Marine Invertebrates (other than corals): 3-30-10

Some nice, some not so.

Sea Walnut, Beroe sp.

Comb Jelly, Mnemiopsis sp. – a main source of tropical bioluminescence

Mnemiopsis showing its bioluminescence.

SPEAKING OF BIOLUMINESCENCE: WHAT IS IT?

It is light produced in a living organism. It occurs in many different life forms. In all life forms, the light is produced in the

same way:– Oxygen + luciferin are catalyzed by the enzyme

luciferase– Oxyluciferin and light are produced– This is a very efficient form of light production, with

no energy lost due to heat production

WHAT ARE THE STAR-LIKE SPECKS FLASHING IN SALT WATER? These small flashes are usually caused

by a microscopic dinoflagellate, Noctiluca.

WHY DOES NOCTILUCA BIOLUMINESCE?

The basic answer is: agitation– Anything that goes bump-in-the-night: a fish swims by,

someone stirs the water with a stick, a diver plunges in, a boat propeller churns along (sometimes leaving a green light trail in its wake), etc. Noctiluca washed up on a sandy beach twinkle as one walks by.

A common interaction:– A predatory copepod approaches the Noctiluca.– The Noctiluca flashes– The copepod is confused and distracted – The Noctiluca escapes– A nearby fish understands what is happening and zips in

and consumes the copepod (sometimes the Noctiluca is also consumed)

Have you ever seen a bioluminescent angel? (from Spalding 2004, p. 148)

Obviously he’s waving his arms in water with lots of bioluminescent organisms.

WHAT IS FLUORESCENCE?

Fluorescence occurs when the chemistry or structure of something causes light to be given off from a surface that is exposed to another form of light.

This occurs when the wave length of the reflecting light is longer than the impinging light.

We are most aware of fluorescencing signs and posters.

“Brightening” detergents contain substances that cause fluorescence, thus making clothes appear “whiter” to the eye.

If fluorescence is occurring, the glow disappears immediately when the light source is turned off.

WHAT IS PHOSPHORESCENCE?

Phosphorescence occurs when the chemistry or structure of a surface glows (same wave-length change as discussed for florescence), but it gradually fades over time after the light source is turned off.

Bioluminescence, in contrast, results from the internal luciferin-oxygen-luciferase reaction. It is not reflection.

HOW DO JELLYFISH & HYDROIDS STING?

Nematocysts are the stinging organs of jellyfish and their relatives. They are spring-loaded, and inject a venom loaded barb in the target.

From Jan A. Pechenik, Biol. Of Invertebrates, p. 79.

Hydroids are relatively small, but can give you a good sting.

Moon Jelly, Aurelia – not harmful to humans.

Cabbagehead Jellyfish – Normally associate in schools, but rarely as abundant as the view below in the harbor in Trinidad.

Box Jellyfish (aka Marine Stinger or Sea Wasp), Chironex fleckeri - Northern Australia’s deadly visitor. They are along the Australian coast north of the Tropic of Capricorn between October & May.

This beautiful animal can . . .

From National Geographic.

. . . cause severe reactions, if not death. One box jelly has enough venom to kill 60 humans. People

have died in just 4 minutes.

From National Geographic

Yet another bioluminescent jelly.

Be wary of these “plastic bags.” It is the floatation portion of a Portuguese Man-of-War, Physalia. It is accompanied by long tentacles, sometimes invisible in the sand around the float, that can sting horribly.

How do Portuguese Man-of-War move?

They have a “sail” on top of the float. The sail is positioned so that the critter

moves at 45º off the wind (the same way sailors set their sails).

About half are slanted opposite the others, thus insuring that not all will be blown up on beaches at the same time.

Is the Portuguese Man-of-War a simple jellyfish?

It is a floating complex of many individual living things.

There are a number of polyp-like critters.

There are many medusa-like individuals.

They all work together to make an eating machine that can be very dangerous to humans.

Structure of a Portuguese Man-of-war.

Small fish are commonly seen swimming about among the tentacles. All are immune to the venom. 50 or more species of fish are known to

spend at least some time living among the tentacles of jellyfish.

Most are juveniles, and they leave as they grow.

Some are specialized enough to always live in jellyfish tentacles.

Sea Nettle, Chrysosora, is one of the most common jellies in the Caribbean.

Upside-down Jellyfish, bottom at the margin of mangrove

Brittle stars can be very abundant.

Brittle stars are often found clinging to sponges and corals underwater along walls.

Some sea stars can be locally abundant, and we typically see them when snorkeling in the mangroves of Turneffe Atoll.

Sea stars and their relatives move about by means of a water vascular system that very efficiently uses water pressure.

Steer clear of Sea Urchins, but enjoy their beauty.

The long-spined urchin can be quite common in the Caribbean.

Sand Dollars are related to sea stars. Though delicate, they are architecturally sound.

Sea biscuits, a relative of sand dollars, from the Philippines.

A relative of sea star is the sea cucumber. This specimen is a Donkey Dung Sea Cucumber (duh, how’d it get its name?).

Dorsal view.

Ventral view.

Katie Greely and her new friend.

The Tigertail is a sea cucumber that sticks out from under corals on the sea floor after dusk.

Feather Worms, Spirobranchus giganteus (on brain coral) – Australia. There are many in Belize.

Christmas Tree Worm – Belize Photo by Tony Rath.

Feather Duster Worm on brown coral

Polychaete worms (this is a Bearded Fireworm) are usually abundant in marine situations, especially in estuaries and grassbeds.

Fireworms are polychaete worms that sting when touched. Be aware of any “worm” with fuzzy, hairy areas.

Bioluminescent benthic “glow worm” polychaetes, Odontosyllis luminosa (Syllidae). First noted by Christopher Columbus in November, 1492, but

the species was described in 1990. Happens for about 15 minutes per evening, around 7 pm, for

just a few days after a full moon. Gravid females, about 20 mm long, swim to the surface from the

bottom with their eggs and associated bioluminescent materials. The also bioluminescent males, about 12 mm long, follow them. If males are very near them, the females’ gonopores spew their

glowing load with eggs at the surface, and the eggs are fertilized externally by the males. If no males approach a female, she releases bioluminescent material, but no eggs.

The females presumably live to mate again, after sinking back to the bottom and forming mucous tubes.

Sponges come in three types, based on their anatomy and how water flows through them.

A more anatomic model:

The sponge itself is not a single living organism. It is a colonial organism made of spongin, spicules, and choanocytes that line the channels and cavities and move the water (by flapping their flagella) and feed on the food that is thus moved through. The choanocytes are the living elements

of the sponge.

Sponges maintain their shape with the help of supportive spongin (L) and/or glass-like spicules.

The Hawksbill Sea Turtle, Eretmochelys imbricata, feeds almost exclusively on sponges. They are able to tolerate having large balls of needle-like spicules in their stomachs.

Sponges come in many sizes, colors, and varieties.

LSU sponges, other sponges in Tobago.

Golden Eagle Sponges.

Variations of the Purple Tube Sponge, Belize.

Brown Variable Sponge, Belize.

Barrel sponges are incredible animals.

A small barrel sponge, Belize.

It’s not nice to sit on a barrel sponge!

Dark Variable Sponge, The Cathedral.

I love sponges.

Sally Lightfoot Crabs, so typical of the Galápagos, are also found throughout the Caribbean.

This large (1 ft leg span) Channel Clinging Crab was encountered on a wall at about 60 ft below the surface.

Channel Crab carapace – empty.

The Sponge Crab places a sponge on its back for camouflage. This one was found in the mangroves in Turneffe Atoll, Belize.

Where’s Waldo? There is a Decorator Crab in here somewhere.

Arrow crabs are not uncommon, but are rarely seen by new divers.

Ooops! Jessica just saw one. Can you read her divers sign language?

Myra found a recently shed skin of a Spiny Lobster at Half Moon Caye, Belize.

A Spiny Lobster in shallow water, Half Moon Caye.

Barnacles are crustaceans that live in a self-secreted shell.

Marine slugs can be incredibly ornate. Here is a Lettuce Nudibranch (“nudibranch” means naked gills – those protuberances on its back).

Nudibranch, Cyrce nigra, Australia (from Time-Life)

Alabaster Nudibranch, Dirona albaliniata

A pelagic nudibranch that specializes on eating porpita.

Nudibranch, Dialula sandiegensis, Southern California.

Most species of clams live in the substrate and use siphons to move water (and food) in and the out (with poo).

Flat Mangrove Oyster, Isognoman alatus, Turneffe. This species grows on algae, mangroves, and other objects.

Flamingo Tongue snails are wonderful to find. Follow Aimée!

What a beauty!!! The shell is white, but the mantle that covers it has large orange spots. (from Martin and Winnie)

Turban snails (Tegula brunnea) live along the shore of Half Moon Caye and is used by the Land Hermit Crabs.

Doesn’t that look delicious?

Ship worms that drill into wood (in the old days they sank ships) are actually bivalve mollusks (note the few barnacles).

The moon snail, Polinices duplicatus, is a predaceous species that plows through the sand searching for other snails and bivalves.

Moon snails lay their eggs in a peculiar “sand collar.”

How does a moon snail get into something with a hard shell? It uses its accessory boring organ (ABO) to produce hydrochloric acid, enzymes, and other substances that soften the shell. Then it scrapes the shell away with its rasping “tongue” called a radula (actually an elongate, self replicating radular ribbon). Once a hole opens, it injects digestive fluid and then sucks out the fluid.

The holes bored in the predated mollusks by moon snails are easy to recognize – the holes are beveled.

Octopi can change colors in a heartbeat. This south Pacific species mimics a fish (top) and a venomous snake (bottom). Mimic on left, model on right.

An elusive squid (about 10” long) feeding at Half Moon Caye. Note how it curls its tentacles back (right).

Tunicates are Protochordates, in the Phylum Chordata. This is a cluster of Mangrove Tunicates.

Some tunicates cover the surface of objects, like this Encrusting Tunicate on a ball of coral.

Another type of tunicate.

This stuff’s much cooler in the wild!!!