You might say this is a strange title – “meet the barnacle” – because everyone knows what a barnacle is… or do they?
As a marine science instructor, I gave my students what is called a lab practical. This is a test where you move around the room and answer questions about different creatures preserved in jars. Almost every time that got to the barnacle they were stumped. I mean they knew it was a barnacle but what kind of animal is it? What phylum is it in?
Going through a thought process they would more often than not choose that it was a mollusk. This makes perfect sense because of the calcium carbonate shell it produces. As a matter of fact, science thought it was a mollusk until 1830 when the larval stage was discovered, and they knew they were dealing with something different. It is not a mollusk. So… what IS it? Let’s meet the barnacle…
Barnacles along the seashore is a common site for many.
Photo: NOAA
The barnacle is actually an arthropod. Yep… the same group as crabs and shrimp, insects and spiders. Weird right…
But that is because the creature down within that calcium carbonate shell is more like a tiny shrimp than an oyster. It is in the class Cirripedia within the subphylum Crustacea. It is the only animal in this class and the only sessile (non-motile) crustacean.
Barnacles are exclusively marine. This has been helpful when conducting surveys for terrapins or assessing locations for living shorelines – if you see barnacles growing on rocks, shells, or pilings, it is salty enough. There are over 900 species described and they live independently from each other attached to seawalls, rocks, pilings, boats, even turtle shells. Louis Agassiz described the barnacle as “nothing more than a little shrimplike creature, standing on its head in a limestone house kicking food into its mouth.”
This image from a textbook shows the internal structure of a barnacle. Notice the shrimplike animal on its back with extendable appendages (cirri) for feeding.
Image: Robert Barnes Invertebrate Zoology.
The planktonic barnacle larva settles to the bottom and attaches to a hard substrate using a cement produced from a gland near the base of their first set of antenna (crustaceans, unlike insects and spiders, have two sets of antenna). It is usually head down/tail up and begins to secrete limestone plates forming the well known “shell” of the animal. Some barnacles produce a long stalk near the head end (called the peduncle) which holds the adhesive gland and it is the peduncle that attaches to the hard substrate, not the head directly. The goose neck barnacle is an example of this. We find them most often in the wrack along the Gulf side of our beaches attached to driftwood or marine debris.
Lucky was found in the Gulf of Mexico. He had been there long enough for these goose neck barnacles to attach and grow.
Photo: Bob Blais
The “shell” of the barnacle is a series of calcium carbonate plates they secrete. These plates overlap and are connected by either a membrane or interlocking “teeth”. The body lies 90° from the point of attachment on its back.
There are six pairs of “legs” which are very long and are extended out of the “doors” of the shell and make a sweeping motion to collect planktonic food in the water column. They are most abundant in the intertidal areas were there are rocks, seawalls, or pilings.
Most species are hermaphroditic (possessing both sperm and egg) but cross fertilization is generally the rule. Barnacles signal whether they are acting males or females via pheromones and fertilization occurs internally, the gametes are not discharged into the water column as in some mollusks and corals. The developing eggs brood internally as well. Our local barnacle (Balanus) breeds in the fall and the larva (nauplius) are released into the water column in the spring by the tens of thousands. The larva goes through a series of metamorphic changes until it settles on a hard substrate and becomes the adult we know. They usually settle in dense groups in order to enhance internal fertilization for the next generation. Those who survive the early stages of life will live between two and six years.
So, there you go… this is what a barnacle is… a shrimplike crustacean who is attached to the bottom by its head, secretes a fortress of calcium carbonate plates around itself, and feeds on plankton with its long extending legs. A pretty cool creature.
Reference
Barnes, R.D. 1980. Invertebrate Zoology. Saunders College Publishing. Philadelphia PA. pp. 1089.
As I write this, we are in the middle of our 2023 Scallop Search, an event we do each year to assess whether the scallops in Pensacola Bay are trying to make a comeback on their own. Each year I am amazed at how popular this little mollusk is. On the day I am writing, I will be working with a marine science class from the University of Southern Mississippi driving over from Ocean Springs. This past weekend I worked with two families who trailered their boat from Enterprise Alabama to participate. Those on the eastern end of the panhandle are well aware of the popularity of this creature. Folks from all over the southeast travel there to go scalloping. Many of the locals in my area, when I am training them how to do a scallop search, tell me that they head east and go scalloping every year. Some even have condos for that week and it is a large part of their annual vacation plans. And many of the locals here would love to see them return to Pensacola Bay.
This is a creature that draws a lot of attention. But most know very little about it. They know it has small eyes and can swim – actually… I have recently found that not everyone knows they can swim. We know they like grassbeds and they can be harvested in the summer. They may have done this long enough to know the prime spots within the grassbeds to search for them – their “sweet spots”. But not much more.
So… let’s meet the bay scallop.
Volunteers conducting the great scallop search.
Photo: Molly O’Connor
Its scientific name is Argopecten irradians. It is a mollusk in the class Bivalvia and the family Pectinidae. There are numerous species, and the group is found all over the world. The greatest variety of them are from the Indo-Pacific region, and in each case, they are a popular seafood. Most can swim, though erratically – they are not Michael Phelps – and they use this ability to avoid predators such as starfish, which they can see with the set of simple eyes.
There are five subspecies of A. irradians. A. irradians irradians, known as the bay scallop, or Atlantic Bay scallop (and from here is just “the scallop”) is our local variety. It is found from Cape Cod to the Gulf of Mexico. They begin life as a microscopic egg produced during the mass spawning of the hermaphroditic parents (hermaphroditic meaning each parent can produce sperm and egg). The timing of the release of gametes is triggered by warming water and usually occurs in the late summer/early fall. This early egg stage sinks to the bottom where it remains for a few weeks before hatching.
The hatched larva remain microscopic, are transparent, resemble the parents, and are called spat. The spat become part of the plankton in local estuaries but eventually return to the grass in what is called “spatfall” where they attached to the seagrasses using byssal threads. They continue to grow, eventually release from the grass, and become the scallops we all know and love. Many species of scallops can live over 20 years, but our local one only lives for one.
As most know, adult scallops have two shells (bivalves) connected at the hinge on the dorsal side of the animal. Though they do add weight to the shell, a disadvantage for a swimmer, the “ribs” provide a sturdier shell. The two shells are connected by a single, large adductor muscle, which is used to open and close the valves during swimming. It is this adductor muscle we eat when consuming scallops.
Like all bivalves, scallops are filter feeders but unlike most bivalves they lack siphons to draw water in and out of the digestive tract. Rather they lie with their valves slightly gaped and allow water to pass over them. Plankton is collected by a mucous layer and then moved to the gut by cilia (small hair-like structures) where it is digested.
Bay Scallop.
Photo: FWC
Like all bivalves, scallops lack a brain as we know it but rather function using a series of ganglia (groups of nerve cells) connected to a nerve ring. These ganglia can control movement of the muscle, gills, eyes, and are connected to a statocyst, which tells the scallop how it is oriented in the water column.
There are numerous eyes aligned along the edge of each valve that can detect movement and shadows. It is believed that they use their eyes to detect potential predators and possibly initiate the swimming behavior they are famous for.
Living only one year, and reaching maximum size in late summer during spawning, scallop harvesting is regulated to that time of year in Florida. Once common from Pensacola to Miami, they are now only found in large numbers in the Big Bend region. Due to the loss of scallops in other areas, many visit the Big Bend each year to go scalloping, putting heavy harvest pressure on those stocks. There have been efforts to try and enhance the existing populations as well as restore historic ones. Here in Pensacola Bay, Florida Sea Grant works with volunteers to monitor the water quality and seagrasses, as well as assess how the few existing scallops are doing.
For more information on panhandle scallops, contact your local Sea Grant Agent at the county extension office.
Welcome to Red Snapper Season 2023! The season began June 1, 2023 at 12:01am for “For Hire” vessels fishing in federal waters and continues through August 25, 2023.
For Florida recreational anglers in state waters, the season started a few days later on June 16. While the summer season ends on July 31, 2023, fishing enthusiasts can look forward to 3-day fishing weekends in Florida State waters later in October and November 2023. This means there are still additional days of red snapper fishing opportunities in 2023, giving you ample time to plan exciting fishing adventures.
Here, we present Bay County’s recent artificial reefs, which serve as prime fishing locations for this year’s seasons. This select collection includes three distinct areas: east (State), south (Federal), and west (State). These sites have had the opportunity to grow and mature, with over 290 reef modules deployed between May 2019 and December 2020.
East Location – Sherman Site
Walter Marine deploys one of nine super reefs deployed in Bay County’s NRDA Phase I project located approximately 12 nautical miles southeast of the St. Andrew Pass. Each massive super reef weighs over 36,000 lbs and is 15 ft tall. Multiple modules deployed in tandem provides equivalent tonnage and structure similar to a medium to large sized scuttled vessel. Photo by Bob Cox, Mexico Beach Artificial Reef Association.
This project was completed in May 2019 in partnership with the Mexico Beach Artificial Reef Association, Florida Fish and Wildlife Conservation Commission, and Florida Department of Environmental Protection. The deployment site in the Sherman Artificial Reef Permit Area is approximately 12 nm southeast of St. Andrew Bay Pass at a depth of approximately 80 feet. A total of twenty-five modules were deployed, including nine 18-ton reefs and sixteen 3-ton reefs.
South Location – Large Area Artificial Reef Site (LAARS) A
Large 45,000 lbs. concrete modules staged for deployment. These were placed by HG Harders and Son in July of 2019.
This project was completed in July 2019 in partnership with the Bay County Artificial Reef Association and the Florida Fish and Wildlife Commission. The deployment site in LAARS A is approximately 12 nm south of the pass, with reef modules located around the center of the permitted area. The reefs are situated in about 105 feet of water. There are seventeen reef modules, including five 22-ton reefs with a height of 18 feet and twelve 2.5-ton reefs with a height of 5 feet.
West Location – SAARS E – L
This area has the largest number of reef modules and permit sites. It includes 154 small pyramids that are 8 ft tall and weigh about 10 tons. There are also 26 large pyramids that are 18 ft tall and weigh about 18 tons. Additionally, 25 concrete disk reefs, weighing about 3 tons each, were deployed nested inside select Super Reefs, adding to the complexity and diversity of the reefs. In total, approximately 980 tons of engineered concrete artificial reef material were placed in 8 permitted areas. These deployments were completed in December 2020 with the support of the Mexico Beach Artificial Reef Association.
Bay County’s NRDA Phase II deployment in Small Area Artificial Reef Sites (SAARS) E – L are located 11 – 15 nautical miles (nm) southwest of St Andrew Bay Pass in Florida state waters. (Source ArcGIS mapping software).
This monitoring dive was conducted by FWC in January 2021, shortly after the reefs were deployed. You can move the 360 deg video image to experience what the divers see and observe.
Below is an overview map of these three prime snapper sites!
Wishing everyone great fishing days on the water with family and friends!
Chantille Weber, Coastal Resource Coordinator, UF/IFAS Extension Bay County
L. Scott Jackson, Bay County Extension Director, UF/IFAS Extension Bay County and Florida Sea Grant
An Equal Opportunity Institution. UF/IFAS Extension, University of Florida, Institute of Food and Agricultural Sciences, Andra Johnson, Dean for UF/IFAS Extension. Single copies of UF/IFAS Extension publications (excluding 4-H and youth publications) are available free to Florida residents from county UF/IFAS Extension offices.
When snorkeling the grassbeds of the Florida panhandle encountering a reptile has a low probability, but it is not zero. Of all the reptiles that call this part of the state home, few enter marine waters and most of those are very mobile, moving up and down the coast heading from one habitat to another. In fact, there are no marine reptiles that would be considered residents of our seagrasses, only transients.
The one species that you might encounter is the green sea turtle (Chelonia mydas). This is the largest of the “shelled” sea turtles and has a vegetarian diet. With a serrated lower jaw, they can be found grazing in the seagrass beds feeding on both the grasses and the species of algae found there. The carapace length of these large reptiles can reach four feet and they can weigh up to 400 pounds. Their coloration is similar to that of the loggerhead sea turtle (Caretta caretta) but their heads are smaller and there are only two large scutes between the eyes rather than the four found in the loggerheads. The colors of the skin and shell have shades of brown, yellow, orange, and some black and can be quite beautiful. The name “green” sea turtle comes from the color of their internal fatty tissue. Feeding on a diet of seagrasses, it becomes green in color, and this was discovered by early fishermen who hunted and consumed this species. It is the one used most often in what is called turtle soup and is actually farmed for this dish in other countries.
The green sea turtle.
Photo: Mile Sandler
Like all sea turtle species, they are born on the Gulf side of our barrier islands. If they successfully hatch, they work their way to the open water and spend their early years in the open sea. Some have been associated with the mats of Sargassum weed floating offshore, feeding on the variety of small invertebrates that live out there. They will also nip at the Sargassum itself. As juveniles they will move back into the coastal estuaries where they begin their vegetarian lifestyle. As adults they will switch time between the open sea and the grass filled bays. Once unfortunate side effect of feeding in our grassbeds is the frequency of boat strikes. There are tens of thousands of motored vessels speeding through our grassbeds and the turtles surfacing for air can be targets for them. Our hope is that more mariners are aware of this problem and will be more vigilant when recreating there.
Another turtle who IS a resident of the estuary is the much smaller diamondback terrapin. Though terrapins much prefer salt marshes they will enter seagrass beds, and some spend quite a bit of time there. Terrapins prefer to feed on shellfish so, moving through the grassbeds it is the snails and bivalves they seek. Because of their size they feed on the smaller mollusk. A typical terrapin will have a carapace length of about 10 inches and may weigh two pounds. They will take small crabs and shrimps when the opportunity is there, and they are known to swim into submerged crab traps seeking the bait. Unfortunately, being air breathing reptiles, they will drown after becoming entrapped. It is now required that all recreational crab traps in Florida have bycatch reduction devices (BRDs) on each of the funnel openings to reduce this problem. Many studies, both here in Florida and elsewhere, have shown these BRDs do not significantly reduce crab catch and so you can still enjoy crabbing – just not while catching terrapins. Encountering one snorkeling would be a very rare event, but – particularly in the eastern panhandle – has happened.
Diamondback terrapin.
Photo: Rick O’Connor
A third reptile that has been seen in our grassbeds is the American alligator (Alligator mississippiensis). Preferring freshwater systems, encounters with alligators in an open seagrass bed are rare, but do happen. There are plenty of freshwater ponds on some of our barrier islands that the alligators will use. They have been seen swimming out into the seagrass beds and often will cross the bay, or Intracoastal Waterway, to mainland side. They have also been seen swimming near shore in the Gulf of Mexico. Though they can tolerate saltwater, they have a low tolerance for it and do not spend much time there.
Alligators are top level carnivores feeding on a variety of wildlife. Like most predators, they tend to seek and capture the easiest prey. Most often these are fish, reptiles, or small mammals. But they will take on large birds or deer if the opportunity presents itself. Despite their natural fear of humans, they have taken pets and also have attacked humans.
Having only canines in their mouths, they must grab the prey and swallow it. Lacking molars, they cannot chew. So, more often than not, they select prey they can swallow whole. If they do grab a larger animal, they are known to drown the creature in what has been termed the “death role” and cache it beneath the water under a log (or some structure) where it will soften to a point where they can cut small pieces and swallow it. All of the alligators I have seen in our grassbeds were definitely heading somewhere. They were not spending time there. After heavy rains the salinity may drop enough to where they can tolerate being out there longer and encounters could increase. But they are still rare.
Alligator
Photo: Molly O’Connor
I will mention here that there are several species of snakes that, like the alligator, are swimming from one suitable habitat to another – crossing the seagrass in route. All snakes can swim and encounters in brackish water are not unheard of. I have several photos of diamondback rattlesnakes (Crotalus adamanteus) swimming across the Intracoastal Waterway between the mainland and the islands.
Eastern diamondback rattlesnake swimming in intracoastal waterway near Ft. McRee in Pensacola.
Photo: Sue Saffron
Encounters with reptiles are rare in our seagrass beds but pretty exciting when they do occur. There is certainly no need to fear swimming or snorkeling in our bay because they are so rare. But maybe one day you will be one of the lucky ones who does see one.
One of the community science volunteer projects I oversee in the Pensacola area is the Florida Horseshoe Crab Watch. The first objective of this project is to determine whether horseshoe cabs exist in your bay – FYI, they do exist in Pensacola Bay. The second objective is to determine where they are nesting – we have not found that yet, but we have one location that looks promising. One of the things my volunteers frequently find are the molts of the horseshoe crabs. Many keep them and I have quite a few in my office as well. One volunteer was particularly interested in the fact that they even molted and that they could leave this amazing empty shell behind and yet still be crawling around out there. So, I decided to write an article explaining the process in a little more depth than I typically do.
Horseshoe crab molts found on the beach near Big Sabine.
Photo: Holly Forrester.
I titled the article “The Molting of Crabs” but it could be the molting of any member of the Phylum Arthropoda – they all do this. The Phylum Arthropoda is the largest, most diverse, and successful group of animals on the planet. There are at least 750,000 species of them. This is three times the number of all other animal species combined. One thing unique to this group is the presence of an exoskeleton.
The exoskeleton is made of chiton and is secreted by the animal’s hypodermis in two layers. It provides the protection that the calcium carbonate shells of mollusk do but is much lighter in weight and allows for much more movement. Arthropods have jointed legs, hence their name “arthropod – jointed foot”, to enhance this movement even more. The entire body is covered by this exoskeleton.
The outer layer is thin and called the epicuticle. It is composed of proteins and, in many arthropods, wax. The inner layer is the thicker procuticle. The procuticle consists of an outer exocuticle and an inner endocuticle. These are composed of chiton and protein bound to form a complex glycoprotein. The exocuticle is absent at joints in the legs and along lines where the shell will rupture during molting. In the marine arthropods the procuticle includes salts and minerals. Where the epicuticle is not waxy and is thin, gases and water can pass into the animal’s body. The cuticle also has small pores that allow the release of compounds produced by glands within the animal. Not all of the cuticle is produced on the outside of the body. Some portions of it are produced around internal organs.
The colors of the crabs and other arthropods are produced by concentrations of brown, yellow, orange, and red melanin pigments within the cuticle. Iridescent greens, purples, and other colors are produced by striations of the epicuticle refracting light.
One disadvantage of the protective exoskeleton is the fact that it does not grow as fast as the interior soft tissue. They have solved this problem by periodic shedding, or molting, of the shell. Science calls this ecdysis, but we will continue to call it “molting”.
Step one is the detachment of the hypodermis from the skeleton. The hypodermis now secretes a new epicuticle. Step two, the hypodermis releases enzymes which pass through the new epicuticle and begin to erode the untanned endocuticle of the old skeleton. During this process the muscles and nerves are not affected and the animal can continue to move and feed. Step three, the old endocuticle is now completely digested. With the new procuticle produced by the hypodermis, the animal is now encased by both the old and new skeleton. Step four, the old skeleton now splits along predetermined lines, and the animal pulls out of the old skeleton. The new exoskeleton is soft – hence, the “soft-shelled blue crab” – and can be stretched to cover the increased size of the new animal. This stretching occurs due to tissue growth during steps 1-3, and from the uptake of air and water. The hardening of the new skeleton occurs due to the tanning of the new cuticle.
Stages between molts become longer as the animal grows older. Thus, there are numerous molts when the animal is young and as they age, they become fewer and farther between. Most insects have a finite number of molts they will go through. The marine arthropods seem to molt throughout their lives, though some species of crabs cease molting once they reach sexual maturity.
Molting is under hormonal control. Ecdyisone is secreted by certain endocrine glands, circulated through the blood stream, and acts directly on the epidermal cells. There are hormones that, if secreted, will inhibit the molting process. These are usually released if the animal senses trouble and that is not a good time.
During the period when the old shell is being digested many of the salts and minerals are absorbed by the tissue of the animal. Some people can eat crab but have allergic reactions when consuming soft shell crabs – most likely due to the increased salts and minerals in the tissue at this time. During step 3, many crustaceans will seek shelter and will remain there for a period of time after molting allowing the new shell to harden. The regeneration of lost limbs occurs during the molting process as well.
Molts of many species are hard to find because the “soft-shelled” animal can consume the molt to increase needed salts and minerals – or other marine animals may do so for the same reason. But horseshoe crab molts are pretty common and cool to collect. Another common molt found is that of the cicadids in the pine forest areas of our panhandle. The entire process is pretty amazing.
Reference
Barnes, R.D. 1980. Invertebrate Zoology. Saunders College Publishing. Philadelphia PA. pp. 1089.
“I can’t do what? – because of a mouse? – it’s only a mouse.”
This was a comment made by many who lived on Perdido Key when a small beach mouse found only there was added to the endangered species list. It is a comment heard often when many species are listed. A major reason most species begin to decline and become endangered is loss of habitat. We enter and change the habitat to suit our needs. Much of this includes construction of buildings and altering landscapes to a more artificial setting and much of the local wildlife is lost. So is the case with this little mouse.
The Choctawhatchee Beach Mouse is one of four Florida Panhandle Species classified as endangered or threatened. Beach mice provide important ecological roles promoting the health of our coastal dunes and beaches. Photo provided by Jeff Tabbert
The Perdido Key beach mouse (Peromyscus polionotus trissyllepsis) is one of seven subspecies of beach mice found in Florida, five of those found in the Florida panhandle. Beach mice are a subspecies of the Old-Field mouse (Peromyscus polionotus). They are small, about 5 inches long, with tails that have hair (which are an additional 2 inches). Beach mice typically have a brown/gray color on top and a lighter white underbelly allowing them to blend into their environment very well. The difference between the subspecies is the extent of the coloration.
The subspecies status, and genetic isolation, is part of the reason these mice are listed. Members of a population who are genetically isolated from others can undergo a process called speciation where the genetic changes that occur in one isolated group cannot/do not flow through the gene pool of the other isolated group. Over time, the genetics, and morphology, of one isolated group becomes different enough that a new subspecies, or even species, develops. This is the case with the Perdido Key beach mouse. It is isolated on Perdido Key, a barrier island, and does not interbreed with their closest neighbors – the Alabama beach mouse (P.p. ammobates) and the Santa Rosa beach mouse (P.p. leucocephalus). Because of this, ALL of the Perdido Key beach mice in the world live on Perdido Key. Their population is small and vulnerable.
These mice are dune dwellers living in small burrows. They prefer the primary dunes (closest to the Gulf) which are dominated by the grasses whose seeds they like to feed on. They forage at night (nocturnal) feeding on the seeds of the sea oat (Uniola paniculate), panic grass (Panicum amarum), and blue stem (Schizachrium maritimum) usually in the secondary dunes. Highly vegetated swales (low wet areas between the primary and secondary dunes) are used to move between these habitats, and they are also found in the tertiary dunes (on the backside of the island where trees can be found) where their burrows are more protected from storm surge during hurricanes. During periods when seeds are not available, beach mice will turn to small invertebrates to support their diet. Their foraging range averages around 50,000 ft2.
Breeding takes place in the winter, though can occur anytime of year if enough food is available. They are monogamous (males pairing with only one female for life) with the females giving birth after 23 days to four pups. New members of the family can move up to half a mile in search of a foraging range for themselves. It is understood that with limited available habitat on an isolated island, the carry capacity of the beach mouse would be low. Owls and snakes are some of the predators they face, but the beach mice have evolved to deal with few predator issues.
The increase of humans onto the barrier islands has negatively impacted them. The leveling of dunes for houses, condos, swimming pools, and shopping centers has significantly reduced suitable habitat for them as well as reduced the seed food source. Introduced feral and free roaming domestic cats have also been a large problem. Bridges connecting these islands to the mainland have allowed foxes and coyotes to reach, and increase pressure on, them. With these increased pressures, and small populations, these mice are now listed under the Endangered Species Act.
Conservation measures have included, predator control, building and landscaping restrictions, translocation (moving mice from large populations to those that are smaller), and reintroduction (releasing mice into areas where they once existed but no longer do). There has been success with the Choctawhatchee beach mouse in the Grayton Beach area, as well as the Perdido Key beach mouse in Gulf Islands National Seashore. Things that beach residents can do to help beach mice populations include keeping your pets inside at night, plant native grasses in your landscape, reduce night lighting, do not walk over dunes – use the cross walks.
Things seem to be improving for beach mice, but the development pressure is still there. Hopefully we will have these creatures as part of our panhandle barrier island communities for many years to come.
References
Beach Mouse Fun Facts. Gulf Islands National Seashore. U.S. Department of Interior.
