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Previous articleNext article FreeAbout the CoverPDFPDF PLUSFull Text Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinked InRedditEmailQR Code SectionsMoreCoverThe cover features the Hawaiian endemic shrimp, Halocaridina rubra, known by native Hawaiians as ‘ōpae ‘ula (literally, tiny red shrimp). These shrimp live in anchialine pools, which are small, shallow surface bodies of water with extensive subterranean connections to the sea and underground aquifers that can experience widely fluctuating gradients in temperature, salinity, and light. True to their Hawaiian name, they reach a maximum length of around one centimeter and typically display a red coloration with substantial variation. Halocaridina rubra is distributed across the islands of Oahu, Maui, and Hawaii, and at least eight unique genetic lineages have been identified. In the cover photo, each shrimp represents a different genetic lineage and displays the “typical” coloration observed for that lineage, highlighting the variation.In this issue (pp. 119–130), R. J. Weaver, B. K. Gonzalez, S. R. Santos, and J. C. Havird identify and quantify the pigment responsible for red coloration in H. rubra. Using chromatography and spectrophotometry, they found that the red carotenoid, astaxanthin, was more abundant in lineages that appeared redder than in lineages that were less colorful. Carotenoid supplementation experiments revealed that less colorful lineages were not limited by dietary access to pigments, suggesting a possible genetic basis for red coloration. By using a bioinformatic approach to explore the genetic basis for production of astaxanthin, they found that the gene responsible for astaxanthin production in H. rubra and other crustaceans is more closely related to a carotenoid metabolism gene found in fungi than to an astaxanthin gene found in birds and turtles. Despite the prevalence of red carotenoid coloration in animals, the genetic basis for this phenotype has only recently been explored and then mostly in vertebrate animals. Identifying the genetic basis for carotenoid coloration in non-vertebrate animals may prove useful in understanding the selective forces that drive the evolution of conspicuous coloration in this group.Credits: Photo, Ryan J. Weaver, University of Texas at Austin. Cover design, Jeannie Harrell, University of Chicago Press, and Ryan J. Weaver. Previous articleNext article DetailsFiguresReferencesCited by The Biological Bulletin Volume 238, Number 2April 2020 Published in association with the Marine Biological Laboratory Article DOIhttps://doi.org/10.1086/709957 © 2020 by The University of Chicago. All rights reserved.PDF download Crossref reports no articles citing this article.