Boy or Girl?: A Climate-Fated Adventure In Lizards

Posted by Alex H. |0 comments

Niveoscincus ocellatus (Photo credit)

Ever caught yourself wondering what it might be like if you could know the sex of your future children? Several methods allow for this to be determined with modest accuracy in the late stages of a human pregnancy, but what about early pregnancy? Before pregnancy? In other animals?

Sometimes the answers to these questions can be predicted based on the context in which they are asked. For example, I came across this article this article a few months ago, and would like to share its findings (full paper here; additional source). Essentially, the researchers found that climate, combined with genetics, was a main determinant of what sex-determining system emerged in a species of lizard.

But isn't sex in vertebrates determined by chromosomes? Not always. For instance, in many (not all) reptiles, sex is influenced by environmental factors, often temperature (i.e., temperature-dependent sex determination, or TSD). But how would a knowledge of TSD help you predict the sex your offspring? Well consider the example offered by our study in question.

In these experiments, an international cohort of herpetologists collected and observed female Spotted Skinks, Niveoscincus ocellatus from two types of habitats in Tasmania: highland and lowland. The habitats differ in altitude and therefore atmospheric oxygen, UV irradiation, moisture, and temperature, among others. Female N. ocellatus from the lowland habitat, when raised in a lab setting, varied in the ratios of male/female lizards based on the amount of sunlight they were exposed to (4 hr or 10 hr; sunlight functioning as a natural variable in temperature, UV irradiation, and light). Surprisingly, although the same species, female N. ocellatus from the highland habitat did not demonstrate this discrepency between sunlight exposure times.

What does this mean? The authors of this paper predict that in N. ocellatus, the lowland-dwelling lizards are more likely to give birth to female lizards than male lizards when temperature is higher. Lowland female lizards born earlier (as a result of warm temperatures earlier in the year) have a reproductive advantage over lowland female lizards born earlier in the year. Neither highland lizards or male lowland lizards experience a similar boost from being born earlier (resulting in more females in lowland species in warmer years). For the highland lizards, the overall temperature is colder and there is not a significant reproductive advantage to being born earlier in the year. Additionally, the paper revealed a possible mechanism for species divergence (i.e., cladogenesis) - that of environmentally-sensitive evolution of sex-determination systems.

Remember our question about predicting the sex of future offspring?  The authors also suggest that if the warming trend continues in the species' habitat, more females will be expected. Hypothetically, lowland N. ocellatus mothers can plan on more female offspring in their future (assuming it remains an evolutionary stable strategy for the species). Greeting card companies for newborns take note!

It a Gril! (via Cake Wrecks)

The Great Turtle-Egg Evacuation

Posted by Alex H. |2 comments

The Deepwater Horizon oil spill is a very, very sad story. No matter how you look at it, the whole thing is spelling disaster.

What is surprising to me is how the event is being labeled as an ecological disaster by the mainstream media. Even though the explosion of the oil platform has left 11 dead (plus 2) and 17 injured, these facts have been essentially forgotten as the yet-contained oil continues to spew into the Gulf of Mexico and its surrounding shoreline. The focus is not unwarranted in most respects, as the consequences of this input of crude into the Gulf and associated cleanup efforts have and will have staggering effects on the ecology of the Gulf of Mexico and the Atlantic Ocean.

Unsurprisingly, an already-struggling effort for effective sea turtle conservation is being hit with very difficult decisions about what to do. Several species of adult sea turtles are running the risk of being cremated alive when caught inside oil slicks being burned. Additionally, as eggs hatch from nests on the beaches of the Gulf, juvenile turtles would face thousands of miles of oil-polluted water in the most vulnerable time of a sea turtle's life.

This last situation is why the US Fish and Wildlife Service, the National Marine Fisheries Service, and the Florida Marine Fisheries Service have developed a plan to relocate an estimated 70,000 sea turtle eggs from almost 800 beaches along Alabama and Florida. Read more here: The Great Turtle-Egg Evacuation

The plan is very risky for turtles inside eggs. As the article states:

"[...] within 12–24 hours of the eggs being laid, embryos attach to an oxygen-supplying membrane. So any movement of the eggs could cause detachment and death [...]."

A former student from my university completed a series of research projects on sea turtle conservation in the last few years which illuminated my perception of the effectiveness of current conservation efforts. This last point about the eggs dying if moved at the wrong point in time is correct, and is a major concern in these operations.

This topic has been a hot one in many email listservs I am subscribed to (especially C-TURTLE), and the point most interesting to me in all of this is the question of how the relocated hatched juveniles will respond to being transported to beaches several hundred miles from where they were laid. The previously-linked article continues to talk about potential affects of this operation on the relocated turtle's behavior:

Moving the eggs is not generally viewed as problematic. "We have adequate data showing that eggs moved with competence at that age have no difference in survivorship to those not moved," said Mike Salmon, a biologist at Florida Atlantic University in Boca Raton. 

But the release could be another matter. "What we don't know is what impact it might have on other aspects of behaviour," says Salmon. 

"The $64,000 question is, if you take hatchlings that would normally emerge in northwest Florida to the east coast," he said, "will they return there, or to the northwest, where they should go?" Because scientists don't know for sure whether imprinting occurs in the nest or after emergence, this remains a mystery.

This point is one where conservation, ecology, and ethology intersect. My favorite! I anticipate some interesting research will come out of this project, especially if local behavioral research-heavy universities (e.g., University of Florida) are asked to become involved. So much is known about sea turtle navigation and spatial perception, but I do not know of any test which has analyzed how moving recently hatched eggs 500 miles away affects the survival of individuals. Normally, this is not a practical situation which would not require testing (and thus, I see why there is a paucity of research on this specific topic).

Finally, it is worth noting that Heppell et al. (1996) found that the most effective contributors to sea turtle conservation were not efforts directed towards very young sea turtle (particularly 'headstarting', or catching recently hatched individuals and raising them for a year before release). Instead, turtle excluder devices (TEDs) attached to shrimp trawling nets offer the greatest positive effect on their survival. I wonder how meaningful this project to move ~70,000 eggs will be in light of these results.

Thank you for reading, I hope you are doing your part to support relief and clean-up efforts in the wake of this ecologically-disruptive event.

Addendum: I could insert lots of opinion on the oil spill, but I'll pass for two reasons: 1) I'm not a geologist, and 2) no one wants to read my whining (not even me). You can read more about sea turtle headstarting here.

Museum of Living Art (MOLA) - Now Open

Posted by Alex H. |1 comments

As summer approaches, I am getting mixed news about what I'll be doing for the next few months. I had applied to several internships, but none of them had positions open :/

One place that I am interested in is the Forth Worth Zoo. I had a post at the beginning of the year which described the zoo and a new exhibit - the Museum of Living Art (MOLA). This exhibit replaces their Herpetarium built in 1960.

Upon visiting the FW Zoo's website, I see that MOLA opened in March of this year!

Check out their over-the-top promotional videos here or here.

The size and scope of the exhibit are phenomenal. The 30,000 sq. ft. facility houses (at current) around 1,000 individuals representing a hundred different species of reptiles and amphibians.

I'm super-pumped! I'll report in when I have the chance to visit them next.

Update: When searching for images for this article, I spotted one of my pictures in the top results of a Google Search. Moving up the food chain. We also recently hit 1,000 pageviews. Hooray!:

Museum of Living Art

Posted by Alex H. |0 comments

2009 was a rough year for everyone. Possibly the least popular year of the decade. One of the biggest let-downs I experienced in 2009 was the delayed opening for the Fort Worth Zoo's Museum of Living Art. Before I explain, allow me to remind you that my family visited the Ft. Worth Zoo last year with intentions of seeing some progress on this world-class project. Unfortunately, it appeared that delays had pushed its opening to sometime this spring.

What the heck am I talking about, pray tell? Only the construction of the world's most awesome herpetarium (like an aquarium, but for reptiles and amphibians)! This thing's going to be huge - probably the largest in the world (both in square footage, number of species, and possibly number of individuals).

When the zoo's current herpetarium opened in 1960, it held more species of reptiles and amphibians than any other facility. Throughout it's history, the staff have been responsible for the breeding of several individuals, included many rare and endangered species. This new facility will continue their previous vision, but with the world-class resources deserving of their world class efforts. In addition to housing more species than any other facility, the MOLA will continue and expand upon their significant conservation efforts for amphibians (If you would like to know more about their conservation efforts, read this article here).

The MOLA will have several different "habitat" areas for viewing by patrons, including a deserts, swamplands, and rain forests. Just check out this huge list of species the MOLA will be keeping, or should I say curating? If that doesn't get you salivating, you can view the online floor-plan for the new facility which indicates generally what will be exhibited. For zoo activity in the new decade, keep an eye out for the MOLA.

Here are two shinglebacks in the Fort Worth Zoo's current herpetarium. Shinglebacks are highly monogamous (single pair breeders). There are cases of them breeding with their mate (to the exclusion of other individuals) for up to twenty years:

Art and Biodiversity

Posted by Alex H. |0 comments

I love combining topics. My field of study is a combination of biology, psychology, and ecology; I'm attending a liberal arts institution, as a Boy Scout I earned over 60 merit badges (far above average), and the list goes on. When all is said and done, my favorite combination of two topics is animals and artwork (as can be witnessed by a previous post of mine). I'm just giddy to see two of my favorite topics combining with such a natural feel!

My passion for seeing art and animal diversity combined may be why I have been drawn to a couple of articles lately.

First check out this summary of a project done by an undergraduate through the School for Field Studies (SFS). This student organized the painting of several murals in Baja, Mexico emphasizing the conservation of sea turtles. That's herpetology, conservation biology, and artwork - all rolled into one!

Additionally, my academic adviser relayed this neat project to me: The Hyperbolic Coral Reef. Here's a quote from their website:

The Institute For Figuring is crocheting a coral reef: a wooly celebration of the intersection of higher geometry and feminine handicraft, and a testimony to the disappearing wonders of the marine world.

What a wild idea, right? There's a lot going on here, but to summarize, a feminist crocheting organization has responded to declining coral reefs by expressing their beauty in a knitted form. Using a fairly new style of knitting, "hyperbolic crochet," inanimate yarn is 'brought to life' in the form of corals, anemones, urchins, you name it. One of the organization's representatives, Margaret Wertheim delivered a lecture on our campus yesterday, but unfortunately, I arrived at the wrong location and missed the boat. Bummer luck, but their expansive website should please your visual palate.

Share your favorite art-fusion links in the comments below.

Here are a few more pictorial examples:

NOVA Series - Lizard Kings

Posted by Alex H. |0 comments

Perusing some other blogs, I discovered a fascinating NOVA series on monitor lizards titled "Lizard Kings."

http://www.pbs.org/wgbh/nova/lizard/

NOVA is well known for their awe-inspiring filming, and this program certainly does not come up short.

I'm posting this because it's free to watch online, visit their website and click "Watch online." The whole program runs at 52 minutes.

Reptile Communal Nesting

Posted by Alex H. |2 comments

Check out this cool article about normally-solitary reptiles laying eggs in communal nests.

Communal nesting!? What's that, Alex? For one, it has traditionally been thought of as a non-reptilian behavior. Communal nesting is simply the laying of eggs by a female animal into the nest of a conspecific (same species) animal. This behavior is different than cooperative breeding, which could be thought of as a "daycare system" - individuals care for the young of other individuals, even at the expense of their own breeding abilities.

A quote that summarizes the opinions of the authors on why communal nesting occurs in some reptiles:

Building a nest can be hard work for reptiles. Some female lizards, for example, may spend days digging a hole deep enough to deposit eggs. During those days, she is not doing other important things such as finding food. She is also more vulnerable to predators. Females can avoid these costs by simply laying eggs in a nest that someone else has gone to the trouble to build.

The model, the authors argue, could be advantageous in an evolutionary sense. It is common sense to note that anything that reduce an animal's required level of energy expenditure to successfully pass on genetic material is good for the species in the long-run. This argument does NOT always hold true; however, that's the common sense approach. It is still true that parental care is not the norm in most described species behaviors THUS FAR, but read on...

While searching around for the topic, I found another well-cited article summarizing review articles (articles that synthesize scientific literature) which argues that communal nesting is probably much more common in reptilian species than first thought. If you read through the article, you note how little is known about nests in most species of reptiles. In fact, for most named species, nests have never even been reported in the scientific literature! Just another opportunity to grab your hiking boots and go outside!

Review - "The Fascination of Reptiles"

Posted by Alex H. |0 comments

The Fascination of Reptiles by Maurice Richardson is nowadays innaccurate and historical, at best.

This book is a decent read for the only the most enthusiastic herpetologist.

Reptiles is written from the author's personal experiences as a herp enthusiast, with a fond eye focused on all things reptilian. Species descriptions and anecdotal accounts of reptilian behavior swap places back and forth covering the snakes, lizards, turtles, crocodiles, and alligators. The author's emphasis is extrordinarily heavy on appealing to an assumed-British audience. For example, whole chapters are devoted to the very few British reptiles, while mere paragraphs are allotted to a slew of Indonesian or South American treasures.

A common theme in Reptiles appears to be the author's unrelenting obsession with the degenerative features found in skinks, legless lizards, and burrowing snakes. Truly, it was obnoxious. Evolution does not have a goal or purpose - get over it!

A common flaw in the field of herpetological description is its lack of mention for ancestrally-related reptilians - birds. A mention or two of birds, or even dinosaurs, would make me smile a bit.

Illustrations by Shaun Milne are cute, but you can't help but wonder about their accuracy at times. Some sense of scale in the plates and drawings would have been appreciated.

Chapter topics: Classification and Evolution, The Living Ancestor, The Lizards: Suborder Sauria, British Lizards at Home, The Marvellous Chameleon, The Snakes: Suborder Serpentes, Pythons and Boas, Poisonous Snakes [2 chapters], British Snakes at Home, The Chelonians: Tortoises and Turtles, The Crocodilians, Some Reptiles of North America, Herpetologists I Have Known, Reptiles In Captivity, and An Anthology of Reptilian Belles-Lettres.

Overall: 2/5 - a fun read, but not particularly useful or entertaining