June 26,  2011

SAND WASPS
Flitting above the sand on paths between buildings here you see a certain kind of wasp frequently landing and digging little pits. The wasp digs with such gung-ho obsessiveness that damp sand sprays several inches behind it. Typically the digging breaks off in a few seconds, though, the wasp returns to flying back and forth above the sand, then lands again and digs a few more seconds scattering more sand. This, again and again.

That's something you see nearly every day here, but lately there was a new twist. A wasp landed at a pit and instantly began moving very fast BACKWARD away from the hole. Then it'd fly around a bit, land, and move backward again. Several wasps were circulating in the area and anthropomorphically it seemed to me as if the digging wasp were trying to draw attention to the pit. You can see one just landed at its hole, moments before beginning its backward rush, at https://www.backyardnature.net/n/11/110626wp.jpg.

You can almost guess the name volunteer identifier Bea in Ontario ferreted out for this sand-digging wasp: sand wasp. But of course there are jillions of kinds of sand wasp. Probably what's in the picture is a member of the Bembicini tribe of crabronid wasps, of which aabout 20 genera are recognized, and many species. Wasps in this group dig short, simple burrows in which they lay an egg, and provision the burrow with sting-stunned prey, which the wasp larva feed on when the egg hatches. The different wasp species vary in their preferences for kind of prey, kind of sand, etc.

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CRUNCHY WHITE TUFTS OF.... WHAT?
From one day to another you never know what you'll find on the beach. One day there's a knee-high pile of Turtlegrass, the next day that's all washed away and there are just a few shells. A while back the beach was strewn with white items looking like tufts of what Northerners know as Reindeer-moss Lichen, as shown at https://www.backyardnature.net/n/11/110626br.jpg.

Like dry Reindeer-moss Lichen, these tufts were so brittle that with your hand you could crush them into powder. However, they were too pretty to crush. Notice how the stems form Y-shaped branches. Such branching is said to be "dichotomous."

But, what kind of being is this? A coral, a sponge -- plant, animal, alga?

It was a kind of aquatic, invertebrate animal known as Bryozoa. Bryozoan colonies may grow as large as a meter across (3.3ft) but the individual tiny animals covering the white "skeleton" are microscopic. The colonies come in various shapes and forms, depending on the species -- treelike, sheetlike or fanlike, for instance. A fanlike bryozoan we've met is the Sea Fan, one of whose "skeletons" we show at https://www.backyardnature.net/yucatan/sea-fan.jpg    

The world of bryozoans is so huge and diverse that you might enjoy browsing Wikipedia's bryozoan page, found at http://en.wikipedia.org/wiki/Bryozoa.

Doing a Google image search for Caribbean bryozoans, it wasn't long until I had a name for my Reindeer-moss-like bryozoan. It's the White Tangled Bryozoan, BRACEBRIDGIA SUBSULCATA, found from the Gulf of Mexico south in the western Atlantic to Argentina. I read that at depths between 15 and 40 meters it lives on deep vertical walls and under slanted walls, and usually is associated with certain sponges and corals.

Who knows what tore our washed-up bryozoans off their walls? Maybe just currents, maybe a boat dragging an anchor.

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A BLACK, LONG-SPINED SEA URCHIN
Especially when the tide is out, in tide pools you see a fair number of the Variegated Sea Urchins we profile at https://www.backyardnature.net/yucatan/urchin.htm.

This week finally I saw a second species, one with black spines much longer than the Variegated's. You can see this new species underwater in a tide pool at https://www.backyardnature.net/n/11/110626ur.jpg.

Sea Urchins have a hard, Chinese-lantern-like interior skeleton technically referred to as a "test." When an urchin dies, its spines fall off exposing the test. In a pool not far from the one photographed above another of this black, long-spined species had recently died, and its test was just beginning to be revealed. You can see it, also submerged in shallow water, at https://www.backyardnature.net/n/11/110626us.jpg.

Strangely, among rocks surrounding the tide pools where I found these two urchins, waves were depositing thousands of what looked like bleached spines of this same urchin species. I had no idea how to interpret this.

Back in Marcia's visitor library, Humann & Deloach's Reef Creature Identification: Florida, Caribbean, Bahamas quickly pointed me toward a species known variously as the Long-spined, Black, or Lime Sea Urchin, DIADEMA ANTILLARUM. Moreover, the essay accompanying the picture told a story that might explain the recently dead urchin and all those loose, bleached spines.

For, in the Caribbean, Long-spined Sea Urchins used to be the most common of all sea urchins. The species, because of its abundance, was very important for maintaining the health of coral reefs because Long-spined Sea Urchins ate algae that otherwise would cover the coral, choking it out.

Then in 1983 a yet unidentified disease killed about 93% of the Caribbean's Long-spined Sea Urchins, up to 99.9% in some areas. Consequently growth of coral in the region slowed or even reversed, and the fish and other animals living on coral reefs declined in numbers due to less food and shelter. I even read that this reduced biodiversity of the coral reefs affected tourism in several small countries, stressing their economies, because they depended on the natural beauty of their reefs to attract visitors. If you Google the keywords "Mass Mortality in Diadema antillarum" you'll get pages providing very detailed descriptions of the disaster.

Who knows if our dead sea urchin had died from that disease, and whether the bleached spines being heaped up by waves that day had anything to do with this disease? It's true that this is the first time since I've been here that I've come across a sea urchin who died so recently it was in the process of shedding its spines, and that I've seen such masses of discarded spines.

I read that in some areas Long-spined Sea Urchins are making a comeback.

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SEA PURSLANE
All up and down the beach there's a certain sprawling perennial herb that habitually, among all the flowering plants along the beach, grows closest to the breaking waves. Clearly this plant is especially well adapted for thriving in salty sand and being coated by salt spray. The plant forms ankle-deep carpets on the sand and drapes itself over driftwood, as shown at https://www.backyardnature.net/n/11/110626sv.jpg.

Seeing the plant's succulent leaves and stems the average wildflower lover might guess that this is a Sedum, Crassula or Portulacca. However, with something like this you don't guess until you see flowers and/or fruits. That's because lots of different kinds of plants living next to the sea, through convergent evolution, develop sprawling species with short, dense, thickly succulent leaves, because that combination of features is especially adaptive for the salty seashore environment.

In fact, the plant's many-stamened flowers are unlike blossoms most of us are familiar with. For one thing, they lack petals. The things looking like white petals are "petaloid sepals." Usually sepals are green. You can see the un-petaled, many-stamened blossom at https://www.backyardnature.net/n/11/110626sw.jpg.

One of the plant's mature, already-split-open fruits is at https://www.backyardnature.net/n/11/110626sx.jpg.

A story goes with that last picture. After pollination, the fruit developed into a green, egglike capsule closely enveloped by the flower's five, green sepals. Upon maturation the sepals bent backwards (became "reflexed") and the capsule developed a fracture line around its middle, or equator -- which is very different from most splitting fruit capsules, which split lengthwise. When the capsule's top came off, black seeds were exposed lying in the capsule bottom, looking like little black eggs in a bowl. When raindrops hit inside the bowl, the water's force splashed the seeds out of the cup, dispersing them. In the last picture you can see one black seed still perched on the bowl's rim.

So, our seaside plant's main English names are Sea Purslane and Shoreline Purslane. It's SESUVIUM PORTULACASTRUM, and it's a member of the Aizoaceae, sometimes known as the Fig-Marigold Family. As that family is defined now, about 96% of its ±2500 species in 130 genera are endemic to arid or semi-arid parts of southern Africa. That explains why in the Americas we're not too familiar with the family, unless we snoop around garden centers looking at tags. Plants in the family often are sold commercially because of their pretty flowers and/or groundcover value.

Our Sea Purslane, however, is one of those rare species in the mainly African family that's native to mostly coastal, tropical and subtropical zones nearly worldwide. In the US it's found along the Gulf of Mexico and as far north on the East Coast to North Carolina.

I've never known a plant whose leaves and stems are more edible than Sea Purslane's. You can simply plop down beside a plant, pull off handfuls of succulent leaves and eat them raw without further ado. There's no hint of stringiness or bitterness, though to my taste they're a little too salty, even when washed. I think a salad of two-thirds lettuce, chopped cucumber and tomatoes, one-third Sea Purslane leaves, a bit of garlic, and doused with vinegar and oil, would make a memorable hermit salad.

You can see the succulent, crunchy interior of a leaf at https://www.backyardnature.net/n/11/110626sy.jpg.

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MANGROVE POLYPORE
We've seen that the relatively arid Yucatán is not a great place for mushrooms. Therefore, I had mixed feelings the other day when a couple of ear-shaped mushrooms suddenly appeared on a prettily varnished wooden railing that keeps me from falling off the observation deck of my second-story room. You can see them -- the larger 2.5 inches across (55mm) -- at https://www.backyardnature.net/n/11/110626po.jpg.

Such ear-shaped mushrooms are commonly referred to as shelf or bract fungi. In North America probably the best known shelf fungi are the banded little "Turkey- tails" frequently seen on logs in the woods. A feature of my railing fungus distinguishing it from most other shelf fungi was that its cap was thickly wooly with brown, hairlike, outward-leaning scales, as you can see at https://www.backyardnature.net/n/11/110626pp.jpg.

Mushrooms reproduce by spores typically formed on closely spaced gills on the mushroom cap's underside. Our railing fungus, instead of having gills on its undersurface, had many closely-packed pores, as shown at https://www.backyardnature.net/n/11/110626pq.jpg.

In that picture, shot from below, not only can you see the fungus's dark-based, off-center stem but also my own shiny noggin as I peered down from above. When you see such a fungal body with pores instead of gills, usually you have one of two big mushroom groups. If the fruiting body has a regular "mushroom shape," with a central stem, then most likely it's a member of the Boletus Family, the Boletaceae, many of which are good eating. If the mushroom has no stem or a very off- center stem, like ours, it's a member of the Polypore Family, the Polyporaceae, of which most are too tough to eat.

So, I began Googling tropical members of the Polypore Family and before long came up with an ID: Here we have DATRONIA CAPERATA, which grows on dead wood in the American and African tropics. It's a variable species usually recognized in the field by its cap being covered by long, slender, dark brown scales. The species may have a special fondness for mangrove swamps. In our mangroves it's the only fungus I've seen yet, growing on many standing trunks of trees killed by Hurricane Dean in 2007. I find no English name for it, but henceforward I'll be thinking of it as "Mangrove Polypore."

The big question was whether our Datronia caperatas was actively weakening the railing by consuming wood contributing to the railing's strength, or whether it was just feeding on the by products of other decay organisms in the wood, and therefore not really damaging the wood. I found a reference saying that the species causes "dry rot," and at least one definition of dry rot is that the organism causing it digests parts of the wood which give the wood strength and stiffness. Therefore, what little I can find about Datronia caperata suggests that it's not to be welcomed on my railing.

Therefore, Marcia, I've already removed the two little mushrooms from your railing. However, mushrooms are nothing but the fruiting bodies, or reproductive structures, of a fungus, so the railing-eating fungal "body" remains behind inside the railing, probably to issue new mushrooms in the future.

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COASTAL STRAND VEGETATION
The long, narrow sand ridge I'm living on now, wedged between the Caribbean on the east and a big mangrove swamp to the west, is cloaked with a fragile and unique plant community known as coastal strand vegetation. You can see an example I visit daily at https://www.backyardnature.net/n/11/110626st.jpg.

Coastal strand vegetation forms along shores in loose sand just above the high tide mark. Many plant species in this special kind of environment are endemic -- in the whole world occurring naturally only in this small region. Species diversity in coastal strand vegetation is low because few plant species can tolerate the zone's harsh conditions, which include high wind, salt spray in the air and high salt concentrations in the sandy soil, and that sandy soil itself -- basically plain sand -- has a very low holding capacity for both nutrients and water. Many plants in such zones are succulent.

An interesting feature of coastal strand vegetation is that very often its structure and general appearance is very similar to coastal strand vegetation in other parts of the world, even though the species in the two communities may be completely different. Most coastal strand environments are windblown and salty, so plants growing there, no matter what their kinship is, will be highly adapted to wind and high levels of salt. Salt-tolerant plants are often succulent because succulent stems and leaves retain more water than non- succulent ones.

In the above picture of our local coastal strand vegetation, the shrub with large, round leaves up close is Seagrape. The low, scrambling, mat-forming plant behind it is Sea Purslane. The dense, grayish shrub at the right is Sea-Lavender. The orange-green shrub behind and to the right of the Sea-lavender is Gullfeed. These coastal strand plants and others of this area can be reviewed on our "Notes on Flowering Plants & Ferns of Beaches & Saltwater Lagoons" page at https://www.backyardnature.net/yucatan/seashore.htm.

You might enjoy Googling the keywords "coastal strand vegetation º" with º replaced by the name of another part of the world, such as California or Australia. On resulting pages you can see what plants in those places have evolved to occupy the coastal strand environment. You've seen that Beach Gentian is one of our coastal strand wildflowers. I see Beach Gentian missing on a list of California's coastal strand vegetation, but they have Bush Lupines, which must be nice, too.

Of course a prime danger to the coastal strand is human beings building on the beach. Often large parts of the beach are scalped so that prospective land buyers can more easily see the land.

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SHELL SAND
If you sprinkle sand from our beach into the palm of your hand for a close examination, it looks like this: https://www.backyardnature.net/n/11/110626sd.jpg.

The neat thing about our sand is that it's nearly entirely composed of tiny particles of coral and shells. In the above sprinkling I don't see a single piece I'd call quartz, which would dominate in a sand sample taken, say, from the bottom of a bayou back in Mississippi. In Mississippi sand we'd find irregularly spherical quartz particles and at least some tiny, black sheets of biotite mica, reddish hematite, pink or amber feldspar, and more.

In fact, sand is fascinating if you look at it closely. Once I backpacked from one side of Chihuahua's Copper Canyon to the other, and the only thing I brought back from the trip was a vial of sand collected in the bottom. I'd read that the canyon cuts through mineralogically interesting strata, so its sand should have been extraordinary, and it was.

I'm looking forward to making such pictures of sand in other places, so we can just sit back and admire more variations on the sand theme.

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DISORGANIZED ZONE OF DISTURBANCE
For over a week storms broke out all along the Nicaraguan Caribbean coast, but the system generating them never organized itself enough to be called a tropical depression, much less a tropical storm. Forecasters dismissed it as a "disorganized zone of disturbance," explaining that it'd never amount to anything because of high upper-level windshear and low humidity toward the north. Eventually the disturbed zone drifted northwestward, toward us, and last weekend it moved across our area.

All day and night showers and downpours swept in off the water, and the next day and night, too. After so many look-alike perfect tropical days, what a change was all that wind-howling, those angry-acting waves, the raw chilliness in the wind whistling around corners, whirring among radio-tower wires, beating the big yellowish-green Coconut Palm fronds against windows, the windows themselves knocking against latches, and wind-driven rainwater bubbling beneath the windows, running down walls into shiny pools on tiled floors.

Two days and nights of agitation, of wetness and darkness, but it was all like the Bougainvilleas. I mean, in the subdued light, the Bougainvilleas' flowers exploded with eye-popping crimson heaving and slinging against the self-possessed chill greenness of everything else. I mean, when wind howls and thumps and screams, the call of a lone gull at sea is more plaintive than any other sound. I mean, when the sea rages and you walk along it exactly where the waves can't reach, and a crab is there in its den gazing out over the water, just like you, there's no other little brother as close to you as that crab in his den of cozy shifting sand.

So, "disorganized zones of disturbances" have their value, and I count myself as a connoisseur of them, if not one actually addicted to them. All evolutionary impulses root in disorganized disturbances. All rainbows, poesy and moving music starts out as disorganized disturbance. In fact, I myself aspire to a permanent and glorified state of disorganized disturbance.

That, even though I know that all disorganized disturbances are almost by definition unstable, and unsustainable. For, ever so easily such a zone abandoning its Middle Path in favor of too much disturbance drifts into gratuitous destruction. Or, if it abandons its Middle Path in favor of too much disorganization, it dissipates into deadening mediocrity.

But, how beautiful to be an eyeball on the beach as a "disorganized zone of disturbance" approaches, runs right over you, and heroically departs inland. How fine to be all ears when the howling commences, reveals itself as orchestrated genius, and then departs, diminuendo. How grand to be exactly here recognizing a "disorganized zone of disturbance" when I see it, and being ready to walk to the beach laughing to greet it.

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Best wishes to all Newsletter readers,

Jim