Abstract
Cave animals are a fascinating group of species often demonstrating characteristics including reduced eyes and pigmentation, metabolic efficiency, and enhanced sensory systems. Asellus aquaticus, an isopod crustacean, is an emerging model for cave biology. Cave and surface forms of this species differ in many characteristics, including eye size, pigmentation, and antennal length. Existing resources for this species include a linkage map, mapped regions responsible for eye and pigmentation traits, sequenced adult transcriptomes, and comparative embryological descriptions of the surface and cave forms. Our ultimate goal is to identify genes and mutations responsible for the differences between the cave and surface forms. To advance this goal, we decided to use a transcriptomic approach. Because many of these changes first appear during embryonic development, we sequenced embryonic transcriptomes of cave, surface, and hybrid individuals at the stage when eyes and pigment become evident in the surface form. We generated a cave, a surface, a hybrid, and an integrated transcriptome to identify differentially expressed genes in the cave and surface forms. Additionally, we identified genes with allele-specific expression in hybrid individuals. These embryonic transcriptomes are an important resource to assist in our ultimate goal of determining the genetic underpinnings of the divergence between the cave and surface forms.
Highlights
Cave animals are fascinating organisms that frequently share a common suite of characteristics, including reduced eyes, reduced pigmentation, metabolic differences, and enhanced sensory systems.Questions that have long fascinated cave biologists include how and why these characteristics have evolved and whether the same underlying mechanisms mediate trait loss between different cave populations and different cave species.Historically, it has been challenging to understand how and why cave characteristics have evolved, due to difficulties with rearing cave organisms in captivity and a lack of contemporary experimental resources for most cave species
Less is known about metabolic and behavioral differences between the cave and surface populations, but a recent study showed that acetylcholinesterase and glutathionine S transferase had lower activity in cave individuals as compared to the surface individuals, supporting the idea that the cave form has lower metabolic and locomotor activity [33]
Differences in allele-specific expression were seen in glutathione S transferase mu 5 from a previous analysis [6]
Summary
Cave animals are fascinating organisms that frequently share a common suite of characteristics, including reduced eyes, reduced pigmentation, metabolic differences, and enhanced sensory systems.Questions that have long fascinated cave biologists include how and why these characteristics have evolved and whether the same underlying mechanisms mediate trait loss between different cave populations and different cave species.Historically, it has been challenging to understand how and why cave characteristics have evolved, due to difficulties with rearing cave organisms in captivity and a lack of contemporary experimental resources (e.g., genomic, genetic, and functional molecular tools) for most cave species. Cave animals are fascinating organisms that frequently share a common suite of characteristics, including reduced eyes, reduced pigmentation, metabolic differences, and enhanced sensory systems. Questions that have long fascinated cave biologists include how and why these characteristics have evolved and whether the same underlying mechanisms mediate trait loss between different cave populations and different cave species. It has been challenging to understand how and why cave characteristics have evolved, due to difficulties with rearing cave organisms in captivity and a lack of contemporary experimental resources (e.g., genomic, genetic, and functional molecular tools) for most cave species. Genes 2020, 11, 42 the complete genomic sequence is available for a limited number of cave-dwelling species [1,2]. For the vast majority of these projects, adult samples have been utilized due to the challenge of obtaining embryonic samples of natural, cave-dwelling species. For several cave species, many trait differences are established early in embryonic development, underscoring the importance (and value) of analyzing gene expression differences across embryonic development
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