Recording from Snail Motor Nerves to Investigate Central Pattern Generation.

Feeding in pond snails has long been a model system for central pattern generation and its modulation. The pattern is generated by a small set of neurons in the buccal ganglia, which innervate the buccal mass, esophagus, and salivary glands. In this exercise, students observe feeding behavior and then record and quantify rhythmic motor activity and its response to feeding stimulants and neuromodulators. In a standard three-hour class period, students do a dissection, record from several nerves, and perform experimental manipulations such as adding feeding stimulants, serotonin, or dopamine to the preparation. Depending on the course goals, data can be presented qualitatively or cyclic measurements and spike-rate analysis can be done. This exercise leads to discussion of neural circuitry and intrinsic properties that support pattern generation for rhythmic activities such as feeding, locomotion, and respiration.

Transcriptome and proteome of Conus planorbis identify the nicotinic receptors as primary target for the defensive venom.

Most venomous predators have evolved complex venom primarily to immobilize their prey and secondarily to defend against predators. In a new paradigm, carnivorous marine gastropods of the genus Conus were shown to rapidly and reversibly switch between two types of venoms in response to predatory or defensive stimulus, suggesting that the defensive use of venom may have a more important role in venom evolution and specialization than previously thought. To further investigate this phenomenon, the defensive repertoire of a vermivorous species, Conus planorbis, was deciphered using second-generation sequencing coupled to high-throughput proteomics. The venom gland transcriptome of C. planorbis revealed 182 unique conotoxin precursors from 25 gene superfamilies, with superfamily T dominating in terms of read and paralog numbers. Analysis of the defense-evoked venom revealed that this vermivorous species uses a similarly complex arsenal to deter aggressors as more recently evolved fish- and mollusk-hunting species, with MS/MS validating 23 conotoxin sequences from six superfamilies. Pharmacological characterization of the defensive venom on human receptors identified the nicotinic acetylcholine receptors as a primary target. This work provides the first insights into the composition and biological activity of specifically evolved defensive venoms in vermivorous cone snails.