March 22, 2015
During the night's early hours along Río Lagartos's Malecón -- the broad, estuary-side avenue on the town's western, northern and eastern shores -- usually atop the knee-high, stone storm-wall you find local folks with flashlights and long-handled dip-nets seining the waters at the wall's base. After being dragged through the water a few feet normally when the net is pulled up it contains a few shrimp jumping around trying to escape. The shrimp are dumped into a plastic bucket on the sidewalk. Half an hour of seining might catch enough for a family to eat all the shrimp they want for a day or two. Here a kind of shrimp soup is popular, and a dish called ceviche.
One night my friends Rayo and Jorge also got a flashlight and long-handled dip-net, and went seining from atop the Malecón's storm wall. They seined for just a few minutes, though, for all they wanted were a few shrimp for the aquarium they were setting up. You can see one of the pale, well camouflaged shrimp they caught, whose body was about 1¾ inches long (45mm), exploring the aquarium's sandy floor at http://www.backyardnature.net/n/15/150322sh.jpg.
Such shrimp usually are referred to as camarónes rosados, or pink shrimp, even though ours from along the Malecón's storm wall weren't very pink. Three pink shrimp species are listed for Ría Lagartos Biosphere Reserve, so which was this? It was harder to figure that out than I'd expected, one main reason being that our red shrimp were juveniles. It's a feature of red shrimp natural history that immature ones gather in estuaries such as ours, where they feed relatively safely among seagrass stems and leaves in shallow water. As pink shrimp grow, they look for more and more saline areas, eventually leaving their nursery-estuaries and returning to begin lives in the sea.
Of the three red shrimp species occurring in Ría Lagartos Estuary, Penaeus notialis is mainly found on the Yucatán's eastern, Caribbean Coast, so we're a little beyond their main distribution are, and that species is less common here. Another species, Penaeus brasiliensis, is common in the area, but tends to be much redder than our aquarium individual. The third species, PENAEUS DUORARUM, seems to be what we have, a species whose center of distribution is the Gulf of Mexico, though it's found from Maryland on the eastern US coast south to the Yucatan Peninsula. Sometimes all three of these species are placed in the genus Farfantepenaeus, and sometimes Penaeus duorarum is called the Northern Pink Shrimp.
Females of Northern Pink Shrimp can reach 11 inches long (28cm) in length, so our 1¾-inch one (4.5cm) is small. The preferred habitat of adults who have left their nursery estuaries is between ±35-120 feet deep (11-36m), where they live on firm mud and silt with sand and shells.
Though local fishermen assure me that the estuary is full of pink shrimp, on flamingo-viewing trips you seldom see them, for they stay well hidden in seagrass on the estuary's floor. However, this week I did find one along shore in water hardly a finger-width's deep, in a tangle of Widgeongrass at very low tide. The shrimp was so lethargic and its eyes were so clouded eyes that it seemed to be almost dead for some reason, but I still took its picture, shown at http://www.backyardnature.net/n/15/150322sk.jpg.
The pale bands of pink stipples around its abdomen are typical of the species. I read that when Northern Pink Shrimp are cooked, their shells turn a deeper shade of pink than other species, and their meat turns from translucent to pink. A close-up of this individual's head is at http://www.backyardnature.net/n/15/150322si.jpg.
The serrated crest atop the head extending beyond the eyes is known as the "rostrum" and is typical of pink shrimp species. As individuals grow, the rostrum becomes more impressive. Trying for a picture of the creature's bulbous eyes I got what's shown at http://www.backyardnature.net/n/15/150322sj.jpg.
When that picture came onto the computer screen I was amazed because it's clear that the top of the head is split open, with the head cavity being empty. Yet, in my hand the shrimp definitely had moved around, albeit slowly. Then it dawned on me that surely our shrimp was molting -- in the process of abandoning its old exterior skeleton, or "exoskeleton," so could grow into a new exoskeleton that would harden around it. Our shrimp was in the process of withdrawing his head from the front part of the old exoskeleton and probably was about to buckle inside the old covering, rip through the exoskeleton back, and begin a new stage of life as a somewhat larger shrimp.
But, back to the bulging eyes. The reason for their bulging had become apparent the moment we first dropped the Malecón storm-wall ones into the aquarium. Landing on the aquarium's floor, they immediately began furiously thrashing their legs, stirring up currents of swirling sand, and causing their bodies to sink into the cavities below them formed by the whipped-up sand. Within seconds their entire bodies had sunk into the sand, leaving only their bulging eyes poking above the sand's surface. Shrimp eyes bulge so the shrimp can see what's happening around them when their bodies are buried in sand.
According to the United Nation's FAO agency, in 1977 the total world catch of Penaeus duorarum reached a peak with 23,237 tons. Since then the catch has gone into a general decline, presumably because of overfishing and habitat destruction (especially of mangrove-bordered estuaries such as Ría Lagartos). In 2012 the catch was only 4522 tons. The FAO page with this and other information, as well as a distribution map, is at http://www.fao.org/fishery/species/3402/en.
Rayo and I were returning by boat from a wander in mudflats left exposed at low tide when a friend of Rayo's turned up on the canal's banks cleaning fish next to his boat. All night he'd been fishing far offshore in the Gulf of Mexico. Now he was headed home, but needed to clean his catch before settling down. He didn't see any reason to mess up things at his house, so he was cleaning fish at the water's edge, tossing guts and such to dozens of gulls swarming around him. Rayo snooped in his friend's catch box, let out a whoop, and pulled out what's shown at http://www.backyardnature.net/n/15/150322gr.jpg.
A close-up of the head, showing short canine teeth for ripping into prey projecting downwards from the top mandible, and side-by-side rows of short, sharp teeth on the bottom, for holding prey, is at http://www.backyardnature.net/n/15/150322gs.jpg.
I always feel bad seeing critters snatched from the wild ending up like this, but that's the way people here live, and this is when I get to see the fish. At least now I could admire the species'' wonderful adaptations and the esthetic flourishes it was graced with.
Rayo said the fish was a grouper, and that was interesting because in this Newsletter we've already profiled two grouper species from the Gulf's waters here. You might enjoy comparing the present grouper with the others, one of which was the Calico Grouper shown at http://www.backyardnature.net/mexnat/grouper2.htm.
The other was the Red Grouper, shown at http://www.backyardnature.net/mexnat/grouper.htm.
This one's basic structure -- its generally chunky body, its big mouth with massive lower lip, the configuration of its fins and spines -- was similar to the other species, but its coloration and patterning definitely was different.
Groupers are important fish for commerce, so there's plenty of information about them. For example, on the Internet we can freely download the 1994 US-government NOAA publication by Mark Grace and others, in PDF format, entitled Pictorial Guide to the Groupers (Teleostei: Serranidae) of the Western North Atlantic, which treats about 25 grouper species, and is available at http://spo.nwr.noaa.gov/tr118.pdf.
Using that work and others, our big fish with its white-fringed fins and dark splotches on a pale background, and blackish smudge on the rear or caudal fin, turned out to be the Black Grouper, MYCTEROPERCA BONACI. Most Black Grouper photos show them with larger, darker splotches than ours. I think ours has faded a lot during its overnight stay a catch-box.
Black Groupers inhabit rocky zones and coral reefs of the Western Atlantic, from Bermuda and Massachusetts south through the Gulf of Mexico and Caribbean to southern Brazil. Commonly Black Groupers reach about 2.3 feet long (70cm), though they can grow to 5 feet (1.5m), so ours is a fair-sized one, but not close to as big as they can get. Black Groupers are thought of as providing excellent eating, so there's a market for them, largely explaining why the species now is listed on the IUCN Red List as Near Threatened. One feature working against the Black Grouper it is that it reproduces relatively slowly.
Black Groupers are "protogynous hermaphrodites," which means that the young are predominantly female, but transform into males as they grow larger.
Adults feed mainly on other fish and squid, though younger fish feed on crustaceans, especially shrimp.
CHECKERED PUFFER IN ITS HABITAT
Last week we looked at our phlegmatic, poisonous Checkered Puffers. I showed one caught by net and held in the hand, understandably looking a little put-out. This week during a flamingo-viewing trip during a low tide our boat passed through very clear, shallow water where hundreds of Checkered Puffers, seen individually and in small groups of ten or so, were clearly visible. Seeing so many, it was easy to believe that a study of the Reserve's fish found Checkered Puffers contributing 71.5% of the total fish biomass here. A picture showing a puffer hanging at peace on the estuary floor is at http://www.backyardnature.net/n/15/150322pf.jpg.
One morning about a month ago during a very low tide Rayo spotted something interesting in the mud between stranded boats at the dock. That was when we were putting the aquarium together and looking for things to put in it, so he gave his discovery a new home there. At first the organism was just a small, brown, squishy blob, but after it'd settled down it astonished everyone by sprouting slowly waving, worm-like tentacles, as shown at http://www.backyardnature.net/n/15/150322ao.jpg.
Our creature was a sea anemone, so in the picture the low, crater-like structure in the center of the tentacles is both the creature's mouth and anus. Prey such as small fish and shrimp are pulled into the opening by the tentacles, the food is digested in the stomach-like "gastrovascular cavity," and the remains are ejected through the same opening.
A few days later our sea anemone amazed us even more by developing a stout trunk below the tentacles, making the about three inches tall (8cm), shown at http://www.backyardnature.net/n/15/150322an.jpg.
The creature didn't always remain treelike. Sometimes it'd shorten its trunk and pucker its tentacles, as shown in a photo take a few days after the above one , at http://www.backyardnature.net/n/15/150322ap.jpg.
Sea anemones are water-dwelling, predatory animals of the Order Cnidaria, which besides sea anemones incorporates corals, jellyfish, hydras and such. Animals in this order, called cnidarians, are radially symmetrical and their mouths are surrounded by tentacles bearing explosive cells known at "nematocytes," which can shoot out microscopic, poison-dart-like "cnidae." Tentacles coming into contact with prey shoot their cnidae into it, then slowly, weakly but persistently conduct the stunned or killed prey into the mouth.
Over 10,000 Cnidaria species are known, all aquatic and mostly marine, so here along the Yucatan coast cnidarians are worth knowing about.
None of the usual websites helping with identification of organisms of the Gulf of Mexico, Caribbean or Yucatan showed or mentioned a sea anemone like ours. After several weeks of trying to identify it I wondered if we might have a species not yet known to science. In one last effort, however, I contacted Karen Sanamyan in Russia, co-producer of the excellent Actiniaria.com website dedicated just to sea anemones and their kin.
Karen was unfamiliar with our species but in passing he pointed out its similarity to Aiptasia pallida. When I looked up that species, pictures of it on the Internet more closely matched our aquarium species than any others I'd seen. In fact, surely our sea anemone is a member of the genus Aiptasia, which on Wikipedia is described as "... a widely distributed genus of temperate and tropical sea anemones of benthic lifestyle typically found living on mangrove roots and hard substrates." That fits us perfectly, the term "benthic" referring to the ecological region at an ocean's or lake's bottom.
In the genus Aiptasia, which currently embraces 17 species, the most commonly occurring and best known species is Aiptasia pallida, whose pictures look like our animal. Therefore, even though I can't be sure, I'm filing our aquarium occupant under the name AIPTASIA PALLIDA, sometimes known as the Brown Glass Anemone. Aiptasia pallida is distributed along the entire Atlantic coast of the US, south across the Gulf of Mexico and throughout the Caribbean.
Despite Aiptasia pallida not appearing on the usual identification web pages, the species enjoys a certain fame. One reason is that aquarium hobbyists regard the species as a pest, because its powerful nematocytes can kill other aquarium occupants. Also, Aiptasia pallida can reproduce so prodigiously that its offspring take over the aquarium. The species also is famous because it's been chosen by scientists as a study organism in their efforts to understand the problem of coral bleaching. Coral bleaching is when stressful conditions of temperature, light, or nutrients cause corals to expel the symbiotic algae living in their tissues, causing them to turn completely white. Without the algae, the coral eventually dies.
One reason Aiptasia pallida was chosen for the study of coral bleaching is that the creature's brown color is caused by an alga, Symbiodinium microadriaticum, which lives symbiotically within the anemone's tissues the same way algae lives in the tissue of reef-building corals. These microscopic algal cells photosynthesize carbohydrates which the sea anemone uses as food, and in return the sea anemone provides the algal cells with a home.
Aiptasia pallida mostly reproduces asexually by fragmentation, but sometimes it has sex, with individuals being either male and female. During mating season, ova and sperm are released into the water, fertilization takes place there, and the fertilized ova develop into microscopic larvae called planulae. The planulae settle onto many kinds of substrates and develop into new sea anemones.
A SPECTACULAR TRUE TULIP
Last December we admired pretty clusters of frilly-edged egg cases produced by the predatory sea-snail known as the True Tulip, FASCIOLARIA TULIPA. They're "tulips" because their shells' overall shapes supposedly look like closed tulip flowers, and they're "true" because several tulip species exist and someone decided that this is the true one. You can see the egg case at the bottom of the page at http://www.backyardnature.net/yucatan/tulipa.htm.
In Ría Lagartos's shallow, brackish waters True Tulip's egg cases turn up fairly regularly, so I wasn't surprised when a True Tulip itself appeared in the aquarium being put put together at restaurant/ecotour headquarters. What did surprise me was that the 2½-inch long (6.5cm) gastropod was so brilliantly red. You can see the critter moving along the aquarium's sandy bottom at http://www.backyardnature.net/n/15/150322tt.jpg.
Another shot showing him at the water's surface is shown at http://www.backyardnature.net/n/15/150322tu.jpg.
In that picture the tulip's fleshy parts are wrapping around a smaller, dark snail. We may be seeing more than the clumsy passage of a big snail over a smaller one. True Tulips are voracious predators and feed on a variety of clam-like bivalves and gastropods like themselves. The tulip seems to be trying to dislodge the smaller snail from the aquarium wall so it can be eaten.
I read that three species of tulip sea-snails occur in the Gulf of Mexico. Though pictures of tulip-type sea-snails -- species of the genus Fasciolaria -- are easy to find on the Internet, of the hundreds I've looked at not a single shell was as vibrantly and completely red as ours.
However, at the website of the Gulf States Marine Fisheries Commission in a PDF draft document by Perry & Larsen entitled Guide to Shelf Invertebrates, Gulf of Mexico, I read that with regard to the True Tulip, "A beautiful orange-red color variety is not uncommon on the Lower Florida Keys and Yucatan. Giants reach a length of 10 inches."
So, just with photographs I can't determine which tulip species this is, but since so many True Tulip egg cases turn up here, and it's known that a beautiful, orange-red variety turns up in the Yucatan, I'm guessing that our pictures show the orange-red variety of the True Tulip, Fasciolaria tulipa.
True Tulips turn up from North Carolina on the US southeastern coast south through the Gulf of Mexico and Caribbean to the coasts of northern South America and Brazil, and from what I can see on the Internet, our Yucatan ones are the brightest, prettiest of the bunch.
On the Yucatan Peninsula's Caribbean side north of Mahahual we saw many Queen Conchs and often they were fairly large. Our Queen Conch Page with some nice pictures is at http://www.backyardnature.net/yucatan/conch.htm.
At Río Lagartos we also have Queen Conchs, but so far every one I've seen has been young and small -- to small for the local folks to catch and eat. These are beautiful creatures and young ones can have shells that look a little different from big ones, so I'm providing photos of them just for the record. One with a pale, yellow-orange shell is shown at http://www.backyardnature.net/n/15/150322qc.jpg.
When you turn the shell over, however, the familiar brighter hues appear, shown at http://www.backyardnature.net/n/15/150322qd.jpg.
WHITE PELICANS WITH "FINS" ON THEIR BEAKS
During a flamingo trip we dropped by a mudbar barely rising above the estuary's surface most of the time populated by hundreds of terns, gulls, Black Skimmers, pelicans and a variety of little long-legged waders, mostly sandpipers and plovers. This week the White Pelicans surprised us by bearing orangish, fin-like growths atop their beaks. Some birds had them while others didn't. You can see some with them at http://www.backyardnature.net/n/15/150322wp.jpg.
A closer look at http://www.backyardnature.net/n/15/150322wq.jpg.
I'd heard of this phenomenon but never had a good look at it. It's described as a fibrous plate and sometimes is called a nuptial tubercle. Males develop them during the breeding season, but they fall off once the season is over. They're thought to contribute to the mating display. Before disappearing from the beak the tubercles may split vertically, forming irregular groupings of adhering fibers. In places up north where White Pelicans are found toward the end of the breeding season, birds with fraying tubercles sometimes called rough-bills. Such tubercle are peculiar to White Pelicans; our Brown Pelicans don't have them.
Down here, along with the recent outburst of daily singing of Tropical Mockingbirds and Northern Cardinals, these nuptial tubercles are yet another sign of spring rambunctiously dawning, and heading north.
A BANDED YUCATAN WREN
On an inland trip through the thornforest/savanna zone an endemic Yucatan Wren turned up wearing orange leg bands, shown at http://www.backyardnature.net/n/15/150322yw.jpg.
Somebody is clearly studying them here. Diego said folks from Cornell University have been banding in the area.
ORNATE BLUE CRAB
I'm such a landlubber that when I first came to the Yucatan I thought that all crabs lived on sandy beaches. Then one day on a boat ride to Cozumel Island not only was I astonished by flying fish popping from the surrounding water but also by pale, ghostly crabs that sometimes surfaced, paddled furiously alongside us, then sank back below. For a long time I've wanted a close look at one of those aquatic crabs with paddles on their legs, so when some caught in the estuary turned up in the aquarium I was tickled to meet them. You an see one seeming to examine me through the aquarium's glass walls, at http://www.backyardnature.net/n/15/150322cc.jpg.
This view doesn't show paddles but it does afford a good luck at his stalked, greenish eyes and, between the eyes, two pairs of antennae, which constantly quivered and jerked and waved about as the water was being felt, smelled and tasted with an exquisite sensitivity I couldn't imagine. As if sensing my interest in seeing the paddles, the crab suddenly turned around, providing the view at http://www.backyardnature.net/n/15/150322cb.jpg.
The blue, white and orangish paddles reveal themselves as flat segments of the crab's "swimming legs." If you look up crab swimming-legs on the Internet you find that each segment has its own name. The segment attaching to the body is the coxa, and the coxa attaches to the basi-ischium, and then comes the merus, the carpus, the propodus, and finally the dactyl. Even the spines along the sides of the top of the shell, or carapace, have a name -- anterolateral teeth -- and bear official numbers, with the big, white-tipped ones at the bottom being the lateral spines.
This the Ornate Blue Crab, CALLINECTES ORNATUS. It's similar to the Atlantic Blue Crab, Callinectes sapidus, famous among crab eaters along the US eastern coast, but the Ornate Blue is slightly different in terms of tooth arrangement along the carapace sides, and other obscure details. Our Ornate Blue occurs from North Carolina south through the Gulf of Mexico and Caribbean to Rio Grande de Sul, Brazil. It lives at depths of up to 250ft (75m) on sand and mud bottoms. Though often it's found in river mouths, more commonly it turns up offshore. Juveniles usually occur in shallower habitats.
Ornate Blue Crabs often feed on decaying matter, but they can hunt and kill as well. The species may dig into mud and sand looking for prey such as clams, other crabs, algae, polychaetes, echinoderms, etc. This flexibility of behavior is one reason the species is so successful and common over its distribution. In the aquarium, our Ornate Blues often bury themselves almost completely, keeping their stalked eyes above the sand. You can one peeping from his sand cover at http://www.backyardnature.net/n/15/150322cd.jpg.
Often Ornate Blues are accidentally caught during commercial fishing for Atlantic Blue Crab, but so far they are not considered to be threatened as a species.
Part of the joy of being in an area of high species diversity is that you never know what spectacular organism will greet you around the next corner. A big surprise this week in the thorn forest was a 15-ft-high (4.5m) tall tree I'd passed many times without noticing but which this week attracted attention with its large, white flower clusters. The tree's general form couldn't be made out because its branches were so entangled with those of other trees and bushes, but you can see a typical branch with snowy inflorescences handsomely set amid dark green, glossy, simple leaves at http://www.backyardnature.net/n/15/150322pw.jpg.
Despite the tree's impressive appearance, I had no idea what it could be, and so needed to "do the botany." The flowers were too high to examine closely but from the ground it could be seen that the blossoms were arranged in panicle-type inflorescences -- panicles having branches off their main axes themselves branched -- as shown at http://www.backyardnature.net/n/15/150322px.jpg.
With the camera's modest telephoto ability and by pushing PhotoShop to its limit, a shot was obtained of a single flower with six corolla lobes -- contrasting with most flowers having only five lobes -- and a similar number of stamens, and a yellow, four-divided style, as seen at http://www.backyardnature.net/n/15/150322py.jpg.
Mingled among the flowering clusters were other clusters of brown items, which I assumed to be fruits. A blown-up picture of these things proved that they were otherwise, as shown at http://www.backyardnature.net/n/15/150322pz.jpg.
The brown, papery, 5-lobed item at the picture's top, left corner best shows that the brown things actually were corollas that as they aged dried and turned brown, retaining the corolla's original shape. Below the tree the ground was littered with discarded corollas, some of which are shown in my hand at http://www.backyardnature.net/n/15/150322pv.jpg.
The corolla at the image's top, right corner retains a few shriveled stamens. The two corollas at the left show objects attached at their bases which at first glance one assumes to be hairy fruits. However, if one of the hairy things is torn open it's discovered to be a dried-up calyx enclosing a fruit.
The tree's whitish trunk bearing termite tunnels leading between the ground and upper branches is shown at http://www.backyardnature.net/n/15/150322pu.jpg.
Features of flowers and fruits led me to the Borage Family, the Boraginaceae, which most Northern gardeners think of as a family consisting mainly of herbs -- Borage, Hounds-Tongue, Bluebells, Forget-me-not -- but which in the tropics produces fair-sized trees. Knowing our tree's family, it was easy to discover our tree's identity by scanning the list of Borage Family members occurring in the Yucatan.
Our pretty tree is CORDIA GERASCANTHUS, sometimes known in English as Princewood or Spanish Elm, though it's not closely related to elms at all. The name Princewood reflects people's appreciation of the wood's beauty, workability and durability. Princewood occurs in arid environments, especially on limestone, from southern Mexico and the Caribbean south to northern South America.
This is the second tree we've encountered here whose main English name appears to be Princewood. The two trees are not closely related, but that's how common names work: Just about any tree whose name is highly admired might be called Princewood by someone.
LOGWOOD HEAVY WITH LEGUMES
In January and February, Logwood trees -- the ones famous for the dye their heartwood produces, and for their history as a reason for the foundation of the country now known as Belize -- were spectacularly decked with pale, yellowish blossoms, as shown on our Logwood Page at http://www.backyardnature.net/mexnat/logwood.htm.
Nowadays our Logwood trees are as heavily laden with dry, tan-colored, legume-type fruits as they were earlier with flowers. A branch of them is shown at http://www.backyardnature.net/n/15/150322lg.jpg.
As legumes go, Logwood's are unusual for being so extremely flattened and for containing on the average only two beans, sometimes only one, sometimes three. A view of some pods held against the sun so that the beans inside appear as dark spots is at http://www.backyardnature.net/n/15/150322lh.jpg.
In that picture the bottom-most legume shows yet a third unusual feature of Logwood fruits. Notice the crease-like ridge running across the legume's face from end to end. That's where the fruit will split open so the beans can be ejected. In the big Bean Family to which Logwood belongs, legumes of the vast majority of species open along their edges, not across their flat faces.
These are peculiar legumes.
MERMAID'S WINEGLASS ALGA
During a flamingo tour up Ría Lagartos Estuary, Paco the guide spotted a young crocodile sunning on a log at the mangrove's edge, circled the boat back and drew close so the tourists could take their pictures. I've seen plenty of crocodiles so I was busy looking at other things; for example, the innocent-looking, alga-cloaked Red Mangrove root shown submerged just below the water's surface at http://www.backyardnature.net/n/15/150322mp.jpg.
What caught my attention with this particular root was that besides the usual coat of reddish/yellowish/greenish algae, here and there arose small sprouts of seedling-like greenery. As tourists excitedly angled for good shots of the crock, whose throat was being tickled by the intrepid Paco, I leaned over the boat's edge and plucked some of the sprout-like things, which to me proved more exciting than the sunbathing crocodile. You can see what I'd found at http://www.backyardnature.net/n/15/150322mq.jpg.
Seldom have I seen such a graceful, pretty alga. A closer shot is shown at http://www.backyardnature.net/n/15/150322mr.jpg.
I figured that any such beautiful, idiosyncratic alga would be easy to identify, and that was right. First of all, it seemed unlikely that any common English name for the organism could avoid using the words "green," "parasol" and "alga," so a Google image search was made on the keywords "green parasol alga." On the first resulting page of thumbnails a picture turned up of an alga looking like ours, labeled "Acetabularia." Google had found the image because accompanying text described it as being parasol shaped. Happily, the list of alga species known to occur in Ría Lagartos Reserve included ACETABULARIA CRENULATA, and when other pictures of that species were sought, they looked just like our boatside discovery.
English names for this lovely little alga include Mermaid's Wine Glass and Mermaid's Parasol. Several parasol-shaped, aquatic organisms share these names, so probably it's best to use the Latin: Acetabularia crenulata. The species inhabits warmer waters practically wordlwide. In our part of the world we find it from Florida south through the Gulf of Mexico and Caribbean to Brazil. It grows mostly in shallow, quiet waters attached to stones, rocks, shells and other submerged objects -- such as submerged Red Mangrove roots.
Our individuals were about an inch tall (25mm) but I read that they can reach three times that size. In the last picture the disk consisting of radiating segments, or filaments, is split, and that's typical of the species. Since this organism is a green alga, its filaments lack the kind of vascular network found in higher plants. In fact, technically, since the alga has no cell walls, with all cell contents residing together in a sort of big, parasol-shaped package, the whole organism is regarded as a single cell. In the literature it's described as a "single-celled organism, but gigantic in size and complex in form, making it an excellent model organism for studying cell biology."
In Acetabularia individuals, the single nucleus is located in the root-like rhizoid, so if the cap is snipped off, the cell can completely regenerate it. The caps of two Acetabularia can be exchanged -- even between two different species. If a piece of the stem is removed, with no access to the nucleus in the rhizoid, this isolated stem piece can also grow a new cap. Species of the genus Acetabularia are considered to be among the largest single-celled organisms, and each organism's nucleus is regarded as remarkably large.
What an amazing being to encounter amid a messy tangle of algae on a Red Mangrove root next to a sunbathing crocodile!
FEATURED ESSAYS FROM THE PAST:
"Silk Cottontree in a Secret Place" from the March 21, 2010 Newsletter, at http://www.backyardnature.net/n/p/100321.htm
"Worshiping Rocks?" from the March 32, 2008 Newsletter, at http://www.backyardnature.net/n/p/080331.htm
Best wishes to all Newsletter readers,
All previous Newsletters are archived at http://www.backyardnature.net/n/.