Ache, Barry W.

Antennular chemoreceptors of P. argus were surveyed electro-physiologically
to determine their relative sensitivity to low molecular
weight components of the shrimp, Penaeus duorarum. An ultrafiltrate
(less than 1,000 molecular weight) of shrimp extract did not differ
significantly in stimulus value from the total extract itself. A
mixture of the 19 amino acids present in the ultrafiltrate was slightly
less stimulatory than the total extract. Taurine alone approximated
the stimulus value of the amino acid mixture at its component concentration.
Taurine was also the most stimulatory of the 19 amino acids when
compared at the homogeneous 10^-3 M concentration. Taurine is the major
individual stimulant of shrimp extract but a contribution is also made
from other non-amino acid low molecular weight compounds.

The physiological effect of antennular flicking was analyzed
behaviorally and electrophysiologically in the spiny
lobster, Panulirus argus. Behavioral studies indicate
that glycine and L-glutamic acid cause a transient
concentration-dependent increase in flick rate. Electro-physiological
analysis of primary chemosensory afferents
indicates that flicking modulates ongoing chemically-elicited
activity in approximately half of the units
observed by causing either a brief increase or decrease
in the frequency of impulses. Responses of remaining units
were not altered by flicking. Antennular flicking is
discussed as a mechanism to prolong the address of the
peripheral chemoreceptors to the central nervous system
and allow the lobster to prolong its awareness of the
chemical environment.