408
M. V. L. BENNETT
Fig. 34. Response of the submental organ of Steatogenys elegans. Recording
in a bridge circuit (Bennett, 1961). Rostra1 positivity up. ( A ) A brief stimulus
depolarizing the innervated (caudal) faces evokes a brief spikelike potential at
short latency followed by a smaller potential. (B) Following curarization ( about
0.1 mM) the brief spikelike potential is unaffected but the longer latency component is abolished. ( C ) Before curarization a brief stimulus hyperpolarizing the
innervated faces evokes a response with a latency of about 1 msec. ( D ) Following
curarization the same stimulus evokes no response.
but the transepidermal potentials are affected similarly because opposite
ends of the organ are connected to the exterior and interior of the animal.
The function of these accessory organs is presumably to increase sensitivity of the electrosensory system in the head region, but there are no
experimental data.
e. Gymnorhamphichthys. Gymnorhamphichthys usually rests buried
in sand during the day and emerges to swim around and feed at night.
When in the sand it emits pulses at a quite constant rate of about 10-15/
sec. When actively swimming it increases its discharge rate to a new and
also quite constant frequency which it maintains for prolonged periods.
Disturbances also cause increase in discharge rate. It has been shown to
exhibit a circadian rhythm of motor activity and (perhaps secondarily)
of discharge frequency under conditions of constant darkness ( Lissmann
and Schwassmann, 1965).
The main organ of Gymnorhamphicthys is cytologically and, as inferred by recording from the intact fish, electrophysiologically like that
of Steatogenys. Gymnorhamphichthys also has submental electrocytes as
does Steatogenys. They are located beneath the dermis and thus are not
obvious, which accounts for their not being seen previously. Each cell
has multiple stalks from its posterior faces. External recording indicates
that the submental cells fire before the main organ and generate mono-
M. V. L. BENNETT
Fig. 34. Response of the submental organ of Steatogenys elegans. Recording
in a bridge circuit (Bennett, 1961). Rostra1 positivity up. ( A ) A brief stimulus
depolarizing the innervated (caudal) faces evokes a brief spikelike potential at
short latency followed by a smaller potential. (B) Following curarization ( about
0.1 mM) the brief spikelike potential is unaffected but the longer latency component is abolished. ( C ) Before curarization a brief stimulus hyperpolarizing the
innervated faces evokes a response with a latency of about 1 msec. ( D ) Following
curarization the same stimulus evokes no response.
but the transepidermal potentials are affected similarly because opposite
ends of the organ are connected to the exterior and interior of the animal.
The function of these accessory organs is presumably to increase sensitivity of the electrosensory system in the head region, but there are no
experimental data.
e. Gymnorhamphichthys. Gymnorhamphichthys usually rests buried
in sand during the day and emerges to swim around and feed at night.
When in the sand it emits pulses at a quite constant rate of about 10-15/
sec. When actively swimming it increases its discharge rate to a new and
also quite constant frequency which it maintains for prolonged periods.
Disturbances also cause increase in discharge rate. It has been shown to
exhibit a circadian rhythm of motor activity and (perhaps secondarily)
of discharge frequency under conditions of constant darkness ( Lissmann
and Schwassmann, 1965).
The main organ of Gymnorhamphicthys is cytologically and, as inferred by recording from the intact fish, electrophysiologically like that
of Steatogenys. Gymnorhamphichthys also has submental electrocytes as
does Steatogenys. They are located beneath the dermis and thus are not
obvious, which accounts for their not being seen previously. Each cell
has multiple stalks from its posterior faces. External recording indicates
that the submental cells fire before the main organ and generate mono-