Danio rerio in K-12 classrooms: sparking interest in the new generation of scientists.

Zebrafish are ideal for experimental studies in the classroom because, in contrast to chicks or mammals, fish embryos are relatively easy and inexpensive to maintain, and embryonic development can be observed with common classroom equipment. The eight student-developed laboratory exercises described here have been used by students in Neuroscience Research at Sidwell Friends School. This course uses zebrafish as a vertebrate model to study genetics, development, behavior, neurobiology, regeneration, learning, and memory. The students develop protocols through collaboration with the teacher and scientists in specific fields. Through individual research, students develop and perform their own experiments, formulate and test hypotheses, learn basic laboratory and microscopy techniques, collect and analyze data, read original scientific literature, and collaborate with prominent zebrafish researchers.

Semiconductor gel in shark sense organs?

Sharks can sense bioelectric fields of prey and other animals in seawater using an extraordinary system of sense organs (ampullae of Lorenzini) [R.D. Fields, The shark's electric sense. Sci. Am. 297 (2007) 74-81]. A recent study reported that these sense organs also enable sharks to locate prey-rich thermal fronts using a novel mode of temperature reception without ion channels. The study reported that gel extracted from the organs operates as a thermoelectric semiconductor, generating electricity when it is heated or cooled [B.R. Brown, Neurophysiology: sensing temperature without ion channels, Nature 421 (2003) 495]. Here we report biophysical studies that call into question this mechanism of sensory transduction. Our experiments indicate that the material exhibits no unusual thermoelectric or electromechanical properties, and that the thermoelectric response is an artifact caused by temperature effects on the measurement electrodes. No response is seen when non-metallic electrodes (carbon or salt bridges) are used, and ordinary seawater produces the same effect as shark organ gel when silver wire electrodes are used. These data are consistent with the voltages arising from electrochemical electrode potentials rather generated intrinsically within the sample. This new evidence, together with the anatomy of the organs and behavioral studies in the literature, best support the conclusion that the biological function of these sense organs is to detect electric fields.