Search

Recent genomic/transcriptomic studies have identified a novel peptide family whose members share the carboxyl terminal sequence -GSEFLamide. However, the presence/identity of the predicted isoforms of this peptide group have yet to be confirmed biochemically, and no physiological function has yet been ascribed to any member of this peptide family. To determine the extent to which GSEFLamides are conserved within the Arthropoda, we searched publicly accessible databases for genomic/transcriptomic evidence of their presence. GSEFLamides appear to be highly conserved within the Arthropoda, with the possible exception of the Insecta, in which sequence evidence was limited to the more basal orders. One crustacean in which GSEFLamides have been predicted using transcriptomics is the lobster, Homarus americanus. Expression of the previously published transcriptome-derived sequences was confirmed by reverse transcription (RT)-PCR of brain and eyestalk ganglia cDNAs; mass spectral analyses confirmed the presence of all six of the predicted GSEFLamide isoforms - IGSEFLamide, MGSEFLamide, AMGSEFLamide, VMGSEFLamide, ALGSEFLamide and AVGSEFLamide - in H. americanus brain extracts. AMGSEFLamide, of which there are multiple copies in the cloned transcripts, was the most abundant isoform detected in the brain. Because the GSEFLamides are present in the lobster nervous system, we hypothesized that they might function as neuromodulators, as is common for neuropeptides. We thus asked whether AMGSEFLamide modulates the rhythmic outputs of the cardiac ganglion and the stomatogastric ganglion. Physiological recordings showed that AMGSEFLamide potently modulates the motor patterns produced by both ganglia, suggesting that the GSEFLamides may serve as important and conserved modulators of rhythmic motor activity in arthropods. [ABSTRACT FROM AUTHOR]

A possible role of the insect stomatogastric nervous system (STNS) in ecdysis was first implied in early studies reporting on internal air pressure build-up in the digestive tract and air swallowing during ecdysis. The frontal ganglion, a major component of the insect STNS, was suggested to play an important part in this behaviour. Recent neurophysiological studies have confirmed the critical role of the STNS in the successful completion of both larval and adult moults in insects. In aquatic arthropods, though much less studied, the STNS plays an equally important and probably very similar role in water swallowing. Water uptake is instrumental in splitting the crustacean cuticle and allowing successful ecdysis. Current data are presented in a comparative view that contributes to our understanding of the role of the STNS in arthropod behaviour. It also sheds light on the question of homology of the STNS among the different arthropod groups. New insights into the neurohormonal control of ecdysis, related to the STNS in both insects and crustaceans, are also presented and comparatively discussed. [ABSTRACT FROM AUTHOR]

The article reports indications for a persistent Na+ conductance were found in motor neurons of the gastric mill network in the stomatogastric ganglion of the spiny lobster, Panulirus interruptus. The conductance is believed to correspond to the persistent Na+ current, described in cultured stomatogastric neurons.