Bulusu Kartik V, Racan Samantha, Plesniak Michael W
Department of Mechanical and Aerospace Engineering, The George Washington University;
Department of Mechanical and Aerospace Engineering, The George Washington University.
J Vis Exp. 2020 Jul 10(161). doi: 10.3791/61379.
The silver carp, Hypophthalmichthys molitrix, is an invasive planktivorous filter feeder fish that infested the natural waterways of the upper Mississippi River basin due to its highly efficient filter feeding mechanism. The characteristic organs called gill rakers (GRs), found in many such filter feeders, facilitate the efficient filtration of food particles such as phytoplankton that are of a few microns in size. The motivation to investigate the rheology of the GR mucus stems from our desire to understand its role in aiding the filter feeding process in the silver carp. The mucus-rich fluid, in a 'thick and sticky' state may facilitate the adhesion of food particulates. The permeation and transport through the GR membrane are facilitated by the action of external shear forces that induce varying shear strain rates. Therefore, mucus rheology can provide a vital clue to the tremendous outcompeting nature of the silver carp within the pool of filter feeding fish. Based on this it was posited that GR mucus may provide an adhesive function to food particles and act as a transport vehicle to assist in the filter feeding process. The main objective of the protocol is to determine the yield stress of the mucus, attributed to the minimum shear stress required to initiate flow at which irreversible plastic deformation is first observed across a structured viscoelastic material. Accordingly, rheological properties of the GR mucus, i.e., viscosity, storage, and loss moduli, were investigated for its non-Newtonian, shear-thinning nature using a rotational rheometer. A protocol presented here is employed to analyze the rheological properties of mucus extracted from the gill rakers of a silver carp, fished at Hart Creek location of the Missouri River. The protocol aims to develop an effective strategy for rheological testing and material characterization of mucus assumed to be a structured viscoelastic material.
鲢鱼（Hypophthalmichthys molitrix）是一种具有侵入性的食浮游生物的滤食性鱼类，由于其高效的滤食机制，它侵扰了密西西比河流域上游的天然水道。许多这类滤食性动物身上都有称为鳃耙（GRs）的特征性器官，有助于高效过滤尺寸为几微米的浮游植物等食物颗粒。研究鳃耙黏液流变学的动机源于我们想要了解其在辅助鲢鱼滤食过程中的作用。这种富含黏液的流体处于“浓稠且黏腻”的状态，可能有助于食物颗粒的黏附。外部剪切力的作用会诱导不同的剪切应变率，从而促进黏液透过鳃耙膜的渗透和传输。因此，黏液流变学可以为鲢鱼在滤食性鱼类群体中具有巨大竞争优势的特性提供关键线索。基于此推测，鳃耙黏液可能为食物颗粒提供黏附功能，并作为一种运输载体来辅助滤食过程。该实验方案的主要目的是确定黏液的屈服应力，它归因于启动流动所需的最小剪切应力，在这个应力下首次在一种结构化的黏弹性材料中观察到不可逆的塑性变形。相应地，使用旋转流变仪研究了鳃耙黏液的流变特性，即黏度、储能模量和损耗模量，以了解其非牛顿、剪切变稀的性质。本文介绍的实验方案用于分析从密苏里河哈特溪地点捕获的鲢鱼鳃耙中提取的黏液的流变特性。该方案旨在制定一种有效的策略，用于对被认为是结构化黏弹性材料的黏液进行流变测试和材料表征。
