May 22, 2011
Here in mid May little flocks of Western Sandpipers, CALIDRIS MAURI, still work up and down the beach probing their black beaks into sand and wads of wind-heaped-up seaweed. Two birds can seen at http://www.backyardnature.net/n/11/110522sp.jpg.
Western Sandpipers are listed as winter visitors in this part of the world, so shouldn't they be on their way to their nesting grounds in western coastal Alaska? And why haven't the birds in the picture acquired the rusty backs of their summer plumage?
Their being here so late makes sense because at this time of year western Alaska still is a bit wintry. You may recall the last time we met Western Sandpipers, which was in southwestern Oregon in 2009. At that time Greg, a local expert, told us in mid August that "The adults already migrated through, with their very worn and faded plumage that they received new in early spring, migrated to the Arctic, bred, and migrated back." So, Western Sandpipers arrive in Alaska late, and leave early.
It's an accepted ecological rule that chick growth in high-latitude breeding shorebirds is very fast. By the way, a study in Alaska found that on the average Western Sandpiper nests fledged only 1.7 chicks.
In A Guide to The Birds of Mexico and Northern Central America, Howell writes that rarely Western Sandpipers summer locally along both Mexican coasts. I wonder if maybe those rare birds remaining here all summer might represent the species testing the strategy of just not making that long trip North in the first place. Or maybe they're just too young, too old or too sick to make the flight.
SERGEANT MAJOR IN A COTTAGE CHEESE BOWL
At low tide interesting critters turn up in tide pools -- depressions in rock and sand holding water when the tide goes out. Here the most frequently appearing fish in tide pools is the half-finger-long one shown at http://www.backyardnature.net/n/11/110522sm.jpg.
I got that picture by scooping the fish into a cottage cheese bowl washed onto the beach, then slowly dribbling water out until the fish lay on his side in the dish's bottom.
In Humann & Deloach's Reef Fish Identification: Florida Caribbean Bahamas it was easy enough to match the fish with a picture, since it's one of the most abundant and best known reef fish in the Caribbean, one often seen while snorkeling, and one often included in tropical fish aquaria. It's the Sergeant Major, ABUDEFDUF SAXATILIS, in the family of fish comprising damselfishes and clownfishes. They're called Sergeant Majors because of their militaristic stripes.
Sergeant Majors grow to about 9 inches (23 cm), so my inch-long catch is a juvenile. However, in our tide pools, all I found were juveniles, and the one I caught was the largest of all. I read how hundreds of Sergeant Majors may school around reef caves, old shipwrecks and the like, how they change colors to camouflage themselves, how the males when they guard their red or purple patches of eggs turn dark bluish... and begin picturing a complex, endearing little fish. I feel guilty for having caused one to lie so nakedly in the bottom of a trashy cottage cheese container.
Sergeant Majors live in reef and rocky environments in the Atlantic Ocean -- from Canada to Uruguay in the west, and from western Africa to Angola in the east.
There's a lot of life-history info about this fish at http://www.sms.si.edu/irlspec/Abudefduf_saxatilis.htm.
BLEEDING TOOTH ON A ROCK
At the rocky point a few kilometers south of us, algae-darkened limestone rocks emerging at low tide were covered with hundreds of dark, speckled, Four-tooth Nerites, which we looked at a couple of Newsletters ago. Also, there was one individual shell on a wet rock like all the rest, but a little smaller, a little paler, and blotched instead of speckled. He's at http://www.backyardnature.net/n/11/110522bt.jpg.
Recalling that the opening at the bottom of the Four-tooth Nerite's shell bore four white "teeth," to see if this one had a different dental formula I turned it over and saw the very different configuration shown at http://www.backyardnature.net/n/11/110522bu.jpg.
The next day volunteer seashell-identifier Bea in Ontario told me that we had a Bleeding-tooth Nerite, NERITA PELORONTA. Anyone looking at the above picture immediately sees where that name came from.
This is the third nerite species we've run into, the first being a mangrove species up at Río Lagartos some years ago. Though I'd never heard of nerites before visiting the Yucatán's shores, it's beginning to occur to me that here they're important coastal mollusks.
Nerites, I find it written, are thought of as medium-sized sea snails. They're found in tropical waters worldwide in the middle and upper intertidal zones, and they are gregarious herbivores. In general they spend their days peacefully grazing alga growing on wet rocks. Those teeth we've seen at the bottom edge of the shells' openings vary from species to species, from many and fine in some species to few and robust in others. Those teeth aren't used in eating, but I can't find mention of any use they may have.
Our Bleeding-tooth Nerite appears to be the most famous of all nerites. Many online stores sell their polished shells as ornaments, and others sell them as colorful aquarium items.
Soon after arriving here, at low tide and in shallow water in a sandy tide pool, I found two flat, round organisms the size of saucers. They felt like soft, crumbly mats of sand-coated jelly. You can see one at http://www.backyardnature.net/n/11/110522ca.jpg.
I wanted to take close-ups of the surface but camera-destroying waves irregularly washed in. Since this was my first walk along the beach at low tide, I figured I could always come back for more pictures, maybe when the tide was lower. But, though I've looked each day for nearly a month, I've never seen them again.
In Humann & Deloach's Reef Fish Identification: Florida, Caribbean, Bahamas no matches were found, though some features of its structure resembled "carpet anemones." Our picture was sent to a coastal expert in Florida who was stumped. Days passed and the expert showed the picture to other experts, until finally one day one opined that, yes, it looks like it could be a carpet anemone.
I'm guessing that we have the Caribbean Carpet Anemone, STICHODACTYLA HELIANTHUS, though other carpet anemones are found here. Internet pictures of the species look different because nearly always they're photographed on irregular rock surfaces where their bodies are not flat, not round, and not heavily blanketed with sand like ours. A picture of one in clear water on rocks and not covered with sand is shown here.
Now Google has taught me that sea aemones are water-dwelling, predatory animals. Helping make sense of our picture is Wikipedia's statement that "The mouth is in the middle of the oral disc surrounded by tentacles armed with many cnidocytes, which are cells that function as a defense and as a means to capture prey." So, that depression in the center must be where the mouth is, and the bumps around the mouth are fingerlike things with poisonous little darts in them used for capturing food and self-defense.
Elsewhere I read that "The mouth should be closed and tight, and will open when hungry, having an oval look, yet a gaping mouth is a warning signal." I should love to see this sand-strewn creature warning me with its gaping maw.
Also I read that beneath the mouth and tentacles lies a foot with which the anemone can move about. Maybe that's why ours were gone the next day.
What extraordinary creatures live on this beach!
An introduction to anemones in general, and a diagram of the anatomy of a carpet-like anemone, is at http://www.reefland.com/articles/rho/be-a-host-to-your-anemone.
PALMS IN THE MANGROVE SWAMP
On the low, narrow sandy rise I now occupy between the sea on the east and a vast mangrove swamp to the west, so far I've found only two palm species, both of which are abundant. One is the Coconut Palm and the other is the Chit Palm, which we've nicely illustrated at http://www.backyardnature.net/yucatan/chitpalm.htm.
Entering the mangrove zone, which much of the year is flooded, you begin seeing a third palm species that at first glance is very similar to the Chit. It's shown at http://www.backyardnature.net/n/11/110522pm.jpg.
Up North this mangrove species is known as the Everglades Palm because it's the characteristic palm of southern Florida's Everglades. But that name won't do here, or in other parts of Mexico, Central America and the Caribbean where it also occurs. Other English names for it include Paurotis Palm, Madiera Palm and Silver Saw Palmetto. It's ACOELORRHAPHE WRIGHTII. Probably here Paurotis Palm is the best English name for the species.
Comparing Paurotis Palms with Chit Palms you might see that the main differences visible at a distance are that the Paurotis's trunks are more slender than most Chits. Also the Chit's fronds are divided into fewer and more flexible sections than the Paurotis's, whose divisions are finer and stiffer.
Also up close you see that Paurotis Palm petioles bear large, broad-based, forward-curving spines while Chits bear no spines. The Paurotis's petiole spines are seen at http://www.backyardnature.net/n/11/110522po.jpg.
The Paurotises in the picture are sprouting old inflorescences, but they don't always have those. Paurotis Palms clump while Chit Palms may or may not.
In the mangroves, Paurotis Palms mostly occupy the edges, avoiding the most flooded areas. You could say that Chits favor sand, while Paurotis Palms go for mud, but not mud where water stands for too long.
Paurotis Palms are very much planted in the tropics and subtropics worldwide as ornamentals. In fact, many have been robbed from the Everglades for sale in the nursery trade.
Among palm lovers, certain stereotypes predict what kind of palm should appeal to what kind of people. "Paul, The Palm Doctor" on the Internet says, "If you associate royal palms with tuxedos and Washingtonias with three piece suites, the paurotis palm is tank top, cutoffs and sandals."
The rocky point just south of us has lots of fossils. There's a good fossil forum on the Internet where experts offer to identify your fossils, so I photographed a fossiliferous slab of limestone with my foot for scale and uploaded it. The fossil forum is found at http://www.thefossilforum.com/.
The picture of the fossil found just south of us is at http://www.backyardnature.net/n/11/110522fo.jpg.
Several kinds of fossils occurred there but I photographed the largest, best preserved ones I could find, thinking I'd start with something easy. I even took a close-up of the surface structure, shown at http://www.backyardnature.net/n/11/110522fp.jpg.
I was impressed with the forum. On a Sunday morning fifteen minutes after I'd uploaded my material the picture had been viewed 22 times and already I had two responses.
Piranha in the US wrote, "Excellent close-up. The diagnostic characteristics should be easy to deduce. I'm on it!"
In a couple of hours Piranha came back with, "They certainly appear to be dead ringer spongiform fossils. Unfortunately nothing is lining up in the literature."
The next day, the pictures having received over 100 viewings, among the responses were Piranha again, this time writing, "Having looked at a few hundred possible sponges in the treatise and now those corals from the Pleistocene ... I'm waving the white flag and crying uncle on this one. It could be either and this appears to fall in the category of: not on the visible radar... "
So, my easy fossil wasn't so easy. Piranha's diagnosis of "spongiform" didn't reveal much, since that term only means "shaped like a sponge." I'm amazed that they couldn't even determine whether what we have is a sponge, a coral, or something else.
The best I can tell from geological literature on the Internet, the rocks of our rocky points are probably Miocene-Pliocene in age -- 1.8 to 23 million years old. Therefore, our fossils shouldn't be too different from living organisms found now offshore. Yet here's a large, well-preserved fossil that's stumped the experts!
What a pleasure to be where so many of the everyday plants and animals around us -- living and extinct -- are poorly known or maybe even "unknown to science."
A GARBAGE DUMP
Every day new garbage floats onto the beach here, but last weekend a particularly bad mess washed up -- mostly tattered sheets of plastic. Part of it is shown at http://www.backyardnature.net/n/11/110522tr.jpg.
Marcia has seen many incidents like this. She tells how once garbage piled two feet deep in front of her place, apparently having been dumped from a passing ship.
"I'll bet this is from a dump in Venezuela, Columbia or Honduras," she prophesied as we began filling our garbage bags. "We get lots of stuff from there, though very little from Guatemala, which is closer."
The first printed material found in the mess was written in Chinese, which surprised us. Marcia began thinking that maybe it had floated up from Belize, since a large Chinese population lives down there. However, as the morning progressed we turned up items originating in Barbados, Honduras, Jamaica, Trinidad, Mexico and other places.
Eventually Marcia's best bet became that a ship hop- scotching the Caribbean had chosen the sea off our beach for dumping its long-accumulated garbage.
If you ever need to identify a large ship you see dumping garbage or polluting, you might find useful the site at http://www.shipdetective.com/ships/.
For instance, on Tuesday morning this vessel passed by here: http://www.backyardnature.net/n/11/110522cr.jpg.
The ShipDetective website helped me peg this ship as the Norwegian Spirit which departs New Orleans each Sunday for a seven-night Caribbean cruise. Her Wikipedia page says she has 13 decks and carries 1996 passengers. Her interesting history is outlined at http://en.wikipedia.org/wiki/Norwegian_Spirit.
ENCHANTED CITY AT DAWN
Each Monday morning about half an hour before sunup a white cruise ship with all its outside lights ablaze glides through the darkness right in front of my sea-facing, second-story window. The ship is heading to dock at Mahahual 20kms south of us. In predawn darkness the splendidly lit vessel looks like a glowing, enchanted city dreamily drifting by, and that sets me to thinking during the following morning jog.
Sometimes I daydream of starting my own cruise-ship line. My ships would be slow ones, though, mostly drifting with the currents, and using solar energy for navigating in port. I'd offer passengers low-key, homey settings where linens would be clean but not chlorine-bleached. Instead of offering gourmet meals, the emphasis would be on fresh, tasty, nutritious dishes with ingredients grown locally at our ports of call. Guests would empty their own trash, clean their own bathrooms and wash their own clothing, these chores undertaken as meditations on the beauty of being a working component of a healthy, sustainable environment.
For entertainment there'd be participatory sports, fitness programs and classes on the cultures and ecosystems we're visitiing. When we'd dock, everyone aboard would know the local history, the distinctive features of the culture and ecology about to be experienced, and at least a few phrases of the local language.
My ships would be big enough for entire decks to be given over to themes of diversity. Deck Six, maybe, would support a tropical rainforest, while Deck Ten might host an entire traditional Maya community with cornfields, thatch-roofed huts and all. In fact, my cruise ships would be so large that they'd constitute biospheres all by themselves...
At this point in my jogging day-dreaming it starts dawning on me that what I'm visualizing already has been done. Already the Earth is a splendidly lit, multi-leveled ship on a lonely but enchanted voyage, one adrift on a current vaster than I can imagine.
On and on I jog, the revelation dawning, the day itself dawning, me running, almost laughing, unable to keep track of which metaphor I'm running through, which metaphor is making me want to laugh, and why.
Best wishes to all Newsletter subscribers,
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