Modulation of gill surface area does not correlate with oxygen loss in Chitala ornata

Air-breathing fish risk losing aerially sourced oxygen to ambient hypoxic water since oxygenated blood from the air-breathing organ returns through the heart to the branchial basket before distribution. This loss is thought to have helped drive the evolutionary reduction in gill size with the advent of air-breathing. In many teleost fish, gill size is known to be highly plastic by modulation of their anatomic diffusion factor (ADF) with interlamellar cell mass (ILCM). In the anoxia-tolerant crucian carp, ILCM recedes with hypoxia but regrows in anoxia. The air-breathing teleost, Chitala ornata has been shown to increase gill ADF from normoxic to mildly hypoxic water by reducing ILCM. Here, we test the hypothesis that ADF is modulated to minimize oxygen loss in severe aquatic hypoxia by measuring ADF and gas exchange, and by using CT scans to reveal possible trans-branchial shunt vessels. Contrary to our hypothesis, ADF does not modulate to prevent oxygen loss and despite no evident tran..., , , # Modulation of gill surface area does not correlate with oxygen loss in *Chitala ornata*

[https://doi.org/10.5061/dryad.pg4f4qrzr](https://doi.org/10.5061/dryad.pg4f4qrzr)

## Description of the data and file structure

The data was collected using intermittent closed respirometry and stereology techniques. 

### Files and variables

#### File: Respirometry\_and\_stereology\_data.xlsx

* Sheet 1: The Respirometry Excel sheet contains the following columns.
* Sheet 2: The Stereology Excel sheet contains the following columns.
* Sheet 3: The harmonic mean of blood-water diffusion distance.

Variables:

##### Sheet 1: Respirometry Excel sheet contains the following columns:

A) An ID column showing which fish is measured (F for fish and number for date)

B) A column describing the number of measurements, each number is one measurement.

C) A treatment column showing if water was normoxic or hypoxic.

D-F) Columns show O2 uptake from air, water, and total in addition to branchial loss in ...