November 16, 2014
INVASION OF GIANT ASIAN TIGER SHRIMP
Earlier this year local fishermen began speaking of a kind of gigantic shrimp being caught in Ría Lagartos estuary, something never seen in these parts. This week my host, naturalist and guide Diego Nuñez, was shown two frozen specimens from a local fisherman's freezer. One of Diego's pictures of the creature, white with freezer frost, can be seen at http://www.backyardnature.net/n/14/141116sh.jpg.
When Diego asked around, another fisherman showed him a snapshot of one he'd caught -- this specimen displaying its colors -- seen at http://www.backyardnature.net/n/14/141116si.jpg.
With pictures in hand, it didn't take long to identify this as the Asian Tiger Shrimp, also called Giant Tiger Prawn and other names. It's PENAEUS MONODON, and in our waters it's an invasive species. Its a native of waters of the eastern coast of Africa and the Arabian Peninsula to Southeast Asia, the Sea of Japan, and northern Australia.
Asian Tiger Shrimp is world's second most widely cultured prawn species. The term "prawn" refers to any large shrimp or small lobster with long, slender claws. By "cultured prawn" is meant that the prawn is grown commercially in ponds, tanks, or other controlled environments. In 2009, US$3,650,000,000.00 of Asian Tiger Shrimp were sold on the world market, and the updated graph showing yearly production displays impressive growth. On the FAO's web page profiling the species we read that "In general, Penaeus monodon is the most prominent farmed crustacean product in international trade and has driven a significant expansion in aquaculture in many developing countries in Asia." That FAO page is at http://www.fao.org/fishery/culturedspecies/Penaeus_monodon/en.
What does it mean that Asian Tiger Shrimps are establishing themselves in the Ría Lagartos Biosphere Reserve? In Asia's tropical waters, the cultivation of Asian Tiger Shrimp has been good for those who sold them, including small farmers in impoverished rural settings, but the effects on the environment often have been bad. Large acreages of mangrove have been converted to shrimp-growing ponds. High prices for the prawn and need for seed stock for cultivation have caused wild Asian Tiger Shrimp to be overharvested. Asian Tiger Shrimp are vulnerable to a variety of diseases, and water issuing from their confinement pools often contains those diseases as well as waste matter, medicine and other pollutants.
Besides announcing the identification here, I've sent our pictures to both the USDA department dealing with invasive species and the biodiversity specialist at the Centro de Investigación Científica de Yucatán, in Mérida, so I have done what I can to alert the proper officials.
LONG-TAILED METALMARK BUTTERFLY
At http://www.backyardnature.net/n/14/141116mm.jpg you can see one of the prettiest butterflies I've run across in a long time. Another view from the top better showing how like an opening and closing mouth the wings might look as they slowly oscillate between near-horizontal to vertical position is at http://www.backyardnature.net/n/14/141116mn.jpg.
The thick body cues us that this is a skipper-type butterfly. Doing an image search on Mexican skippers, soon an image of this gaudy species jumps from the screen, and the name it bears is Long-tailed Metalmark, RHETUS ARCIUS.
Our Long-tailed Metalmark turned up in a small patch of sunlight along an otherwise deeply shaded trail tunneling through a thick stand of mangroves. The visual effect of the scintillating blues and pinks on the field of black banded with white was otherworldly, such colors and designs seeming almost out of place in such a shadowy, somber environment. I'd never seen the species and wondered whether it might be yet another of northern coastal Yucatan's many endemic species.
But, no, looking up the name one finds that Long-tailed Metalmarks not only enjoy a wide distribution, from southern Mexico south through Central America to Amazonian Peru in South America, but they were even known by Linnaeus, who named them in 1763. I like to imagine Linnaeus opening his box of specimens sent from travelers in all parts of the world, first seeing this beauty's explosive colors in sometimes-subdued-seeming Sweden.
Long-tailed Metalmarks -- called Sword-tailed Doctors by a website featuring butterflies of the Amazon -- like wet areas such as stream sides, ditches and mangroves. That website also lists its food plants as members of the Combretum and Spurge Families. Among the Yucatan's four species of mangrove, two are members of the Combretum Family -- White Mangrove and Buttonwood -- and Euphorbia Family members are common weeds here, so our mangroves are a good place for them.
Nowadays it's easy to find Caspian Terns, HYDROPROGNE CASPIA, in Ría Lagartos. You can see some in their winter, or basic, plumage, and admire their distinctively massive, red beaks at http://www.backyardnature.net/n/14/141116t2.jpg.
A bird closer up, with wings lifted in flight, is at http://www.backyardnature.net/n/14/141116t3.jpg.
With a wingspread of 53 inches (1.35m), this is our largest tern and can only be confused with the Royal Tern, whose orange beak can at times look a little reddish, and is nearly as big. However, the Royal Tern's tail is more deeply forked than the Caspian's, plus notice that the tip of our Caspian's reddish beak darkens. The Royal Tern's beak doesn't display such a bruised-looking tip.
Caspian Terns turn up in waters worldwide, except in South America. In the Yucatan they're nonbreeding winter visitors.
What's the difference between a tern and a gull? With a little practice, you can distinguish them by the terns' longer, narrower wings and more buoyant flight. Most terns have forked tails while most gull species have rounded ones. Also, terns have sharp-pointed bills while gulls have hooked ones.
FLAMINGOS, PINK AND WHITE
At http://www.backyardnature.net/n/14/141116fl.jpg you see a typical view of Flamingos lounging in Ría Lagartos estuary. Notice that the larger adults are pink but smaller immature birds can be white. Another picture of a pink adult with a white kid is at http://www.backyardnature.net/n/14/141116fm.jpg.
Young Flamingos first grow white feathers, and then the feathers eventually turn pink as the birds eat brine shrimp and other tiny crustaceans, as well as algae, containing pigments called carotenoids. Enzymes in the Flamingo's liver break down the carotenoids into pink and orange pigment molecules, which then are distributed to the bird's feathers, bill, and legs. The more carotenoids a Flamingo eats, the pinker it gets.
REDDISH EGRET WITH A SHRIMP
A nice picture of a Reddish Egret dangling a wild shrimp by its antenna is at http://www.backyardnature.net/n/14/141116eg.jpg.
The egret is stepping lively because nearby gulls and herons tended to mob any bird who caught a meal and didn't immediately swallow it or show signs of defending the meal with vigor.
IMMATURE BLACK HAWK
Common Black Hawks are common here. On boat tours up the estuary normally half a dozen or more are spotted along shore. If we're carrying tourists looking for picture-taking opportunities, sometimes the guide carries along a dead fish to be thrown into the water when we approach a Black Hawk. The hawk usually swoops down, grabs the fish in its talons and carries it back to a perch. If you time it just right you can get a great picture. So far I've always been too early or too late for the classic hawk-snatches-fish picture, but my time will come, and you'll see the results. Meanwhile, I did get a decent picture of an immature Black Hawk eyeing a potential meal in the water just below his perch, shown at http://www.backyardnature.net/n/14/141116bh.jpg.
Nowadays along weedy roadsides through the savanna and ranch areas south of Río Lagartos a much branched subshrub from knee to head high is prettily adorned with branch-tip clusters of five-petaled, thumbnail-sized, pink flowers, a stem of which is shown at http://www.backyardnature.net/n/14/141116me.jpg.
Notice how the alternate leaves (one leaf per stem node) are so curiously toothed. Each tooth bends away from the blade's plane causing an unusual scalloped effect. A close-up of a flower is at http://www.backyardnature.net/n/14/141116mf.jpg.
That blossom bears five well developed stamens with brownish, pollen-releasing anthers, but we can't see anything of a female pistil. However, if you remove one side of the blossom, you find the pistil with its green, oval ovary where it should be in the center of the bottom of the flower, bearing its 5-branched, stigma-tipped styles atop a slender column, though the style branches reach only about half the stamens' lengths. This is shown at http://www.backyardnature.net/n/14/141116mg.jpg.
Having such short styles nestled below overarching anthers is a little curious because usually this kind of simple flower projects its style beyond the stamens' anthers, to avoid having an approaching pollinator brush pollen from the flower's own anthers onto its own female parts lower down.
In the above picture we can also see that the narrowly triangular calyx lobes, or sepals, are thickly covered with glandular hairs -- hairs topped with sticky, spherical glands. Also, at the bottom, left side of the blossom, notice a bulge with an open space just beneath it. That's the nectary, where the pollinator finds the nectar it wants.
The most interesting thing, however, is seen if you check several of these plants. In our last picture the female pistil rises only half as high as the stamens; on about half of other plants the situation will be just the opposite. Pistils will extend well beyond the corolla, but stamens rise only half as high. Such a blossom with dominant female parts is seen in cross section at http://www.backyardnature.net/n/14/141116mh.jpg.
To understand what was going it, first the plant needed to be identified. It's called Teabush or Pyramid Bush, MELOCHIA TOMENTOSA. On the Internet we can read that Teabush is a classic example of a plant that is "heterostylous-distylous." That means that the species produces two distinct "morphs." The flowers of one morph have vigorous stamens but degenerate pistil, while the other morph's flowers produce large pistils with undersized stamens. The flowers are thus predominantly male or female, though in each morph reduced structures of the repressed sex are present. Flowers with dominant female parts are called "pin flowers" while those with dominant stamens are called "thrum flowers"; the two morph types are present in approximately equal proportions.
Teabush is mostly a tropical plant distributed from Brazil north to southern Texas and Florida. In many places it's a typical roadside wide, as here, but it also lives in openings on rocky limestone hills, in coastal thorn thickets, savannas, and piney woods.
Teabush is a member of the big Hibiscus or Mallow Family, though before the days of genetic sequencing it was assigned to the mainly tropical Chocolate or Cacao Family, the Sterculiaceae. The Chocolate Family now has been lumped into the Hibiscus Family.
On the Internet you might be interested in a freely downloadable PDF document by Isabel Machado and Marlies Sazima entitled "Pollination and breeding system of Melochia tomentosa L. (Malvaceae), a keystone floral resource in the Brazilian Caatinga." The document is available at http://www.cpatsa.embrapa.br/public_eletronica/downloads/OPB1810.pdf.
On thin soil atop limestone in low areas occasionally flooded, nowadays you find blooming a little wildflower that at first glance you might assume to be a member of the Evening Primrose Family, shown at http://www.backyardnature.net/n/14/141116cf.jpg.
However, up closer you see that the stamens are united at their filament bases into a cylinder around the ovary's slender neck, or style, indicating membership in the big Hibiscus or Mallow Family, the Malvaceae, as shown at http://www.backyardnature.net/n/14/141116ch.jpg.
A closer look at the "staminal column" formed by the confluent stamen filaments, with the fuzzy stigma topping the style coming up through the staminal column, is shown at http://www.backyardnature.net/n/14/141116ci.jpg.
If you look at the blossom from below you'll see gland-dotted ribs running the length of the sepals so unlike anything you've ever seen that you suspect you may have something special. A flower's underside is shown at http://www.backyardnature.net/n/14/141116cg.jpg.
A fruiting pod in the process of splitting open is shown at http://www.backyardnature.net/n/14/141116cj.jpg.
This is indeed something special, yet another plant of limited distribution, only occurring coastally in the Yucatán, Cuba, Bahamas and on the Florida Keys, where it's listed as Endangered in Florida. It's CIENFUEGOSIA YUCATANENSIS, usually called Yellow Hibiscus or Yucatan Flymallow. Most literature on the species deals with the small population in the Florida Keys so not much is known about our plants.
An interesting feature of members of the genus Cienfuegosia is that their leaf forms vary drastically. The ones in our picture are slender and simple like willow leaves, but lower down on other plants, I read, they can become trifoliate like a three-toed bird foot, or even be fig-leaf shaped, or broad like sycamore leaves.
Studies on the evolution of the Yellow Hibiscus indicate that it split from a South American member of the genus, Cienfuegosia heterophylla, centered in or near Paraguay. Yellow Hibiscus's pattern of distribution suggests that it arrived from South America into our area via ocean currents.
In waters of the Ría Lagartos estuary usually you can find floating alga such as what's shown at http://www.backyardnature.net/n/14/141116sg.jpg.
With no definite stem, this alga branches in all directions and with no obvious pattern. It's free-floating and bears no roots. The spherical, BB-size items are air-filled sacs or bladders enabling the organism to float. A close-up of the alga's bladders and irregularly toothed blade margins is at http://www.backyardnature.net/n/14/141116sf.jpg.
In 2011 we profiled a rootless, air-bladder-equipped alga very similar to this washing up on a sandy beach of the Caribbean 20 kms north of Mahahual, Quintana Roo. You can see how similar that species was to our present one at http://www.backyardnature.net/yucatan/sargasso.htm.
That alga was one of the famous sargasso species, Sargassum fluitans, sometimes called Broadleaf Sargasso. Now here at Río Lagartos I find not only that species but also this second sargasso species, SARGASSUM NATANS, sometimes known as Narrowleaf Sargasso or Narrowleaf Gulfweed. Narrowleaf Sargasso is distinguished from our previous sargasso not only by its narrower leaves, but also by its air bladders being topped by tiny projections that sometimes are spine-like and sometimes branched.
Sargasso is "famous" because it has a whole sea named after it, the Sargasso Sea, a region in the Northern Atlantic Ocean about 1100kms wide (700mi) and 3200kms long (2000mi). The Sargasso Sea forms in the center of a vast, clockwise-turning system of ocean currents -- a "gyre." The whole system is referred to as the North Atlantic Gyre, and nowadays the Sargasso Sea coincides with what's also known as the North Atlantic Garbage Patch. Similar gyres with similar collections of trash and floating vegetation occur in other oceans.
Sargasso is a "brown algae" belonging to the class Phaeophyceae, in the order Fucales. It's distributed in oceans worldwide, generally in shallow water and coral reefs. Around Río Lagartos we don't have coral reefs, but the Gulf of Mexico across the barrier island north of town provides plenty of shallow water.
Floating sargassum makes a good hiding place for tiny animals trying to avoid larger animals who might eat them. European and American Eels meet in the Sargasso Sea to lay their eggs in sargassum. The hatched young then make their ways to their respective continents. It's also thought that after hatching, young Loggerhead Sea Turtles travel in currents such as the Gulf Stream to the Sargasso Sea, where sargassum provides cover from predation until they are larger and can travel the seas.
Sometimes enormous masses of sargassum blow onto beaches that homeowners like to keep clean, and the decaying alga can smell bad. In the past people knew to collect the sargassum to compost and mix with their soil to improve the soil. A 2010 article by Williams and Feagin in Envirorn Manage magazine -- Nov;46(5) -- reported that "... sargassum can increase soil nutrients and produce increased growth in dune plants" and thus should be used by those trying to stabilize sand beaches by establishing plantings. "Beach raking" by neatness-minded landowners destabilizes beaches, making them more vulnerable to storm damage.
POWDERY TWIG LICHEN
Both mushrooms and lichens are uncommonly seen in the area around Río Lagartos. The largest lichen I've yet seen here, about the size of a turkey egg, is shown at http://www.backyardnature.net/n/14/141116li.jpg.
A close-up of the granular-textured, ribbonlike body with cuplike apothecia is at http://www.backyardnature.net/n/14/141116lj.jpg.
This fruticose, or shrubby, lichen with its color, form and habitat reminded me of the Cartilage Lichen we saw back in Texas, shown at http://www.backyardnature.net/n/x/ramalina.htm.
Cartilage Lichen is a member of the genus Ramalina, so I did a web search on Ramalina lichens found in the Yucatan and what turned up looked pretty much like what's in our picture. It was the Powdery Twig Lichen, RAMALINA POLLINARIA, one of a few species known to occur worldwide. It's described as having a very variable morphology, and it's true that many images of the species on the Internet look a bit different from ours, but some look practically identical. The species description at LichenPortal.Org says that usually it occurs on rock, but sometimes on twigs, like ours.
Our twig lichen was on a dead twig along a road through the savanna east of town, south of the mangroves.
UPLAND OR SEA-ISLAND COTTON?
The following is a little technical but I'm including it because the presence of wild cotton here on the Yucatan's northern coast is important, and the exact identity of the various cottons can be hard to determine.
The wild Upland Cotton, Gossypium hirsutum, we've documented in the last two Newsletters as growing among the dunes here on the Yucatan's northern coast raised some questions with me. For, both Upland and Sea-Island Cotton (the latter being Gossypium barbadense, of South American origin) are listed as growing in the Ría Lagartos Biosphere Reserve. These two species are very closely related, very similar, and are known to hybridize. Therefore, I've been double-checking my identifications.
Even features of well defined plants of each species overlap a great deal, though a practiced eye usually can tell them apart. Here's a review of certain differences between the two species as detailed in PA Fryxell's 1992 treatment of the Hibiscus Family in the Flora de Veracruz:
|G. BARBADENSE||G. HIRSUTUM|
|leaves||3-7 lobed||3-5 lobed|
|leaf middle lobe||oval to lance-shaped||oval to triangular|
|leaf middle lobe||> 1.5 x longer than wide||< 1.5 x longer than wide|
|capsular fruits||3 cells||3-5 cells|
|capsular fruits||narrowly ovoid||ovoid|
|bracts||5-17 teeth||3-19 teeth|
|bract sinuses||rounded/ U-shaped||more or less V-shaped|
LH Bailey's 1949 Manual of Cultivated Plants further distinguishes them by saying that G. barbadense's anthers are "compactly arranged on uniformly short filaments" while anthers of G. hirsutum are "loosely arranged on filaments of varying lengths." If you're at a loss as to what's "compact" and what's "loose" in anther terms, pictures on the Internet can help develop an eye for this feature.
First take a look at the yellow, "compact" cluster of anthers in a public-domain picture of a G. barbadense flower made available by CT Johansson of Sweden, at http://www.backyardnature.net/n/14/141116go.jpg.
Compare those anthers with the ones in our own G. hirsutum flower from local northern Yucatán dunes at http://www.backyardnature.net/yucatan/hirsutum.htm.
To me this matter of compact and loose filaments seems to be the most dependable for distinguishing the two species. Using that feature, I find that maybe all the cotton plants I've seen so far in the Yucatan -- wild and planted next to Maya huts, both low herbs and woody, small trees -- have been Upland Cotton, Gossypium hirsutum.
ON NOT OFFERING NEW ESSAYS HERE
For years I ended Newsletters by doing a little philosophizing in this spot. I enjoyed writing those pieces, and people seemed to respond to them more than anything else in the Newsletters. Sometimes nowadays when a Newsletter ends without an essay I feel a little sheepish, knowing I'm disappointing some folks.
The main reason for no longer ending most Newsletters with essays is that after so many years of writing them, I've said what I wanted to say.
Some of my best-received essays of the past were those consisting of mere descriptions of things, and I'd like to write more of those. However, you have to be in a certain mood to write such pieces well. During the recent Texas years, that mood just dried up, but maybe a little of it is returning; I don't know. Also, here in Río Lagartos I'm discovering so many new-for-me and interesting things deserving to be written about that I just don't have time for cloud-sniffing kinds of writing.
Anyway, that's the thinking now. I just thought the situation should be addressed.
FEATURED ESSAYS FROM THE PAST:
"Why are So Many Plants Medicinal?" from the June 1, 2003 Newsletter, at http://www.backyardnature.net/n/p/030601.htm
"Percentages" from the January 30, 2011 Newsletter, at http://www.backyardnature.net/n/p/110130.htm
Best wishes to all Newsletter readers,
All previous Newsletters are archived at http://www.backyardnature.net/n/.