For many of the blogs we have posted on marine life of the Gulf of Mexico I have used the term “amazing” – but these cephalopods are truly amazing. There have been numerous nature programs featuring not just marine invertebrates but rather highlighting the cephalopods specifically. We have been amazed by their looks, their colors, their intelligence, and their ferocity. They are the animals of ancient mariner legends – the “kraken”.
These are not your typical mollusk. The elongated body and lack of external shell changes everything for cephalopods.
Photo: California Sea Grant
But for us who just visit the beach to play and walk – we rarely see them. They are quite common. The squid are almost transparent in the water column as they swim and usually run deep until nighttime. The only ones I have ever encountered were hauled up in shrimp trawls – but they are usually hauled up each time, and sometimes in great numbers. Octopus are more nighttime roamers as well. I have occasionally seen them diving during daylight hours, but they are very secretive and well camouflaged. I have found cephalopods both in the Gulf and within the estuaries – again, they are more common than we think.
A study conducted in the 1950s logged 42 species within the Gulf of Mexico. Many of them live in the open sea and at depths of 350-500 feet. There are actually four types of cephalopods – the octopus and squid we know, the cuttlefish and nautilus less so because they are not common in the Gulf region.
They are mollusk but differ from their snail and clam cousins in that they have very little, if any shell. The nautilus is an ancient member of this group and still possess an external shell. However, it is chambered and can be filled with gas like a hot air balloon allowing the nautilus to hover off the seafloor – something their snail/clam cousins can only dream about.
The squid and cuttlefish have reduced their shell to a surfboard looking structure that is found internally, serving almost like backbone. It allows them some rigidity in the water column, and they can grow to greater size. Actually, the squid are the largest invertebrates on the planet, with the “giant squid” (Architeuthus) reaching lengths of 50 feet or more.
The octopus differs from the squid in that it lacks a shell all together. Thus, it is smaller and lives on the ocean floor.
Photo: University of South Florida
The octopus lack a shell all together. Without this rigid bone within, they cannot reach the great size of the giant squid – so giant octopus are legend. However, there is a large one that grows in the Pacific that has reached lengths of 30 feet and over 500 pounds – big enough!
The lack of a shell means they must defend themselves in other ways. One is speed. With no heavy shell holding you down, high speed can be achieved. Again, squid are some of the fastest invertebrates in the ocean – being clocked at 16 mph. This may not outrun some of the faster fish and marine mammals, and many fall victim to them. Birds are known to dive down and eat large numbers of them. But they can counter this by having chromatophores. These are cells within the skin filled with colored pigments that they can control using muscles. This allows them to change color and hide. And their ability to change color is unmatched in the animal kingdom. I recommend you find some video online of the color change (particularly of the cuttlefish) and you will be amazed. Yes… amazed.
The chromatophores allow the cephalopods to change colors and patterns to blend in.
Photo: California Sea Grant
To control such color, they must have a more developed brain than their snail/clam cousins – and they do. The large brain encircles their esophagus and not only be used to ascertain the colors of the environment (and how to blend in) but also has the capability of learning and memory. The octopus in particular has been able to solves some basic problems – to escape, or get food from a closed jar, for example. Many of these chromatophores possess iridocytes – cells that act has mirrors and enhance the colors – again, amazing to watch.
All cephalopods are carnivorous and hunt their prey using their well-developed vision. Squid prefer fish and pelagic shrimp. Octopus are inclined to grab crustaceans and other mollusk – though they will grab a fish when the opportunity presents itself. Cephalopods hunt with their tentacles – which are at the “head end” of the body. The squid possess eight smaller arms and two longer tentacles. Each have a series of sucker cups and hooks to grab the prey. They keep their tentacles close to their bodies and, when within range, quickly extend them grabbing the fish and bringing back to the mouth where a sharp parrot-like beak is found. They bite chunks of flesh off and some have seen them bite the head off a mackerel. I was bitten on the hand by a squid once – one of the more painful bites I have ever had.
The extended tentacles of this squid can be seen in this image.
The octopus does not have the two long tentacles – rather only the eight arms (hence its name). They move with stealth and camouflage (thanks to the chromatophores) sneaking up on their prey – or lying in wait for it to come close. Here things change a bit. Octopus possess a neurotoxin similar to the one found in puffer fish. They can bite the crab – inject the venom – which includes digestive enzymes similar to rattlesnakes and spiders – and ingest the body of the semi-digested prey after it dies. They can drill holes into mollusk shells and inject the venom within. Most will give a painful bite but there is one in the Indo-Pacific (the blue-ringed octopus) whose venom is potent enough to kill humans.
Making new octopus and squids involves the production of eggs. The male will deposit a sac of sperm called a spermatophore into the body of the female. She will then fertilize her eggs and excrete them in finger like projections that do not have hard shells. Squid usually die afterwards. Octopus will remain with the eggs – oxygenating and protecting them until they hatch. At which time they will die.
Though we have a variety of cephalopods near shore – the real grandeur is offshore. Out there are numerous species of bioluminescent cephalopods – most living at 500 feet during the day and coming within 300 feet at night. Many swim, while some float, others have developed a type of buoyant case they can carry their eggs in. Far too much to go into in a blog such as this one. I recommend you do a little searching and learn more about these amazing animals.
Enjoy the Gulf!
This is a good name for this group. They are mollusk that have two shells. They tried “univalve” with the snails and slugs, but that never caught on – gastropods it is for them. The bivalves are an interesting, and successful, group. They have taken the shell for protection idea to the limit – they are COMPLETELY covered with shell. No predators… no way. But they do have predators – we will talk more on that.
An assortment of bivalves, mostly bay scallop.
Photo: Florida Department of Environmental Protection.
As you might expect, with the increase in shell there is a decrease in locomotion – as a matter of fact, many species do not move at all (they are sessile). But in a sense, they do not care. They are completely covered and protected. Again, we will talk more about how well that works.
The two shells (valves) are connected on the dorsal side of the animal and hinged together by a ligament. Their bodies are laterally compressed to fit into a shell that is aerodynamic for burrowing through soft muds and sands. Their “heads” are greatly reduced (even missing in some) but they do have a sensory system. Along the edge of the mantle chemoreceptive cells (smell and taste) can be found and many have small ocelli, which can detect light. The scallops take it a step further by having actually eyes – but they do live on the surface and they do move around – so they are needed.
The shells are hinged together at the umbo with “teeth like structures and the shells open and close using a pair of adductor muscles. Many shells found on the beach will have “scars” which are the point of contact for these muscles. They range is size from the small seed clams (2mm – 0.08”) to the giant clam of the Indo-Pacific (1m – 3.4 ft) and 2500 lbs.! Most Gulf bivalves are more modest in size.
Being slow burrowing benthic animals, sand and mud can become a problem when feeding and breathing. In response, many bivalves have developed modified gills to help remove this debris, and many actually remove organic particles using it as a source of food. Many others will fuse their mantle to the shell not allowing sediment to enter. But some still does and, if not removed, will be covered by a layer of nacreous material forming pearls. All bivalves can produce pearls. Only those with large amounts of nacreous material produce commercially valuable ones.
Coquina are a common burrowing clam found along our beaches.
Another feature is the large foot, used for digging a burrowing in the more primitive forms. It is the foot we eat when we eat clams. They can turn their bodies towards the substrate, begin digging with their foot but also using their excurrent from breathing to form a sort of jet to help move and loosen the sand as they go – very similar to the way we set pilings for piers and bridges today.
These are the earliest forms of bivalves – the burrowers. Most are known as clams and most live where the sediment is soft. Located near their foot is a sense organ called a statocyst that lets them know their orientation in the environment. Most have their mantles fused to their shells so sand cannot enter the empty spaces in the body. To channel water to the gills, they have developed tubes called siphons which act as snorkels. Most burrow only a few inches, some burrow very deep and they are even more streamlined and elongated.
Some have evolved to burrow into harder material such as coral or wood. One of the more common ones is an animal called a shipworm. Called this by mariners because of the tunnels they dig throughout the hulls of wooden ships, they are not worms but a type of clam that have learned to burrow through the wood consuming the sawdust of their actions. They have very reduced shells and a very long foot.
This cluster of green mussels occupies space that could be occupied by bivavles like osyters.
Other bivalves secrete a fibrous thread from their foot that is used to grab, hold, and sometimes pull the animal along. These are called byssal threads. Many will secrete hundreds of these, allow them to “tan” or dry, reduce their foot, and now are attached by these threads. The most famous of this group are the mussels. Mussels are a popular seafood product and are grown commercial having them attach to ropes hanging in the water.
Another method of attachment is to literally cement your self to the bottom. Those bivalves who do this will usually lay on their side when they first settle out from their larval stage and attach using a fluid produced by the animal. This fluid eventually cements them to the bottom and the shell attached is usually longer than the other side, which is facing the environment. The most famous of these are the oysters. Oysters basically have lost both their “head” and the foot found in other bivalves. These sessile bivalves are very dependent on tides and currents to help clear waste and mud from their bodies.
Oysters are a VERY popular seafood product along the Gulf coast.
Photo: Rick O’Connor
Then there are the bivalves who actually live on the bottom – not attached – and are able to move, or even swim. Most of these have well developed tentacles and ocelli to detect danger in the environment and some, like the scallops, can actually “clap their shells together” to create a jet current and swim. This is usually done when they detect danger, such as a starfish, and they have been known to swim up to three feet. Some will use this jet as a means of digging a depression in the sand they can settle in. In this group, the adductor has been reduced from two (the number usually found in bivalves) to one, and the foot is completely gone.
As you might guess, reproduction is external in this group. Most have male and female members but some species (such as scallops and shipworms) are hermaphroditic. The gametes are released externally at the same time in an event called a mass spawning. To trigger when this should happen, the bivalves pay attention to water temperature, tides, and pheromones released by the opposite sex or by the release of the gametes themselves.
Scallop life cycle.
Image: University of Florida IFAS
The fertilized eggs quickly develop into a planktonic larva known as a veliger. This veliger is ciliated and can swim with the current to find a suitable settling spot. Some species have long lived veliger stages. Oysters are such and the dispersal of their veliger can travel as far as 800 miles! Once the larval stage ends, they settle as “spat” (baby shelled bivalves) on the substrate and begin their lives. Some species (such as scallop) only live for a year or two. Others can live up to 10 years.
As a group, bivalves are filter feeders, filtering organic particles and phytoplankton as small as 1 micron (1/1,000,000-m… VERY small). In doing this they do an excellent job of increasing water clarity which benefits many other creatures in the community. As a matter of fact, many could not survive without this “eco-service” and the loss of bivalves has triggered the loss of both habitat and species in the Gulf region. Restoration efforts (particularly with oysters) is as much for the enhancement of the environment and diversity as it is for the commercial value of the oyster.
Now… predators… yes, they have many. Though they have completely covered their bodies with shell, there are many animals that have learned to “get in there”. Starfish and octopus are famous for their abilities to open tightly closed shells. Rays, some fish, and some turtles and birds have modified teeth (or bills) to crush the shell or cut the adductor muscle. Sea otters have learned the trick to crush them with rocks and some local shorebirds will drop them on roads and cars trying to access them. And then there are humans. We steam them to open the shell and cut their adductor muscle to reach the sweet meat inside.
It is a fascinating group – and a commercial valuable one as well. Lots of bivalves are consumed in some form or fashion worldwide. Take some time at the beach to collect their shells as enjoy the great diversity and design within this group. EMBRACE THE GULF!
One of the largest groups of invertebrates in the Gulf are the Mollusk… what many call “seashells”. Shell collecting has been popular for centuries and, in times past, there were large shows where shells from around the world were traded. Almost everyone who visits the beach is attracted to, and must take home, a seashell to remind them of the peace beaches give us. Many are absolutely beautiful, and you wonder how such small simple creatures can create such beauty.
One of the more beautiful shells from the sea – the nautilus.
Well, first – not all mollusk are small. There are cephalopods that rival the size of some sharks and even whales.
Second, many are not that simple either. Some cephalopods are quite intelligent and have shown they can solve problems to reach their food.
But beautiful they are, and the colors and shapes are controlled by their DNA. Just amazing.
There are possibly as many as 150,000 different species of mollusks. These species are divided into 8-9 classes (depending which book you read) but for this series on Embracing the Gulf we will focus on only three. First up – the snails (Class Gastropoda).
There are an estimated 60,000 – 80,000 species of gastropods, second only to the insects. They are typically called snails and slugs and are different in that they produce a single coiled shell. The shell is made of calcium carbonate (limestone) and is excreted from tissue called the mantle. It covers their body and continues to grow as they do. The shell coils around a linear piece of shell called the columella. Most coil to the right, but some to the left – sort of like right and left-handed people. There is an opening in the shell where the snail can extend much of its body – this is called the aperture – and some species can close this off with a bony plate called an operculum when they are inside. Some snail shells have a thin extension near the head that protects the siphon – a tube that acts like a snorkel drawing water in and out of the body.
The black siphon can be seen in this crown conch crawling across the sand.
Photo: Franklin County Extension.
They have pretty good eyes and excellent sense of smell. They possess antenna, which can be tactile or sense chemicals in the water (smelling) to help provide information to a simple brain.
They are slow – everyone knowns this – but they really don’t care. Their thick calcium carbonate shells protect them from most predators in the sea… but not all.
Their cousins the slugs either lack the shell completely, or they have a remnant of it internally. You would think “what is the point of an internal shell?” – good question. But the slugs have another defense – they are poisonous. Venomous and poisonous are two different things. Being poisonous means you have a form of toxin within your body tissue. If a predator eats you – they will get very sick, maybe die. But you die as well, so… Not too worry, poisonous slugs are brightly colored – a universally understood signal to all predators.
There is one venomous snail – the cone snail, of which we have about five species in the Gulf. They possess a stylet at the tip of their siphon (similar to the worms we have been writing about) which they can use as a dart for prey such as fish. Many gastropods are carnivores, but some are herbivores, and some are scavengers.
Many shells are found on the beach as fragments. Here you see the fragment of a Florida Fighting Conch.
Photo: Rick O’Connor
Most have separate sexes and exchange gametes in a sack called a spermatophore. Fertilized eggs are often encased in structures that resemble clusters, or chains, of plastic. These are deposited on the seafloor and the young are born with their shell ready for life.
This group is not as popular as a food item as other mollusk but there are some. The Queen Conch is probably of the most famous of the edible snails, and escargot are typically land snails. I am not aware of any edible slugs… and that is good thing.
Some of the more common snails you will find along our portion of the Gulf of Mexico are:
Crown Conch Olive Murex Banded Tulip
Whelks Cowries Bonnets Cerith
Slippers Moon Oyster Drills Bubble
The most encountered slug is the sea hare.
A common sea slug found along panhandle beaches – the sea hare.
I hope you get a chance to do some shelling – I hope you find some complete ones. It is addictive!
Sea pork comes in a wide variety of shapes and sizes. Photo credit: Carrie Stevenson, UF IFAS Extension
Recently I was walking the beach, enjoying a sunset and looking around at the shells and other oddities in the wrack line where waves deposit their floating treasures. Something bright green and oblong caught my eye. It was emerald in color, smooth yet fuzzy at the same time, and firm to the touch. At first, I thought it was a sea bean–a collective term for the many species of seeds and fruits that float to our shores from tropical locations in the Caribbean or Central/South America. The bright green definitely seemed like something botanical in nature. However, the vast majority of sea beans have a woody, protective shell similar to our more familiar pecans or acorns.
I remembered a family member asking about finding a mystery chunk of pink mass she found on the beach a few years ago. It resembled a pork chop more than anything else.
A different variety of sea pork that really lives up to its name. Photo credit: Stephanie Stevenson, Duval County Master Gardener
Looking closer and consulting a couple of resources, I realized we had both (most likely!) happened upon one of the oddest and often-questioned finds on our beaches: sea pork. Ranging in color from beige and pale pink to red or green, sea pork is a tunicate (or sea squirt), a member of the Phylum Chordata, home to all the vertebrate and semi-vertebrate animals. While they look and feel more like a cross between invertebrate slugs or sponges, the tunicates are more advanced organisms, possessing a primitive backbone in their larval “tadpole” form. Despite their blob-like appearance, they are more closely related to vertebrate animals than they are to corals or sponges.
The unusual life cycle of the tunicate. Photo credit: University of Washington, used with permission with Florida Master Naturalist program
During their short (just hours-long) larval stage, the tunicate larvae uses its nerve cord (supported by a notochord similar to a vertebrate spine) to communicate with a cerebral vesicle, which works like a brain. Similar to fish, this primitive brain uses an otolith to orient itself in the water, and an eyespot to detect light. These brain-like tools are utilized to locate an appropriate location to settle permanently. Using a sticky substance, the tunicate will attach its head directly to a hard surface (rocks, boats, docks, etc.) and go through a metamorphosis of sorts. The tunicate reabsorbs its tail and starts forming the shape and structure it needs for adulthood.
As an adult, the organism has a barrel shape covered by a tough tunic-like skin (hence “tunicate”). Adult bodies have two siphons, one to bring water in, another to shoot it out (giving them their other nickname, the sea squirt). The water passes through an atrium with organs that allow it to filter feed, trapping plankton and oxygen. The tunicates will spend most of their lives attached to a surface, pumping water in and out as filter feeders. They may be solitary or live in colonies, and vary widely in color and shape, lending variety to those chunks of sea pork found washing up.
I am still awaiting positive identification from an expert on my green find to confirm that it is, indeed, a tunicate and not an unfamiliar plant. Consulting with Extension colleagues, for now we are pretty confidently going with green sea pork. If you have seen one of these before or something resembling sea pork, let us know! It is fascinating to see the variety and unusual shapes and colors.
As we embrace the marine life of the Gulf of Mexico during this year of “Embracing the Gulf”, we are currently hooked on worms. In the last article we talked about the gross and creepy flatworms. Gross because they are flat, pale in color, only have a mouth so they have to go to the bathroom using it – and creepy in that many of them are parasites, living in the bodies over vertebrates (particularly fish) and that is just creepy. You may ask why would we even “embrace” such a thing? Well… because they do exist and most of us know nothing about them.
A nemertean worm.
Photo: Okinawa Institute of Science
This week we continue with worms. We continue with a different kind of flatworm. They are not as gross, but maybe a little creepy. They are called nemertean worms and I am pretty sure (a) you have never heard of them, and (b) you have never seen one. So why “embrace” these? Well… again it is education. They do exist, and one day you MAY see one – and know what you are looking at.
Nemerteans are flatworms. They are usually pale in color but a different from the classis fluke or tapeworm in a couple of ways.
1) They do have a way for food to enter and another for waste to leave, what we call a complete digestive tract – and that’s nice.
2) They have this long extension connected to their head called a proboscis. Many of them have a dart at the end they can use to kill their prey – and that’s creepy.
3) And as mentioned, most are carnivores, feeding on small invertebrates – and that’s okay.
We rarely see them because they are nocturnal – hiding under rocks, shells, seaweed during the day and hunting at night. Most are about eight inches long but some in the Pacific reach almost eight feet!
I would put that in the creepy file.
As we said, they are usually pale in color, though some may have yellow, orange, red, or even green hues to them. Their heads are spade shaped and, again, hold a retracted proboscis. This proboscis can be over half the length of the worm. At the end is a stylet (a dart) which they can use to stab their prey (small invertebrates). They can stab repeatedly, like using a knife, – they may stab and grab, like using a claw – or they may be a species that has toxin and kills their prey that way.
Some would add this to the creepy file as well. A long pale worm, moving at night, extending a long proboscis when they get near you with a sharp dart at the end they essentially “sting” you like a bee.
But we NEVER hear about such things with humans. They hunt small invertebrates like amphipods, isopods, and things like that. If you picked one up, would it stick the dart in you? My hunch would be yes – I honestly don’t know, I have only seen one to two in the 35+ years I have been teaching marine science and I did not pick them up. I have never met anyone who has and have never read “DON’T PICK THESE UP – VERY DANGERSOUS”. So, my hunch is that it would not be very painful at all.
But don’t take my word for it – again, I have rarely seen one… so, don’t pick them up 😊
There are about 650 species of nemertean worms in the world, 22 live in the Gulf of Mexico, and 16 live in the northern Gulf (near us). They are basically marine, move across the environment on their slime trails, seeking prey primarily by the sense of smell at night. Unlike the flukes and tapeworms, there are male and females in this group. They fertilize their eggs externally to make the next generation of these harpooning hunters of the Gulf.
I don’t know if you will ever come across one of these. You will know it by the flat body, pale color, and spade-shaped head, but I think it would be pretty neat to find one. There are more worms to learn about in the Gulf of Mexico, but we will do that in another edition.
I’d like to be a jellyfish… cause jellyfish don’t pay rent…
They don’t walk and they don’t talk with some Euro-trash accent…
Their just simple protoplasm… clear as cellophane
They ride the winds of fortune… life without a brain
These lyrics from Jimmy Buffett’s song Mental Floss sort of sums it up doesn’t it. The easy-going lifestyle of the jellyfish.
Everyone who visits the Gulf coast knows about these guys, but few people… very few… like them. For most, the term jellyfish signals “pain”, “fear”, and “death”. The purple flag is flying, and no one wants to enter the water. Folks from the Midwest call local hotels and condos asking, “when are the jellyfish going to be there?” It’s understandable. Who wants to spend their week vacation on the Gulf inside a hotel because you can’t go swimming?
I found this along the shore last winter. These are cannonball jellyfish.
I would almost (…almost) rather be diving with a shark than hundreds of jellyfish. When you spot them, they are everywhere. Quietly swarming like ghosts. You push them off and they appear to move towards you – almost like smoke from a campfire, you can’t get away.
They are creepy things. But amazing too!
As Mr. Buffett’s points out, they are simple “protoplasm”. Their body is primarily a jelly-like substance called mesoglea – and most of that is water. If you place a dead jellyfish on your dock and come back that afternoon, you will probably find just a “stain” of where it was – there is almost nothing to them.
The “bell” of the jellyfish is mostly mesoglea. Some jellyfish have thick layers of this, others much thinner. Some have a small flap of skin along the margins of the bell called the velum which they can undulate and swim – but they are not strong swimmers. If the tide is going out, swim as they may… their heading out also.
The bell shaped body of a jellyfish with numerous tentacles.
Many species of jellyfish have interesting markings within the bell. One has a white-colored structure that forms a 4-leaf clover. Another has red triangles all connecting at the center of the bell. For many, these structures are the ones that produce the gametes. Jellyfish reproduce sexually but are hermaphroditic – meaning they produce female eggs and male sperm in the same animal. There is no physical contact between animals, they just release the gametes into the ocean when they are in thick swarms and wah-la… new jellyfish – many new jellyfish.
On the bottom of the bell is a single opening that leads to a single pouch. This opening is the mouth, and the pouch is called the gastrovascular cavity. Jellyfish are predators – carnivores. There are no teeth, and most do not seek their prey – their prey finds them. Hanging from their bell are the tools of the killing trade, the part of this animal we do not like… the tentacles. Some tentacles can extend for several feet beyond the bell, others you can hardly notice them – but this is where the killing happens.
Along the tentacles there are small capsules called cnidoblasts which contain small cells called nematocyst. These nematocyst contain a coiled dart which at the end contains a drop of venom. There is a trigger associated with this cell. The jellyfish does not fire it – instead, the prey bumps the trigger and the nematocyst “fires”. The drop of venom is injected, along with the hundreds of other nematocysts along the tentacle the fish just bumped. This venom paralyzes the prey, other tentacles coil around it firing more nematocysts, and the tentacles retract towards the mouth – bingo… lunch.
This box jellyfish was found near NAS Pensacola in November of 2015.
Photo: Brad Peterman
Of course, the same happens when people bump into them. For us it is painful and unpleasant – but we are not consumed. That said, some species are quite painful. Some will force people to the hospital, and some have even killed people. The Box Jellyfish is the most notorious of these deadly ones. Known for their habits in Australia, there are at least two species found in the Gulf. The ones found here are not common, and there are no reported deaths, but they do exist. The Four-Handed is the one more widespread here. It actually has eyes, can detect predators and prey and swim towards or away from them, and the male fertilizes the female internally – not your typical jellyfish.
The more familiar painful one is the Portuguese Man-of-War. This creature is more like a sponge in that it is not just one creature but a large “condo” of many. Some cells are specialized in feeding, these are found on their long tentacles. Others specialize in reproduction; these are found near the blue colored air bag. They produce this blueish colored air bag which is exposed above the surface. The wind pushes on the bag like a sail and this moves the creature across the environment in search of food. Hanging from the bag are long tentacles which are made up of individuals whose stomachs are all connected. So, when one group of cells makes contact and kills a prey – they consume it and the tissue is moved through the connecting stomachs to feed the whole colony. To feed a whole colony, you need a big fish – to kill a big fish, you need a strong toxin, and they have it. These are VERY painful and have put people in the hospital, some have died. Some say that the Portuguese man-of-war is not a “true” jellyfish. This is true in the sense that they belong to a different class of jellyfish. There are three classes, the Scyphozoans being what we call the “true” jellyfish – Portuguese man-of-wars are not scyphozoans, but rather hydrozoans.
The colonial Portuguese man-of-war.
Another interesting thing about jellyfish, is that they are all not jellyfish-like. As we just mentioned, there are two other classes and one other phylum of jellyfish-like animals. Hydrozoans and anthozoans are not your typical jellyfish. Rather than being bell-shaped and drifting in the ocean looking for food, they are attached to the seafloor and look more like flowers. Their tentacles are usually smaller but do contain nematocysts. Their toxin can be strong, some do eat fish, but most have a weaker toxin and feed on very small creatures – some only eat plankton. These would include the hydra, sea anemones, and the corals. As mentioned above, this also would include the Portuguese man-of-war.
Comb jellies are those jellies that drift in the currents and have no tentacles. We commonly collect them and toss them at each other. When I was growing up, we referred to them as “football jellies” because of this. The reason they do not sting is not because they do not have tentacles (some species do) but rather they do not have nematocyst and cannot. Rather they have special cells called colloblast that produce a drop of sticky glue at the end which they use to capture prey. Not having toxins, they cannot kill large prey but rather feed on smaller creatures like plankton and each other – they are cannibals. For this reason, they are in a whole different phylum.
The nonvenmous comb jelly.
Photo: Bryan Fluech
The jellyfish of the Gulf are a nuisance at times but are actually amazing creatures.