by Rick O'Connor | Apr 21, 2022
It is now spring, and wildlife is beginning to stir more. However, on this April day another cold front had just past the area and the morning temperature was 59°F. To add to this, there was a strong west wind that made it feel colder. Despite the fact it was an early spring morning in Florida, I had my fleece on and was dubious that I would see any reptiles.
This month’s hike was out at Big Sabine near Park East. The Gulf of Mexico was churning like a washing machine due to the passing front and the beach had a sharp scarp to it. There were a few plovers out trying to probe the sand for food, but not much else. Usually after hard winds you will find an assortment of things washed up on the beach but there was little really, possibly removed by the storm. There were however signs of digging by humans. It is now sea turtle nesting season, and we remind folks that these large holes can be a real problem for the mothers trying to nest. Please fill them in before you leave the beach.
Diopatra are segmented worms similar to earthworms who build tubes to live in. These tubes are often found washed up on the beach.
Large holes like this can be problematic for many island wildlife species – like nesting sea turtles. Please fill them in when you leave for the day.
“Blow outs” are formed by people walking over the dunes. They will increase the erosion of these dunes and enhance flooding during storms. Please cross over on boardwalks.
The Gulf of Mexico was churned up due to the passing cold front.
Beach scarps are formed during heavy surf changing the dynamics of the beach for creatures living there.
“Sea Beans” are seeds of tropical plants that wash ashore this time of year. Most do not germinate and those that do are usually on a high energy beach and do not survive.
As you head north into the dune fields the wind typically slows, but this morning it was blowing plenty hard, and I was getting “sand blasted” at some points. Not the best day to find wildlife. The sun was out and I decided to check the leeward side of shrubs and bushes, but had no luck.
One thing I did find was the sandhill milkweed in bloom. This plant is host to the monarch butterfly caterpillars and produces a mildly toxic “milk” which the caterpillars accumulate making them toxic to birds. This toxin is carried on to the adult butterfly stage and many birds learn to avoid butterflies with the monarch coloration because of the bad taste. Though I saw lots of milkweed, it was too windy for the butterflies.
The blooms of the false rosemary, which appear in late winter, had all fallen but it was obvious that the pine trees had release their pollen. Most of the scrubby pines in the dunes had new growth on them.
There were several ephemeral ponds scattered amongst the dunes. All had water in them from the recent rains and I was hoping to maybe find a basking snake or singing frog. No luck on either. There were damp areas where water had recently been, and the carnivorous sundews and spore producing club moss, known as ground pines, were doing very well.
The path used by wildlife to reach the ponds of the dune field.
Two invasive Chinese tallow trees were found growing in the dune field. These will be removed.
Devil’s Joint is a common cactus in the dunes. Wear shoes when exploring!
The high winds of the beach can form some interesting dunes. This one resembles the mesa’s of the American southwest.
There are numerous freshwater ponds in the low areas of the dune field. Many of them are ephemeral.
Freshwater ephemeral pond.
Ground pine is a type of club moss found in the wet-damp areas of the dunes.
The sandhill milkweed is bloom this time of year.
Pine scrub areas like this are found in the dune fields and are great places to find snakes and lizards.
Since some of our snakes are venomous, it is recommended you wear good boots and have a hiking stick to move logs and high grass before stepping in or over.
Seaside rosemary produces a wonderful smell that reminds many of the beach.
As I moved from the dunes into the maritime forest, I was expecting to see birds. I did, but not many. Most were small woodland birds I could not identify, and there was an osprey flying over briefly, but for the most part the bird action was slow today – again, probably due to the high winds. I was again hoping to maybe find a basking snake on the sunny leeward side of a bush or fallen tree but had none. I did find a common parasitic plant that was becoming more common this time of year. It is called “love-vine” or dodder. This yellow-colored string looking vine lacks chlorophyll and wraps around host plants to remove much needed nutrients. It begins to appear this time of year and is not restricted to the beaches. I have seen it 10 miles inland.
One thing that was very evident in the maritime forest was sign of armadillos. Their tracks and digs were found everywhere. I did locate a few burrows and found even more along the beach of the Sound. These animals are very abundant on this island I am curious as to what predators they have and how their populations are controlled. They can be found day or night and dig frequently looking for grubs and other invertebrates to eat. Whether they seek out turtle or bird eggs I do not know. More on this guy next month.
I will add that I did see tracks of raccoons who do eat turtle eggs and also what I think was a “slide” of an otter. The number of otter encounters has increased in recent years. Individuals have been seen not only on the beach but around Bayou Texar and Project Greenshores. These are very elusive animals and produce a high pitched “chirp” or “bark” when approached. I have seen them near Ft. Pickens on a couple of occasions in the ponds. There are the old hatchery ponds at Big Sabine, and it was there that I found the “slide”. These slides are used by the otters to slide into the water. I have seen video of them exiting the water, sliding back in, only to repeat this as if they were playing like kids – and I think that is what they are doing… playing. Otters are the largest members of the weasel family, mustelids, and pretty cool.
Many creatures use the same trails we do. This is a good place to look for tracks.
Armadillos are all over the island. This is a burrow of one.
The digging of armadillos can be found everywhere as well.
Dodder (or “love vine”) is a parasitic plant that begins to appear this time of year.
This is what I think to be an otter slide. Though I could not find tracks to confirm, I have seen them build and use these before.
Raccoons are common all over the island.
The marsh of Big Sabine was pretty quiet on this windy day. I did see two Canadian geese walking along the shore. I recently saw several nesting on an island in Okaloosa County and was told they were now year-round residents. I am not sure whether these were residents to Big Sabine or not, I had not seen them before, but will note this as this series continues this year.
Canadian geese are becoming residents on some islands along the panhandle.
Wood piles like these can be good habitat for some beach wildlife.
The beach of Santa Rosa Sound was quiet as well. Again, I probed around to seeking a basking snake, a nesting terrapin, or maybe a nesting horseshoe crab (it was a spring tide day) but found nothing. There are piles of wood gathered by locals cleaning the beach and these actually make good habitat for some wildlife. I poked around in them but did not find anyone today. This was also where I found most of the armadillo burrows. Why they preferred this over the forested areas I am not sure. There may be many more in the forest that I just did not see. The spring tide was rising and much of the beach was exposed but I saw no fiddler crabs or other creatures and there was nothing swimming nearshore in the grass beds. Again, the lower temperatures and high winds I am sure had everyone in a warmer calmer place.
Despite little wildlife today it was a great walk and despite the high winds, the weather was actually nice. It is spring and nesting should be going on across the island. We will visit Ft. Pickens in May and see what is going on then.
Santa Rosa Sound.
by Rick O'Connor | Mar 24, 2022
When exploring local coastal environments, the salt marsh is one not frequently visited by residents. When first seen, the large field of grass appears inviting. But when you reach it appears impenetrable, full of bugs and snakes, and there must be an easier way around.
The Salt Marsh – the land of the wet and Muddy
Photo: Molly O’Connor
There are three ways to access a salt marsh. One, to just begin walking into the field of grass, pushing your way through like a boat on the ocean. Second, using a trail cut but someone else, that meanders its way to the high ground or open water. And third, from the open water following a creek. This can be done on foot or by a paddle craft.
Entering the salt marsh can be tricky.
Photo: Rick O’Connor
If entering by foot into the field of grass, the explorer is first met with a tall grass with a pointed end – black needlerush. This rather stiff, thin, cylinder-shaped grass has a good name, the pointed end is sharp and hurts as you begin to move it out of the way with your forearms. When in college I was told “you might want to wear jeans”. I did not see wearing jeans in the summer heat as a good idea so, chose not to, but understood quickly why they recommended it. Honestly, I am not sure it would have helped anyway. Needlerush pokes your arms, legs, and care must be taken and avoid bending over to pick something up, else you will get a poke in the face or eye.
Black Needlerush is one of the two dominant plants of our salt marshes. Photo: Rick O’Connor
After quickly meeting black needlerush you meet the mud. They do not call it the land of the wet and muddy for nothing. They mud is like pudding and some sections feel like there is no solid ground. This mud is a slate gray color, smells like rotten eggs, and you can sink into it up to your knees in places. Shoe selection in a place like this is important. Many an explorer has placed their shoe covered foot into the mud only to bring up a shoeless foot the next step. Shoes that can tied or synched to the foot are best. They need a good thick bottom to protect the foot from shells, like oysters. I will tell you “crocs” are not what you want.
The sediment in a marsh is not always as solid as it looks.
Photo: Rick O’Connor
The rotten egg smell is the gas hydrogen sulfide, produced by bacteria breaking down organic material trapped within the marsh. And much becomes trapped here. By definition a marsh is a wetland that is dominated by grasses rather than trees. Being a wetland, it is low in elevation and holds water either from rainwater run-off or from the incoming tide. As the water recedes, leaf litter, animal carcasses, and other debris become trapped in the marsh. In fact, the ability of the marsh to hold this decaying layer of mud plays an important role in keeping the open water clear.
As you labor your way across the marsh, pulling each footstep through the mud while moving the sharp grass, you may see signs of life. Most animals have trouble walking through the grass and mud as well and choose another route. But the density and biomass of the open marsh is impressive. Trying to count the blades of grass would be like trying to count the stars in the sky. It is a very biologically productive place. One creature you may encounter is the bird known as the clapper rail. This brownish bird blends in well in the sea of grass and often builds their nest here. When you come upon them, they will let out a loud squawking sound that will honestly terrify you at first. Sometimes they fly, sometimes they move to a new location, sometimes they hold their position and continue to try and scare you away.
The marsh periwinkle is one of the more common mollusk found in our salt marsh. Photo: Rick O’Connor
Another common creature seen is the marsh periwinkle. This small white snail is often seen on the blades of needlerush. As the tides rises, so does the periwinkle, crawling up the grass to avoid predators like the blue crab and diamondback terrapin. At low tide they are on the surface of the organic mud feeding on bits of decaying material. Again, caution if you are going to bend over to look for them. You may get a needlerush in the eye!
There are times as you are crossing you will come to an open area with little or no grass. These are known as salt pans and are areas with lower elevation that the surrounding marsh. Saltwater lies here during high tide and low. As the pool of water evaporates the salinity of the remaining water increases and becomes too salty for most plants to grow. It becomes a “dead zone” within the marsh. There are a few salt tolerant plants that do grow here. You may see the tracks of other creatures exploring, like raccoons, but otherwise it is a break for you from the constant shoving of needlerush and you step in there.
Occasionally you will cross the opposite in elevation. A high ridge of quartz sand where small shrubs like salt bush or even a small oak can be found. These little oasis’s can be places where other travelers of the marsh will rest. Fiddler crabs, cactus, and maybe even a basking snake could be found here.
A finger of a salt marsh on Santa Rosa Island. The water here is saline, particularly during high tide. Photo: Rick O’Connor
There are times when you will cross a creek. These creeks meander their way through the marsh and to the open water. Many travelers, for obvious reasons, choose to follow these routes. Some creeks are shallow and full of mud where you may sink above your knee. Others are a bit deeper and have more solid bottoms of sand. Walking through the water can give some relief from the needlerush. Here you will see several species of fish. Most are killifish or mullet, but as you get closer to the open water you might find redfish or flounder. It is much easier to see the periwinkles here. You will also notice the ribbed mussels anchored near the base of the needlerush. There are oyster clumps scattered here and there and huge colonies of fiddler crabs. The creeks are good hunting grounds for the stilted legged birds such as the great blue heron and American egret. Clapper rails often nest along the creek edges and there is a lot of sign of raccoons and sometimes otters.
The “snorkel” is called a siphon and is used by the snail to draw water into the mantle cavity. Here it can extract oxygen and detect the scent of prey.
Photo: Franklin County Extension
The crown conch is a frequent visitor to the creeks. This predatory snail moves slowly across the sand and mud seeking other mollusks to feed on. Often you will find their shells not inhabited by them but rather the striped hermit crab, a scavenger in this world.
The nonvenomous Gulf Salt marsh Snake.
Photo: Molly O’Connor
Many fear the marsh due to its reptile community. Over the years of leading hikes here I have heard “are there any snakes here?”. There is only one resident of the salt marsh – the Gulf salt marsh snake. This is a nonvenomous member of the watersnake group known as Neroidia and are more nocturnal in habit. That said, the venomous cottonmouth has been seen here. They are most often seen on one of the high sandy banks, coiled and waiting for potential prey to swim by.
Alligator
Photo: Molly O’Connor
Alligators will venture into salt marshes, but I have only seen few in my years of exploring them in the Pensacola area. They tend to be afraid of people and want to avoid us. Once I saw one in a sandy area before I entered the marsh. It was pointing left with one foot off the ground and not moving – it was frozen in space. I had learned that animals tend to go through what I call the “3 Fs” when they detect a predator. Freeze – Flight – Fight. This one was at F1 – freeze. It thought I was a predator and just as well. If I tried to approach it, theoretically it would have moved to F2 – flight, and would have made a hasty escape. But I chose not to test that.
Mississippi Diamondback Terrapin (photo: Molly O’Connor)
There is a resident turtle here known as the diamondback terrapin. However, it is very elusive and difficult to find. It is the only resident brackish water turtle in North America. Though I have seen terrapins in the water, and more rarely on the beach, I do find evidence of their presence by tracks on the beach and nests that have been predated by raccoons. I did once see one basking on a log.
Smooth cordgrass
Photo: FDEP
If you follow the creek, you will eventually reach open water. Here the marsh converts from a sea of black needlerush to a zone of shorter, greener, more flexible smooth cordgrass. The cordgrass is home to many of the creatures we have mentioned. Killifish, crabs, and snails are abundant. The silt birds frequently this zone hunting for their prey, and you might find additional clams and snails. You might find more open water species as well, like gulls, sand pipers and plovers, and maybe a horseshoe crab.
Though the road is tough, the experience is unique and worth the trip. Many prefer to enter the marsh using a known trail or a paddle craft in the creek. There is a lot less needlerush to poke and mud to sink in doing it this way. However you visit, it is an amazing place. The land of the wet and muddy.
by Rick O'Connor | Mar 18, 2022
When you look over the species of sea basses and groupers from the Gulf of Mexico it is a very confusing group. Hoese and Moore1 mention the connections to other families and how several species have gone through multiple taxonomic name changes over the years – its just a confusing group.
Gag grouper.
Photo: National Oceanic and Atmospheric Administration
But when you say “grouper” everyone knows what you are talking about, and everyone wants a grouper sandwich. This became a problem because what people were serving as “grouper” may not have been “grouper”. And as we just mentioned what is a grouper anyway? The families and genera have changed frequently. Well, this will probably get more technical than we want, but to sort it out – at least using the method Hoese and Moore did in 1977 – we will have to get a bit technical.
“Groupers” are in the family Serranidae. This family includes 34 species of “sea bass” type fish. Serranids differ from snappers in that they lack teeth on the vomer (roof of their mouths) and they differ from “temperate basses” (Family Percichthyidae) in that their dorsal fin is continuous, not separated into two fins. These are two fish that groupers have been confused with.
Banked Sea Bass.
Photo: National Oceanic and Atmospheric Administration.
We can subdivide the serranids into two additional groups. The “sea basses” have fewer than 10 spines in their dorsal fin. There are 10 genera and 18 species of them. They have common names like “bass”, “flags”, “barbiers”, “hamlets”, “perch”, and “tattlers”. They are small and range in size from 2 – 18 inches in length. Most are bottom reef fish with little commercial value for fishermen. Most are restricted to the tropical parts of the Atlantic basin but two are only found in the northwestern Gulf, one is only found in the eastern Gulf, and one has been found in both the Atlantic and Pacific. The biogeography of this group is very interesting. The same species found in both the Atlantic and Pacific suggest an ancient origin. The variety of serranid sea bass suggest a lot of isolation between groups and a lot of speciation.
The ”groupers” have 10 or more spines in their dorsal fin. There are two genera in this group. Those in the genus Epinephelus have 8-10 spines in their anal fin and have some canine teeth. Those in the genus Mycteroperca have 10-12 spines in their anal fin and lack canine teeth. Within these two genera there are 15 species of grouper, though the common names of “hind”, “gag”, “scamp” are also used. Most of these are found along the eastern United States and Gulf of Mexico. Five species are only found in the tropical parts of the south Atlantic region, five are also found across the Atlantic along the coast of Africa and Europe, and – like the “sea bass” two have been found in both the Atlantic and the Pacific. They range in size from six inches to seven feet in length. The Goliath Grouper can obtain weights of 700 pounds! Like the sea bass, groupers prefer structure and can live a great depths. Unlike sea bass they are heavily sought by commercial and recreational anglers and are one of the more economically important groups of fish in the Gulf of Mexico.
The massive size of a goliath grouper. Photo: Bryan Fluech Florida Sea Grant
One interesting note on this family of fish is that most are hermaphroditic. The means they have both ovaries (to produce eggs) and testes (to produce sperm). Sequential hermaphrodism is when a species is born one sex but becomes the other later in life. This is the case with most groupers, who are born female and become male later in life. However, the belted sand bass (Serranus subligarius) is a true hermaphrodite being able to produce sperm and egg at the same time – even being able to self-fertilize.
For many along the Florida panhandle, their biogeographic distribution and sex do not matter. It is a great tasting fish and very popular with anglers. For those with a little more interest in natural history of fish in our area, the biology and diversity of this group is one of the more interesting ones.
Reference
1 Hoese, H.D., Moore, R.H. 1977. Fishes of the Gulf of Mexico; Texas, Louisiana, and Adjacent Waters. Texas A&M Press. College Station TX. Pp. 327.
by Rick O'Connor | Mar 11, 2022
The month of March is the last of winter. For todays hike we returned to Gulf Islands National Seashore/Ft. Pickens where it was 63°F, overcast with a strong breeze from the northwest. A cold front is coming through to remind us that winter is not over yet. It was not 44°F as it was on our February hike but with the wind and cloud cover, it was a bit cool and not ideal for most wildlife to be out. But the ospreys were…
Osprey perched.
Photo: Rick O’Connor
An osprey pair building a nest on the chimney of the ranger station at Ft. Pickens.
Photo: Rick O’Connor
Another osprey pair with a nest in a large pine.
Photo: Rick O’Connor
They were everywhere. Building nests in live pines, dead snags, platforms built just for this, and on the chimney of the ranger station. Their sounds were everywhere – it is breeding season for them. The great blue herons were still nesting, we saw them first in January, but there are still a few around. American egrets were out as were numerous mourning doves. As with the colder February day, it was primarily bird action right now. I did see evidence of armadillos, and would guess other mammals were on the move, but did not see evidence of any others. The reptiles and amphibians are still missing – but should not be for long.
The herons began nesting in January. Some are still there.
Evidence of armadillos digging.
The plant I know as beach heather, many call false rosemary, and has the scientific name Conradina, was in full bloom. After the hollies of the Christmas season, these are the plants I often see bloom first. Though I have seen bees around my home already, and wasps, I did not see/hear any insect movement this morning.
Beach heather (false rosemary) is one of the first plants to bloom on our islands.
The north beach (Pensacola Bay) was rough due to the northwest wind. It was difficult to see if anything was moving around in the shallows. There were a lot of shells on the shore. Two particularly caught my eye. The Florida Fighting Conch was pretty abundant, more than normal – and there were several scallops shells. There are two species locally, the calico scallop (often found in the Gulf) and the bay scallop (the estuarine version and the one of “scalloping” fame). Calcio scallops are often pinkish in color and often with spots. The bay scallop is usually gray in color. Those I saw this morning were all bleached white but, based on other variety of shells in the mix, I am thinking these were calcio scallops.
There were several Florida Fighting Conch shells on the beach this month.
There was very little marine debris today and no tracks of any kind seen. There was only one lone pelican spotted, maybe due to the high winds they settled somewhere else. Maybe they have moved off to smaller islands for breeding themselves, I am not sure.
We only saw this one lone pelican today.
Though the wildlife has been more restricted to birds at the moment, the birding is excellent right now and the beach has relatively few people – it is a great time to take a hike out there.
This large tanker awaits its turn to enter Pensacola Bay.
This skull found along the side of the side of the road is believed to be a raccoon.
Lichen is an organism that is a partnership between algae and fungus. They were a brilliant white-green this month.
Razor clam shells are quite common along the shoreline.
Sand dollars are not as common on the bay side of the island but there were several today.
The remains of a ghost crab.
Believe it or not, walking along the road is a great spot to find wildlife.
by Rick O'Connor | Feb 10, 2022
It is now mid-winter and much colder than our trip in January. During February’s hike the temperature was 44°F, compared to 62°F in January. It was overcast with a cold breeze from the northeast – again, colder. When conditions are like this I am not expecting to see much. If I did find something I would expect it to be one of our warm blood friends, mammals or birds, and even they would prefer a day with more sun and less breeze. But I came to see what was out roaming. So, a hike I made.
The Gulf front at Park East near Big Sabine.
This month I hiked the Big Sabine area east of Pensacola Beach. It began with a shore walk along the Gulf and then a transect across the different dune fields to the marshes and seagrasses along the Santa Rosa Sound.
There was no one out today. You could see footprints in the sand, and it had that characteristic “squeak” sound of fresh sand or snow. The only wildlife I saw on the Gulf side was a group of pelicans sitting on very calm water, obviously enjoying the morning. However, you could see footprints of mammals that had come earlier. There are raccoons, armadillos, mice, coyotes, and occasional reports of otters on Santa Rosa Island. There were a lot of skunks on the island prior to Hurricane Ivan (2004), but I have not seen any since. There have been reports of bears on the island as well. I have never seen one, nor their tracks, so do not think they are frequent visitors. I did find a dead shark tossed up on the beach by a fisherman. Not sure if they were trying to catch it or not.
A variety of mammals are found on barrier islands. Most move at night and you know they are there only by their tracks.
This small shark was found on the beach during the hike. I am not sure why they did not return it to the Gulf.
As I began my transect across the island I ventured into the secondary dune field, which during summer is extremely hot. This part of the island reminds me somewhat of a desert. Very dry, open, and at times very hot. Like the desert it comes alive more at night, but during winter you might see animal movement during the warm parts of the day. I did see mammalian tracks, which included humans and dogs.
This dune field also holds ephemeral ponds which can harbor a variety of life during the warmer months. Today I only found one blooming yellow-bladder wort as well as other carnivorous plants along the bank such as sundews and ground pines.
Yellow bladder wort is one of the small carnivorous plants that live on our barrier islands.
Sundews are another one of the small carnivorous plants found here.
From the open dune field, you venture into the tertiary dunes and the maritime forest. Trees grow here but their growth is stunted due to the salt content in the air. None the less, pine and oak hammocks liter this dune area providing great hiding places for wildlife. Though we did not see any today, I am expecting to find some as the weather warms.
The backside of the island is where you will find the salt marsh. This brackish wetland harbors its own community of creatures, which were not visible today but will be in the spring. Between the tertiary dunes and the marsh runs a section of the Florida Trail. Hikers can walk this section and observe wildlife from both ecosystems.
The larger dunes of the tertiary dune field.
Tree hammocks are common in the tertiary dune fields and provide good places for wildlife.
I eventually reached the Sound and the seagrass beds that exist there. Today, here was nothing really moving around, though I did find a dead jellyfish drifting in the waves. As the island wildlife tends to hideout the winter in burrows, the fish move to deeper water where it is warmer.
The backside of these large dunes drop quickly back to sea level.
Many plants in the tertiary dunes exhibit “wind sculpting”. It appears someone has taken a brush and “brushed” the tree towards the Sound.
Scat is another sign used to identify mammal activity in the dunes.
Portions of the Florida Trail cut through the tertiary dune field of Big Sabine.
The salt marsh
This holding pond is a remnant of an old fish hatchery from the late 1950s and is primarily freshwater.
Seagrass meadows can be found in Santa Rosa Sound and harbor a variety of marine life.
Jellyfish are common on both sides of the island. This one has washed ashore on Santa Rosa Sound.
There was little out today other than a few birds. We will see what late winter will expose next month.
by Rick O'Connor | Jan 27, 2022
Members of the family Poeciliidae are what many call “livebearers”. Live bearing meaning they do lay eggs as most fish do, but rather give birth to live young. But this is not to be confused with live-bearing you find in mammals – which is different.
Most fish lay eggs. The females and males typically have a courtship ritual that ends with the female’s eggs (roe) being laid on some substrate, or released into the water column, and the male’s sperm (milt) are released over them. Once fertilized the gelatinous covered eggs begin to develop.
Everything the developing young need to survive is provide within the egg. The embryo is suspended in a semi-gelatinous fluid called the amnion. Oxygen and carbon dioxide gas exchange occurs through this amnion and through the gelatinous covering of the egg itself. Food is provided in the form of yolk, which is found in a sac attached to the embryo. There is a second sac, the allantois, where waste is deposited. When the yolk is low and the allantois full – it is time to hatch. This usually occurs in just a few days and often the baby fish (fry) are born with the yolk sac still attached. Parental care is rare, they are usually on their own.
With “livebearers” in the family Poecillidae it is different.
The males have a modified anal fin called a gonopodium. They fertilize the roe not externally but rather internally – more like mammals. The fertilized eggs develop the same as those of other fish. There is a yolk sac and allantois, and the embryo is covered in amnion within the gelatinous egg covering. But these eggs are held WITHIN the female, not laid on the substrate or released into the water column. When they hatch the live fry swim from the mother into the bright new world – hence the term “livebearer”.
There are advantages to this method. The eggs are protected inside the mother, and she obviously provides parental care to her offspring. However, this does make her much slower and an easier target for predators. There is some give and take.
This differs from the “live-bearing” of most mammals in that there is still an egg. Mammals do still have a yolk sac but feeding and removing waste is done THROUGH THE MOTHER. Meaning the embryo is attached to the mother via an umbilical cord where the mother provides food and removes waste trough her placenta. There is no classic egg in this case. I say most mammals because there are two who live in Australia that still do lay eggs – the platypus and the spiny anteater, and the marsupials (kangaroos and opossums) are a little different as well – but marsupials do no lay eggs.
Biologists have terms for these. Oviparous are vertebrates that lay eggs – such as fish, frogs, turtles, and birds. Ovoviviparous are vertebrates that produce eggs but keep them within the mother where they hatch – such as some sharks, some snakes, and the live bearing fish we are talking about here. Then there are the viviparous vertebrates that do not have an egg but rather the embryo is attached, and fed by, the mother herself – like most mammals.
Sailfin Molly. The male is the fish above with the large “sailfin”. Note the gonopodium on his ventral side.
Photo: University of Florida
The livebearers of the family Poeciliidae are ovoviviparous. They are primarily small freshwater fish that are very popular in the aquarium trade. But there are two species that can tolerate saltwater and enter the estuaries of the northern Gulf of Mexico: the sailfin molly and the mosquitofish.
The Sailfin Molly (Poecilia latipinna) is the same fish sold in aquarium stores as the black molly. The black phase is quite common in freshwater habitats, but in the estuarine marshes the fish is more of a gray color with lateral stripes that is made up of a series of dots. They are short-stout bodied fish and the males possess the large sail-like dorsal fin from which the species gets its common name. The females resemble the males albeit no large sailfin and most found are usually round and full of developing eggs. They are very common in local salt marshes and often found in isolated pools within these habitats. The biogeographic range of this species is restricted to the southern United States, reported from South Carolina throughout the Gulf of Mexico. One would guess temperature may be a barrier to their dispersal further north along the Atlantic seaboard.
The mosquitofish.
Photo: University of Florida
The Mosquitofish (Gambusia affinis) is familiar to many people whether they know it or not. Those who know the fish know they are famous for the habit of consuming mosquito larva and some, including our county mosquito control unit, use them to control these unwanted flying insects. For those who may they are not familiar with it, this is the fish frequently seen in roadside ditches, ephemeral ponds that show up after rainstorms, retention ponds, and other scattered bodies of freshwater within the community. Most who see them call them “minnows”. There is always the question as to “where did they come from?” You have a vacant lot – it rains one day – these small fish show up – where did they come from? The same can be said for community retention ponds. The county comes in a digs a hole – it rains one day, and the retention pond fills – and there are fish in it. One explanation to their source is the movement of fish by wading birds, where the fish incidentally become attached to their feet. Again, they are often released intentionally to help control local mosquito populations. This fish is found in our coastal estuaries but does not seem to like saltwater as well as the sailfin molly. It is found in cooler water ranging throughout the Gulf and as far north as New Jersey.
Both of these fish make excellent aquarium pets, and the sailfin molly in particular can be beautiful to watch.
Reference
Hoese, H.D., Moore, R.H. 1977. Fishes of the Gulf of Mexico; Texas, Louisiana, and Adjacent Waters. Texas A&M Press, College Station TX. Pp. 327.
