Analysis of deformation of setae on the first antennae of copepods

• Main Author: Lee, Raphael Jia Ying
• Other Authors: Marcos
• Format: Thesis-Master by Research
• Language: English
• Published: Nanyang Technological University 2023
• Subjects: Engineering::Mechanical engineering
• Online Access: https://hdl.handle.net/10356/169838
• Institution: Nanyang Technological University

Copepods are small crustaceans that rely on their mechanoreceptors which are biologically linked to setae present on the first antennae of copepods to carry out daily activities such as predating and escaping from prey. Mechanoreceptors of copepods detect hydrodynamic disturbances induced by other organisms in the surroundings by bending of setae on the first antennae which triggers a neural signal to elicit a reaction. The process of detection is very efficient and most of the studies on mechanoreception focus only on the relationship between a copepod’s physiological and behavioural responses, but lacking in the physical threshold aspect. This experimental study aims to investigate the stiffness of setae by studying the physical threshold of setal deformation when subjected to hydrodynamic disturbance in the form of artificial stimulus. The current work using Pseudiaptomus annadalei as the specimen has shown significant experimental results for this study’s progress. Morphological observations are similar to past studies, finding two types setae present on the first antennae, smooth and long, as well as short and tapered. The first antenna’s length measures at 1040 µm approximately and the smooth and long type of seta has an average length of 84 µm. To produce artificial stimulus, a syringe pump is used in conjunction with a tubing line which connects to a syringe tip that is submerged in the same medium as the specimen. The syringe then injects water through the tubing line to the syringe tip outlet which creates hydrodynamic disturbance in the same medium as the copepod. This hydrodynamic force is subjected onto setae on the first antenna perpendicularly, to achieve setal deformation in both directions, towards the distal tip of the antenna and proximally towards the body are observed. The purpose of the siphon flow device is to fix the outlet position which is connected to the syringe pump to better define the artificial stimulus and setal deformation. This device is able to produce a constant and quantifiable flow as the artificial stimulus as compared to past studies, in order to attain more accurate measurements of setal deformation. These experiments will then be translated to quantify the deformation of setae on the first antenna, based on the flow velocity that each seta is subjected to. A simple spring model which depicts the resistance at the setal root utilizes the flow velocities, deformation and morphological results, based on the Resistive Force Theory, to estimate the spring constant of the long and smooth type of seta.