The Muller F element (4.2 Mb, ~80 protein-coding genes) is an unusual autosome of Drosophila melanogaster; it is mostly heterochromatic with a low recombination rate. To investigate how these properties impact the evolution of repeats and genes, we manually improved the sequence and annotated the genes on the D. erecta, D. mojavensis, and D. grimshawi F elements and euchromatic domains from the Muller D element. We find that F elements have greater transposon density (25–50%) than euchromatic reference regions (3–11%). Among the F elements, D. grimshawi has the lowest transposon density (particularly DINE-1: 2% vs. 11–27%). F element genes have larger coding spans, more coding exons, larger introns, and lower codon bias. Comparison of the Effective Number of Codons with the Codon Adaptation Index shows that, in contrast to the other species, codon bias in D. grimshawi F element genes can be attributed primarily to selection instead of mutational biases, suggesting that density and types of transposons affect the degree of local heterochromatin formation. F element genes have lower estimated DNA melting temperatures than D element genes, potentially facilitating transcription through heterochromatin. Most F element genes (~90%) have remained on that element, but the F element has smaller syntenic blocks than genome averages (3.4–3.6 vs. 8.4–8.8 genes per block), indicating greater rates of inversion despite lower rates of recombination. Overall, the F element has maintained characteristics that are distinct from other autosomes in the Drosophila lineage, illuminating the constraints imposed by a heterochromatic milieu.
BackgroundAlthough rare, human–shark interactions can result in a wide spectrum of injuries. This is the first study to characterize shark-related injuries (SRIs) in Hawai’i.MethodsThis is a retrospective review of the State of Hawai’i Division of Aquatic Resources Shark Incidents List between January 1, 2009 and December 31, 2019. Trauma registry data and medical records of patients treated for SRIs at the only level 1 trauma center in Hawai’i were reviewed.ResultsSixty-one patients sustained SRIs in the Hawaiian Islands: 25 in Maui, 16 in O’ahu, 12 in Hawai’i, and 8 in Kaua’i. In cases where the shark species could be identified, tiger sharks were the most frequent (25, 41%). Four cases were fatal—all died on scene in Maui with the shark species unknown. Forty-five survivors (79%) received definitive care at regional facilities. Twelve (21%) were treated at the level 1 trauma center, of which two were transferred in for higher level of care. Of the 12 patients, 11 (92%) had extremity injuries, with 3 lower extremity amputations (25%), 2 with vascular injuries (17%), and 5 with nerve injuries (42%). One had an injury to the abdomen. All patients had local bleeding control in the prehospital setting, with 9 (75%) tourniquets and 3 (25%) hemostatic/pressure dressings applied for truncal or proximal extremity injuries. The mean time from injury to emergency department arrival was 63 minutes.DiscussionMost SRIs are managed at regional facilities, rather than at a level 1 trauma center. Prehospital hemorrhage control is an important survival skill as time to definitive care may be prolonged. For cases treated at the level 1 trauma center, nerve injuries were common and should be suspected even in the absence of major vascular injury. Correlating shark behavior with observed injury patterns may help improve public awareness and ocean safety.Level of evidenceLevel V, epidemiological.
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