Genetic differentiation and phenotypic plasticity drive troglomorphic character development in European cavefish
Data files
Jan 19, 2024 version files 36.57 KB
-
Aach_cavefish_basis_data.xlsx
33.24 KB
-
README.md
3.33 KB
Abstract
The Aach cave loach (Barbatula barbatula), a recently discovered member of the Nemacheilidae family, offers a unique opportunity to understand the mechanisms underlying evolutionary change. In a common garden experiment, we reared groups of laboratory-bred cave, surface, and hybrid loach under different light conditions. Troglomorphic characters varied significantly among the fish, influenced to a different extent by parental origin and light conditions. Cavefish progeny consistently exhibited smaller eyes, lighter pigmentation, longer barbels, and larger olfactory epithelia than surface fish, while hybrids displayed intermediate characteristics. Surface and hybrid fish raised in complete darkness resembled the cavefish phenotype, while cavefish raised under a natural photoperiod approached the surface form. Characters associated with eye degeneration were found to be primarily heritable. Conversely, traits related to chemo- and mechano-reception were enhanced in the surface and hybrid groups reared in complete darkness, suggesting phenotypic plasticity. Our findings offer valuable insights into the interplay between genetic differentiation and phenotypic plasticity to troglomorphic adaption. This contributes to the broader understanding of the early stages of adaptation, where phenotypic plasticity, drift, and selection shape phenotypes. Relatively recently established cavefish, such as the Aach cave loach, are promising candidates for comparative research investigating evolutionary mechanisms.
README: Genetic differentiation and phenotypic plasticity drive troglomorphic character development in European cavefish
https://doi.org/10.5061/dryad.fbg79cp2w
To gain insight into the early environmental adaptation process of the Aach cave loach and its underlying mechanisms, we reared cave, surface, and hybrid offspring in a common garden under either cave (complete absence of light, DD) or surface conditions (natural light:dark cycle, DL). The dataset contains morphometric data of 94 fish from the DD and 93 from the DL treatment group, encompassing all origins. Measurements were extracted from photographs of formalin-fixed fish using ImageJ. Lateral images were used to measure the eye and lens diameter, as well as the length of the second barbel. Dorsal images were used to determine head length and the size of the olfactory epithelium. Head length was measured from the tip of the snout to the posterior margin of the neurocranium . The olfactory epithelium size (longest axis) of the olfactory epithelium was measured as the distance between the anterior and the posterior nostrils on one side of the fish . All length measurements were recorded to the nearest µm.
Using the lateral images, lenses were categorized into one of four classes to indicate quality: Class 3 (normal), featuring a uniformly cloudy lens with a circular shape approximately half the diameter of the eye; Class 2, characterized by an inconsistently cloudy or milky lens with a diameter ranging from 80 to 100 % of Class 3 lenses; Class 1, where the lens is less than 80 % of the size of Class 3 and appears milky or completely white; and Class 0, indicating no lens detected. Images of anesthetized fish were examined to compare pigmentation via grey-scale analysis. The image was opened in ImageJ, and a representative rectangular area between the pelvic fin and the beginning of the dorsal fin selected. A score was obtained using the grey-scale measurement tool, which provides a number from 0 (black) to 254,000 (white).
The dataset also contains size-corrected measurements for some selected morphometric data. Size effects were removed with a normalization equation that considers each origin group separately by calculating a unique regression coefficient for each group (Reist 1985; Chan and Lee Grismer 2021)..
Description of the data and file structure
Each row corresponds to an individual. Individuals are assigned to several groups (Origin, Treatment, Family). Information on the hatching date and age of the fish is also provided. The morphometric data is arranged in columns. The column headings refer to the morphometric measurement.
Label code: Each individual has a unique identification number.
Origin codes: Cave = cave stone loach offspring, Rdz = Offspring of surface stone loach from the Radolfzeller Aach River, Do = Offspring of surface stone loach from the Danube River
Treatment codes: DD = complete absence of light, DL = natural light:dark cycle
Family codes: These refer to the Origin and are numbered
References
Reist, J. D. 1985. An empirical evaluation of several univariate methods that adjust for size variation in morphometric data. Can. J. Zool. 63:1429–1439.
Chan, K. O., and L. Lee Grismer. 2021. Correcting for Body Size Variation in Morphometric Analysis. bioRxiv 1–16.