Crayfish Case Study

Crayfish are decapods pertaining to the phylum arthropoda, which are invertebrates and contain an open-circulatory system.1 The system works by the hemolymph getting re-oxygenated in the gills before being transporting to the heart by brachio-cardiac veins and then pumped to sinuses that bathe tissues with oxygenated hemolymph.2 The crayfish contain a neurogenic heart that depends on neuronal input from cardiac ganglion.3 The neurogenic heart requires nerve impulses to produce contractions in contrast to a myogenic heart that can contract independently from the nervous system.3 The crayfish heart will beat due to the reaction of the ganglion to stimuli in the environment.4 Stimuli will affect the autonomic nervous system in the crayfish that control involuntary actions such as the heart rhythm.4 Neurotransmitters are the chemical signals in which the nervous system regulates both heart rate and contraction.3The autonomic nervous system breaks into two categories as parasympathetic system that is involved in relaxation of organs and the sympathetic system that will stimulate increased activity. Neurotransmitters can either increase or decrease heart rate by altering the patterns in neural activity of the heart.4 Crayfish are poikilotherms, which means they cannot metabolically thermoregulate thus conform to the ambient temperature in the water.

Internal temperatures can modify the contraction of the heart by increasing or decreasing heart rate.5 The goal of the experiment was to subject the crayfish to different conditions to monitor the change in contractility of the