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

December 28, 2014

WOOD STORK CATCHES A FISH
Our Flamingo-watching boat was passing a Wood Stork staring penetratingly into the shallow water before him, not flying away despite our nearness. We saw why he tarried when he ran forward a few steps and stabbed his big beak into the mostly submerged mass of Widgeongrass, and withdrew a squirming, catfish-shaped fish. That's shown at http://www.backyardnature.net/n/14/141228sn.jpg.

Again and again the stork jerked back his head, briefly releasing the pressure on the fish so it'd shift into a new position, then he'd clamp down hard again, probably breaking a few of the poor fish's bones in the in the process. From our distance the fish looked like a Banded Blenny, Paraclinus fasciatus, a common tropical species of shallow, salty water in the northern and central Western Atlantic.

Two or three times the fish slipped free, but the stork just snatched him up again. Several minutes passed until the fish was subdued enough for the big bird to begin orienting it in his beak so that the fish's head pointed toward the gullet, as shown at http://www.backyardnature.net/n/14/141228sm.jpg.

The moment before the stork raised his head and the fish slipped into oblivion is shown at http://www.backyardnature.net/n/14/141228sl.jpg.

*****

REDHEAD DUCKS WHERE THEY'RE NOT SUPPOSED TO BE
Redhead ducks, AYTHYA AMERICANA, are commonly seen throughout much of North America, at least during migration. Though they migrate through most of northern and central Mexico and overwinter in central Mexico's highland volcanic belt, according to distribution maps and the memory of local birders, they're not supposed to occur here in the Yucatan.

However, this week several Redheads are visiting Ría Lagartos Estuary, despite the distribution maps. You can see them at http://www.backyardnature.net/n/14/141228rh.jpg.

To those used to seeing Redheads in their usual freshwater lakes of North America's interior, it might seem strange seeing them here coasting by flamingo and pelicans in saltwater lagoons with crocodiles.

*****

MACKEREL HANGING FROM A WINDOW
That day someone in town must have hit it lucky out fishing because several people appeared in the streets carrying long, silvery fish. And when I stepped out to go buy tortillas, here came a car with my friend Julio dangling his own outside the car window. You can see Julio showing off his treasure, with the end of my street in the background, and the estuary beyond, at http://www.backyardnature.net/n/14/141228mc.jpg.

I'm a real landlubber so I had no idea what fish it was. Julio called it a Peto, which when Googled turned up a kind of women's bibbed coverall, so for me the ID process had start from the beginning. And this fish that arrived so ingloriously dangling outside a car window turned out to be royalty among fish species, one of the most sought-after gamefish along the Western Atlantic coast from Canada south through the Gulf of Mexico and Caribbean to Brazil: It's the King Mackerel, SCOMBEROMORUS CAVALLA. It's mostly a tropical and subtropical species so it extends into cooler waters only erratically.

In the picture, it's hard to miss the narrow, ringlike constriction encircling the fish's body about a quarter of the distance back from the head. That's where the fish was caught in the net. Though King Mackerel often are caught on lines using live bait or trolled lures, this one was caught with a gill net, and must have stayed stuck for a long time. Commercially King Mackerel are sold for the making of fishsteaks, or to be canned or salted.

Just by looking at the King Mackerel's smooth, streamlined body it's easy to guess that this fish doesn't lazily wander about the ocean's floor, but rather streaks through its landscape. In fact, King Mackerels are voracious, opportunistic predators of other fish and squid. They keep moving so fast that they have no swim bladder, which is not needed because forward motion keeps the fish where it wants to be. King Mackerels have been documented as long as 6ft (184cm), but usually they're a little less than half that length.

The name "mackerel" is used for a number of normally slender, silvery fish with vertical stripes on their backs and deeply forked tails. "True mackerel" belong to the Mackerel Family, the Scombridae, of which about 21 species are recognized, including the fish known as tunas, which form a subgroup in the Mackerel Family. The best known species thought of as a mackerel is the Atlantic mackerel, Scomber scombrus.

Just from outside appearances I doubt I could distinguish our King Mackerel from closely related species of the same genus. However, the list of fish known from Ría Lagartos Biosphere Reserve bears only two species of Scomberomorus, and one of those is the King Mackerel.

On the day when it seemed that most folks in town got their King Mackerel, I received more than one invitation for a Peto taco, being assured that this was one of the best tasting of all fish, especially when sprinkled with a little hotsauce. And that we vegetarians needn't worry about eating them, because they don't count as meat.

*****

PEAR WHELK EGG CASE
In our December 14th Newsletter we looked at the pretty egg cases of the True Tulip sea snail washed ashore here, which you can review at http://www.backyardnature.net/yucatan/tulipa.htm.

This week yet another kind of egg case turned up on the sandy, Gulf-facing beach of the slender finger of land separating Ría Lagartos Estuary fro the sea. You can see it at http://www.backyardnature.net/n/14/141228bu.jpg.

A close-up of a shattered bladder inside which tiny, white forms in the shape of snails were discernible with magnification, is at http://www.backyardnature.net/n/14/141228bv.jpg.

By now we know that such floating egg cases are produced by gastropod-type mollusks of the kind producing shells of the often-ornamented and prettily colored kind people like to pick up from sandy beaches. This particular egg case, with its individual bladders bearing short spines along both their upper and lower margins, and the bladders themselves with one side broader than the other and with different-shaped spines, was produced by what's commonly called the Pear Whelk, BUSYCOTYPUS SPIRATUS.

Pear Whelks are classic seashell-type, pear-shaped sea snails that feed on sandy bottoms of the Gulf of Mexico, and on the US Atlantic coast reach as far north as about North Carolina. They prey on clam-type mollusks -- bivalves. Pear Whelks need only fifteen minutes to an hour to pry open and consume a thin-shelled, clam-type mollusk.

*****

TARANTULA HAWK WASP #2
Last week we looked at the all-black Mexican Tarantula Hawk, which is so big that often birders confuse it with a hummingbird. That was Pepsis mexicana, and you can see it and read about it at http://www.backyardnature.net/yucatan/hawkwasp.htm.

In these parts, that's the most commonly seen tarantula hawk species. This week a second tarantula hawk species allowed itself to be photographed  It's of about the same size as the Mexican Tarantula Hawk and also looks like a hummingbird when it flies, but this new one is easily distinguished form the Mexican by its orangish wings and antennae. You can see one feeding atop flowers of the eupatorium-like bush Chromolaena laevigata at http://www.backyardnature.net/n/14/141228wp.jpg.

This one sometimes is called Milde's Tarantula Hawk. It's PEPSIS MILDEI, distributed from the arid US southwestern states south throughout Mexico to Panama. In our area you see about one Milde's Tarantula Hawk for every five Mexican ones. I've only seen this species zipping through the air with its long legs dangling behind, looking like a long-tailed hummingbird, and feeding on nectar and pollen, and those behaviors are identical to what the Mexican normally does.

Its tarantula-hunting habits are the same, too. When an adult female is ready to lay an egg, she locates a tarantula by smell, possibly having to enter the tarantula's burrow to drag it out, and then the wasp may need to wrestle with the tarantula until it can deliver a sting. The sting paralyzes the tarantula almost immediately, and the tarantula stays paralyzed for the rest of its sad life. The paralyzed tarantula is dragged into a burrow the wasp has dug into the ground, the wasp lays her egg on the tarantula, and the underground nest is sealed. When the egg hatches, the tiny larva immediately begins feeding on the tarantula, which remains alive, but paralyzed, until the final stages of the larva's growth.

Tarantula hawk wasps also sting humans, and their stings are regarded as among the most painful of all insect stings. However, they're not dangerous unless there's a special sensitivity. The wasps aren't aggressive toward humans, though, and sting only when aggressively provoked.

*****

FIGURING OUT A HYDROID
On the Gulf of Mexico beach we were combing through seaweed heaped up by waves when my biologist friend Willi found something unlike anything either of us had ever seen. It was a small, slender, stiff, cylindrical, stem-like thing from which emerged pale, translucent, intricately feathery items as shown at http://www.backyardnature.net/n/14/141228hx.jpg.

It didn't make sense. The stem was clearly photosynthetic and containing a vascular network like a typical flowering plant, but the "leaves" seemed to lack chlorophyll and were so delicate and flimsy that surely they lacked xylem and phloem. The "stem" didn't have nodes from which leaves normally emerge, and the leaves were unequally spaced. Under magnification with a hand lens, the mystery only increased, as you can see at http://www.backyardnature.net/n/14/141228hy.jpg.

The "leaf" looks even more exquisite and at its base arise cone-like things held erect above the central stem. Moreover the base of the leaflike object's "petiole" seems to wrap around the green stem with some kind of transparent noose. A closer look at these otherworldly features is seen at http://www.backyardnature.net/n/14/141228hz.jpg.

Really at first I didn't know whether this was an animal or a plant, a fungus or an alga. I had to review the whole array of Life on Earth to get my bearings, and make sure I wasn't forgetting some obscure kind of life form capable of looking like this.

The first breakthrough was to realize that here we had two things. The stiff, green "stem" was actually a Manatee Grass leaf. The mystery organism attached itself to the Manatee Grass leaf with a transparent noose. The mystery item exhibited symmetry, so it wasn't something like a sponge. The cone-like items appear jellylike and translucent like something animal-based, not of plant origin. The "nooses" around the leaf were unlike anything an alga might create. Surely these were animals. On Caribbean beaches we've seen Bryozoa consisting of fan-like colonies of tiny animals, but no Bryozoa could be found looking like our discovery.

Reviewing the Tree of Life and seeing how the Bryozoa form a phylum -- phyla being the second big subdivision below the Kingdom of Animalia, the animals -- and disqualifying the various other animal phyla such as the sponges, the amoeba-like Placozoa, etc., finally nothing was left but the Cnidaria, the jellyfish phylum. What I hadn't realized until this review is that many Cnidaria are colonial, organizing themselves into colonies like the Brozoa.

By doing an image search on the Internet of the many forms of Cnidaria, finally I found organisms looking like our find within the Class Hydrozoa -- the "hydrozoans," or "hydroids." The feathery structures on our Manatee Grass leaf were tiny, colonial hydroids.

Furthermore, among the hydroids there's a family known as the Aglaopheniideae that embraces many species whose individual minute animals organize themselves into feathery structures like ours. Though literature is relatively scant, I'm guessing that our discovery is the genus Aglaophenia, and if you want to see an organism looking a good bit like our particular find, check out Aglaophenia pluma, which occurs in shallow marine waters worldwide. About 38 Aglaophenia species are recognized. Field marks leading me to this corner of the Aglaopheniideae include the manner in which the scale-like things arise opposite one another on the "feather's" branches, not alternating as in most hydroid species. Also, the shape of the pinecone-like structure is important.

Most hydroids have a life cycle in which two very different-looking forms alternate with one another. One form is the "polyp stage" and the other is the "medusa stage." Our feathery colony is composed of many individual polyps, so it's the polyp stage. Each colony produces either all male or all female reproductive polyps. The pinecone-like structure on our colony is called a "corbula." Inside corbulae there are "medusoids," which are not real medusas, but something special for this group of species. Medusoids inside corbulae of male colonies shed sperm into the sea that fertilize eggs in the medusoids of female colonies. The resulting zygotes on the female colony develop into tiny larvae called "planula larvae," which move about with the help of hairlike cilia. The larvae settle someplace and metamorphose into the first polyp of a new, feathery colony. Subsequent polyps arising from this first polyp differentiate into different forms specializing in feeding, defense or reproduction.

This life cycle is different from most life forms in the Cnidaria in that there are no real medusas, but rather immobile medusoids that stay on the colonial structure, where larvae emerge from it.

On each "barb" of our feathery, polyp-stage colony, every triangular-shaped section consists of two scale-like structures. From behind each of those scale-like structures, when the colony is in water and its polyps are alive, a minute polyp extends tiny tentacles into the surrounding water, with which it traps microscopic floating organisms. Just below each feeding polyp are similarly tiny defensive polyps equipped with stinging cells called nematocysts.

These are general life cycle details of the genus Aglaophenia, and I'm only guessing that they are the same for our species, whichever it is.

What a pleasure on a balmy morning at the beach to be introduced to a whole new form of life, whose presence and beauty until now have gone unnoticed by me!

What else am I missing? Where is it?

*****

BLACK MANGROVE
In our area the swampy mangrove forests surrounding the estuary are composed of four species. You may want to review them on our Mangrove Page at http://www.backyardnature.net/yucatan/mangrov2.htm.

The main mangrove species along the usually flooded shore is the Red Mangrove, the one with multiple, "stilt-roots" descending from the tree's main branches, sprouting multiple roots on the way down before plunging into water. However, in some places another mangrove species dominates the estuary margins, in which case the stilt roots are replaced by thickets of slender, grayish, fingerlike poking up from the water. These are pneumatophores, which help the tree acquire air. The tree producing the pneumatophores is the Black Mangrove, AVICENNIA GERMINANS, a member of the mostly tropical Acanthus Family, the Acanthaceae. A Black Mangrove with pneumatophores at the estuary's edge is shown at http://www.backyardnature.net/n/14/141228mf.jpg.

A close-up of pneumatophores emerging from mud at low tide is at http://www.backyardnature.net/n/14/141228mg.jpg.

Black Mangrove leaves are simple, evergreen and leathery, and arise two per stem node (opposite). The leaves, smaller than those of Red Mangrove, are shown at http://www.backyardnature.net/n/14/141228mh.jpg.

The leaf bases opposing one another on the stem are shown at http://www.backyardnature.net/n/14/141228mi.jpg.

One feature to notice in that picture is that no salt-excreting glands appear on the petioles at the blade bases, as with the White Mangrove and Buttonwood, which are two of our four mangrove species. This lack of petiole glands helps distinguish Black Mangrove from those two species while the lack of stilt roots and presence of pneumatophores separate it from the Red Mangrove. All mangrove species have special adaptations for dealing with salt in the brackish water they live in. Black Mangrove's way of dealing is to expel it from the surfaces of its leathery leaves.

The Black Mangrove's trunk isn't black, but its heartwood is blackish. The bark is a little dusky, though, as shown at http://www.backyardnature.net/n/14/141228mj.jpg.

Of our four mangrove species, Red Mangrove usually occupies the deepest water, and normally as the water becomes shallower Red Mangrove give way to Black Mangrove. White Mangrove and Buttonwood live on often exposed ground, with Buttonwood typically in the driest places, often forming the mangrove forest's outer border. All four mangrove species work together to stabilize the shoreline, provide buffers from storm surges, trap debris and detritus brought in by tides, and provide feeding, breeding, and nursery grounds for a huge variety of fish, shellfish, birds, and other wildlife.

Black Mangrove occurs in tropical and subtropical regions of the Americas on both the Atlantic and Pacific coasts, and on the Atlantic coast of tropical Africa. In the US it reaches coastal areas of Texas and Florida, and even southern Louisiana and coastal Georgia.

*****

CHROMOLAENA/ "EUPATORIUM"
Most days, along the twenty or so miles (30kms) of coastal road just south of Río Lagartos running between San Felipe and Las Coloradas, I go biking for the exercise and just for the pleasure of it. Nowadays along that whole stretch there's just one colony of the bushy, white-topped, Composite Family member shown at http://www.backyardnature.net/n/14/141228eu.jpg.

The first time I saw this car-size cluster of plants I slammed on the bike's brakes and circled back for a closer look, because the plants' stem-top flowers were busy with the biggest collection of butterflies seen since I've been here. Mostly there were orange Gulf Fritillaries and White Peacocks, but also a few Zebra Heliconians, Monarch-like Soldiers, a dusky Glassy-winged Skipper, and a few others. The plant reminded me of the similar looking Lateflowering Boneset, Eupatorium serotinus, we had back in Texas which similarly attracted hoards of butterflies and whose white blossoms also smelled intensely sweet.

In fact, most North American wildflower fanciers seeing our roadside composite without a blink would assume that it's just another member of the big, commonly encountered, often weedy Eupatorium genus. The flowering heads certainly look like those of Eupatorium, especially with the long, stringy style branches rising above each head, as shown at http://www.backyardnature.net/n/14/141228ew.jpg.

Up closer, however, doubts arise about this being just another Eupatorium, because the greenish bracts composing the urn-shaped involucre surrounding the disc flowers look different from "normal" Eupatorium bracts, as you can see at http://www.backyardnature.net/n/14/141228ex.jpg.

Notice how each bract bears just one strong, green midrib with much smaller, green veins paralleling it for its length, and that the bracts' margins are white and papery. Eupatorium bracts aren't supposed to do that. Still, individual disc flowers removed from a broken-open head look enough like standard Eupatorium flowers, as seen at http://www.backyardnature.net/n/14/141228ey.jpg.

Also, the stems' lower leaves, which arise two to a node (opposite) could belong to any Eupatorium, as shown at http://www.backyardnature.net/n/14/141228ev.jpg.

However, besides the strange bracts, there's one other matter that was visible in the first photo that arouses doubt about this being a Eupatorium. That is, our roadside plant has branching, woody bases. Eupatorium species are perennials, but they seldom branch, and I've never seen one that was genuinely woody like these.

Our roadside butterfly attracter is CHROMOLAENA LAEVIGATA, which early botanists with Eupatorium on their mind called Eupatorium laevigatum. Chromolaena is mostly a tropical American genus and embraces about 165 species found from the southeastern and south-central US south into Brazil, with a center of evolution being in Brazil. Despite our Chromolaena laevigata being one of the most widely spread of the genus, sometimes becoming an agressive weed, it's little known in English speaking countries. When English speakers refer to it often they just call it Chromolaena. It enjoys many Spanish and Portuguese names, however, one of the most interesting being Purgación, which refers to purification, purging or atonement.

Studies have shown that oils obtained from Chromolaena laevigata show antibacterial action

*****

ESTUARY WATER ENTERING THE SEA
In front of Río Lagartos, directly north of town across Ría Lagartos Estuary, a manmade canal cuts through the narrow finger of land separating the estuary from the Gulf of Mexico. At one edge of the canal's seaward outlet there's a seawall topped with a Jesus-on-the-Cross fisherman's chapel lighted at nights with solar power stored in a battery, as shown at http://www.backyardnature.net/n/14/141228xx.jpg.

Beyond the chapel, notice how the Gulf's water changes color. The dark blue water on the left is issuing from the estuary during ebb tide -- when the water is going down.

Inside the estuary, water issuing from the mangrove forests typically is dark amber colored, as shown at the bottom of our Mangrove Page at http://www.backyardnature.net/yucatan/mangrov2.htm.

The water's darkness is caused by orangish tannin pigments derived from decomposing organic matter in the mangrove area, and from organic matter itself suspended in the water. Mangrove trees are especially rich in tannins.

These tannin- and organic-matter-rich waters are profoundly important to offshore biological communities, especially the corals. As Lucaya Luckey-Bethany writes in the paper "Mangrove Forest Decline and its Effect on Coral Reefs," "The destruction of mangrove forests in the coastal wetlands is drastically decreasing the amount of natural tannins in the water and thus subjecting the nearby coral reefs to undue UV radiation. In effect, the reefs are being sunburned and eventually coral bleaching occurs." This paper is freely available online here.

Therefore, when fishermen exit the canal on their way to unknown fortunes on the high sea, they may tip their hats to Jesus on his Cross in his solar powered chapel, but it would also be appropriate to show their respect for the dark water below them, which assures the productivity of the fisheries they're going out to exploit.

Its water dark with organic matter and tannins -- not to mention zooplankton, phytoplankton and immature organisms that have used the mangroves as a nursery -- is the very lifeblood of the offshore ecosystems they depend on.

*****

FEATURED ESSAYS FROM THE PAST:

"Waves" from the July 31, 2011 Newsletter, at http://www.backyardnature.net/n/p/110731.htm

"Harmoniously Humming" from the January 9, 2011 Newsletter, at http://www.backyardnature.net/n/p/110109.htm

*****

Best wishes to all Newsletter readers,

Jim

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