Bactrian camel (Camelus bactrianus), dromedary (Camelus dromedarius) and alpaca (Vicugna pacos) are economically important livestock. Although the Bactrian camel and dromedary are large, typically arid-desert-adapted mammals, alpacas are adapted to plateaus. Here we present high-quality genome sequences of these three species. Our analysis reveals the demographic history of these species since the Tortonian Stage of the Miocene and uncovers a striking correlation between large fluctuations in population size and geological time boundaries. Comparative genomic analysis reveals complex features related to desert adaptations, including fat and water metabolism, stress responses to heat, aridity, intense ultraviolet radiation and choking dust. Transcriptomic analysis of Bactrian camels further reveals unique osmoregulation, osmoprotection and compensatory mechanisms for water reservation underpinned by high blood glucose levels. We hypothesize that these physiological mechanisms represent kidney evolutionary adaptations to the desert environment. This study advances our understanding of camelid evolution and the adaptation of camels to arid-desert environments.

9 l e t t e r sFlatfish have the most extreme asymmetric body morphology of vertebrates. During metamorphosis, one eye migrates to the contralateral side of the skull, and this migration is accompanied by extensive craniofacial transformations and simultaneous development of lopsided body pigmentation 1-5 . The evolution of this developmental and physiological innovation remains enigmatic. Comparative genomics of two flatfish and transcriptomic analyses during metamorphosis point to a role for thyroid hormone and retinoic acid signaling, as well as phototransduction pathways. We demonstrate that retinoic acid is critical in establishing asymmetric pigmentation and, via cross-talk with thyroid hormones, in modulating eye migration. The unexpected expression of the visual opsins from the phototransduction pathway in the skin translates illumination differences and generates retinoic acid gradients that underlie the generation of asymmetry. Identifying the genetic underpinning of this unique developmental process answers long-standing questions about the evolutionary origin of asymmetry, but it also provides insight into the mechanisms that control body shape in vertebrates.

High-resolution genetic maps are essential for fine mapping of complex traits, genome assembly, and comparative genomic analysis. Single-nucleotide polymorphisms (SNPs) are the primary molecular markers used for genetic map construction. In this study, we identified 13,362 SNPs evenly distributed across the Japanese flounder (Paralichthys olivaceus) genome. Of these SNPs, 12,712 high-confidence SNPs were subjected to high-throughput genotyping and assigned to 24 consensus linkage groups (LGs). The total length of the genetic linkage map was 3,497.29 cM with an average distance of 0.47 cM between loci, thereby representing the densest genetic map currently reported for Japanese flounder. Nine positive quantitative trait loci (QTLs) forming two main clusters for Vibrio anguillarum disease resistance were detected. All QTLs could explain 5.1–8.38% of the total phenotypic variation. Synteny analysis of the QTL regions on the genome assembly revealed 12 immune-related genes, among them 4 genes strongly associated with V. anguillarum disease resistance. In addition, 246 genome assembly scaffolds with an average size of 21.79 Mb were anchored onto the LGs; these scaffolds, comprising 522.99 Mb, represented 95.78% of assembled genomic sequences. The mapped assembly scaffolds in Japanese flounder were used for genome synteny analyses against zebrafish (Danio rerio) and medaka (Oryzias latipes). Flounder and medaka were found to possess almost one-to-one synteny, whereas flounder and zebrafish exhibited a multi-syntenic correspondence. The newly developed high-resolution genetic map, which will facilitate QTL mapping, scaffold assembly, and genome synteny analysis of Japanese flounder, marks a milestone in the ongoing genome project for this species.

Introduction: Lifelong premature ejaculation (LPE) is characterized by persistently shorter intravaginal ejaculation latency time (IELT) than found acceptable by the patient or his partner. It has been postulated to be a neurobiological dysfunction with genetic vulnerability and is related to disturbances of central serotonin (5-hydroxytryptamine, 5-HT) neurotransmission and 5-HT receptor function. Aim: To investigate the relationship between the C–759T and G–697C polymorphisms of the 5-HT_2C receptor and LPE. Methods: A prospective study was conducted in 106 Han Chinese men with LPE, characterized by IELT of less than 1 min, and 84 healthy controls with IELT of more than 3 min. All subjects were genotyped for the C–759T and G–697C polymorphisms located in the promoter region of the 5-HT_2C receptor. The frequencies of genotypes and single nucleotide mutations were compared between the two groups. Results: Three genotypes were detected both in the men with LPE and in the control group: –759C/–697G, –759T/–697C, and –759C/ –697C. Genotype –759T/–697G was not detected. The frequency of genotype –759T/–697C was higher in patients with LPE than in the control group (30.2 vs. 11.9%, p < 0.05), whereas the frequency of genotype –759C/–697G was lower in patients with LPE than in the control group (66.0 vs. 83.3%, p < 0.05). No difference was found for genotype –759C/ –697C between the two groups. Mutations at –759T and –697C were more frequent in patients than in the control group (–759T: 30.2 vs. 13.3%, p < 0.05; –697C: 30.4 vs. 16.7%, p < 0.05, respectively). Conclusions: Our findings indicated that polymorphisms in the 5-HT_2C receptor gene are associated with LPE, and men who carry the –759T or –697C genotype have increased odds of premature ejaculation. Further investigation in this field is necessary.

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