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ATTINE ANTS have been a theme at my blog recently. They first showed up in a discussion of their evolutionary tree, then in a post examining their relationship with the actinomycete bacteria that help protect their fungal gardens from parasites. In my reading I stumbled across the article that I will write about today, which seems to have discovered another part to the attine ant symbiosis. As of now this is the sole report on the occurrence of black yeasts living apparently parasitically on the attine ants, reliant upon the cuticular crypts that normally house helpful actinomycetes.
I’m about to become really busy. I’m not sure exactly how busy, but my posting level will probably drop significantly. I’ve been posting on science every other day, and I expect this to drop to 2-3 times a week. Of course, I could be pleasantly surprised and things may go easier than expected.
WHILE THE ATTINE ants are not well-studied, I posted this week about a study into their evolution that revealed the history of innovations in their cultivation of fungus. The attine ants are part of a symbiotic network between the ants, their fungal cultivars, the parasitic fungus Escovopus, and actinomycete bacteria that serve to suppress this parasite. These bacteria are members of Pseudonocardia and grow in filamentous mycelia on the insects’ integument, where the ants have evolved cuticular crypts to house the bacteria and glandular secretions that support their growth.
The actinomycetes are an order of bacteria that are know to produce a wide range of biologically active molecules, many of which are active against other bacteria and against fungi. Some of these natural products are now used clinically, such as the antibacterial antibiotics streptomycin, erythromycin, and tetracycline, anticancer drugs daunorubicin and doxorubicin, and antifungal drugs amphotericin B and natamycin. Actinomycetes inhabit a variety of environments, but many are ubiquitous soil bacteria.
WILL BAIRD of Dragon’s Tales posted Wednesday on the topic of dicynodonts, complete with artistic renditions. He mentions the last dicynodont fossil known showed up in the early Cretaceous, and speculates some might have survived to the end of the Cretaceous. Too bad they couldn’t make it to the present day! Since these creatures were a branch on the line to mammalian evolution, retain features of our therapsid ancestors, and are long extinct I think there are a lot of paleontologists and evolutionary biologists out there who would sacrifice various body parts if it would enable us to find a living example. I’m not even a paleontologist and I’d consider giving up a little toe.
WHILE CNIDARIA are considered to have radial symmetry, a new article proposes that the cnidaria had a bilaterian ancestor and may properly be placed in Bilateria.1
THE ATTINE ANTS are a clade of New World ants that cultivate fungal gardens for use as a food source. The most widely known group are the leaf-cutter ants, which spend most of their time harvesting slices of leaves that are chewed up and placed in the fungal gardens in their underground colonies. There are many other lesser-known species, and these practice different forms of fungal agriculture. A new study of the phylogenetics of attine ants show that the different methods of fungal cultivation emerged in single events.
I HAVE ALREADY mentioned one type of selfish genetic element. These are mobile elements that can move about and reproduce within the genome, and include the transposon and retrotransposons. A second similar type of selfish genetic element are the homing endonucleases. These come in two forms, as introns which are spliced out of RNA and then translated into protein instead of being discarded, or as inteins that splice out of the protein once it has been synthesized. In both cases the homing endonuclease then during meiosis attacks the allele that does not contain the homing endonuclease intron or intein and triggers DNA repair that duplicates the homing endonuclease’s sequence. Since mobile elements and homing endonucleases either attack at a wide variety of sites or duplicate onto both of a pair of chromosomes, they are passed on according to Mendelian inheritance patterns. But there are other selfish genetic elements that are passed on preferentially, and a new paper in Genetica focuses on the effects of these selfish elements upon fertility in carrier males.
I HAVE BEEN planning on writing this post for quite a while and hope to do the topic justice. The Cambrian explosion refers to the sudden radiation of metazoan life during the Cambrian period, and is usually placed between about 540-530 million years ago. It is often said that during the Cambrian explosion all of the modern phyla appeared. This statement has been seized upon by creationists who claim that the Cambrian explosion proves a sudden supernatural creation of life, rather than evolution of organisms over time.
THERE IS A new article published online at PNAS reporting the results of a 36-year experiment on the Italian wall lizard Podarcis sicula. A population of lizards was already living on a small islet called Pod Kopiste, and the authors moved five females and five males to the nearby islet Pod Mrcaru. This was originally an experiment in “competitive exclusion”, as the islet was already inhabited by the Dalmatian wall lizard, Podarcis melisellensis, which was apparently outcompeted and is now extinct on that islet.
IN HIS RECENT big cats post Darren Naish of Tetrapod Zoology mentioned something about aquatic proto-people coming up on his blog. I figured this was the Aquatic Ape hypothesis, which is popular among some circles, and says along the line of human descent our ancestors first became primarily aquatic and then our species reemerged onto land. This aquatic phase is supposed to be responsible for some traits of humans such as our long hair (for swimming babies to hold on to), relative lack of body hair (more streamlined), and our subcutaneous fat (supposedly for insulation and streamlining). While it is an unusual idea, it doesn’t rate “snort your coffee up your nose” funny. I can’t say the same for the idea that he is really reporting on–initial bipedalism.