Opposing effects of dopamine on agonistic behaviour in crayfish

Simultaneous Dopamine and Serotonin Monitoring in Freely Moving Crayfish Using a Wireless Electrochemical Sensing System

Dopamine (DA) and serotonin (5-HT) are neurotransmitters that regulate a wide range of physiological and behavioral processes. Monitoring of both neurotransmitters with real-time analysis offers important insight into the mechanisms that shape animal behavior. However, bioelectronic tools to simultaneously monitor DA and 5-HT interactive dynamics in freely moving animals are underdeveloped. This is mainly due to the limited sensor sensitivity with miniaturized electronics. Here, we present a semi-implantable electrochemical device achieved by integrating a multi-surface-modified carbon fiber microelectrode with a miniaturized potentiostat module to detect DA and 5-HT in vivo with high sensitivity and selectivity. Specifically, carbon fiber microelectrodes were modified through electrochemical treatment and surface coatings to improve sensitivity, selectivity, and antifouling properties. A customized, lightweight potentiostat module was developed for untethered electrochemical measurements. Integrated with the microelectrode, the microsystem is compact (2.8 × 2.3 × 2.1 cm) to minimize its impacts on animal behavior and achieved simultaneous detection of DA and 5-HT with sensitivities of 48.4 and 133.0 nA/μM, respectively, within submicromolar ranges. The system was attached to the crayfish dorsal carapace, allowing electrode implantation into the heart of a crayfish to monitor DA and 5-HT dynamics, followed by drug injections. The semi-implantable biosensor system displayed a significant increase in oxidation peak currents after DA and 5-HT injections. The device successfully demonstrated the application for in vivo simultaneous monitoring of DA and 5-HT in the hemolymph (i.e., blood) of freely behaving crayfish underwater, yielding a valuable experimental tool to expand our understanding of the comodulation of DA and 5-HT.

Serotonin and dopamine regulate the aggressiveness of swimming crabs (Portunus trituberculatus) in different ways

Bioamines act as a pivotal part in the regulation of aggressive behavior in animals as a type of neuroendocrine, but the patterns of how they regulate aggressiveness in crustaceans are still unclear due to species-specific responses. To determine the effects of serotonin (5-HT) and dopamine (DA) on the aggressiveness of swimming crabs (Portunus trituberculatus), we quantified their behavioral and physiological characteristics. The results showed that an injection of 5-HT at 0.5 mmol L^-1 and 5 mmol L^-1 could significantly enhance the aggressiveness of swimming crabs, as well as an injection of DA at 5 mmol L^-1. The regulation of 5-HT and DA on aggressiveness is dose-dependent, and these two bioamines have different concentration thresholds that can trigger aggressiveness changes. 5-HT could up-regulate the 5-HTR1 gene expression and increase lactate content at the thoracic ganglion as the aggressiveness enhances, suggesting that 5-HT may activate related receptors and neuronal excitability to regulate aggressiveness. As a result of DA injection at 5 mmol L^-1, lactate content in the chela muscle and hemolymph increased, glucose content in the hemolymph increased, and the CHH gene was significantly up-regulated. Pyruvate kinase and hexokinase enzyme activities in the hemolymph increased, which accelerated the glycolysis process. These results demonstrate that DA regulates the lactate cycle, which provides substantial short-term energy for aggressive behavior. Both 5-HT and DA can mediate aggressive behavior in the crab by activating calcium regulation in muscle tissue. We conclude that the enhancement of aggressiveness is a process of energy consumption, in which 5-HT acts on the central nervous system to induce aggressive behavior, and DA affects muscle and hepatopancreas tissue to provide a large amount of energy. This study expands upon the knowledge of regulatory mechanisms of aggressiveness in crustaceans and offers a theoretical foundation for enhancing crab culture management.

A chromosome-level genome of the kuruma shrimp (Marsupenaeus japonicus) provides insights into its evolution and cold-resistance mechanism

Marsupenaeus japonicus is an important marine crustacean species. However, a lack of genomic resources hinders the use of whole genome sequencing to explore their genetic basis and molecular mechanisms for genome-assisted breeding. Consequently, we determined the chromosome-level genome of M. japonicus. Here we determine the chromosome-level genome assembly for M. japonicus with a total of 665.19 Gb genomic sequencing data, yielding an approximately1.54 Gb assembly with a contig N50 size of 229.97 kb and a scaffold N50 size of 38.27 Mb. With the high-throughput chromosome conformation capture (Hi-C) technology, we anchored 18,019 contigs onto 42 pseudo-chromosomes, accounting for 99.40% of the total genome assembly. Analysis of the present M. japonicus genome revealed 24,317 protein-coding genes and a high proportion of repetitive sequences (61.56%). The high-quality genome assembly enabled the identification of genes associated with cold-stress and cold tolerance in kuruma shrimp through the comparison of eyestalk transcriptomes between the low temperature-stressed shrimp (10 °C) and normal temperature shrimp (28 °C). The genome assembly presented here could be useful in future studies to reveal the molecular mechanisms of M. japonicus in response to low temperature stress and the molecular assisted breeding of M. japonicus in low temperature.