Smithsonian Science » zoology

Caribbean box jellyfish now thriving in southern Florida

John Barrat — Thu, 02 Feb 2012 14:28:41 +0000

A box jellyfish from the Caribbean has recently become established in the red mangroves of Florida near Boca Raton, adding to a rising number of marine invasions observed along the world’s coasts in recent years. Since 2009, when a single male specimen of Tripedalia cystophora was discovered in Florida’s Lake Wyman and identified by Allen Collins, curator of Invertebrate Zoology at the Smithsonian’s National Museum of Natural History, and Evan Orellana of the Gumbo Limbo Nature Center in Boca Raton, this box jellyfish has appeared in Florida in much greater numbers.

“Based on the numbers that have been reported, the population seems to be pretty healthy,” Collins says. “I do not think this is something that people should be overly alarmed about,” he adds. “They are not large. Their bell is only about a centimeter. There aren’t any reports of them causing bad stings to swimmers, but the venom has not been specifically studied.”

Image right: The box jellyfish Tripedalia cystophora. (Photo by Jan Bielecki)

With the gradual warming of the oceans a number of marine species from the Caribbean have been observed moving into areas of the southern and mid-Atlantic coasts of the United States. “We’re seeing this happening everywhere all over the planet. Species ranges are changing because of human activities,” Collins says. “In general, it’s another symptom of a changing world.”

Image right: Diagram of a box jellyfish from the paper “First report of the box jellyfish Tripekalia cystophora (Cubozoa: Tripedaliidae) in the continental USA, from Lake Wyman, Boca Radon, Florida” by Evan Orellana and Allen Collins.

Tripedalia cystophora has taken up residence in southern Florida’s red mangroves, which is “a really good habitat for larval fishes,” Collins explains. “So, they could be competing with larval fishes for food, or if the fish larvae are small enough, perhaps even eating them, but they specialize on copepods. This box jellyfish is probably here for good.”

New exhibition looks at fishes from the “Inside Out”

John Barrat — Thu, 02 Feb 2012 12:01:33 +0000

“X-Ray Vision: Fish Inside Out,” is a new exhibition of striking x-rays that reveal the complex bone structure of fishes in the collections of the Smithsonian’s National Museum of Natural History. These x-rays allow scientists to study “the skeleton of a fish without dissecting or in any other way altering the specimen,” says curator Lynne Parenti. Ichthyologists at the museum study fish skeletons, fin spines, teeth and other morphological features to differentiate one species from another and exmaine evolutionary development. “X-Ray Vision: Fish Inside Out,” from the Smithsonian Traveling Exhibition Service, opens at the Natural History Museum in Washington, D.C. on Saturday, Feb. 4. More information about each of the fish species featured is available at: eol.org/info/xrayvision.”(All images by Sandra J. Raredon, Division of Fishes, National Museum of Natural History.)

Moray eel. Moray eels are legendary predators on coral reefs. Note the second set of jaws in the “throat”; these are the gill arches, which are present in all fish. Gill arches support the gills, the major respiratory organ of fish.

Lookdown. Because of its sloped head and the enlarged crest on its skull, the Lookdown appears to “look down” as it swims. These fish often swim in small schools.

Alligator Pipefish. Pipefish may be thought of as seahorses unfurled. The numerous bony body rings are used to differentiate one species of pipefish from another.

Ox-eyed Oreo. The name Oreosoma (“mountain body”) refers to the cone-shaped bony structures on the underside of this larval specimen. Adults are more elongate, less oval, and covered with scales.

Dhiho’s Seahorse. Just over one inch long, this elegant fish is readily identified as a seahorse by its characteristic head. The body ends in a tail that can curl around and hold on to algae or coral. This species is found only in the waters around Japan.

Five funky and 5 fun facts about fishes

John Barrat — Sun, 29 Jan 2012 20:12:51 +0000

1

Hagfishes, known as slime eels or slime hags, are so named because of the huge amounts of mucus they produce. One disturbed hagfish can fill a 2-gallon bucket with slime in a matter of minutes. The slime makes them virtually inedible.

2

The eyes of the Four-eyed Fish are split in half horizontally, each having two pupils and a retina that is divided into top and bottom sections. It swims with half of its eye out of the water, searching for insects, and the other half looking down into the water.

3

African lungfish enclose themselves in a mud tunnel and, after their lake has dried up, can live for years buried in the mud, breathing air and waiting for the rains to return. The structure of their heart and lungs first tricked scientists into thinking the South American lungfish was a reptile, the African lungfish an amphibian.

4

Anemone fishes live in groups where the two largest fish only are sexually mature, the largest being female and the next largest male. If the female dies, the male changes sex to female and the next largest fish in the group matures to male. If the animated film “Finding Nemo,” had been true to life, Nemo’s dad, Marlin, should have become Nemo’s mother shortly after his original mother was eaten by a barracuda.

5

A few fishes specialize on, or at least supplement their diets with, the eyes of other fishes. A narrow-bodied cichlid in Africa’s Lake Malawi, the Malawi Eyebiter, does not make a good aquarium pet because of its eye-popping activities.

6

Peters Elephantfish is the only fish ever observed playing with objects. In captivity, these fish will repeatedly take a small ball of aluminum foil and carry it to the outflow tube of an aquarium filter so the ball is pushed across the tank by the water current.

7

Most fish are countershaded: darker on top, gradually lighter or silver on their sides and brightest on their bellies. Seen from above, beside or below, this pattern makes them less visible in the water column against the background color of the water.

8

The cusk eels are the world’s deepest living family of fishes. One was netted with a bottom trawl in the Puerto Rico Trench at a depth of 27,500 feet. At such a depth a fish would experience a pressure of approximately 12,000 pounds per square inch.

9

As they sleep (and fish do sleep), parrotfishes and wrasses secrete a mucous cocoon around themselves at night, perhaps to thwart the highly-developed senses of moray eels and blood-sucking parasitic invertebrates.

10

Menhaden, the fishes the Indians taught the Pilgrims to plant with their corn, today rank as America’s most important fishes. Menhaden oil is used in cosmetics, linoleum, health food supplements, margarine, soap, insecticides and paints. Their pulverized bodies end up as feed for cats, dogs, poultry and pigs.

All fish facts are from the new book Fishes: The Animal Answer Guide, by Bruce Collette, National Systematics Laboratory, Smithsonian’s National Museum of Natural History; and Gene Helfman, University of Georgia.

Why did the tortoise cross the road? A recent study indicates few do.

John Barrat — Tue, 17 Jan 2012 12:29:07 +0000

Scientists studying genetic variation and gene flow in a population of tortoises (Gopherus agassizii) in California’s Mojave Desert, were surprised recently to discover that two roads built in the desert in the 1970s had a noticeable impact on the population’s genetic structure. Tortoise pairs from the same side of the roads exhibited significantly less genetic differentiation than pairs from opposite sides of the roads, the scientists report in a recent paper in the journal PLoS ONE. The study was a fine-scale local genetic analysis of the population, rather than a broad, regional scale, which is more commonly done.

Image left: A desert tortoise, Gopherus agassizii. (Image by Mike Jones, courtesy Encyclopedia of Life)

“Roads are barriers to dispersal for lots of species and usually it takes many generations to show up in the genetic structure of an animal,” says one of the paper’s co-authors Emily Latch, a postdoctoral researcher at the Smithsonian Conservation Biology Institute’s Center for Conservation and Evolutionary Genetics, and now an assistant professor at the University of Wisconsin-Milwaukee. “Because tortoises have such a long life span, we didn’t think the roads would influence their genetic structure so quickly, but they did.”

The study shows for the first time that recent landscape features such as roads “can have rapid effects on the genetic structure of a localized population and are detectible almost immediately,” in as little as one generation, the scientists report. As a result, the scientists conclude, “Roads may become increasingly important in shaping the evolutionary trajectory of desert tortoise populations.”

For the study, DNA samples were taken from 859 tortoises living in an area of 23,969 acres. “A huge number of samples,” for such a small area, Latch says. Data also was taken on each animal’s sex, location, and location elevation and slope.

Image right: A tortoise in the Mojave Desert. (Image courtesy Wikipedia)

The tortoises were sampled as part of a tortoise relocation effort at Fort Irwin Army Training Center and the animals were located by having people walk map transects in the desert. They picked-up, labeled and took data and DNA samples for every tortoise encountered.

“The adult individuals were initially genotyped to develop a baseline genetic database of translocated and resident tortoises so that family groups hatched after the translocations could be identified to particular parents, and the reproductive success of translocated and resident tortoises compared,” says Smithsonian geneticist Rob Fleischer, head of the Center for Conservation and Evolutionary Genetics and senior author on the paper. “This is important to determine if translocation is really an effective mitigation step. It was serendipity that led to our finding a surprising level of genetic structure.”

Roads may inhibit gene flow in desert tortoises by the reptiles being hit by cars, picked up by travelers, and predation and disease associated with pets released by the roadside. Eroded banks and increased vegetation along desert roads also may provide places for the tortoises to burrow and forage for food, causing them to move along a road rather than to cross it.

The article “Fine-Scale Analysis Reveals Cryptic Landscape Genetic Structure in Desert Tortoises,” by Emily K. Latch, William I. Boarman, Andrew Walde, and Robert C. Fleischerappeared recently in the journal PLoS ONE.

-John Barrat

New Book: “Fishes: The Animal Answer Guide”

John Barrat — Tue, 10 Jan 2012 13:21:43 +0000

One of many facts the authors of this fascinatingly informative book reveal is that worldwide there are some 30,000 species of fishes. They range in size from tiny gobies to the massive ocean sunfish, which can weigh thousands of pounds. Fishes live in just about every body of water on the planet.

Ichthyologists Gene Helfman, professor emeritus at the University of Georgia, and Bruce Collette, of the Division of Fishes at the Smithsonian’s National Museum of Natural History, provide accurate, entertaining, and sometimes surprising answers to more than 100 common and not-so-common questions, such as “Can fishes breathe air?” “How smart are fishes?” and “Do fishes feel pain?”

They explain how bony fishes evolved, the relationship between fishes and sharks, and why there is so much color variation among species. Along the way we also learn about the devils hole pupfish, which has the smallest range of any vertebrate in the world; “Lota lota,” the only freshwater fish to spawn under ice; the Candiru, a pencil-thin Amazonian catfish that lodges itself in a very personal place on male bathers and must be removed surgically; and many other curiosities.

With more than 100 photographs—including two full-color photo galleries—and the most up-to-date facts on the world’s fishes from two premier experts, this fun, accessible, and informative book is the perfect bait for any curious naturalist, angler, or aquarist.

Why did the tortoise cross the road? A recent study indicates few do.

John Barrat — Tue, 10 Jan 2012 05:05:28 +0000

Image left: A desert tortoise, Gopherus agassizii. (Image by Mike Jones, courtesy Encyclopedia of Life)

Image right: A tortoise in the Mojave Desert. (Image courtesy Wikipedia)

-John Barrat

VIDEO: Meet our Scientist Rachel Page. She studies frog-eating bats, and other animals, in Panama

John Barrat — Mon, 09 Jan 2012 18:33:40 +0000

Members of small monkey groups more likely to fight, researchers find

John Barrat — Wed, 28 Dec 2011 03:13:54 +0000

Small monkey groups may win territorial disputes against larger groups because some members of the larger, invading groups avoid aggressive encounters. In a new report published in Proceedings of the National Academy of Sciences, Margaret Crofoot and Ian Gilby of the Smithsonian Tropical Research Institute in Panama and the Max Planck Institute of Ornithology show that individual monkeys that don’t participate in conflicts prevent large groups from achieving their competitive potential.

Image above: Is this monkey a wimp? A new study by Margaret Crofoot and Ian Gilby carried out at a research station run by the Smithsonian on an island in the Panama Canal shows that the answer may depend on the size of the group it belongs to. (Photo by Marcos Guerra)

The authors used recorded vocalizations to simulate territorial invasions into the ranges of wild white-faced capuchin monkey groups at the Smithsonian reasearch station on Barro Colorado Island in Panama. Monkeys responded more vigorously to territorial challenges near the center of their territories and were more likely to flee in encounters near the borders.

Defection by members of larger groups was more common than defection by members of smaller groups. Groups that outnumbered their opponents could convert their numerical superiority to a competitive advantage when defending the center of their own range against neighboring intruders, but failed to do so when they attempted to invade the ranges of their neighbors, because more individuals in large groups chose not to participate. According to the authors, these behavior patterns even the balance of power among groups and create a ‘home-field advantage’ which may explain how large and small groups are able to coexist.

Mistletoe facts from a Smithsonian botanist

John Barrat — Tue, 20 Dec 2011 15:50:07 +0000

When you’re caught under the mistletoe, the tradition is to kiss the person next to you. But this holiday season you may want to wow them first with some cool mistletoe facts from Smithsonian botanist Sylvia Orli.

Image right: American Mistletoe (Phoradendron flavescens) by Mary Vaux Walcott, 1923. (Image courtesy Smithsonian American Art Museum)

* Mistletoe is found mainly in tropical or temperate areas. Its name refers to species of parasitic plants from families in the order of flowering plants known as Santalales. There are some 1,300 species of mistletoe worldwide.

Image left: The mistletoe Phoradendron serotinum. (Photo by Jorg and Mimi Fleige)

* The word “mistletoe” is thought to derive from the Anglo-Saxon “mist” or “mistel”, meaning dung, and “tan”, meaning twig, or “dung twig”. This derivation stems from the fact that mistletoe is mostly spread by birds, through their droppings.

* Birds also squeeze mistletoe seeds from the fruits before eating them and wipe the seeds on a branch. Mistletoe seeds are covered in a sticky substance so they stay put on a limb until they sprout.

* Mistletoe is semi-parasitic, meaning it invades a living branch of a host tree or bush with a shallow root (called a “hastorium”) and absorbs food, minerals and water, and also produces food through photosynthesis in its evergreen leaves.

* Viscum album, the European mistletoe, and Phoradendron serotinum, from North America, are the two mistletoe species most commonly harvested and sold during the Christmas holidays.

Image right: The mistletoe Vicsum album (Photo by Malcom Storey)

* Mistletoe is considered a pest in many areas of the world. A host tree or bush heavily infested with mistletoe can be stunted or even die. Still, mistletoe provides an important food source and a nesting place for a variety of bird species.

Reptiles may be spreading deadly amphibian disease in the tropics

John Barrat — Wed, 14 Dec 2011 20:24:30 +0000

Reptiles that live near and feed upon amphibians in the tropics may be spreading the deadly amphibian disease Chytridiomycosis (caused by the chytrid fungus Batrachochytrium dedrobatidis), holding and transporting reservoirs of the fungus on their skin, say researchers from the Smithsonian Tropical Research Institute and Canada’s McGill University. In fact, chytridiomycosis may not be strictly a disease of amphibians, as many believe. It also may be killing reptiles and be partially responsible for the noticed decline in reptile populations around the world.

Image right: Common basilisk lizard female, Basiliscus basiliscus. (Photo by Steven Johnson)

In a study recently published in the journal Diseases of Aquatic Organisms, scientists took skin swabs from individuals of 13 different species of lizards and 8 different species of snakes caught in western and central Panama. DNA analysis of the swabs revealed that 16 percent of the lizards and 38 percent of the snakes carried the chytrid fungus on their skin. None of the reptiles that tested positive for the disease showed signs of infection or sickness comparable to what is observed in amphibians stricken with the disease.

Image left: The anolis lizard Anolis humilis. (Photo by Shawn Mallan)

“Lizards and snakes will harbor Batrachochytrium dedrobatidis at non-pathological levels,” the researchers write, and infection in reptiles is highly plausible. “By potentially maintaining the pathogen in the environment without succumbing to the disease, these reptiles may be important vectors or reservoir hosts for Batrachochytrium dedrobatidis… and may allow virulent strains of it to spread.”

While the study presents no evidence that chytridiomycosis is lethal to reptiles, its presence on the skin of reptiles in areas that have witnessed the decline of both amphibians and reptiles in recent years is cause for concern, the scientists say.

Image right: The tropical snake Imantodes cenchoa. (Photo by Geoff Gallice)

“Reptiles as potential vectors and hosts of the amphibian pathogen Batrachochytrium dendrobatidis in Panama,” by Vanessa Kilburn and David Green of McGill University and Roberto Ibanez of the Smithsonian Tropical Research Institute, was published in December in the journal Diseases of Aquatic Organisms.