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

March 15, 2015

CHECKERED PUFFER
Rayo wanted to add something new to the aquarium so he got together some buckets and a toss-net, and invited me to come along. On his first toss he caught what's shown in his hand moments before being returned to the water, at http://www.backyardnature.net/n/15/150315pf.jpg.

That's a Checkered Puffer, SPHOEROIDES TESTUDINEUS, listed in a recent study as the second-most numerically abundant fish species in Ría Lagartos Estuary. Also, Checkered Puffers were found to provide an astonishing 71.5% of the estuary's fish biomass, and the fish is one of five species in the estuary able to tolerate the least salty water. These observations are presented in a 2010 Spanish-language work by Peralta-Meixueiro et al, entitled "Evaluación Espacio-temporal de los Ensamblajes de Peces en el Sistema Lagunar de Ría Lagaratos, México," freely downloadable at http://nsgl.gso.uri.edu/flsgp/flsgpw10002/data/papers/051.pdf.

So, Checkered Puffers definitely are among the most abundant and ecologically important fish species in the estuary, so it's no surprise that on Rayo's first net toss he got one. During subsequent tosses he netted several more, and all were returned to the water, regarded as too common to feature in an aquarium. Even I have grown accustomed to seeing them from day to day, for in shallow water just below the Malecón's wall they're commonly seen wandering by nonchalantly, and in tide waters flowing through culverts beneath the Malecón, Checkered Puffers often are visible "going with the flow." There's something about them almost creepily easy-going, self-confident and familiar.

Yet, they're curious little beings. They're called puffers because when attacked they puff up like balloons. Sometimes locals fishing from the Malecón's walls toss Checkered Puffers they catch onto the street to die, instead of back into the water, so sometimes puffers lie around looking like half-inflated footballs.

A 2012 study by Chi-Espínola and Vega-Cendejas found that Checkered Puffers in the Ría Lagartos Estuary throughout the year ate bivalves such as oysters, and gastropods such as sea snails, but largely shifted to aquatic vegetation during rainy periods and when it was windy.

And Checkered Puffer flesh can be toxic, which may explain their apparent nonchalantness in a predator-prey world. The toxins are in the fish's intestines, liver, skin and reproductive organs, which normally are discarded when a fish is cleaned, but the poison is so potent that it can contaminate the flesh during the clearing process. Eating Checkered Puffers has killed people. The poisoning is known appropriately as "puffer poisoning"; sometimes Checkered Puffer flesh is used to kill unwanted dogs and cats.

Checkered Puffers occur in inshore water and on rocky bottoms from Rhode Island on the US Atlantic coast south through the Gulf of Mexico and the Caribbean to southeastern Brazil.

Here we have three puffer species -- members of the genus Sphoeroides -- but the other two species are much less common, and I've not seen them.

*****

TARPON FINGERLINGS
In a shallow pool next to the road into Río Lagartos, next to shallow lagoons and mangrove swamps, three-inch-long (8cm), slender, silvery fish were darting about. "Minnows," a Northerner might call them. Some boys from San Felipe thought they were interesting enough to coax into a plastic bag and carry to the restaurant/tour-office building, where our aquarium has become a local attraction. You can see one in the aquarium at http://www.backyardnature.net/n/15/150315tp.jpg.

When Diego saw the little fish he got excited because he offers catch-and-release fly-fishing for Tarpon in the estuary, and he recognized the fish as young Tarpon, MEGALOPS ATLANTICUS, called Sábalos in Spanish. You might be interested in pictures of big Tarpon caught by Diego's customers at http://www.flyfishingyucatan.com/.

Part of what caused Diego's excitement is that, despite Tarpon being considered on the great "game fishes," not much is known about Tarpon spawning. One reason for this lack of information is that Tarpon aren't considered commercially valuable as food fish, so little effort has been made to understand them.

Tarpon regularly inhabit both sides of the Atlantic Ocean, from Senegal to the Congo on the Atlantic's eastern shores, to the Gulf of Mexico and the Caribbean on the western shores. However, Tarpon range widely, and have been caught as far north as Nova Scotia and as far south as Argentina. Tarpon routinely migrate through the Panama Canal, but haven't been shown to breed in the Pacific Ocean. They tolerate wide ranges in salinity throughout their lives and eat almost anything dead or alive, and their movements seem to be limited mainly by water temperatures. They prefer water temperatures of 72 to 82°F (22-28°C). Below 60°F (15.5°C) they become inactive, and temperatures below 40°F (4.5°C) can be lethal. They're thought to spawn in the Yucatan Channel, which is the strait between Mexico and Cuba connecting the Caribbean with the Gulf of Mexico.

Once the Tarpon were recognized and admired, they were released. It's unlawful to keep Tarpon in aquaria here.

*****

LESSER YELLOW-HEADED VULTURE EATING A FISH
We've looked at Lesser Yellow-headed Vultures before, profiled at http://www.backyardnature.net/yucatan/y-h-vult.htm.

This week a good view came up of one feeding on a washed-up fish on a Gulf of Mexico Beach, shown at http://www.backyardnature.net/n/15/150315vu.jpg.

I read that Lesser Yellow-heads are dependent on other animals to open the hides of larger animal carcasses, since their bills aren't strong enough to do so. This one seems to have found the fish's soft underbelly, however, so maybe it had done its own work.

*****

THREE TERNS ON A MUDFLAT
During a flamingo-viewing trip we passed a mudflat loaded with Black Skimmers, Laughing Gulls, White Pelicans and terns. It was the terns who caused us to turn the boat back, park and study awhile, because something didn't seem right here. You can see the situation at http://www.backyardnature.net/n/15/150315t3.jpg.

The little tern in the middle is a Forster's Tern, very common here at this time of year. Of the tern species found in our area, the two largest are the Royal and Caspian Terns, and the two terns flanking the Forster's are definitely of the larger kind. We always say that the Royal Tern's beak is orangish, while the Caspian's beak is red. The confusing thing is that the two big terns in the picture clearly are different from one another, yet they both have orangish beaks. Caspian Terns are bigger than Royal Terns, with more massive beaks and their winter plumage includes darker foreheads, so we thought that the bird at the right should be a Caspian with a red beak, not orangish.

Finally we found in Howell's A Guide to The Birds of Mexico and Northern Central America a description of the juvenile Caspian Tern's beak, saying that it's "reddish orange to orangish with dark tip." Well, our bird's beak if anything is pale tipped, but at least now we know that immature Caspian Terns can have orangish beaks.

Immature birds and adults in winter plumage, which is the case with most birds in the estuary at this time of year, can be real challenges.

*****

NEOTROPIC & DOUBLE-CRESTED CORMORANTS SIDE BY SIDE
Yet another opportunity for a side-by-side comparison of two similar species was made possible this week with the grouping shown at http://www.backyardnature.net/n/15/150315cm.jpg.

On the left, that's our permanent-resident the Neotropic Cormorant, while on the right there's the Double-crested Cormorant, which along most of the Yucatan Peninsula's coast is a winter visitor, but which nests in certain dispersed breeding colonies along the coast.

Plumage colors are changeable and not dependable. However, the picture reminds us that Neotropic Cormorants are fairly consistently smaller than Double-cresteds. The most decisive difference, however, is seen on the "face." A close-up of the faces side-by-side is at http://www.backyardnature.net/n/15/150315cn.jpg.

Note that the Neotropic's bill connects with the feathered part of the head forming a kind of V-on-its-side, and that a whitish border is forming at the connection. In contrast, the Double-crested's orangish skin doesn't make such a connection and there's no pale fringe. A more technical way of describing this is that on the Neotropic the "posterior edge of the gular skin is pointed," but that's not the case with the Double-crested. Also, note that the Double-crested has yellow skin above and in front of the eye, but the Neotropic doesn't.

*****

A NONCONFORMIST LEAST SANDPIPER
At the estuary's edge a small, long-legged sandpiper probed mud beneath shallow water with his sharp, straight beak, as shown at http://www.backyardnature.net/n/15/150315sp.jpg.

Sandpipers in their winter plumage can be especially hard to identify. This one could have been a Least Sandpiper, common here, except that in its setting it looked too large, didn't have the well formed white eyebrow shown in field guide illustrations, and Least Sandpipers legs are supposed to be yellow, but the legs of this individual seemed greenish to me.

Still, after conferring with more birders more expert than I, the consensus was that our bird was indeed a Least Sandpiper. It was another example of birds sometimes not fitting the ideas we develop about them.

*****

SMOOTHTAIL SPINY LOBSTER
At low tide Rayo and I were exploring in and around an old, metal, decaying dredging pipe left over from when the canal in front of Río Lagartos was dug. From inside an open-topped part of the pipe, Rayo plucked from the water the crayfish-like creature shown on his wrist at http://www.backyardnature.net/n/15/150315lb.jpg.

Rayo was excited because lobster fishing is big business around here, but normally you see them much larger than this one, and in much deeper water beyond the estuary, out in the Gulf of Mexico. Rayo assumed he was seeing a juvenile of that species, and learning that young ones live in the estuary. Soon the lobster curled into a shrimp-like pose, shown at http://www.backyardnature.net/n/15/150315ld.jpg.

A close-up of the creature's oval eyes and the forward-projecting spines around them is at http://www.backyardnature.net/n/15/150315lc.jpg.

You might guess that many kinds of lobster exist, if only because you know that lobsters eaten in restaurants up north bear big claws, while the one on Rayo's wrist doesn't. Taxonomically, big-clawed ones belong to the Lobster Family, the Nephropidae, while Rayo's is a member of the Spiny Lobster Family, the Palinuridae. So, technically, Rayo's lobster isn't a lobster; it's a SPINY lobster. The Spiny Lobster Family embraces about 60 species worldwide, and are recognized by being shaped like crawfish, bearing no big claws, and by having very long antennae armored with low spines.

Sipse.Com reports that during the 2014-2015 lobster season, 395 metric tons (435 US short tons) of spiny lobster were harvested in the waters off Yucatán State. This is reported, in Spanish, here.

The lobster species the Yucatan's fishermen catch is Panulirus argus, known as the Caribbean Spiny Lobster. You can see what that looks like on its Wikipedia page at http://en.wikipedia.org/wiki/Panulirus_argus.

When I compared Rayo's spiny lobster with pictures of Caribbean Spiny Lobsters, there were mismatches. For one thing, Caribbean Spiny Lobster tails display a different arrangement of spotting from ours. More strikingly, Caribbean Spiny Lobster legs bear long, narrow, dark lines on tan backgrounds, while our spiny lobster's legs bore broad bands and blotches.

It turns out that only 99% of the Yucatan's spiny-lobster catch consists of Caribbean Spiny Lobsters. 1% of the catch consists of a species called the Smoothtail Spiny Lobster, PANULIRUS LAEVICAUDA, and that's the lobster Rayo plucked from the decaying dredging pipe in the estuary that day. Caribbean Spiny Lobsters occur farther out to sea in deeper waters. The habitat of our Smoothtail Spiny Lobster is described as coastal waters, down to 165ft deep (50m), on rock or coral. To that we can add that they cluster around man-made structures such as collapsing metal pipes.

The feeding habit of Smoothtail Spiny Lobsters is described as "predatorily opportunistic," meaning that they feed mostly on easy-to-catch crustaceans, annelids, echinoderms and mollusks more or less randomly encountered. They feed mainly at night.

Smoothtail Spiny Lobsters occur in the western Atlantic from Bermuda and Florida south through the Caribbean to Brazil. They can reach a body length of over a foot long (32cm) but most are about eight inches long (20m). They're not regarded as especially desirable for eating, and seem to be caught incidentally during the harvest of Caribbean Spiny Lobsters.

The IUCN Red List of Threatened Species doesn't rate our Smoothtail Spiny Lobster because there's not enough information about the species to decide. Now we've added a tiny bit more to that limited knowledge.

*****

STRIPED HERMIT CRAB
At low tide as you wade across shallowly submerged seagrass meadows of Shoalgrass, you see conch and whelk shells on the estuary floor. Often these shells are just the remains of dead gastropods, and are inhabited by hermit crabs. On beaches, in the mangroves, in the intertidal zone, and deeper water out at sea, it's amazing how many hermit crabs, and how many species of them, there are.

Hermit crabs are members of the superfamily, or group of families, known as the Paguroidea, and about 1100 species of hermit crabs are known. Recently someone here brought in a 3½-inch long shell (9cm) emptied of its maker but occupied by a hermit. The shell, covered with green algae, was placed on the aquarium's sandy floor, but in a position inconvenient for the crab. Before long the crab began emerging, needing to turn the shell upright, exposing more of his body than normal. The bodies of regular crabs are much wider than long, but now we could see that this hermit's body was slender like a crawfish's, and curved, enabling it to fit better inside the coiled shell. You can see the hermit emerging with it narrow, curved back, or carapace, clearly visible, at http://www.backyardnature.net/n/15/150315hc.jpg.

Once the hermit had flipped over the shell, he assumed his normal position and with his stalked eyes waving back and forth surveyed his new home. You can see him then at http://www.backyardnature.net/n/15/150315hd.jpg.

Because of his large size, the distinctive yellowish lines ornamenting his legs, and the fact that he's a common species, the hermit's identity was easy to figure out. He's the Striped Hermit Crab, CLIBANARIUS VITTATUS, found in shallow water from Virginia on the US eastern coast south through the Gulf of Mexico and the Caribbean to Brazil. The species is noted for being able to survive outside of water for longer periods than other hermits. Striped Hermit Crabs live on sand or mud, in seagrass meadows, on rock jetties, in oyster beds and other inshore habitats, at depths down to over 70ft (22m).

The University of Southern Mississippi's Scott Aquarium provides a Striped Hermit Crab document in PDF format providing much information about the species, including an illustration of the entire slender, curved body, which looks as vulnerable outside a mollusk shell as it really is, at http://www.usm.edu/gcrl/fisheries_center/docs/brochure.hermit.crab.pdf.

*****

SEA SLUG/ NUDIBRANCH
Some of the most amazing occupants of our new aquarium in Diego's restaurant/ecotour headquarters are introduced incidentally, especially when we add macroalga-encrusted rocks. Leafy rock algae constitute jungles in which the smaller inhabitants only occasionally show themselves, and sometimes what emerges draws a crowd of folks who never dreamed such exotic life forms could exist in our local waters. One such little being was the 3/8ths-inch long (1cm) critter that turned up one night on the aquarium's glass wall near the water's surface, shown at http://www.backyardnature.net/n/15/150315ss.jpg.

Though I've never seen such a thing in the wild, often in books I'd run across pictures of similar creatures. They're nudibranchs -- "nudibranchs" being the preferred plural form, and the end "ch" pronounced like a k instead of how it looks. Nudibranchs are a kind of gastropod (snail-like) mollusk. In fact, from outside the aquarium, the nudibranch's underside as it skims over the glass's inside surface looks just like that of a snail, but a snail without a shell. The shell is replaced by slender, fleshy, fingerlike appendages. Another shot of the above individual, better showing the curve-tipped, bull-horn-like tentacles at the front, and stiff, ringed, sharp-pointed, goat-horn-like "rhinophores" above the tentacles, appears at http://www.backyardnature.net/n/15/150315st.jpg.

Rhinophores are chemical-sensing organs, or "chemosensors," used mostly to inform the nudibranch as to what kind of environment it's in, and what kind of food is thereabouts. The fleshy, fingerlike things on the back are "cerata," the main function of which is to simply increase the nudibranch's body surface-area. The nudibranch has no lungs, so its oxygen simply diffuses from surrounding water into the body, meaning that the more body surface area it has, the more oxygen can enter its body.

Despite our nudibranch's bland, creamy color, nudibranchs in general are thought of as among the most colorful creatures on earth. One explanation for their wild colors is that during the course of evolution they traded their typical mollusk shells for more sophisticated defense mechanisms. Some species evolved forms, colors and textures mimicking surrounding sponges or corals. Others developed intensely bright and contrasting color patterns, believed to warn potential predators that they are distasteful or poisonous.

Best I can tell from photos on the Internet, our nudibranch is DONDICE PARGUERENSIS, not known well enough to have a common name, and distributed in the Caribbean area. Something remarkable about Dondice parguerensis is that it's thought to be entirely parasitic on Upside-down Jellyfish, a species of which we've admired at http://www.backyardnature.net/yucatan/cassiope.htm.

Another species of Dondice found in the Caribbean area, Dondice occidentalis, only eats anemones. Other than their different feeding behaviors, these two species are so similar morphologically that some experts believe they may actually be the same species occupying different ecological niches. Current genetic studies are expected to clarify the issue.

When threatened by predators, jellyfish shoot hundreds of stinging, arrowlike "nematocysts" into surrounding water. However, Dondice parguerensis, who lives in a jellyfish, is immune to such nematocysts. Moreover, by living in a jellyfish, it not only "lives in its food" but also is protected from predators by the jellyfish's stinging nematocysts. As far as is known, this is a strictly parasitic relationship, the jellyfish not benefiting from the nudibranch's presence in any way.

*****

PODOPTERUS FLOWERING Nowadays deep in the dry season some woody plants that have lost all their leaves are flowering. Seeing such fresh, hopeful blossomings on wintry-looking trees and bushes fills one with a sense of spring. You can see one such 10-ft-tall tree (3m) at http://www.backyardnature.net/n/15/150315pd.jpg.

I'd never seen what's shown in that picture, but at first glance I suspected that this tree, protecting itself with short branches that became sharp-pointed like big spines, was a member of the Buckwheat Family, the Polygonaceae. That's because the soft, three-winged fruits shown in the picture are structurally similar to those produced by the Buckwheat Family species known as docks (genus Rumex), whose springtime herbage often I have eaten in the North.

Knowing its family, it was easy to browse the list of Buckwheat Family members known to occur in the Yucatan, and realize that here we had the small tree known as PODOPTERUS MEXICANUS. The species is fairly commonly distributed in most of Mexico's arid thornforests and tropical evergreen forests, south into Costa Rica.

*****

PODOPTERUS MEXICANUS AND THE HUMBOLDT/BONPLAND EXPEDITION OF 1799 to 1804
Meeting Podopterus mexicanus sent my mind into a tangent different from usual.

First of all, when I gave the Latin name, or binomial, as Podopterus mexicanus, I didn't provide the whole name. Technically, I should have included the "authority," which consists of the name or systematized abbreviation of the name of the person or people who first described the species to science. The most famous such authority is Linnaeus, known by the abbreviation L., as in the name Quercus alba L., for North America's White Oak.

The full name for our current plant is Podopterus mexicanus Humb. & Bonpl. The "Humb. & Bonpl." at the end refer to the authorities Friedrich Alexander von Humboldt (1769-1859) of Germany, and Aimé Jacques Alexander Bonpland (1773-1858) of France. Humboldt is the Humboldt of Humboldt Current fame, and I first grew interested in the Humboldt/Bonpland team when I read Humboldt's lengthy, detailed Reise in die Aequinoctial-Gegenden des neuen Continents, describing the expedition these men conducted into tropical America from 1799 to 1804. That adventurous trip was one of the earliest serious scientific expeditions made into the New World. The book describing the expedition, as well as other of Humboldt's books, some in English translation, can be freely downloaded at the Project Gutenberg site at http://www.gutenberg.org/ebooks/author/1995.

The book describes in detail the plants, animals, people and landscapes Humboldt and Bonpland encountered -- including some 60,000 plants that were, until then, mostly unknown in Europe. During the latter part of the trip, in 1803 and 1804, the men passed through Mexico. Bonpland was the main botanist, and did the drawings, but Humboldt was a good botanist, too.

Among the rare books at the Missouri Botanical Garden where I worked during the 1970s is Bonpland's 1808-09 publication entitled Plantes équinoxiales recueillies au Mexique : dans l'île de Cuba, dans les provinces de Caracas, de Cumana et de Barcelone, aux Andes de la Nouvelle Grenade, de Quito et du Pérou, et sur les bords du rio-Negro de Orénoque et de la rivière des Amazones. In that book Bonpland, in French and with an excellent drawing, introduces to the scientific world our currently prettily-flowering Podopterus mexicanus.

Bonpland writes that he and Humboldt discovered the plant near the village of Antigua, a little to the north, northwest of the port city of Veracruz, on the Mexican Gulf Coast. You can see Bonpland's illustration of the plant appearing in the book here.

At the above page you can continue to Bonpland's official Latin description of the plant, and his comments in French, by clicking a few times on the "NEXT" icon at the page's bottom.

Wikipedia's page for Alexander von Humboldt is at https://en.wikipedia.org/wiki/Alexander_von_Humboldt.

Bonpland's Wikipedia page is at https://en.wikipedia.org/wiki/Aimé_Bonpland.

*****

GAUMER'S NOPAL CACTUS
In this year's January 4th Newsletter we looked at a 4.5m tall (15ft), prickly-pear-type cactus, the Wild Nopal Cactus, Nopalea inaperta, common in this area. Our Wild Nopal Cactus Page is at http://www.backyardnature.net/yucatan/inaperta.htm.

On that page I mention that another very similar cactus shars the same limited distribution with the Wild Nopal Cactus, and that's Gaumer's Nopal Cactus, Nopalea gaumeri. Some specialists say that Gaumer's Nopal Cactus is a mere variation of the Wild Nopal Cactus, while others list it as a distinct species. Since publishing the Wild Nopal Cactus Page I've been waiting to find cacti answering to the description of Gaumer's Nopal Cactus, to see what I thought about the situation. Now I've found some, and they were flowering. The plants were much smaller than Wild Nopal Cactus, only about knee high, as shown at http://www.backyardnature.net/n/15/150315no.jpg.

As with the earlier Wild Nopal Cactuses, these plants grew amidst thick brush in thin soil atop limestone. In fact, numerous Wild Nopal Cactus plants inhabited the same area. A 2m tall one (7ft) stood only 3m away (10ft) from the small one in the picture. Several of these smaller cacti were in the area, but also there were cacti of intermediate size. The smaller cactus's joints were less flattened than those of the bigger ones, but there were transition states between cylindrical and flattened, too. So, just focusing on cactus size and joint shape, it was hard to say whether two species were being dealt with, or just one.

However, one big difference between the tall and short plants was that all the smaller ones were flowering, while the larger Wild Nopal Cactuses mostly were not. A branch showing some of the short cactus's spiny pads and flowers is at http://www.backyardnature.net/n/15/150315np.jpg.

A close-up of a flower showing the yellow-green, deeply lobed stigma on its white style protruding beyond a dense cluster of stamens with yellow anthers and pink filaments is shown at http://www.backyardnature.net/n/15/150315nq.jpg.

Another feature the above picture shows is that the green ovary below the red sepals and corolla bears clusters of well formed spines. The larger Wild Nopal Cactus's ovaries also bear spine clusters, but the spines are shorter and more slender than these.

A look at spine clusters on the small cactus's pad is shown at http://www.backyardnature.net/n/15/150315nr.jpg.

So, do I think that these small cacti constitute the distinct species known as Nopalea gaueri, or are they just a local variation of the common Wild Nopal Cactus, Nopalea inaperta?

On the basis of the smaller cactuses all flowering at the same time while surrounding Nopalea inaperta plants were only rarely flowering, and because of the much larger spines on the smaller cactus's ovaries, I'm thinking that probably two species are involved, and that the smaller ones are NOPALEA GAUMERI. This species really has no English name, but we'll call it Gaumer's Nopal Cactus.

Gaumer's Nopal Cactus is endemic to only to the northern third or so of the Yucatan Peninsula, and mostly in the more arid northwest.

*****

NOPALEA INAPERTA FLOWER
Not all the Nopalea inaperta cactuses were flowerless. At least one plant along the road where Nopalea gaumeri was flowering so nicely also had one flower, with more flower buds soon to open. That one flower is shown at http://www.backyardnature.net/n/15/150315n2.jpg.

*****

PINK SALT PONDS AT LAS COLORADAS
Often during flamingo viewing trips when we're in the vicinity of Las Coloradas, the boatman veers from the estuary's center channel and heads for the northern shore. The boat noses onto a narrow bank just below what seems to be a long chest-high ridge, but which in fact is a levee that's part of an extensive system of artificial embankments that surround and contain numerous large evaporation ponds of the saltworks at Las Coloradas. Here tourists can climb atop the levee and enjoy the view shown at http://www.backyardnature.net/n/15/150315pk.jpg.

In that picture Paco, a member of Diego Nuñez's guiding crew, stands with two ladies from San Francisco who are astonished by the water's pinkness. You can see an aerial view of part of the sprawling salt-pond system on the Spanish-language page of the Mexican company operating the Las Coloradas saltworks at http://www.isysa.com.mx/plantas.htm.

In that page's aerial view, all the ponds are pink, though some are pinker than others. Often only one or a few ponds are vividly pink, and the pinkest ponds are those clustering around the instillation where the salt is mechanically gathered from the ponds' floors.

This can be explained by the fact that the water's pinkness results from the presence of algae containing unusually high levels of pigments called carotenoids, especially ß-carotene, or beta-carotene, which is a strongly colored red-orange pigment found in certain plants and fruits. ß-carotene gives tomatoes, carrots, pumpkins and sweet potatoes their color. Carotenoids also give flamingos and Rosette Spoonbills their pink color. When the birds eat carotenoid-rich algae, as well as tiny crustaceans who also feed on the algae and therefore contain large concentrations of carotenoids, enzymes in the birds' livers break down the carotenoids into pink and orange pigment molecules. These pigment molecules then migrate through the birds' bodies to their feathers, bill, and legs, making them pink.

In the salt ponds of Las Coloradas, the main alga species contributing to the salt-ponds' pinkness is DUNALIELLA SALINA, belonging to the Green Algae Phylum, not the Red. Few organisms can survive such highly saline conditions as Dunaliella salina, which doesn't have a good English name.

In normal ocean water Dunaliella salina doesn't impart pinkness to the water, but in the salt ponds as evaporation causes the remaining water's salt content to increases, the alga prospers and causes a pink algal "bloom." One reason Dunaliella salina thrives in very salty water is that other alga species can't survive in it, allowing Dunaliella salina to take over. Since in very salty water about 14% of the dry weight of Dunaliella salina can consist of red-orange ß-carotene, the waters turn red. At Las Coloradas the ponds nearest the salt refining plant are pinkest because the network of evaporation ponds are configured so that regular seawater enters the farthest ponds, then as evaporation concentrates the water's salt, the saltier water is pumped into ponds closer to the factory, and as the water gets saltier, Dunaliella salina creates an ever-more-spectacular algal bloom, and the water becomes pinker and pinker.

Dunaliella salina isn't the only alga species in the saltponds' water, or even the only species of the genus Dunaliella, but it's the one overwhelmingly causing the water to be pink. A 2006 paper in English by Francisca García et all, entitled "Physiological characterization of Dunaliella sp. (Chlorophyta, Volvocales) from Yucatan, Mexico," technically describs the biological details of Dunaliella algae found in the salt-ponds of Las Coloradas and nearby San Crisanto. It can be freely downloaded in PDF format here.

Dunaliella salina is famous for much more than causing the waters of Las Coloradas's salt-ponds to turn pink: The alga is grown commercially as a source of ß-carotene. Different technologies are used, from low-tech, extensive cultivation in lagoons to intensive cultivation at high cell densities under carefully controlled conditions. ß-carotene is valued as a natural food coloring, plus in the body it's changed into vitamin A, needed for good vision, a strong immune system, and for healthy skin and mucous membranes, so it's an important presence in the health-food industry. Also, ß-carotene is an antioxidant, and you've heard of the therapeutic value of antioxidants.

*****

FEATURED ESSAYS FROM THE PAST:

"Rained-on Hut" from the August 22, 2010 Newsletter, at http://www.backyardnature.net/n/p/100822.htm

"Dawn Rain" from the September 26, 2010 Newsletter, at http://www.backyardnature.net/n/p/100926.htm

*****

Best wishes to all Newsletter readers,

Jim

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