JIM CONRAD'S
NATURALIST NEWSLETTER
Issued from Mayan Beach Garden Inn
20 kms north of Mahahual on the Yucatan Peninsula's eastern coast just north of the Belize border, in the state of
Quintana Roo, MÉXICO
(N18º53'17", W87º38'27" )

August 14,  2011

HERMIT CRABS TÊTE-À-TÊTE
On the white sand road we came upon what's shown at http://www.backyardnature.net/n/11/110814h3.jpg.

That picture, taken at about 8:30 AM on a sunny day a meter or so onto the road, shows three hermit crabs, each wearing a borrowed mollusk shell. At the right is an immature crab with a small, white shell, while at the left two larger crabs, each wearing a different kind of snail shell, are doing something.

My first thought was that the two adults were mating and that possibly the younger one was attracted there by sex hormones the adults were emitting. However, when dealing with invertebrate sex it's unwise to make assumptions. For instance, how about this question: Do crabs even have penises?

My friend Martin wanted a closer look so he picked them up... and to my astonishment they stayed connected and made no signs of coming undone, as shown at http://www.backyardnature.net/n/11/110814h4.jpg.

If you study that picture you can see that the bottom crab appears to be cowering passively in the shell while the top one is holding the bottom shell in its pincers. There's no sign of a penis, though.

On the Internet I read that "When hermit crabs mate, the male hermit crab positions the female hermit crab in front of him and passes spermatophore packets into her gonopores, where the female hermit crab's eggs are fertilized."

Spermatophore packets are compact little masses of sperm. Among hermit crabs, sex involves the two sexes aligning themselves so that their gonopores, or sexual openings, are opposite one another, enabling the spermatophores to pass from male to female. Male hermit crabs do not have penises.

My friend Martin, a Maya villager who pays attention to things, suggested that the crabs instead of mating might be fighting. In fact I read that among hermit crabs "Competition for new shells is keen and hermit crabs will often steal shells from one another. They will engage in fierce battles, fought to the death, for the possession of an appropriate shell. The loser of the engagement not only loses its life but will be eaten by the victor. It is because of this tendency towards fighting one another that the hermit crab is alternately named 'soldier crab'."

That description, along with much more, resides at http://www.stjohnbeachguide.com/Hermit%20Crab.htm.

So, who knows what's going on in our pictures? Maybe someday a graduate student working on hermit crab behavior will be thrilled to see them.

*****

SPINY LIZARDS ON THE BEACH
We've met several spiny lizard species, from Oregon to Mississippi to Chiapas, Querétaro and here, all of the big, poorly understood genus Sceloporus. Throughout the day on our hot, sun-drenched sandy beaches you're likely to see a Sceloporus spiny lizard like the one at http://www.backyardnature.net/n/11/110814lz.jpg.

Best I can figure, that's a Yucatán Spiny Lizard, SCELOPORUS CHRYSOSTICTUS, of which we've already seen many in the interior. However, these beach ones seem to have slightly different colors and markings, and they're certainly in a habitat different from those in the interior, so I wonder if they might not constitute at least a special coastal subspecies. I'll just park the picture here on the Internet and let a future expert figure it out.

It's sort of surprising that so many lizards occupy this beach, since our sand rise is so vulnerable to total flooding during hurricanes. Surely Hurricane Dean in 2007, the third most intense Atlantic hurricane to make landfall in history, and which came ashore here, wiped them out along this beach. Maybe the ones seen now hatched from buried eggs.

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BOTTLE BRYOZOAN
A black whisky bottle washed onto the beach. It bore barnacles, so it had been floating a long time. Also part of it was covered with a white coating, as shown at http://www.backyardnature.net/n/11/110814wh.jpg.

The bottle face's webbed pattern is molded into the glass. However, the white film consits of a single layer of tiny, quadrangular cells, as seen at http://www.backyardnature.net/n/11/110814wi.jpg.

Clearly this is a living thing establishing itself across the bottle's face, and it's fascinating to think how the cells forming at the edge "know" how far to grow before branching, and where the branches must hook up to form a cell's wall. In the picture you can see the opposite branches of some cell walls projecting toward one another.

Though I'm a rank amateur with regard to the ocean's living things, mostly by the process of elimination I'm guessing that what we have here is a bryozoan, maybe even the Coffin Box or Lacy Crust Bryozoan, Membranipora membranacea, described (click on photos) at http://www.aquaticintruders.com/aquatic.php?ais=11.

At the above site we learn that this species is an invasive, a weed originally from Europe but now in the Americas, and that it harms larger forms of algae. The site says that the bryozoan "Forms a crust on algae blocking light needed for photosynthesis and making the algal body stiff and brittle, causing it to break when exposed to waves."

Bryozoans are colonial animals, sometimes referred to as moss animals. Some colonies are bush-like or fan-like (sea-fans are bryozoans), or sheet-like, forming lettuce-like structures. Ours is the most common marine form, the encrusting type. The cellular structure on our bottle, then, is the colony's exoskeleton composed mostly of calcium carbonate, or limestone. Each cell of the exoskeleton holds a tiny animal, the zooid.

Wikipedia provides a good overview of bryozoans at http://en.wikipedia.org/wiki/Bryozoa.

*****

MEETING A NEW TREE
By now I've met hundreds of different kinds of tree in many parts of the world. Of all Nature's organisms, trees somehow strike me as being the prettiest, most dignified, most poetic and sacred of all. Encountering a well formed, healthy tree of any kind makes me feel good. It pleases me to just stand and look at such trees, even if they're common, ordinary ones.

Meeting a new kind of tree is like meeting a cousin you've never encountered. Though you know nothing about them, you're fascinated by similarities and differences.

For example, the other day along the road through the swampland between Mahahual and Sian Ka'an Biosphere Reserve I came upon a tree about 15 feet tall (4.5m) of a kind I'd never seen before. That day I savored taking my time getting to know its distinguishing features. You can see its three-inch-long leaves (8cm) and a branch-tip cluster of pea-size, white flowers at http://www.backyardnature.net/n/11/110814my.jpg.

A white-petaled flower with its many stamens is shown at http://www.backyardnature.net/n/11/110814mz.jpg.

In the American tropics when you encounter a tree like this with opposite leaves (two leaves arising at each stem node) and the flowers containing many stamens, the first plant family you should think of should be the Myrtle Family, the Myrtaceae. If crushed leaves issue a strong, spicy aroma, that's confirmation that it's in the Myrtle Family. A crushed leaf of our tree did indeed emit a pleasant, spicy odor, and when I held a leaf against the sun I could see what's shown at http://www.backyardnature.net/n/11/110814m~.jpg.

That image shows leaf veins running through a galaxy of glands embedded in a leaf, the glands filled with aromatic oils. When such leaves are crushed, the resulting fragrance comes from rupturing many of those tiny, oil-filled glands.

Once the family of a mystery plant is known it becomes much easier to identify it. There's a list of all flowering plants for our state of Quintana Roo, with the names organized by family, so by doing a Google image search on each Myrtle Family name on that list I didn't recognize, soon I figured out who our tree was:

It's CALYPTRANTHES PALLENS. Since the species also occurs in southern Florida, where it's a threatened specie, it bears English names such as Spicewood and Pale Lidflower. Other species also are called Spicewood, and "lidflower" doesn't befit such a pretty tree, so I'm just going to call this tree Calyptranthes.

Calyptranthes pallens is native from extreme southern Florida through the West Indies and Mexico well into Central America. In southern Florida's plant nurseries specializing in native plants, Calyptranthes frequently is sold.

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WHITE STAR-SEDGE
Where the paved road between Mahahual and Sian Ka'an Biosphere Reserve cuts through a swamp, at the foot of a levee a bare area was populated with hundreds of the 1½-ft-high, white-topped, grasslike plants seen at http://www.backyardnature.net/n/11/110814ws.jpg.

A close-up showing a slender stem atop which a cluster of white flower heads is subtended by several stiff, downward pointing, green but white-based modified leaves, or involucral bracts, is shown at http://www.backyardnature.net/n/11/110814wt.jpg.

A closer look at the flowers themselves is seen at http://www.backyardnature.net/n/11/110814wu.jpg.

Like last week's Sawgrass, which wasn't a grass, this is a member of the big Sedge Family, the Cyperaceae. It's RHYNCHOSPORA COLORATA, and since it's native from the southeastern US south through Mexico and the West Indies to northern South America, and it's attractive and interesting enough to catch people's attention, it goes by several English names, including White Star Sedge, Star Sedge, White-topped Sedge and Starrush Whitetop. The species is adapted for living on wet- tending sand in meadowy swales and marsh edges, usually on soils tending to be neutral or basic in pH.

Gardeners in the US Southeast welcome White Star Sedge into their bog and water gardens, and any frequently watered regular garden.

*****

BLEEDING GLORY-BOWER
At the base of my stairs Marcia has planted a twining evergreen shrub with very unusual flowers, as seen at http://www.backyardnature.net/n/11/110814cm.jpg.

The prettily white and red, inch-long (2.5cm) blosom is at http://www.backyardnature.net/n/11/110814cl.jpg.

Our gardeners thought it was a kind of bougainvillea, but it's completely unrelated. It's CLERODENDRUM THOMSONIAE, a member of the Verbena Family, the Verbenaceae, originally from tropical western Africa, from Cameroon west to Senegal. Among its English names are Bleeding Glory-Bower, Bleeding Heart Vine, and Bagflower.

The blossom's peculiarity is that its calyx, which in most flower kinds is small, green, and inconspicuously subtending a colored corolla, here is expanded into a white, bladder-like thing almost swallowing up the dark red corolla. From the crimson corolla in a fairly normal way emerge four stiff, long stamens, and a similarly stiff, long style, which bends downward, away from the anthers, the better to avoid self- pollination.

Despite its gorgeousness, Bleeding Glory-Bower isn't one of those recently developed cultivars with over- manipulated genes. In fact, the shrub was most popular during the 1800s, when it was mainly known in the English speaking world as Beauty Bush. The question is, then, why this spectacular species has lost favor among gardeners.

The answer is simple. Nowadays most gardeners don't pay much attention to their plants' individual needs, and this bush has some special needs. Its roots must be partially submerged in water most of the time, and the plant needs full sunlight.

I don't have much hope for Marcia's little plant stuck in dry sand in perpetual shade at the bottom of my stairs.

*****

COLOMBIAN BOTTLES & RIGHT SHOES
I've been reading Curtis Ebbesmeyer's Flotsametrics and the Floating World, which describes the author's career as an oceanographer studying the oceans' currents, especially with regard to what floats on it, flotsam. That got me to thinking more analytically about the mountains of garbage, mostly plastic, perpetually washing onto our beaches.

So, Friday morning I looked closely at the trash along the kilometer of beach between Mayan Beach Garden and what I call the Northern Point. Relatively few items bore labels revealing their country of origin, but enough did to provide a general feeling from where the trash comes from. You can see a collage of snippets indicating the labels' countries of origin at http://www.backyardnature.net/n/11/110814--.jpg.

The home countries of 33 items could be identified, and garbage from 15 countries was found. The nation providing most garbage was Colombia, with 9 pieces, or 27%. The next most represented country was Mexico itself, with 5 pieces, or 15%, and then Venezuela with four pieces, or 12%. Countries contributing 2 pieces, or 6%, were Jamaica, Trinidad and Tobago, Suriname and Honduras. The remaining countries sending only a single piece of trash each were St. Lucia, Haiti, Guatemala, Netherlands, Singapore, China, USA and Russia. I'm guessing that items from the last four countries were dumped from passing ships. Probably the item from the Netherlands entered waters of Dutch-speaking Suriname.

Clearly a one-way trash superhighway operates between here and northern South America. If you consider the island nation of Trinidad & Tobago as part of South America, then 17 pieces, or 52%, originated in South America. A map showing the Caribbean's main currents flowing from northern South America to here is at http://oceancurrents.rsmas.miami.edu/caribbean/caribbean.html.

That map also shows why I've never found trash from Cuba (stiff north-flowing current between Cuba and the Yucatán) and why there's never much from Panama, Costa Rica and Nicaragua (their Caribbean trash travels in circles).

On a separate issue, Ebbesmeyer -- who has beachcombed here at Mayan Beach Garden -- points out that right shoes and left shoes display such different sailing dynamics that during long floats right shoes may drift one way, left another, eventually causing certain beaches to specialize in catching one shoe type over the other. Here some of us have been pretty sure that on our beach right shoes predominate. On my short walk I noted the dispositions of 57 washed-up shoes and sandals. Of those, 31 were right (54%) while 26 were left (46%). That's not much of a statistical difference, but the exercise does remind us that sometimes we can start believing things for no good reasons.

Why is the color blue so dominant on these labels? It's because most were from plastic water bottles, and marketers know that people associate the color blue with cleanliness and purity.

Behold the irony of it.

By the way, Curtis Ebbesmeyer's "Beachcombers' Alert," with stories about interesting flotsam, and an address where you can share your own flotsam stories, is at http://beachcombersalert.org/.

*****

ON THE MEREST HINTS OF SCENTS & HUES
What a curious thing to be on a tropical beach during the rainy season with vegetation maximally rank and green and the ocean eternally churning and spawning howling squalls, and sometimes have the merest hint of a scent or hue of something stun me with nostalgic feelings reminding me of Augusty woods and fields of my childhood rural Kentucky.

Yellow butterflies among salt-sprayed Seagrapes yank me back half a century to August goldenrods along country roads; Cicadas droning in mangroves evoke the same feeling as cicadas in bottomland swamps once did; this great, swirling, turbulent ocean imparts feelings like those I used to feel beside big, lustily photosynthesizing, whirlwind-swept cornfields.

The mental states I'm talking about aren't merely pleasant memories or yearnings to return, but rather instances of my internal world being thrown into a low-gear, deeply plowing, sweet-feeling meditative mood. Why is it happening?

Here's my theory: It's happening because as we age we lose sight of basic truths clearly seen and understood when we are younger -- truths such as the importance of family and local community, the beauty of simple pleasures, healthily functioning ecosystems, and of things simply being themselves.

Thus, given the merest cue, we are programmed to recall truths and beauties of which we were vividly aware as kids. Fragrances of certain flowers, mockingbirds singing at dawn, the roar of waves breaking on a distant reef -- all help us recover that clarity of mind and intent we once enjoyed.

*****

Best wishes to all Newsletter readers,

Jim