Evolution picks from latest PNAS issue
Latest issue of PNAS which has Cubozoan jellyfish Tripedalia cystophora on the cover includes some nice work in evolution and and we will discuss about couple of them here.
First article by Kristopher et al, talks about the discovery of a remarkable annual tetrapod from the arid southwest of Madagascar: the chameleon Furcifer labordi, with a post-hatching life span of just 4–5 months.One amazing thing about this chameleon is that is spends most of its short annual life span inside the egg.The life cycle goes something like this ,hatching emerges -grow rapidly, reach sexual maturity in less than 2 months, and reproduce .All this takes place in active season and this concludes with death of all adult population wide,meaning in dry season the entire population is represented by developing eggs that incubate for 8–9 months before synchronously hatching at the onset of the following rainy season.Authors also mention that these chameleons have shortest life span among tetrapods.More insights about Furcifer labordi might throw light on life history evolution and the ecological, genetic, and/or hormonal determinants of aging, longevity, and senescence.
For complete story of this unique chameleon refer to this article below in PNAS
Kristopher B. Karsten,Laza N. Andriamandimbiarisoa,Stanley F. Fox,and Christopher J. Raxworthy
A unique life history among tetrapods: An annual chameleon living mostly as an egg
PNAS 2008 105:8980-8984; doi:10.1073/pnas.0802468105
Next article is the one which hogged the limelight in the latest issue by appearing on the cover, deals about eyes in Cnidarian Tripedalia cystophora ,a cubazoan jellyfish.Cnidarians which are sister group to all bilaterians are earliest branching phylum (meaning developed eye is seen in these animals for first time -Ctenophores and sponges which occupy a lower position in tree of animals than Cnidarians lack eye like structure) with well developed visual system.Here the authors show that jelly fish uses a ciliary phototransduction cascade and melanogenic pathway like vertebrates use for making eyes,which favor the possibility that vertebrate and cubozoan eyes arose by independent recruitment of orthologous genes during evolution.
Reference for this article on camera type eye develoment of jelly fish:
Kozmik Z, Ruzickova J, Jonasova K, Matsumoto Y, Vopalensky P, Kozmikova I, Strnad H, Kawamura S, Piatigorsky J, Paces V, Vlcek C.
Assembly of the cnidarian camera-type eye from vertebrate-like components.
Proc Natl Acad Sci U S A. 2008 Jun 24.
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