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Dryad

Epidermal club cell densities in fathead minnows: assessment of method and application to a case study

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Jan 16, 2024 version files 22.23 KB

Abstract

Abstract

Many fishes possess epidermal club cells that are the presumptive source of chemical alarm cues and also play a role in innate immune defense. Club cell density has been estimated in some studies but a standardized method for quantifying these cells is lacking.

Here, we assess the repeatability of estimating club cell density in fathead minnows (Pimephales promelas). Thin-sectioned histological samples of fathead minnows were stained and mounted on slides and then digitally scanned for scoring. We estimated epidermal area using the segment tool in ImageJ to simulate the traditional method of scoring microscope slides using an ocular micrometer, where epidermal area was estimated by the lengths of straight-line segments of epidermal thickness and length of the tissue sample. The second approach measured epidermal area using the freehand tool in ImageJ.

The R2 value for repeated estimates of club cell density (club cells/mm2) ranged from 0.959 and 0.969, depending on the method used to estimate epidermal area. Measurement error in estimates of epidermal area was greater than measurement error in cell counts and the freehand tool was more repeatable than the segment tool as a method to measure epidermal area.

We applied these methods to test differences in club cell densities between two sources of fathead minnows; wild-caught fish versus lab-reared fish provided by the Environmental Protection Agency. Lab-reared fish had higher densities of club cells than wild-caught fish did, likely reflecting differences in body condition.epidermal club cells