JIM CONRAD'S
NATURALIST NEWSLETTER
Issued in Río Lagartos, on the northern coast of
Yucatán, MÉXICO
in Ría Lagartos Biosphere Reserve

March 1, 2015

BLUEFIN TUNA
Rayo's grandfather, Don Taila, had spent the night in his little boat no larger than those carrying tourists up the estuary to see flamingos. But Don Taila's boat had been miles out in the Gulf of Mexico, and instead of dragging a net behind his boat, or even using a rod and reel, he'd fished the old way, with no pole, just hook, line and sinker, his hook baited with small chunks of sardine flesh, and he'd tossed the line by twirling it with his hand. Yet that morning after making his way back home to Río Lagartos, pulling up to a dock only a minute walk from his house, he brought an ice chest filled with fish. You can see him standing in his boat, with his biggest catch of the night lying on the dock before him, at http://www.backyardnature.net/n/15/150301tn.jpg.

I'm such a landlubber that Don Taila had to tell me that it was a tuna, though once I noticed the toothlike fins, or " finlets," near the fish's rear end, on the fish's top and bottom, I remembered that tunas do have such things. A close-up showing the bottom row of finlets is at http://www.backyardnature.net/n/15/150301to.jpg.

This only indicated that we had some kind of tuna, however, for several kinds of tuna exist. So, which one was this?

The name "tuna" is a general one, applied to several fish species (as well as to certain cactus fruits). Oceanography textbooks are likely to define a tuna as a saltwater fish belonging to the tribe Thunnini, which is a sub-grouping of the Mackerel Family, the Scombridae – which is the same family to which bonitos, mackerels, and Spanish mackerels belong. The Tuna Tribe Thunnini comprises fifteen species across five genera. Within that tribe there's the genus Thunnus whose members often are referred to as "true tunas." As things stand now, there are about eight species of "true tuna," members of the genus Thunnus, and Don Taila's fish was one of them.

Since tuna fish are so important commercially, several websites provide species identification pages, such as the one at http://www.fishwatch.gov/seafood_profiles/species/tuna/group_pages/.

Different tuna identification pages tend to list different species and use different common names, making the identification process a little tricky. Still, Don Taila's fish displays enough field marks to identity it as the Atlantic Bluefin Tuna, THUNNUS THYNNUS. One good field mark for the Atlantic Bluefin Tuna is the shortness of its side fins directly behind the gills (the pectoral fins), the tips of which don't reach the base of the second top fin (the second dorsal fin), which in our picture is the one in the center of the bottom of Don Taila's orangish shirt.

Another tuna species commonly caught here, but normally in deeper water, is the Yellowfin Tuna. However, its fins, including the ones on its bottom (the ventral and anal fins), are much longer and more slender. Technical guides say that other distinguishing marks of our Atlantic Bluefin Tuna include that its lower sides are splotched with vertical lines of white spots, and a slender, yellow line extends from its snout to about half the length of its body. Don Taila's fish doesn't show these, but local fishermen tell me that within minutes after such a fish is taken, its colors fade and such markings disappear.

Atlantic Bluefin Tunas mature at about eight years, and they typically grow to be around six feet long (2 m) long, weighing some 300 pounds (135 kg), though they've been known to reach about 1,200 pounds (550 kg). Therefore, Don Taila's catch is a small one, as far as Atlantic Bluefin Tunas go. Mostly the species lives in cooler water of the North Atlantic and adjacent seas, but they return to the Caribbean to spawn. It's unusual that a fish would move between such cold and warm waters, but it's been shown that tunas can do so while maintaining a constant internal body temperature.

Juvenile tunas typically prey on crustaceans, small fish and cephalopods such as octopuses, whiles adults feed mainly on fish such as herrings, anchovies, sardines, and mackerel.

Because of overfishing, the IUCN Red List considers the Atlantic Bluefin Tuna an endangered species. In fact, no tuna species is doing very well. The Southern Bluefin Tuna is listed as critically endangered and the Pacific Bluefin as vulnerable. The Fishwatch.Gov web page for Atlantic Bluefin Tunas reports that a giant bluefin tuna "can fetch hundreds of thousands of dollars at fish markets today."

Despite knowing that Don Taila and his family planned to eat his tuna, I felt sorry for it lying there on the dock, its eyes turning opaque and empty. Up close, its body still showed a few colors, however, and its scale patterns were intricate and beautiful. You can see some of this at http://www.backyardnature.net/n/15/150301tp.jpg.

*****

BANDED PIPEFISH
That day wading through a submerged field of aquatic Shoalgrass during a very low tide, we were finding so many amazing things that when Rayo spotted and caught a brown, wormy-like thing shaken loose from a Shoalgrass blade he didn't get excited at all, but still he showed it to me because it was something different. But as soon as a closer look was taken it was clear that if this was a worm it was a very strange one. You can see it http://www.backyardnature.net/n/15/150301pf.jpg.

Other worms we were finding were segmented, but this organism wasn't. Even more surprising, its body had corners, and one end was tipped with a pale, peg-like appendage. Out came the hand lens for a better look at that pale tip, and I saw what's shown at http://www.backyardnature.net/n/15/150301pe.jpg.

The pale thing looked a little like a duck's beak, and right behind it was a depression in which there might have been an eye. And right below and a little to the left of the eye, is that pale, slender thing projecting downward a fin? In fact, atop the critter, behind the eyes, isn't that a kind of top fin, maybe like a fish's dorsal fin?

Gradually it occurred to me that the head looked just like a seahorse's, but of course seahorses have potbellies and slender tails that curl below them. Finally I remembered that there's something called a pipefish, which is like a straight seahorse without a potbelly, and surely that's what we had.

On the Internet we began ordering our thoughts about the world of seahorses and pipefishes. Seahorses and pipefishes are real fish, though highly modified and adapted ones, belonging to the Seahorse and Pipefish Order Syngnathidae. Fish in this family possess long, narrow bodies surrounded by a series of bony rings, and they have small, tubular mouths. In evolutionary terms, that last feature is a huge deal. In fact, the "syngnath" in the family's name Syngnathidae is derived from the Ancient Greek "syn" meaning "together," and "gnathos" meaning "jaw."

The Family Syngnathidae is divided into two subfamilies, one containing seahorses, and the other pipefishes. But, beyond this point, experts don't agree on which organisms belong to which genus and species, and it's surprising that so little information is available of the kind we like to pass along here.

By consulting lists of pipefish species thought to occur in our general area, and by comparing our pictures with those on the Internet -- a sloppy approach but the best we have at this time -- our wormlike discovery was found to be the Banded Pipefish, HALICAMPUS CRINITUS. Some experts place it into a different genus, and most say that many color variations of Banded Pipefish exist. Some of those variations may be undescribed species, even ours. However, at this time, no one really knows. The Halicampus crinitus name is just the best guess, the most obvious name available for the individual in our picture. The Banded Pipefish as it's usually defined now occurs throughout the Gulf of Mexico and Caribbean area, south to coastal Brazil.

Despite the lack of knowledge about this particular species, interesting facts are known about pipefishes in general. For instance, the series of bony rings covering pipefish bodies makes them so rigid that instead of bending their bodies back and forth to swim like normal fish, pipefish swim by rapidly fanning their fins. You can see that our pipefish's fins are very small, which helps to explain why ours was so easy to catch. Still, pipefishes can control their movements with great precision, and can hover in place for a long time.

Among both seahorses and pipefish, females lay their eggs the usual way, the males fertilize them, and then those males carry the eggs during incubation. Male pipefish either carry the eggs in a specialized pouch on the bottom of their bodies, in their ventral pouch, or else attach the eggs to their tails, the technique depending on the species.

Despite having mostly fused jaws, pipefish are predators who eat live foods such as brine shrimp, small ghost shrimp, copepods and amphipods. Their jaws are not entirely fused, however. The elongate, tubular snout formed by the fused parts of their jaws ends with tiny, toothless jaws at the end of the snout. This mouth configuration enables the pipefish to do a fast and powerful kind of feeding referred to as "pivot feeding." Pivot feeding involves rotating the snout at a very high speed, employing a kind of poorly understood "trigger mechanism," resulting in small prey being sucked in.

*****

SNAPPING SHRIMP
During a very low tide, Rayo and I waded at the edge of a shallowly submerged prairie of Shoalgrass, among the remains of an abandoned, metal pipeline about thigh-high, normally underwater. Mostly eroded away, the pipeline formed a long, seaweed- and barnacle-encrusted sort of bathtub. It was left over from the days of cutting and dredging the canal through the narrow finger of land separating Ría Lagartos Estuary from the Gulf of Mexico, in front of the town of Río Lagartos. In this rock-poor, sedimentary environment, it attracted an untold diversity of aquatic organisms needing a stable substrate on which to anchor. You can see Rayo exploring the decaying pipeline at http://www.backyardnature.net/n/15/150301sm.jpg.

You've already been introduced to several organisms found in this accidental diversity hot-spot, the Sargassum Fish and the octopus among them. That day, one of the most attention-getting in the area was the pencil-thin little crawfish-like crustacean shown at http://www.backyardnature.net/n/15/150301sn.jpg.

That little being doesn't look like it would draw attention, except maybe for its larger claw, which seems somehow deformed and useless. A side view showing how the tail curls under, shrimp-like, is at http://www.backyardnature.net/n/15/150301so.jpg.

A closer look at the weirdly shaped large claw is at http://www.backyardnature.net/n/15/150301sp.jpg.

It turned out that the big claw isn't deformed at all, but rather is one of the most remarkable adaptations found in the animal world. For, that claw is used by the shrimp to make a kind of snap that is so powerful that the percussive impact of the snap's shock wave traveling through water can stun or kill small, nearby fish or other prey. The shrimp doesn't use the big claw to grab prey, but to "shoot" it with a shock wave.

That day, as we wandered along the old pipeline's length, we were accompanied by an ongoing series of snapping sounds, averaging maybe every 15 seconds. Unable to see the snapping being made, I wondered whether all of them were used to stun prey, or were some or all of them being used to warn others of the species to stay out of the snapper's territory, or maybe the snapping served in courtship, the notion being that the more powerful the snap, the more robust the potential mate.

I'd never heard of this kind of thing but a little Internet sleuthing turned up a whole new part of the animal kingdom to explore. Our critter is a snapping shrimp, a member of the Snapping Shrimp Family, the Alpheidae, which is of worldwide distribution and embraces about 600 species in 38 or more genera. Most snapping shrimps dig burrows and are common inhabitants of coral reefs, submerged seagrass flats like ours, and oyster reefs, mostly in tropical and temperate coastal and marine waters.

Of the world's 600 species, about 70 are listed for waters of the Gulf of Mexico and even more occur in the Caribbean. Luckily, on the Internet there's a freely downloadable 2012 treatment of the group of snapping shrimp species to which our shrimp seems to belong, Arthur Anker's "Revision of the western Atlantic members of the Alpheus armillatus species H. Milne Edwards, 1837 species complex (Decapoda, Alpheidae), with description of seven new species."

That well illustrated revision indicates that our snapping shrimp probably is ALPHEUS CARLAE, found in the Caribbean but not most of the Gulf of Mexico, occurring from Florida south to South America and southern Brazil. Anker describes its habitat as shallow, protected bays and lagoons, on fine sand and silt, close to mangroves or seagrass beds, which is exactly where we found our individual.

The knock-out snap produced by snapping shrimp fascinates scientists, one reason being that snapping shrimp snaps are a major source of noise in the ocean, even sometimes interfering with SONAR navigation. Technically the snap is said to result from the collapse of a "cavitation bubble" produced by the modified claw. The term cavitation applies to the formation of a partial vacuum in a liquid by a swiftly moving solid body. Studies show that snapping shrimp snaps are so intense that light is emitted. A webpage entitled "How Snapping Shrimp Snap (and flash)," with pictures, audio and video, is at http://stilton.tnw.utwente.nl/shrimp/.

*****

HORSE CONCH
A seashell left on the beach's sand during a very low tide is shown at http://www.backyardnature.net/n/15/150301hc.jpg.

This was more than a seashell, though, because the living creature was still housed inside it. You can see its reddish-orange flesh starting to peep out at http://www.backyardnature.net/n/15/150301hd.jpg.

I hoped to photograph the entire body extended from the shell but this was one of those times when the biting gnats, called chaquistas here, were so bad that it was foolhardy to stay still very long, and staying still was what was needed.

Volunteer identifier Bea in wintry Ontario easily identified this mollusk with its distinctively long, narrow front end, technically known as a siphonal canal, and orangish flesh. Mollusks with such pronounced canals can bury most of their bodies in mud or sand with the canal protruding, taking in water, or sometimes air, with it.

This is the Horse Conch, TRIPLOFUSUS GIGANTEUS. In certain field guides it's labeled the Florida Horse Conch, but that won't do, because the species is distributed from North Carolina in the US south through the Gulf of Mexico and Caribbean, to here in the Yucatan.

The species name "giganteus" means what it seems to, and I wondered about that because our individual's shell was a little less than four inches long (10cm). However, it's true: The species reaches about two feet long (60cm), so ours in a young one. Such small ones are what I find here, though. I suspect that larger ones are quickly harvested by those numerous folks who at low tide wander the beaches and mud flats collecting "conchas" to eat and sell. The Horse Conch is recognized by many as the world's second-largest living gastropod, gastropods being snail-like creatures. In American waters, the Horse Conch is the largest gastropod of all.

Horse Conches live on sand and mud flats from the low intertidal to shallow subtidal zones, to as deep as 20 feet (6 m). The species is carnivorous, feeding on other large marine gastropods, possibly including members of its own species. In aquaria it's been seen eating small hermit crabs.

Large Horse Conch shells were often used by ancient native Americans as drinking vessels, woodworking tools and hammers. In classic Mayan art, Horse Conch shells can be seen used as paint and ink holders for scribes, and as bugles and trumpets.

*****

ROSE-PETAL TELLIN SEASHELLS
You can see a small but eye-catching and fairly commonly encountered, clam-like seashell found on the northern Yucatan's beaches at http://www.backyardnature.net/n/15/150301te.jpg.

Volunteer identifier Bea in Ontario with her new Peterson field guide to seashells offered as her best bet for an identification the name TELLINA LINEATA, often known as the Rose-petal Tellin. That field guide doesn't include everything, though, and doesn't focus on our part of the world, so to confirm the ID I checked out the 2007, well illustrated book by Antonio García-Cubas and Martha Reguero Catalogo ilustrado de moluscos del Golfo de Mexico y Mar Caribe, partly accessible on the Internet via Google Books. Using that, I also settled on Tellina lineata as the most likely name. The bivalve's main field marks are the shells' small size, their general shape, their smoothness and shininess, the many very fine concentric rings on the shells' tops, their rosy color, and the flexible, hinged ligament that normally connects the top and bottom shells freshly washed onto the beach.

Rose-petal Tellins occur throughout the Gulf of Mexico and Caribbean to South America, south to Brazil. Being so extensively distributed, many pictures of them can be found on the Internet, but none are as intensely brightly red as ours. In the literature they are described as white to rose tinted, but our shells go far beyond being rose tinted. Maybe we have a race or subspecies or even a species here not yet documented in literature on the Internet.

Susan Rothschild in her 2004 book Beachcomber's Guide to Gulf Coast Marine Life: Texas, Louisiana, Mississippi, Alabama and Florida, writes that our Rose-petal Tellin, unlike clams, which are filter-feeders, are rather "deposit-feeders." Deposit-feeders are equipped with very long, unfused siphons which act as vacuum cleaners when swept over sediment, gathering edible detritus and algae. Detritus is dead organic material, normally from decomposing organisms.

*****

TRIXIS FLOWERING
Here and there along the weedy coastal road nowadays a woody, much-branching, head-high bush is at its flowering peak, shown next to a Maya stone fence with Mesquite in the background at http://www.backyardnature.net/n/15/150301tx.jpg.

Up close, it's surprising to see that the flowers are grouped into flower-like flowering heads -- announcing that the bush is a member of the Composite or Sunflower Family, the Asteraceae. The heads look like those of the North's groundsels, genus Senecio, as shown at http://www.backyardnature.net/n/15/150301ty.jpg.

Closer up we see that the green, cup-like involucre from which the heads' florets arise is composed of a single series of long, slender, scale-like bracts arranged side by side, which also is like groundsel flowering heads, as seen at http://www.backyardnature.net/n/15/150301tz.jpg.

The North's groundsels are mostly herbaceous, but you might have heard of highland Africa's Tree Senecios. As you "do the botany," you keep all this in mind, and the notion that this might be a bushy groundsel grows and grows. However, notice that the petal-like rays of the flowering head at the picture's left side are turning white and papery as they age. This isn't groundsel-like... The bush's leaves are one per stem node, or alternate, and without lobes or teeth along their margins, which also is unlike groundsels, as shown at http://www.backyardnature.net/n/15/150301tw.jpg.

By now you're starting to doubt that this might be a groundsel or something close to it, so you break open a flowering head looking for more hints as to the bush's identity, and then you see it: Something that in terms of Composite/Sunflower Family taxonomy is as attention-getting as a firecracker going off at your feet. You can see it at http://www.backyardnature.net/n/15/150301tv.jpg.

The individual flowers, or florets, in this bush's flowering heads are not at all typical of those of the Composite/Sunflower Family. Instead of being either distinctly conical disk flowers or flat, strap-shaped ray flowers, all the flowers in our bush's flowering heads are strongly and asymmetrically "two-lipped." In our picture you can see that one of the floret's lips stretches out flatly like a petal, while the other curls beneath itself.

No groundsel has florets anything like this. When you see such bilaterally asymmetrical, two-lipped florets in a Composite/Sunflower Family member, you think of the "tribe" or subdivision known as the Mutisieae. The Mutisieae is a small tribe in a huge family, so recognizing that your unknown plant belongs to it really narrows down the possible identities. Within the Mutisieae, in our part of the world, just noticing that you have a woody shrub with yellowish florets displaying this peculiarity is enough to get you the name.

Our pretty roadside bush is TRIXIS INULA, in some places called the Tropical Threefold, but that "threefold" name alludes to the three-cleft corolla of some other Trixis species and seems so contrived that I can't bear to use it for such a pretty and distinctive plant. I'll go along with Alfred Richardson who in his book Plants of Deep South Texas simply called it Trixis.

Trixis does indeed grow in the scrublands of southern Texas, and all the way south through Mexico's arid regions and the Caribbean islands, south through Central America into northern South America. It's described as inhabiting open, sandy sites, thorn scrub, palm groves, thickets, and roadsides, exactly as we found it.

Trixis is one of several large Composite/Sunflower Family plants Mexicans call Árnica, and most Árnicas are considered medicinal, though their supposed cures vary from place to place. The online Atlas de las Plantas de la Medicina Tradicional Mexicana reports that the whole plant can be brewed to make a hot tea that's good for "rheumatism," motion sickness and "golpes de aire," which translates to something like "air-hits," and refers to the belief that certain pains are caused by build-ups of air in the body, which need to be released. In Michoacán they apply plasters of mashed leaves to sore parts of the body to relieve such pain, and other uses include curing intestinal disorders and venereal diseases.

*****

WILD OREGANO
Back at Hacienda Chichen in the central Yucatan, Chef Cime used Wild Oregano, LIPPIA GRAVEOLENS, in his five-star cooking. Our page profiling the cultivated, much-branched, soft-woody shrub with its pungent smelling leaves is at http://www.backyardnature.net/yucatan/oregano.htm.

Here Wild Oregano commonly grows along backcountry roads and it's flowering conspicuously nowadays, as shown with a head-high bush at http://www.backyardnature.net/n/15/150301li.jpg.

Up closer you see that what from a distance seem like Wild Oregano flowers are actually dense clusters of small, white blossoms with yellow centers, as shown at http://www.backyardnature.net/n/15/150301lj.jpg.

The flowers closer-up, showing their bilaterally symmetrical "faces" -- with enlarged lower lips serving as landing pads for pollinators -- are seen at http://www.backyardnature.net/n/15/150301lg.jpg.

A view of a flower cluster from below, showing the green involucre formed of the head's sharp-pointed bracts is at http://www.backyardnature.net/n/15/150301lh.jpg.

Though pungent, crushed Wild Oregano leaves don't smell much like "real Oregano," nor or they minty or sweet smelling. That's no surprise, though, since real Oregano belongs to the Mint Family while Wild Oregano resides in the Vervain or Verbena Family.

Any plant with strong-smelling herbage is likely to be used in traditional medicine, and that's the case with Wild Oregano, which grows from Texas and New Mexico south through Mexico to Costa Rica. In Mexico a tea brewed from it is used for diarrhea and indigestion in babies. In a liter of boiling water add ten Wild Oregano leaves, and sprigs of Chamomile and "Moro," the latter being Turnera diffusa.

A 2011 study by Marciele Ribas Pilau et al found that oil of Wild Oregano can inhibit various human and animal viruses, at least in a test tube.

*****

SEA GRAPES
At low tide -- the very lowest -- on hard surfaces where waves splash, often you find the green alga shown clumped around a pinkish sponge shown at http://www.backyardnature.net/n/15/150301sg.jpg.

A close-up of some of the alga's succulent, shiny "branches" is featured at http://www.backyardnature.net/n/15/150301sh.jpg.

I thought this would be an easy alga to identify because the species is so common and distinctive. However, pinning down a name was a little tricky because this is one of the most variable-looking species I've ever met. Our alga's branches are club-shaped with rounded tips, but others of the same species found in different habitats and other parts of the world have branches varying from nearly spherical to golf-tee shaped with sunken crowns, to being long, slender and spaghetti-like.

Our alga is sometimes called Sea Grapes. It's CAULERPA RACEMOSA, an invasive species native to the Southern Hemisphere, thought to have originated in Australia, but now found worldwide in shallow coastal waters of both temperate and tropical seas. It began spreading through the Mediterranean in the 1990's and is now found throughout the Europe, Africa, the Pacific and Indian oceans, Caribbean Sea, and the Gulf of Mexico. The SeaweedIndustry.Com web page on Sea Grapes says that the alga's spread across the world's waters "... has had broad deleterious effects such as smothering native seagrass meadows, out-competing native algal species, transforming complex ecosystems into monospecific stands, and overgrowing corals, thereby seriously harming the health and function of reef systems."

Sea Grapes usually reproduces vegetatively by fragmentation, though sexual reproduction is possible by "holocarpy." Holocarpy is when all the alga body's cytoplasm is used up in the creation of enormous numbers of sexual gametes, which break through the body's husk, escape into the water, mate with gametes from other alga bodies, and form new alga plants.

Sea Grapes goes by many names and another English one is Green Caviar, hinting at its use as a raw salad vegetable providing a peppery flavor. It's also used in sauce making. Traditional medicine of the Philippines uses Sea Grapes to lower blood pressure and to treat rheumatism.

*****

HALIMEDA INCRASSATA GREEN ALGA
At low tide as others gawk at flamingos, sometimes you can lean over the boat's edge and pluck from the muddy estuary bottom such nice algae as what's shown at http://www.backyardnature.net/n/15/150301al.jpg.

A close-up of the upper part is shown at http://www.backyardnature.net/n/15/150301am.jpg.

The field marks to notice are that the green photosynthesizing segments are flattish, they arise from atop one another on occasionally branching stems, and that there's a basal gob of mud held together by an extensive rootlike network of very fine "rhizoids." Rhizoids are slender, rootlike filaments that issue from an alga, a fungus, or the gametophyte of a moss, liverwort, or fern, and serve to attach the organism to its substrate, and obtain nourishment.

As soon as I saw this alga and felt its hardness, stiffness and dark greenness, I figured it might be in the same family as the stiff, hard, dark green Mermaid's Fan we profiled a month ago. Our Mermaid's Fan also came up with a blob of mud held together at its base by a system of rhizoids. You might enjoy comparing these similarities on our Mermaid's Fan page, at http://www.backyardnature.net/mexnat/udotea.htm.

Mermaid's Fan belongs to the green alga family Udoteaceae, and the checklist of Udoteaceae for the Ría Lagartos Biosphere Reserve lists four species in that family, one of which looks exactly like the organism in our picture.

And that's HALIMEDA INCRASSATA, reported from tropical waters nearly worldwide. It's a favorite of aquarium keepers because it's pretty, easy to grow, and also because it's so stiff and hard that fish won't eat it. Despite it commonness and familiarity to aquarists, the alga doesn't seem to have a decent common name. I've seen it called Three Finger Leaf but can't see any reason in that, so we'll just use Halimeda incrassata.

Most commonly, Halimeda incrassata is found in shallow, sandy-bottomed waters, including seagrass beds, which is exactly where ours was found, but also sometimes it turns up in sandy, rocky areas on and between reefs.

As with the Mermaid's Fan, the alga's tough body is composed of very many intertwining algal filaments. The filaments lack cell walls, so that cell nuclei, photosynthesizing chloroplasts and other organelles can migrate throughout the plant body. Probably that explains why our specimen has white blotches: Maybe a leaf or something covered part of it, causing its chloroplasts to migrate to parts of the body where more light was available.

Mermaid's Fan, our Halimeda incrassata and other related species are known as "calcareous" algae, which means that they've incorporated the mineral calcium carbonate into their bodies, calcium carbonate being the main ingredient of limestone. Since the entire Yucatan is a big slab of limestone and the estuary's waters are known to contain high levels of dissolved calcium carbonate, that might explain why so many calcareous algae grow in our submerged seagrass prairies.

*****

FEATURED ESSAYS FROM THE PAST:

"Waiting for The Rainy Season" from the May 29, 2011 Newsletter, at http://www.backyardnature.net/n/p/110529.htm

"Tomantzin" from the December 17, 2007 Newsletter, at http://www.backyardnature.net/n/p/071217.htm

*****

Best wishes to all Newsletter readers,

Jim

All previous Newsletters are archived at http://www.backyardnature.net/n/.