Investigation regarding the physiological effects of cobalt on physiological functions in Drosophila, crayfish, and crab: Behavioral, cardiac, neural, and synaptic properties

Abstract

Cobalt, a metallic element found naturally in the earth's crust, is essential to survival. It is the active center of cobalamins such as vitamin B12 and is also a micronutrient for bacteria, algae, and fungi. The effects of cobalt (II) chloride (CoCl₂), the inorganic form of cobalt, are dependent on the dosage. High dosage or chronic exposure to CoCl₂ can have negative effects, such as carcinogenic properties, intoxication, and “beer drinker's cardiomyopathy.” This investigation was designed to test the effects of acute, high-concentration in cobalt exposure on physiological functions in Drosophila, crayfish, and crab, particularly in terms of behavioral, cardiac, neural, and synaptic properties. When exposed to 1 mM of CoCl₂, decreased neural transmission was observed at the neuromuscular junction (NMJ) of both crayfish and Drosophila larvae. Within the crayfish proprioceptive organ, no conclusive changes in activity were observed due to the high variability among individuals, but activity was observed to increase in the crab proprioceptive organ after 10 min immersion the CoCl₂. In larval Drosophila, heart rate decreased to near-cessation, though the in-situ preparations were able to recover regular heart rates after sufficient saline rinsing. Systemic injections of CoCl₂ into crayfish hemolymph produced no significant effects on heart rate or tail flip response. In larval Drosophila that consumed food tainted with CoCl₂, no effects were observed on behavior, mouth hook movements, or body wall movements; however, this led to adults bearing a slightly decreased lifespan, which indicates that 1 mM CoCl₂ has differing effects by tissue and organism.