The evolution of the amniotic egg was one of the great evolutionary innovations in the history of life, freeing vertebrates from an obligatory connection to water and thus permitting the conquest of terrestrial environments1. Among amniotes, genome sequences are available for mammals2 and birds3–5, but not for non-avian reptiles. Here we report the genome sequence of the North American green anole lizard, Anolis carolinensis. We find that A. carolinensis microchromosomes are highly syntenic with chicken microchromosomes, yet do not exhibit the high GC and low repeat content that are characteristic of avian microchromosomes3. Also, A. carolinensis mobile elements are very young and diverse – more so than in any other sequenced amniote genome. This lizard genome’s GC content is also unusual in its homogeneity, unlike the regionally variable GC content found in mammals and birds6. We describe and assign sequence to the previously unknown A. carolinensis X chromosome. Comparative gene analysis shows that amniote egg proteins have evolved significantly more rapidly than other proteins. An anole phylogeny resolves basal branches to illuminate the history of their repeated adaptive radiations.

To provide context for the diversifications of archosaurs, the group that includes crocodilians, dinosaurs and birds, we generated draft genomes of three crocodilians, Alligator mississippiensis (the American alligator), Crocodylus porosus (the saltwater crocodile), and Gavialis gangeticus (the Indian gharial). We observed an exceptionally slow rate of genome evolution within crocodilians at all levels, including nucleotide substitutions, indels, transposable element content and movement, gene family evolution, and chromosomal synteny. When placed within the context of related taxa including birds and turtles, this suggests that the common ancestor of all of these taxa also exhibited slow genome evolution and that the relatively rapid evolution of bird genomes represents an autapomorphy within that clade. The data also provided the opportunity to analyze heterozygosity in crocodilians, which indicates a likely reduction in population size for all three taxa through the Pleistocene. Finally, these new data combined with newly published bird genomes allowed us to reconstruct the partial genome of the common ancestor of archosaurs providing a tool to investigate the genetic starting material of crocodilians, birds, and dinosaurs.

Neonatally castrated (MNC) and control male rats (MC) and female rats treated neonatally with estradiol benzoate (FNE) and female controls (FC) were studied. In Exp. 1 spatial memory was assessed using a 12-arm radial maze. During acquisition, MC and FNE groups were more accurate in choice behavior than FC and MNC groups. In Exp. 2 the discriminative control exerted by different types of cues was evaluated. Alteration of the geometry of the room but not movable landmarks disrupted performance of MC and FNE groups. For the FC and MNC groups, alteration of either geometry or landmarks did not disrupt performance. In Exp. 3 the effect of a 15-min delay was determined. MC and FNE groups were more disrupted by a delay than MNC and FC groups. Together, these data suggest that early exposure to gonadal steroids (probably estradiol) improves acquisition of spatial tasks by reorganizing and simplifying associational-perceptual processes that guide spatial ability. There is general consensus that men outperform women in tasks that require spatial skills (

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Ovarian hormones alter spine density of hippocampal granule and pyramidal cells in young adult and aging female rats (P. Miranda, C. L. Williams, & G. Einstein, 1999; C. S. Woolley, 1998). The present study used a delayed matching-to-place version of the water maze to investigate a behavioral correlate of these hormone-induced changes in hippocampal connectivity in 3- and 8-month-old female rats. When primed with 10-microg injections of estradiol 72 and 48 hr before testing, the memory retention of ovariectomized rats was improved compared with retention after priming with oil. A single injection of progesterone maintained this enhancement if testing occurred within 8 hr of the progesterone injection but not if testing occurred more than 24 hr after the progesterone injection. These findings indicate that estradiol and progesterone alter memory retention and suggest that these changes may be the result of hormone-induced increases in hippocampal connectivity.

This experiment was an examination of the effects of supplemental dietary choline chloride given prenatally (to the diet of pregnant rats) and postnatally (intubed directly into the stomachs of rat pups) on memory function and neurochemical measures of brain cholinergic activity of male albino rats when they became adults. The data demonstrate that perinatal choline supplementation causes (a) long-term facilitative effects on working and reference memory components of a 12-arm radial maze task, and (b) alternations of muscarinic receptor density as indexed by [3H]quinuclidinyl benzilate (QNB) binding and choline acetyltransferase (ChAT) levels in the hippocampus and frontal cortex of adult rats. An analysis of the relationship between these organizational changes in brain and memory function indicated that the ChAT-to-QNB ratio in the hippocampus is highly correlated with working memory errors, and this ratio in the frontal cortex is highly correlated with reference memory errors.

In order to determine brain and behavioral sensitivity of nutrients that may serve as inductive signals during early development, we altered choline availability to rats during 7 time frames spanning embryonic day (ED) 6 through postnatal day (PD) 75 and examined spatial memory ability in the perinatally-treated adults. Two sensitive periods were identified, ED 12–17 and PD 16–30, during which choline supplementation facilitated spatial memory and produced increases in dendritic spine density in CA1 and dentate gyrus (DG) regions of the hippocampus while also changing the dendritic fields of DG granule cells. Moreover, choline supplementation during ED 12–17 only, prevented the memory decline normally observed in aged rats. These behavioral changes were strongly correlated with the acetylcholine (ACh) content of hippocampal slices following stimulated release. Our data demonstrate that the availability of choline during critical periods of brain development influences cognitive performance in adulthood and old age, and emphasize the importance of perinatal nutrition for successful cognitive aging.