAMAS


Hermit Crab ©Melinda Riger @ Grand Bahama Scuba

SHELL HOMES: HERMIT CRABS IN THE BAHAMAS

I’m feeling distinctly crabby right now. In a skilled move that would impress the Bahamas utility providers, the UK’s very own much-vaunted BT selected us for the privilege of being unplugged from the grid last week. From the time of reporting the problem, it has taken them 6 days to plug us back in. It’s a little reminder of the far more persistent Abaco experience! No landline, no wifi, no email for almost a week. To begin with, it was a light relief. After nearly a week, not funny anymore. Here are some nice crabs in conchs to celebrate getting back online while reflecting my crabby mood.Hermit Crab ©Melinda Riger @ G B Scuba Hermit Crab ©Melinda Riger @ GB Scuba copy Hermit Crab ©Melinda Riger @ GB ScubaFind out more about Hermit Crabs – in particular crab racing at Delphi and the intricate rules – here: WACKY RACES AT DELPHIHemit Crab, Delphi (Clare Latimer)

Hermit Crab in a conch ©Melinda Riger @ GB Scuba

Photo credits: all undersea shots – Melinda; potential crab race contestant – Clare

‘ELEGANTLY WEIRD’ – SPOTTED DRUMFISH JUVENILES: BAHAMAS REEF FISH (20)


‘ELEGANTLY WEIRD’ – SPOTTED DRUMFISH JUVENILES: BAHAMAS REEF FISH 20

I’ve posted before about the rather extraordinary SPOTTED DRUMFISH, one of those reef fish which in juvenile form is very different from the adult. This species was first up in the Bahamas Reef Fish series – click above link. Here are a few recent images, courtesy of Melinda Riger. The first three show the juvenile form (note the piscine photobomb in the first one). The last shows a group of adults hanging out on the reef with (I think) some soldierfish. You can see how the juvenile drumfish becomes the adult, but those little stripy bullet-heads with their two long elegantly trailing appendages differ considerably from the rather solid-looking spotty / stripy adults with their dramatic punko-rockabilly quiffs.

Drumfish (juv) 3 ©Melinda Riger @ Grand Bahama Scuba Drumfish (juv) 4 ©Melinda Riger @ Grand Bahama ScubaDrumfish (juv) 2 ©Melinda Riger @ Grand Bahama Scuba Drumfish ©Melinda Riger @ Grand Bahama Scuba