Two studies on reproduction in reptiles have made me go “wow, thats cool” this week. Read the rest of this entry »
Here’s one from the good news but bad news file: The good news is that a Duvaucel’s gecko (Hoplodactylus duvaucelii) has been found on the New Zealand mainland for the first time in nearly 100 years. The bad news is that it was found dead in a mouse trap.
Duvaucels geckos are the largest of our native geckos, and one of the biggest geckos in the world, growing to up to 30cm in total length. They are found on a number of offshore islands off the north-east of the North Island and in Cook Strait, and were thought to be extinct on mainland New Zealand. The last recorded sighting of this species on the mainland was near Thames in the 1920s, but subfossil remains have been found on both the North and South Islands, suggesting it was once widespread across the country.
The dead gecko was found at Maungatautari, in the Waikato. Maungatautari is a 3400 ha nature reserve ringed with a predator-proof fence, making it the largest pest-free area on the mainland. Many rare species have been released into the sanctuary, including kiwi, kaka, takahe and hihi, and reintroductions of many more species are planned. The Duvaucel’s gecko find suggests that there is a remnant nautral population of the species in the sanctuary, which somehow survived the years when the area was overrun with introduced predators. The hunt is now underway for more of the geckos (which will hopefully be found alive).
This discovery shows that you never know what you might find when you protect an area instead of mining it.
More on the discovery on Stuff.
In Biology Letters this week is the report of a new giant monitor lizard discovered in the Phillipines. Varanus bitatawa is 2m long, brightly coloured and has a double penis, and lives high up in the trees on the island of Luzon.
It always amazes me when new species of large vertebrates are discovered in this day and age, when you would think that the majority of the world has been given a thorough going-over, and that 2m long lizards would have been noticed. Actual new discoveries – as in “thats the first time we’ve seen THAT animal”, as opposed to an organism thats been known about for years but only been named as a separate species on the basis of DNA analysis – are pretty rare these days. So I was slightly disappointed to find out that Varanus bitatawa is only a new discovery from a western scientific perspective – Filipino tribal hunters have of course known about it for years.
National geographic has more on the discovery here.
Most New Zealanders can name at least a dozen or so species of native bird, but how many can do the same for our native reptiles? If you starting counting and only got as far as 1. tuatara, you’re probably not alone. Although we are missing some of the major groups of reptiles (like snakes and alligators), we do have a diverse array of lizards. In fact New Zealand has around 80 different lizard species in two major groups – geckos and skinks (tuatara are not lizards, they are Sphenodontids).
Around half of our lizard species are skinks. These are the most commonly encountered native reptiles, being the species most likely to be spotted disappearing under rocks or into long grass on a hot day, and generally being favoured by the domestic moggy. Now new research is improving our understanding of the origins and evolution of our skink fauna, with some exciting fossil finds and the publication of a comprehensive genetic study. Read the rest of this entry »
This from a letter to Nature, in the latest edition:
Could Nature have been unknowingly publishing papers for the past 80 years about crocodilian gastroliths (stomach stones) instead of stones concluded to be 2.5-million-year-old hominid tools? This possibility could cast doubt, for example, on the nature of the Oldowan specimens described by Michael Haslam and colleagues in their Review of primate archaeology (Nature 460, 339–344; 2009).
…Identification of the Oldowan specimens as tools is based on the fact that the soft relict sands of Olduvai Gorge contain no natural stones of their own, so any stone found there must have been moved from distant river beds by some unknown animal transporter — concluded by high science to be Homo habilis. But crocodiles have the curious habit of swallowing rocks: these account for 1% of their body weight, so for a 1-tonne crocodile that’s 10 kg of stones in its stomach at all times. Surprisingly, science has never even considered the crocodile as transporter.
Read the full version here
Earlier this year Keller Autumn from Lewis and Clark University gave a fantastic talk at Victoria University about the amazing properties of gecko’s feet, and how new adhesives are being developed based on these properties. Well, it turns out geckos do pretty neat things with their tails as well – check out this presentation by one of Autumn’s collaborators, Robert Full from UC Berkeley.
Reptiles do all sorts of crazy things when it comes to sex determination. Some use good old fashioned sex chromosomes like mammals do, but in other species the temperature that the egg is incubated at determines the sex of the offspring. For instance in the tuatara, eggs that are incubated at 23 degrees are uniformly male, and eggs incubated at 18 degrees always turn out female. Some reptiles seem to use a combination of both - they have sex chromosomes, but these are overridden when the eggs are incubated at extremely high or low temperatures. Now it seems it could be even more complicated for some species, as a recent study out of Rick Shine’s lab at the University of Sydney has found that egg size is also a determining factor. In their study of the Eastern three-lined skink (Bassiana duperreyi), they found that sex chromosomes, temperature and egg size interact to determine the sex of the offspring, with larger eggs incubated at low temperatures producing females, regardless of their sex chromosomes.
Ed Yong from Not Exactly Rocket Science has a nice write-up about this paper - go check it out!
The paper citation is: Radder, Pike, Quinn and Shine (2009) Offspring Sex in a Lizard Depends on Egg Size. Current Biology in press doi:10.1016/j.cub.2009.05.027
I found this rap video on Hox genes (yes really) on a couple of other blogs over the past week. Its so good I thought I’d post it here.
And now that you’re all familiar with the basics of Hox genes… a recent study in Genome Research has found some rather unusual features of this gene family in lizards. Hox genes play an important role in specifying the anterior-posterior body plan in the developing embryo, and are found in ordered clusters in the genome. Vertebrates have 4 clusters (A, B, C, and D), with each cluster containing multiple Hox genes.
Hox clusters are unusual in that there is very little repetitive DNA between the genes (repetitive elements being a large fraction of most eukaryotic genomes). Thus, in most vertebrates Hox genes are located close together, in a tightly ordered sequence.