Cortical growth marks reveal extended juvenile development in New Zealand moa

Cyclical growth marks in cortical bone, deposited before attainment of adult body size, reflect osteogenetic changes caused by annual rhythms and are a general phenomenon in non-avian ectothermic and endothermic tetrapods. However, the growth periods of ornithurines (the theropod group including all modern birds) are usually apomorphically shortened to less than a year, so annual growth marks are almost unknown in this group. Here we show that cortical growth marks are frequent in long bones of New Zealand's moa (Aves: Dinornithiformes), a recently extinct ratite order. Moa showed the exaggerated K-selected life-history strategy formerly common in the New Zealand avifauna, and in some instances took almost a decade to attain skeletal maturity. This indicates that reproductive maturity in moa was extremely delayed relative to all extant birds. The two presently recognized moa families (Dinornithidae and Emeidae) also showed different postnatal growth rates, which were associated with their relative differences in body size. Both species of giant Dinornis moa attained their massive stature (up to 240 kg live mass) by accelerating their juvenile growth rate compared to the smaller emeid moa species, rather than by extending the skeletal growth period.     

Brevetoxicosis: red tides and marine mammal mortalities

Potent marine neurotoxins known as brevetoxins are produced by the 'red tide' dinoflagellate Karenia brevis. They kill large numbers of fish and cause illness in humans who ingest toxic filter-feeding shellfish or inhale toxic aerosols. The toxins are also suspected of having been involved in events in which many manatees and dolphins died, but this has usually not been verified owing to limited confirmation of toxin exposure, unexplained intoxication mechanisms and complicating pathologies. Here we show that fish and seagrass can accumulate high concentrations of brevetoxins and that these have acted as toxin vectors during recent deaths of dolphins and manatees, respectively. Our results challenge claims that the deleterious effects of a brevetoxin on fish (ichthyotoxicity) preclude its accumulation in live fish, and they reveal a new vector mechanism for brevetoxin spread through food webs that poses a threat to upper trophic levels.     

Generation and annotation of the DNA sequences of human chromosomes 2 and 4

Human chromosome 2 is unique to the human lineage in being the product of a head-to-head fusion of two intermediate-sized ancestral chromosomes. Chromosome 4 has received attention primarily related to the search for the Huntington's disease gene, but also for genes associated with Wolf-Hirschhorn syndrome, polycystic kidney disease and a form of muscular dystrophy. Here we present approximately 237 million base pairs of sequence for chromosome 2, and 186 million base pairs for chromosome 4, representing more than 99.6% of their euchromatic sequences. Our initial analyses have identified 1,346 protein-coding genes and 1,239 pseudogenes on chromosome 2, and 796 protein-coding genes and 778 pseudogenes on chromosome 4. Extensive analyses confirm the underlying construction of the sequence, and expand our understanding of the structure and evolution of mammalian chromosomes, including gene deserts, segmental duplications and highly variant regions.