A hypomorphic cystathionine ß-synthase gene contributes to cavefish eye loss by disrupting optic vasculature

Vestigial structures are key indicators of evolutionary descent, but the mechanisms underlying their development are poorly understood. This study examines vestigial eye formation in the teleost Astyanax mexicanus, which consists of a sighted surface-dwelling morph and multiple populations of blind cave morphs. Cavefish embryos initially develop eyes, but they subsequently degenerate and become vestigial structures embedded in the head. The mutated genes involved in cavefish vestigial eye formation have not been characterized. Here we identify cystathionine ß-synthase a (cbsa), which encodes the key enzyme of the transsulfuration pathway, as one of the mutated genes responsible for eye degeneration in multiple cavefish populations. The inactivation of cbsa affects eye development by increasing the transsulfuration intermediate homocysteine and inducing defects in optic vasculature, which result in aneurysms and eye hemorrhages. Our findings suggest that localized modifications in the circulatory system may have contributed to the evolution of vestigial eyes in cavefish.

Jumping on the Edge—First Evidence for a 2 × 6-meric Hemocyanin in Springtails

Hemocyanins are respiratory dioxygen carrier proteins found in many arthropods including ancient terrestrial species such as spiders and scorpions as well as marine horseshoe crabs. As hemocyanins are highly conserved in this lineage, it is possible to observe an evolutionary descent through its subunits and their overall structure. Unfortunately, little is known about the structure and function of hexapod hemocyanins. Using recent springtail taxa (Collembola) as models for basal hexapods, and the help of electron microscopy, light scattering, SDS PAGE, and Western blot, we could demonstrate for the first time the presence of 2 × 6-meric hemocyanins in the hemolymph of hexapods. The quaternary structure is composed of at least two different subunits and looks nearly identical to the hemocyanin found in decapod crustaceans. In addition, homology modeling and western blotting suggest a close structural relationship between collembolan and crustacean hemocyanin. Such a respiratory protein was possibly helpful in the early terrestrialization process of ancient Collembola. In addition, physiological adaptations to hypoxic or temporarily anoxic conditions could be a possible explanation for the presence of this respiratory protein. Nevertheless, it has to be concluded that the primary benefit of hemocyanin for springtails remains unclear.

The parents of Adam and Eve: missing links

This chapter argues that by the 1870s the popular idea of human prehistory in Britain had become fixated on the concept of the missing link, the as-yet undiscovered creature at the point where the evolutionary descent of humans and apes had split. British showmen and circus owners exploited this fascination by passing off all sorts of creatures as missing links, from actual monkeys to actors in disguise. The two most important missing links are analysed in detail: Pongo the first live gorilla seen in Europe, and Krao, a Burmese girl with congenital deformities. They were promoted in Britain with explicitly evolutionary language. Scientists scoffed, but the public clearly understood the deceit, which they accepted as entertaining and harmless. Pongo and Krao inspired cartoons and humorous songs. They were imitated on stage by acrobats and in pantomimes. And drawings of missing links were used in advertisements. Pongo and Krao were also the last important evolutionary freaks. The globe had been comprehensively explored, evolution and European prehistory were far better understood, and the increasingly commercialised entertainment industry strove for middle class respectability.

Differences in Carotenoid Composition among Hymenobacter and Related Strains Support a Tree-Like Model of Carotenoid Evolution

ABSTRACT Carotenoids are structurally diverse pigments of biotechnological interest as natural colorants and in the prevention of human disease. The carotenoids present in 19 strains taxonomically related to the poorly described, nonphotosynthetic bacterial genus Hymenobacter, including 10 novel isolates cultivated from Victoria Upper Glacier, Antarctica, were characterized using high-performance liquid chromatography (HPLC). Nine chemically distinct carotenoids, present in various combinations irresolvable by conventional crude spectrophotometric analyses, were purified by preparative HPLC and characterized using UV-visible light absorption spectroscopy and high-resolution mass spectrometry. All major Hymenobacter carotenoids appear to be derived from a common backbone of 2′-hydroxyflexixanthin and include previously unreported presumptive hexosyl, pentosyl, and methyl derivatives. Their distribution does not, however, correlate perfectly with 16S rRNA gene phylogeny. Carotenoid composition, therefore, may be strain specific and does not follow a strictly homogeneous pattern of vertical evolutionary descent.