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The mangrove rivulus (Kryptolebias marmoratus) is one of two preferentially self-fertilizing hermaphroditic vertebrates. This mode of reproduction makes mangrove rivulus an important model for evolutionary and biomedical studies because long periods of self-fertilization result in naturally homozygous genotypes that can produce isogenic lineages without significant limitations associated with inbreeding depression. Over 400 isogenic lineages currently held in laboratories across the globe show considerable among-lineage variation in physiology, behavior, and life history traits that is maintained under common garden conditions. Temperature mediates the development of primary males and also sex change between hermaphrodites and secondary males, which makes the system ideal for the study of sex determination and sexual plasticity. Mangrove rivulus also exhibit remarkable adaptations to living in extreme environments, and the system has great promise to shed light on the evolution of terrestrial locomotion, aerial respiration, and broad tolerances to hypoxia, salinity, temperature, and environmental pollutants. Genome assembly of the mangrove rivulus allows the study of genes and gene families associated with the traits described above. Here we present a de novo assembled reference genome for the mangrove rivulus, with an approximately 900 Mb genome, including 27,328 annotated, predicted, protein-coding genes. Moreover, we are able to place more than 50% of the assembled genome onto a recently published linkage map. The genome provides an important addition to the linkage map and transcriptomic tools recently developed for this species that together provide critical resources for epigenetic, transcriptomic, and proteomic analyses. Moreover, the genome will serve as the foundation for addressing key questions in behavior, physiology, toxicology, and evolutionary biology.

Background: To document the course of the median nerve in the distal forearm in palmaris longus (PL) deficient forearms and elucidate features that help distinguish it from the PL., Methods: In the cadaveric study, 56 cadaveric forearms were dissected and the location and course of the median nerve were documented. In the clinical study, 20 healthy subjects with absent PL were examined with provocative tests to elucidate the PL (Schaeffer's test and Thompson's test), and modified Durkan's and Phalen's tests. In the imaging study, one subject with a clearly visible and palpable median nerve was further evaluated with MRI with a superficial fiducial marker., Results: Cadaveric dissection revealed that the median nerve was deep to the antebrachial fascia and superficial to the FDS tendons in the distal forearm. In 9 specimens without a PL, the median nerve was the most superficial structure deep and lay draped over the FDS tendons. In the clinical study, PL absence was bilateral in 4 subjects and unilateral in 16. The nerve was visible and palpable in 4 forearms and palpable but not visible in 20 forearms. In all 24 forearms, the nerve was palpable as a lax, mobile, cord-like structure that could be rolled over the taut FDS tendons. Tinel's and Durkan's signs were positive in 11 subjects. In the imaging study, MRI confirmed that the palpable structure was the median nerve., Conclusions: Unlike the PL, the nerve is non-contractile and remains flaccid on provocative testing. It is usually palpable and may also be visible in thin forearms. Careful scrutiny may reveal it to be distinct from, and draped over underlying FDS tendons. These findings may help avoid inadvertent median nerve harvest in place of a PL tendon graft.